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/ 0cl3
B3
Bulletin 893
Temperature and Relative Humidity
Recommendations for
Storing Bedding Plant Seed
William J. Carpenter and John A. Cornell
c,
C;9
UNIVERSITY OF
FLORIDA
Agricultural Experiment Station
Institute of Food and Agricultural Sciences
UdMdV.-jTY OF h.XALX2P
CONTENTS
ACKNOW LEDGEMENTS .......................................................
INTRO D U C TIO N ............................................................. 1
MATERIALS AND METHODS .................................................... 2
SEED HANDLING AND GERMINATION PROCEDURES ........................... 2
TEMPERATURE AND RELATIVE HUMIDITY INTERACTIONS ....................... 2
RESULTS AND DISCUSSION .................................................... 6
AGERATUM SEED STORAGE RECOMMENDATIONS ............................ 6
COREOPSIS SEED STORAGE RECOMMENDATIONS ............................ 8
DELPHINIUM SEED STORAGE RECOMMENDATIONS .......................... 10
GERANIUM SEED STORAGE RECOMMENDATIONS ........................... 12
GERBERA SEED STORAGE RECOMMENDATIONS ............................ 14
IMPATIENS SEED STORAGE RECOMMENDATIONS ............................ 16
MARIGOLD SEED STORAGE RECOMMENDATIONS ............................ 18
PANSY SEED STORAGE RECOMMENDATIONS ............................... 20
PETUNIA SEED STORAGE RECOMMENDATIONS ............................. 22
PHLOX SEED STORAGE RECOMMENDATIONS ............................... 24
SALVIA SEED STORAGE RECOMMENDATIONS ............................... 26
VINCA SEED STORAGE RECOMMENDATIONS ............................... 28
SUMMARY ...... ........................................................... 30
SEED MOISTURE CONTENT DURING STORAGE .............................. 30
OTHER FACTORS AFFECTING SEED VIABILITY DURING STORAGE ............... 32
COMMERCIAL APPLICATION OF RESULTS ........................................ 33
LITERATURE CITED ....................................... ................ .. 35
APPENDIX TABLES ........................................................ 37
i
ACKNOWLEDGMENTS
This research was partially sponsored by a grant from the Bedding Plants Foundation, Inc. P.O.
Box 27241, Lansing, MI 48909. Donors of seeds for this research were:
Ball Seed Co., West Chicago, Ill.
Bodgers Seeds, Lompoc, CA
Denholm Seeds, Lompoc, CA
Earl J. Small Growers, Inc., Pinellas Park, FL
Goldsmith Seeds, Inc. Gilroy, CA
Pan American Seed, Santa Paula, CA
Sakata Seed America, Salinas, CA
Sluis and Groot, Enkhuizen, Holland
Technical assistance was provided by Eric R. Ostmark
INTRODUCTION
Bedding plants are annual flowering species that are propagated during the winter, spring, and
fall for colorful display in garden or interior landscapes. The U.S. wholesale value of bedding plant sales
exceeds 650 million, with Florida's production at approximately 90 million dollars. The warm and sunny
winter weather makes Florida a major U.S. propagator of bedding plants. Seeds are planted mechanically
by placing 1 or 2 seeds in each cell of 72 plant flats or 200 to 800 cell plug trays. The 759 to 85QF
temperatures best for seed germination can be provided in Florida greenhouses during the winter months,
and the longer days and higher light levels promote vigorous seedling development. Florida growers ship
seedlings in plug trays throughout the US, which are later transplanted to larger containers for rapid
growth and flowering.
Seeds are defined by Hartmann et al. 1990 as special reproductive structures that contain an
embryonic plant and a supply of food in reserve that is enclosed in a protective covering or seed coat.
Propagation by seeds is the major method by which plants reproduce in nature and one of the most
efficient and widely used propagation methods for cultivated plants. Very limited recognition is given to
the adverse effects that improper seed development, damage during harvesting, and improper storage
conditions have on the loss of vigor and aging of bedding plant seeds.
The potential for rapid and vigorous germination increases when seeds are allowed to mature and
dry on the parent plant. Fully mature seeds have the advantage of complete physical and physiological
development needed for the maximal expression of vigor. Moisture content is generally used as an index
of seed maturity. Seeds of bedding plants are harvested at 8% to 14% moisture contents, with specific
levels for the seed of each species. Seeds that are not fully mature at harvest do not store well and may
have low viability because of inadequate reserves of food.
The machines used for harvesting, cleaning, handling, and packaging may injure or damage seed
if not adjusted and operated properly. Mechanically damaged seeds may appear normal, but exhibit less
vigor than undamaged seeds. Physical damage causes microscopic cracks in the seeds, which disrupts
the physiological processes during germination and reduces seed vigor and total germination.
Bedding plant seeds after harvest are stored 2 to 6 months by seed producers to remove seed
dormancies. Commercial growers store surplus seed for as long as one year. Seed germination
percentage and rate after storage depends on a) plant species, b) method of production and seed
handling, and c) extent of seed deterioration during storage. The rate of change or aging of seed during
storage varies with the species and the environmental conditions of storage, principally temperature and
relative humidity. Because of the labor costs in replacing seed that has failed to germinate in plug trays,
commercial growers discard seed lots having total germination percentages below 60% The purpose of
this study was to test the effects of temperature, relative humidity, and storage duration and their
interactions during seed storage or germination.
MATERIALS AND METHODS
Seed handling and germination procedures. Seeds of 12 species of bedding plants were used
in these studies, and the common, scientific, and cultivar names are shown in Table 1. All seeds were
received within 2.5 months after harvest. Four 100-seed samples were removed when the seed of each
species were received and the seed dusted with captain before germination in 9-cm petri dishes on blue
blotter paper 100 (Anchor Paper Co., Charlotte, N.C.) saturated with 6 ml of distilled water (DW). Seeds
were germinated in incubators (Stults Scientific Engineering Corp., Springfield, Il1.) at the recommended
temperature and light or dark condition for the species. In this and other studies, germination counts
were made daily of seeds with radicle protrusion through the testa. Total germination percentages (G),
days to 50% of final germination (T50), and germination span in numbers of days between 10% and 90%
germination (T90 T10) were calculated as described by Furutani et al. (1985).
The relative seed moisture contents were determined from four 100-seed samples collected from
each species when the seeds were received. Each of the four 100-seed lots were weighed, placed in an
open petri dish and dehydrated at 75QC in forced-draft ovens for 48 hours, and reweighed after cooling.
Temperature and relative humidity interactions during seed storage. Seeds of all species were
stored at 11%, 32%, 52%, or 75% relative humidities (RH) at 5s, 15Q, or 259C for storage periods (SP)
Bedding plant species and cultivars having germination evaluated after 3 to 12 months of seed
storage
__l_;_____ ____ ____Name_ __________Y_____L=__
Name
Common Scientific Cultivar
Ageratum Ageratum houstonianum Blue Blazer
Coreopsis Coreopsis lanceolata L. Native
Delphinium Delphinium x cultorum Magic Fountains Lavender
Geranium Pelargonium x hortorum Scarlet Eye Orbit
Gerbera Gerbera jamesonii Painted Center Dark Eye
Impatiens Impatiens wallerana hook. f. Accent Orange
Marigold Tagetes erecta Aurora Light Yellow
Pansy Viola x wittrockiana Magic Giant Yellow
Petunia Petunia hybrida Ultra Rose
Phlox Phlox drummondii Hook. Light Salmon
Salvia Salvia splendens Red Hot Sally
Vinca Catharanthus roseus Tropical Rose
Table 1.
of 3, 9, or 12 months, with one exception being Coreopsis, which was stored up to only 9 months.
Humidity treatments were achieved by placing 100-seed replicates in 15 x 25-cm petri dishes on wire
screens supported by segments of tubing 1 cm above 50 ml of saturated lithium chloride, magnesium
chloride, magnesium nitrate, or sodium chloride to maintain 11%, 32%, 52%, or 75% RH, respectively
(Copeland 1976). Incubators were maintained at constant temperatures during seed storage or
germination. Four 100-seed replications were germinated at the recommended temperature and light or
dark regime immediately following storage at each duration and RH level, while another four replications
were desiccated in forced-draft ovens for 48 hours at 75C to determine the moisture contents of stored
seed. Analysis of variance and response surface regression procedures were used to analyze the data.
Within each storage temperature, a randomized complete block design was used with a factorial treatment
structure (4 x 4) between relative humidity and storage period.
The data were analyzed by fitting multiple regression equations using PROC REG of SAS Institute
(1985) for seed of each of the 12 species. Both storage period and relative humidity were studied at four
levels each (except for Coreopsis which had only three levels of storage period), and the model fitted
initially was a complete third-degree polynomial of the form:
Response = Bo+B1SP+B2RH+B3SPxRH+B4SP2+B35RH2+B6(SPxRH2)+ (1)
B7(SP2xRH) +B8SP3+89RH3+e
In the above model the terms B1SP and B2RH represent the linear effects of storage period (SP) and
relative humidity (RH) on the response; B3SPxRH represents a linear by linear interaction effect between
storage period and relative humidity, and B4SP2 and BgRH2 represent the curvilinear effects (quadratic)
of storage period and relative humidity. The third-degree terms BgSPx RH2 and B7SP2xRH represent the
linear x quadratic interaction effects, with, 86SPxRH2 representing the linear effect of storage period on
the quadratic effect of relative humidity, while 1BSP3 and B9RH3 represent the cubic effects of storage
period and relative humidity, respectively, on the response.
The model fitting exercise consisted of testing the significance of the coefficient estimates of the
parameters B1, 2 ,..., B9 in (1) and dropping or deleting those terms of degree 2 or higher that did not
attain a significance level of P = 0.05. When terms were dropped, the simpler, reduced model form was
refitted and the coefficient estimates retested at the P = 0.05 level of significance. In some cases, the
interaction and curvilinear effects of storage period and relative humidity were negligible resulting in a
final, reduced model being of the form
Response bo+bSP+b2RH
where b1 and b2 represent the linear effects, however small, of storage period and relative humidity,
respectively.
For each fitted model developed, the estimates of the coefficients b3, b4,..., b7 that were found
to be significant (P < 0.05) are given in Appendix Tables Al to A12. The cubic effects terms b3SP3 and
b9RH3 were not significant for any seed species. For each seed species the temperature response
combination is shown in Appendix Tables Al to A12, with the value of the coefficient of determination (R2)
given for the fitted model and the figure designation of each contour plot. The contour plots, generated
by the fitted equation, represent estimated response values that aid in visualizing the shape of the
response surface. The values of the curves represent specific values for the height of the surface above
the plane for different combinations of storage period and relative humidity level. The plotting of different
surface height values enables one to focus on the storage period and relative humidity combinations at
which changes occur in the surface shape.
Across Appendix Tables Al to A12 the value of R2 associated with the fitted regression equations
ranged from 0.243 to 0.952. These values define the proportion of the total variation in the data (4
replicates of each of the 16 storage period by relative humidity combinations in most cases) that is
accounted for or explained by the fitted model. While a value of R2 close to unity (1.0) is desirable, a low
value of 0.243 does not necessarily reflect a poor fit by the model. A low value of R2 sometimes results
because four replicated samples were collected at each SP by RH treatment combination, which Cornell
and Berger 1987 reported can lower the value of R2. Nonetheless, the closer the value of R2 is to one,
the better the fit of the data to the model and the explanation for the variation in the response values.
The surface shapes shown in the contour plots for each plant species were generated by fitting
regression equations to illustrate the effects of storage period duration, relative humidity, and specific
storage temperature later on the germination responses G, T50, and T90-T0o. Based on the surface trends
shown in the contour plots, we have projected specific treatment combinations of SP, RH, and storage
temperature that will produce the maximal G, or minimal T5o or minimum Tgo-T10, even though these
treatment combinations may not have been among those performed in the experiments. In these cases,
we are only indicating trends suggested by data and the subsequent fitting of multiple regression models,
which, even in the presence of experimental error, are likely to produce the assumed results.
RESULTS AND DISCUSSION
The empirically generated contour plots described were used to evaluate the effects of seed
storage at three temperatures, four RH levels, and 3 to 12 month durations on total germination
percentages (G), days to 50% of final germination (T50), and the days between 10% and 90% germination
(T90 Tlo). The effects of each factor with their interactions will be presented for the 12 bedding plant
species in our study.
Ageratum (Ageratum houstonianum Mill.) seed storage. Ageratum seed germinates best at 27T -
299C when uncovered and exposed to light (Ball, 1991), but very limited information has been published
regarding the proper storage of the seed.
Ageratum seed of cultivar Blue Blazer was kept at 11% to 75% RH levels at 59C storage
temperatures for 12 months without loss in total germination (G 93% in Figure 1A). After 12 months
storage at 52C, seed moisture contents at 11%, 32%, 52%, and 75%RH levels were 2.0%, 3.4%, 4.7%,
and 7.3%, respectively. The moisture percentages were calculated on the basis of the dry wieghts of the
seed. The results indicated either our seed moisture levels were inadequate to cause the normal
accelerated aging of seeds at these high RH levels, or 59C storage temperature prevented the
accelerated aging response. Seeds stored at 155C had highest G at 11% and 32% RH, with small
reductions at 52% RH and large reductions at 75% RH during 12 months (Fig. 1B). Highest G for seed
stored at 259C were at 11% and 32% RH, with reduced G during 12 months for seed stored at 52%RH
\iiii1i1iii i
11 32 52 75
Relative Humidity (%)
t1 7
11 32 52 75
Relative Humidity (%)
11..4 .4
11 32 52 75
Relative Humidity (%)
Fig. 1 Ageratum contour plots for total germination percentages (A,B,C), days to 50% of final germination
(D,E,F), and days between 10% and 90% germination (G,H,I) for seeds germinated at 151C in darkness
following storage at 11% to 75% RH for 3 to 12 months at 5C (A,D,G), 15QC (B,E,H), or 250C (C,F,I).
Shaded regions (C,F,I) represent poor germination due to total loss of viability of seeds stored at 75% RH
after 3 to 12 months storage. Regression equations used to generate these plots are listed in Appendix
Table Al.
^ 95 99
^;T\ \
and total loss of viability for seeds stored at 75% RH after 3 to 12 months storage.
The most rapid germination rate, as measured by the lowest T50 values, and most uniform
germination (smallest T90 T1o) occurred after seed storage at 5QC or after storage at 159C or 259C and
11% or 32% RH (Fig. 1 D-F). Storage at 52% and 75% RH at 15"C resulted in delayed and more irregular
germination, and seeds failed to germinate after 3 months or longer at 75% RH and 25.C.
Recommendations for best seed storage:
59C at 11% to 75% RH
159C at 11% to 32% RH
259C at 11% to 32% RH
Coreopsis seed storage. Samfield et al. (1990) reported that recently harvested coreopsis seed
had 33% to 35% total germination. Carpenter and Ostmark (1992) found the total germination
percentages of recently harvested coreopsis seed increased as storage duration at 50C increased at all
relative humidities, achieving 75% germination at 10% to 30% RH after 6.5 to 8 months (Fig. 2A). Highest
total germination at 15QC was after seed storage at 20% to 35% RH, with 80% germination after 7 months
of storage. Total germination at 150C declined after storage at relative humidities above 50% (Fig 2B).
The maximum germination was approximately 60% for seed stored at 259C, and germination rapidly
declined when seeds were stored at above 50% RH (Fig. 2C).
The fewest days to 50% of final germination resulted after 4 to 7 months of storage at 50 or 159C
(Fig. 2D-F). Seeds stored at 59C and 10% to 20% RH or 10% to 40% RH at 159C had T50 of 10 days.
Storing seeds at 52 or 15!C for periods longer or shorter than 5 to 6 months increased the days to T50,
as did above 50% RH (Fig. 2 D and E). The largest delay in germination T50 was after seed storage at
259C and above 40% RH. Increasing the 251C storage from 45% to 70% RH lengthened the T50 from
15 to 25 days (Fig. 2F).
The span in days between 10% and 90% germination lengthened as storage temperatures of
seeds increased from 5s to 259C (Fig. 2G to I). The trends were similar at all temperatures, with more
days required for the T90 Tio span as RH and seed storage durations increased.
A D G
CS
1.
B EH
CF >I
10 30 50 70 10 30 50 70 10 30 50 70
Relative Humidity (%) Relative Humidity (%) Relative Humidity (%)
Fig. 2 Coreopsis contour plots for total germination percentages (A,B,C), days to 50% of final germination
(D,E,F) and days between 10% and 90% germination (G,H,I) for seeds germinated at 151C in darkness
following storage at 11% to 75% RH for 3 to 9 months at 59C (A, D, G), 159C (B, E, H), or 250C (C,F,I).
Regression equations used to generate these plots are listed in Appendix Table A2.
The results indicate that the total germination of recently harvested coreopsis seed can be
increased from 35% to 75 to 80% by storage of seed at 52 to 15QC and 30% to 40% RH for 6.5 to 9
months. Bewley and Black (1982) reported that increased total germination after storing the seeds of
many genera at about 15-C resulted from the increased production of endogenous gibberellin and
cytokinin, either during chilling or after transferring chilled seeds to recommended temperatures.
Recommendations for best seed storage:
59C at 10% to 30% RH for 7 to 9 months.
15 C at 20% to 35% RH for 9 months.
25PC not recommended
Delphinium x cultorum seed storage. The relative humidity and temperature during seed storage
of delphinium determine the total germination after storage. Highest total germination occurred after 59C
storage at 30% to 50% RH, although the germination percentage declined as storage periods lengthened
(Fig. 3A). More rapid losses in total germination occurred when RH was above or below the 30% to 50%
range. Storing seeds at 159C generally led to lower germination percentages than storage at 59C (Fig.
3B). Highest total germination at 159C was at 25% RH, although differences among treatments between
10% and 40% RH were small. Larger losses in seed viability at 159C than 59C occurred above 60% RH.
Seeds stored at 259C had lower total germination after storage than those stored at 52C or 159C at all
relative humidity levels (Fig. 3C).
Seeds achieved T50 in fewer days after storage at 59C than at 159 or 252C (Fig. 3D-F).
Germination T50 required the fewest days after 59 storage at 35% to 55% RH, with longer periods required
at higher or lower RH levels (Fig. 3D). At 159C, shortest periods to T50 occurred after 25% to 50% RH
seed storage, but differences in T50 among relative humidities were small, except above 70% (Fig. 3E).
Storing seeds at 259C delayed germination by lengthening T50 values, with longest delays for seeds
stored above 50% RH (Fig. 3F).
The To9 Tlo values generally were lengthened by storing seeds at high temperatures and high
relative humidities (Fig. 3G-I). Although fewer days to To9 Tlo were required after storage at 59C than
,A / G
00
99
7 85 85 75 5 5
S/E, ~H
0..
0
CF
1 1) 1 1 1 25 31
10 30 50 70 10 30 50 70 10 30 50 70
Relative Humidity (%) Relative Humidity (%) Relative Humidity (%)
Fig. 3 Delphinium contour plots for total germination percentages (A,B,C), days to 50% of final germination
(D,E,F) and days between 10% and 90% germination (G,H,I) for eeds germinated at 209C following
storage at 11% to 75% RH for 3 to 12 months at 59C (A,D,G), 159C (B,E,H), or 250C (C,F,I). Regression
equations used to generate these plots are listed in Appendix Table A3.
at 15QG, both had uniform germination spans below 40% RH (Fig. 3 G-H). At 25CC, the relative humidity
level during seed storage governed the length of T90 T10 (Fig. 3 I). Relative humidity level during seed
storage at 259C had more effect on total germination, Ts0, or Tgo To1 than on extending the storage
period from 3 to 12 months (Fig. 3A-I).
Seed moisture content during storage affects the rate of seed deterioration. In storage, the
moisture content of seeds will come to equilibrium with the RH of the surrounding air. Delphinium seed
stored 12 months at 59C and 11%, 32%, 52% or 75% RH had 4.9%, 6.8%, 8.3%, and 11.1% moisture
contents, respectively. According to computer-generated estimates, the highest germination percentages
occurred following seed storage at 59C and 30% to 50% RH, which resulted in 6.6% to 8.2% seed
moisture content. Shortest T50's were after 52C storage at 35% to 55% RH, or 6.8% to 8.5% moisture
contents, and shortest T90 T,0 after storage at 25% to 50% RH, or 6.1% to 8.2% seed moisture.
Recommendations for best seed storage:
5QC at 30% to 50% RH up to 6 months
159C at 20% to 40% RH up to 6 months (lower G, higher T50 and T90 T1o than 5)C)
251C not recommended
Geranium (Pelargonium x hortorum) seed storage. Standard seed of geranium 'Scarlet Eye Orbit'
were used in this study. No commercial recommendations or results from past research were found in
a literature search regarding the best seed temperature or moisture content during seed storage (White,
1993). Following storage, seeds receiving all treatments were germinated at 259C in darkness, with daily
counts made of seed having root emergence.
No differences in total germination percentages occurred when geranium seeds were stored at
11% to 75% RH levels for 3 to 8 months at 59C (Fig. 4A). At 50C storage, a slow decline in total
germination began after 8 months of storage, with the rate of decline similar at all RH levels. Seeds stored
at 159C and at 11% to 52% RH had total germination percentages similar to that for seeds stored at 59C
(Fig 4B). Total germination declined after 9 to 10 months storage for seed stored at 11% to 52% RH
levels. A more rapid decline resulted for seed stored at 75% RH at 15QC, with total germination of 95%
------92
--96
11 32 52 75
Relative Humidity (%)
S iiii~ii:ii
11 32 52 75
Relative Humidity (%)
2,.2
181.4 1i-
11 32 52 75
Relative Humidity (%)
Fig. 4 Geranium contour plots for total germination percentages (A,B,C), days to 50% of final germination
(D,E,F), and days between 10% and 90% germination (G,H,I) for seeds germinated at 25C in darkness
following storage at 11% to 75% RH for 3 to 12 months at 5C (A,D,G), 159C (B,E,H), or 259C (C,F,I).
Shaded regions (C,F,I) represent poor germination due to total loss of viability of seeds stored at 75%RH
after 3 to 12 months storage. Regression equations used to generate these plots are listed in Appendix
Table A4.
after 6 months storage becoming 80% after 12 months storage. (Fig. 4B). At 25QC storage temperature,
seeds could be stored 8 months at 10 to 52% RH before a rapid decline in total germination began. (Fig.
4C). The onset and rate of decline increased with seed moisture from 11% to 52% RH. No seed
germinated after 3 to 12 months storage at 75% RH (Fig. 4C).
Trends were similar for the rates of germination (T50) and uniformity (T90 T1o) of germination after
storage. The most rapid and uniform germination occurred after seed storage at 11% to 75% RH and
51C, or at 11% to 52% RH and 15 C (Fig. 4D-E and G-H). Germination was delayed and became more
irregular the longer seeds were stored at 75% RH at 159C (Fig. 4E and H). The number of days required
for germination after seed storage at 259C, and the days between 10% and 90% germination, rapidly
increased the longer the seeds were stored at 11%, 32%, or 52% RH (Fig. 4F and I).
Recommendations for best seed storage:
59C at 11% to 75% RH for 8 to 9 months
15 C at 11% to 52% RH for 8 to 9 months
259C at 11% to 32% RH, for 3 to 6 months
Gerbera (Gerbera iamesonii) seed storage. Ball (1991) reported 21 C to 24PC as the optimum
temperature range for germination, and further suggested seeds be covered with finely shredded
spagnum peatmoss. Carpenter et al. (1994b) reported gerbera germination percentages were maximal
and approximately equal at constant 15Q, 209, or 25PC in darkness or light, but lower at alternating
temperatures having the same mean temperature. Germination rate (T50) and uniformity (T90 T1o)
required the fewest days at 259C or 30QC constant temperatures, with longer germination periods at
alternating temperatures. Reducing the seed moisture content from 7.1% to 3.5% had no effect on
germination, but below 3.5% the total germination was reduced and Ts5 and T90 To1 were increased.
Total germination percentages of cultivar Painted Center Dark Eye declined at all temperatures
at RH levels above 32% during seed storage, as storage periods lengthened from 6 to 12 months (Fig.
5A-C). No seeds germinated after 3 months at 15QC or 25QC and 75% RH. As storage periods increased
from 3 to 12 months, germination percentages at 152C declined from 75% to 60% as RH increased from
C
0
a iiiiii2
11 32 2 7 11 2 2 2 2 75
i\\ \ V5
Fig. 5 Gerbera contour plots for total germinion percentages ,BC), ds to 50% of final germinion
12 \C 28 --
S_________________ 34 2. .
11 32 52 75 11 32 52 75 11 32 62 75
Relative Humidity (%) Relative Humidity (%) Relative Humidity (%)
Fig. 5 Gerbera contour plots for total germination percentages (ABC), days to 50% of final germination
(D,E,F), and days between 10% and 90% germination (G,H,l) for seeds germinated at 259C in darkness
following storage at 11% to 75% relative humidity for 3 to 12 months at 5tC (A,D,G), 159C (B,E,H), or
25QC (C,F,I). Shaded regions (B,E,H, and C,F,I) represent poor germination due to total loss of viability
of seeds stored at 75% RH after 3 to 12 months storage. Regression equations used to generate these
plots are listed in Appendix Table A5.
32% to 52%, and at 259C from 70% to 30% at 52%RH (Fig. 5B-C). Similar germination percentages
occurred after seed storage at 11% RH and 32%RH with both having above 80% germination after 12
months storage at 59C, compared with approximately 75% and 70% germination after 12 months storage
at 159C and 259C, respectively. Maximum estimated germination was 82% for seeds stored 9 months
at 22% RH and 50C.
The fewest number of days to 50% of final germination (T50) resulted after 9 months of storage
at 32% RH and 159C (Fig. 5E). Seeds stored at 59C or 15PC and 11% to 32% RH required 2.6 to 2.8
days to T50, while 2.8 to 3.0 days were required after storage at 259C (Fig. 5D-F). The longest delay in
germination T5o was after seed storage at 259C and 52%RH; and in fact, seed stored at 75% RH and 15Q
or 259C failed to germinate. The spans in days between 10% and 90% germination were similar (< 2.5
days) for seeds stored at 11% and 32% RH levels at all temperatures (Fig. G-l).
Recommendations for best seed storage:
52C at 11% to 32% RH, 80% germination rates 3 to 12 months
159C at 11% to 32% RH, 75% germination rates 3 to 12 months
259C at 11% to 32% RH, 70% germination rates up to 9 months
Impatiens (Impatiens wallerana) seed storage. No research reports or recommendations regarding
the storage of impatiens seeds were found in a search of the literature. Seed germination has been
reported by Cathey (1976) to require continuous light, and Ball (1991) recommended continuous light
during germination with uniform temperatures (249C or 259C) and medium moisture content. Carpenter
et al. (1994a) reported that imbibed impatiens seeds kept in darkness for more than 2 days before lighting
had reduced, delayed, and irregular germination. Their results also indicated that impatiens seed
germination was promoted by an initial 1 to 3 days of light, but continued light at 100 fc intensity inhibited
root extension in the latter stages of germination and significantly delayed germination.
The highest total germination (G) occurred after seed storage of cultivar Accent Orange at 5C
at 75% RH and 3 months storage period (Fig 6A). At 32% to 52% RH, no differences in G (= 94%)
resulted by varying storage period from 3 to 12 months. Germination percentages declined from 96% to
B
11 32 52 75
Relative Humidity (%)
j 4 3.4
11 32 52 75
Relative Humidity (%)
1;
11 32 52 75
Relative Humidity (%)
Fig. 6 Impatiens contour plots for total germination percentages (A,B,C), days to 50% of final germination
(D,E,F), and days between 10% and 90% germination (G,H,I) for seeds germinated at 259C in light
following storage at 11% to 75% RH for 3 to 12 months at 5C (A,D,G), 15QC (B,E,H), or 25QC (C,F,I).
Shaded regions (B,E,H and C,F, I) represented poor germination due to total loss of viability of seeds at
75% RH after 3 to 12 months storage. Regression equations used to generate these plots are listed in
Appendix Table A6.
12: : :
3
^ I-.. ..ilI.l..
84% when increasing SP from 3 to 12 months at 50C and 75% RH, indicating that the seed moisture
content promoted active catabolism of stored food. At 11% to 52% RH, germination trends were similar
at 159C and 59C, but no seed germination occurred after storage for 3 to 12 months at 159C and 75%
RH (Fig. 6A,B). At 25CC, the highest germination occurred at 32% RH across all storage durations (Fig.
6C). Germination percentages declined from 90% to below 60% as storage periods increased from 3
to 12 months at 52% RH and 259C, and no seeds germinated after storage at 75% RH.
Trends in the rate (T50) and uniformity (T90 T10) of germination after storage were similar at all
temperatures. The lowest T50 and T90 Tlo values were found at 32% to 52% RH with storage for 6 to
9 months at 52C and 152C (Fig 6 D, E, G, H). Higher values occurred at shorter and longer storage
periods. Seeds stored at 252C had lowest T50 and To9 Tio values after storage at 32% RH for 9 or 6
months, respectively (Fig. 6F and I). Although the differences in germination T50 and T90 Tio values from
the various storage temperature RH durations could be considered small (T5o ranging from 3.0 to 3.6
days and Tgo Tlo from 1.0 to 1.8 days), the trends described were very consistent. No explanation can
be given for these trends in the rates and uniformity of impatiens seed germination, but they could be
related to a non-light controlled seed dormancy.
Recommendations for best seed storage:
5QC at 32% to 52% RH for 3 to 12 months
152C at 32% RH for 3 to 12 months
259C at 32% RH up to 9 months
Marigold (Taqetes erecta) seed storage. Most bedding plant producers believe marigold seeds
during storage are tolerant of a wide range of temperatures and seed moisture levels, although published
research results are lacking. Ball (1991) recommended that seeds be covered lightly with the medium
during germination, and kept at 249C to 26QC temperatures. Seeds of cultivar Aurora Light Yellow were
placed under the storage treatments in our study 5 weeks following seed harvest.
The highest total germination occurred after storage at 59C and 32% RH, and at 159C and 32%
or 52% RH (Fig. 7 A.B.). No seeds germinated after 3 to 12 months storage at 152C, or 259C at 75%
i "'"ijij:
2
11 32 52 75
Relative Humidity (%)
----+-2IIIII! ji|
11 32 52 75
Relative Humidity (%)
.....i i II I
---------------- 2:: i
11 32 52 75
Relative Humidity (%)
Fig. 7 Marigold contour plots for total germination percentages (A,B,C), days to 50% of final germination
(D,E,F), and days between 10% and 90% germination (G,H,I) for seeds germinated at 259C in darkness
following storage at 11% to 75% RH for 3 to 12 months at 5C (A,D,G), 159C (B,E,H), or 259C (C,F,I).
Shaded regions (B,E,H, and C,F,I) represent poor germination due to total loss of viability of seeds stored
at 75% RH after 3 to 12 months storage. Regression equations used to generate these plots are listed
in Appendix Table A7.
G
H
5.iifit
3:::::
1.2i i i i
1 ; :
`~"''~~'~'
_cc~------~
SS----"i~~
~--~
t---,
RH (Fig 7 B,C). Germination percentages were lower after 259C storage, with highest levels after storage
at 11% RH during 3 to 12 months or after 3 or 6 months at 32% to 52% RH. (Fig. 7C).
Very little change in the rate (T50) and uniformity (T90 T1) of germination resulted after storing
marigold seeds for 12 months at 59C and 11% or 32% RH (Fig 7 D,F). Progressively larger T50 and T90 -
Tio occurred after 15C or 25PC storage at all RH levels with increased periods of storage (Fig. 7 D,E,H,
I). Our results indicate that the total germination percentages achieved after storing marigold seeds does
not measure the extent of delay in germination or the increased variability in germination caused by
improper storage temperatures or RH levels.
Recommendations for the best seed storage:
59C at 11% to 52% RH for 6 to 12 months
159C at 11% to 52% RH for 6 to 9 months
256C at 11% to 32% RH for up to 8 months
Pansy (Viola x wittrockiana) seed storage. Because of the year-round demand for pansy plants,
bedding plant producers are facing new challenges of storing seeds for longer periods and germinating
seeds requiring low temperatures during warm seasons. Carpenter and Boucher (1991) reported that no
loss in pansy 'Majestic Giant Yellow' seed viability occurred during 4 months of storage at 59C and 10.5%
to 5.8% seed moisture levels, but primed pansy seed germination decreased at moisture contents below
10% moisture. They found primed pansy seed stored 16 weeks at 5C and 52% RH had 12.5% moisture
content and germination declined by only 2%. Ball (1991) recommends that pansy seed be covered
lightly with the seed germination medium and germinated at 18C to 24C.
In our study, the highest germination (290%) occurred with seed stored for 6 months or less at
5QC across all levels of RH and 4.5 months or less at 159C or 25C at RH levels from 11% to 52% (Fig.
8 A, B, C). Germination percentages declined only slightly (85%) after 59C storage for 12 months at 11%
and 32% RH storage, and to between 78% and 82% at these humidity levels and 15C or 259C.
Declines in total gemination generally were larger after storage at 52% RH than 11% or 32% RH at all
storage temperatures. Seeds stored at 75% RH and 159C or 259C failed to germinate after storage,
.3
.1
----.8 iHIIIIIjii
r2v iiiiiiiiii
----- ; ; i ; ; ; ; ;i
-2-a ,...
o2c ,..
21 o.
2 o .
*1!i ii i~
11 32 52 75
Relative Humidity (%)
8 ....... .
S' ":: ::' :::':,
R6 36 ::::::::::
11 32 52 75
Relative Humidity (%)
11 32 52 75
Relative Humidity (%)
Fig. 8 Pansy contour plots for total germination percentages (A,B,C), days to 50% of final germination (D,
E, F), and days between 10% and 90% germination (G,H,I) for seeds germinated at 209C in darkness
following storage at 11% to 75% RH for 3 to 12 months at 59C (A,D,G), 15C (B,E,H), or 259C (C,F,I).
Shaded regions (B,E,H, and C,F, I) represent poor germination due to total loss of viability of seeds stored
at 75% RH after 3 to 12 months storage. Regression equations used to generate these plots are listed
in Appendix Table A8.
3. 6 .i.i.. jj
3.62 3. 8 ij
767 .........
while seeds stored at 75% RH at 5C had rapidly declining total germination as storage durations
increased (Fig 8A,B,C).
The seed storage temperature, RH, or duration were found to have negligible effects on the rate
(T50), or uniformity (T90 T10) of germination (Fig 8 D-I). No significant differences in T50 were found within
or among Figures 8 D,E,F. The numbers of days between 10% and 90% germination increased at all
temperatures and relative humidities as storage durations increased. However, the trends were smaller
at 52C storage than at 159C or 259C.
Recommendations for the best seed storage:
5C between 11% and 32RH for up to 12 months
159C at 32% to 52% RH for less than 4.5 months
259 at 32% to 52% RH for less than 4.5 months
Petunia (Petunia hybrida) seed storage. Post (1949) reported that poor germination of petunia
seeds was common, and recommended the seed be fresh. Laurie et al. (1969) found best germination
resulted when seeds were sown on the surface of a finely screened propagation medium to assure good
contact with the small seed. Ball (1991) recommended 24Q to 26QC germination temperatures, and
warned against allowing the medium temperature to decline below 22qC. No commercial
recommendations or results from past research were found in the literature giving the best seed
temperature for storing petunia seed. Cultivar Ultra Rose was used in our study.
Petunia seed stored at 5QC between 20% and 35% RH had the highest total germination, but only
slightly lower percentages resulted from storage between 50% to 75% RH or below 20% RH (Fig 9A). At
each storage RH level at 59C, total germination percentages remained constant as the storage durations
increased from 3 to 12 months (Fig 9A). Highest total germination (2 90%) after 15PC storage occurred
with RH between 32% and 45% at 3 months, with lower percentages occurring at longer durations of
storage or with RH below 32% or above 50% at 3 months (Fig. 9B). No seed stored at 152C and 75%
RH germinated after 12 months. At 25C, highest total germination occurred at 32% RH between 4.5 and
9 months, with rapidly declining percentages at 52% RH at storage above 7.5 months. Seeds failed to
11 32 52 75
Relative Humidity (%)
\ \ \ on' ;:; i;:o
\ \ \ ,,oJ:; o;;;
11.o3o 52 75
Relative ,.midity o
\ 2 3 4
336
11 32 52 75
Relative Humidity (%)
.7
iii .......
1. 1 :9 ::,ij
11 32 52 75
Relative Humidity (%)
Fig. 9 Petunia contour plots for total germination percentage (A,B,C), days to 50% of final germination
(D,E,F), and days between 10% and 90% germination (G,H,I) for seeds germinated at 15C in darkness
following storage at 11% to 75% RH for 3 to 12 months at 5C (A,D,G), 15C (B,E,H), or 25QC (C,F,I).
Shaded regions after 12 months storage (B,E,H) and 3 to 12 months storage (C,F,I) represent poor
germination due to total loss of viability of seeds stored at 75% RH. Regression equations used to
generate these plots are listed in Appendix Table A9.
G
H
I
germinate at 3 months and above at 75% RH seed storage (Fig. 9C).
The fewest days to 50% of final germination (lowest T50) occurred at RH levels between 25% and
35% at all storage temperatures. At 159 and 259C, T50 increased as RH levels increased (Fig. 9,E,F).
The most uniform germination (fewest days for T90 T10) generally occurred after seed storage between
11% and 32% RH at all temperatures, with longer periods in days resulting from storage between 52%
and 75% RH (Fig 9G,H,I). Only small changes occurred in T5o and T90 T10 values at each RH level as
storage durations increased from 3 to 12 months.
Recommendations for the best seed storage:
59C between 25% and 35% RH for 12 months
159C between 32% and 45% RH for 12 months
25QC at 32% RH for 9 to 12 months
Phlox (Phlox drummondii) seed storage. No research on the storage of annual phlox seed has
been reported in the literature. Temperature is critical for best germination, with Ball (1991)
recommending 169C and Shirokova et al. (1977) 209C. Cathey (1976) reported that continuous darkness
was required to achieve maximum germination. Carpenter et al. (1993) reported more rapid and uniform
germination of phlox seed in darkness at constant 209C than with 12-hour alternating 15VC/25C. Phlox
cultivar Light Salmon was used in this study.
Total germination of 95% and above occurred after 52C storage at 11% to 40% RH for up to 12
months, while approximately 87% and 75% germination occurred after 12 months storage at 60% and 80%
RH, respectively (Fig 10A). At 15QC, 100% germination resulted after seed storage at 35% to 55% RH
for less than 4 months, but total germination declined more rapidly at 159C than 59C at relative humidity
levels exceeding 60% and storage periods of 8 months or longer (Fig 10A,B). Seeds stored at 251C had
lower germination percentages after storage than seeds stored at 5QC or 151C (Fig 10C). At 259C, the
highest total germination only slightly exceeded 80% after storage at relative humidities lower than 60%.
Most seeds germinated in fewer than 4 days (TV5) after 12 months storage at 5C and below 40%
RH, or at 60%RH and storage periods of less than 6 months (Fig 10D). After storage at 159C, seeds
12- A D
CM
S6
3 3.5 _-_ _ 8
1290\ B E
C \(- c \1A I F / { illiiil
1-C
o
0
I(Us 6-
11 32 52 75 11 32 52 75 11 32 52 75
Relative Humidity (%) Relative Humidity (%) Relative Humidity (%)
Fig. 10 Phlox contour plots for total germination percentages (A,B,C), days to 50% of final germination (D,
E,F), and days between 10% and 90% germination (G,H,I) for seeds of 'Light Salmon' germinated at 209C
following storage at 11% to 95% RH for 3 to 12 months at 5C (A,D,G), 15C (B,E,H), or 25C (C,F,I).
Regression equations used to generate these plots are listed in Appendix Table A10.
required slightly longer germination periods (higher T50 values) at comparable relative humidity levels and
storage periods than after 59C storage (Fig. 10E). The T50 values were at or below 4 days after 12
months storage at 159C and 20% RH or lower. Germination at or below 4 days occurred after seed
storage at 259C only when storage periods were less than 5 months and RH was below 40% (Fig. 10F).
The estimated days to T50 following storage at 25QC increased rapidly as storage period and relative
humidity levels increased above 8 months and 60% respectively.
The span in days between 10% and 90% germination (To9 T1o) generally was lengthened by
storing seeds for long periods at high relative humidities, where similar patterns developed at the 3
storage temperatures (Fig. 10G,H,I). At 54C, increasing the seed storage period had little or no effect
on T90 To spans at lower than 40% RH (Fig. 10G); however, at 159C T90 T10 values remained low
(about 4 days) over the range of relative humidities only with less than 4 months storage (Fig. 1OH). At
259C, the lowest T90 To of 4 days occurred after storage for less than 4 months over all RH levels (Fig.
101).
Recommendations for the best seed storage:
5C between 11% to 40% RH for 12 months
159C below 20%RH for 12 months
25PC below 20% RH for 12 months
Salvia (Salvia splendens) seed storage. No research reports on the storage of salvia seed have
been found in the literature. Ball (1991) recommends that salvia seed be germinated at 249C or 259C
and not covered with the medium since light aids germination. Carpenter (1989) reported priming salvia
seed in aerated polyethylene glycol 8000 (PEG) solutions at 0.8MPa for 10 days at 15 C increased total
germination percentages and promoted more rapid and uniform germination. Salvia cultivar Red Hot Sally
was used in this seed storage study.
The highest total germination percentages occurred after storage at 32% RH at the 5C, 15CC,
and 25QC storage temperatures (Fig 11A, B,C). Germination percentages were slightly higher after
storage at 159C than at the other temperatures (75% vs 70%), and declined with longer seed storage at
12 / A 34 D
Co
3. .__.__2 2..
12 / B E
S H ( H ii....... :: :: Hii
F con u ii lo i (iiiin (s ijoini n
73 jjJ:| :::= 8 !!ii!!!!!!!
Si!! :: : ::::\ !
\ .i : :: \:::::
/ \ \i ii!- i.........i:
0 : :!
3- 8& ............__.__... j
11 32 52 75 11 32 52 75 11 32 52 75
Relative Humidity (%) Relative Humidity (%) Relative Humidity (%)
Fig. 11 Salvia contour plots for total germination percentages (A,B,C), days to 50% of final germination
(D,E,F), and days between 10% and 90% germination (G,H,I) for seeds germinated at 259C in darkness
following storage at 11% to 75% RH for 3 to 12 months at 5QC (A,D,G), 159C (B,E,H), or 25QC (C,F,I).
Shaded regions (B,E,H, and C,F,I) represent poor germination due to total loss of viability of seeds stored
at 75% RH after 3 to 12 months storage. Regression equations used to generate these plots are listed
in Appendix Table Al 1.
5C and 75%RH and 159C and 25QC at 52% RH. No seeds germinated after storage at 15 C or 25 C
and 75% RH.
The fewest days to 50% of final germination occurred after storage at 11% to 32% RH at all
storage temperatures, although the periods required for germination increased as storage temperatures
increased (Fig. 11D,E,F). The most uniform germination (T90 T10) resulted after seed storage at 11% to
32% RH, with only small differences in uniformity among seeds stored at 59C, 159C or 25PC within this
range (Fig. 11G,H,I).
Recommendations for the best seed storage:
5QC at 32%RH for 12 months
15 C at 32% RH for 12 months
259C at 32% RH for 12 months
Vinca (Catharanthus roseus) seed storage. Ball (1991) has reported that vinca seed germinates
better when older than shortly after harvest. For this reason, some companies store vinca seed 4 to 6
months prior to sale to allow the seed to break dormancy for improved germination. Carpenter and
Boucher (1992b) found freshly harvested vinca seed had no dormancy, but 25% to 35% of the seed of
cultivars Grape Cooler, Peppermint Cooler, or Pretty in Rose required darkness for germination. They also
reported vinca seed could be stored 12 months at 59C and 11%, 33%, or 52% RH without reduction in
total germination, but storage at 75% or 95% RH for periods exceeding 1 month reduced total
germination. Vinca seed should be lightly covered with the medium and germinated at 249 to 269C (Ball
1991) or 25QC to 309C (Carpenter and Boucher, 1992b) in darkness. Vinca cultivar Tropical Rose seed
was placed under the storage treatments of this study 43 days after harvest.
Vinca seeds stored at 11%, 32%, or 52% RH and 59C 159C, or 25QC had similar total
germination percentages. (Fig. 12 A,B,C). At each storage temperature and relative humidity level, a
small decline (from 94% to 90%) in total germination occurred as storage durations increased from 3 to
12 months. No seeds stored at 75% RH, at 59C, 15QC, or 252C, germinated after 3 months or longer
------ 4 iiUN
11
Sviit
11 32 52 75
Relative Humidity (%)
.1 i
-2(
11 32 52 75
Relative Humidity (%)
---- iiiiiiiliii
.,,II;I;,I
't' : : : :
~5~3:: : : :: : : :l
,,, ,,,: ::
"\ ,,._ 9 11 ,;jj|
11 32 52 75
Relative Humidity (%)
Fig. 12 Vinca contour plots for total germination percentages (A,B,C), days to 50% of final germination
(D,E,F) and days between 10% and 90% germination (G,H,I) for seeds germinated at 25C in darkness
following storage at 11% to 75% RH for 3 to 12 months at 59C (A,D,G), 159C (B,E,H), or 259C (C,F,I).
Shaded regions (A-I) represent poor germination due to total loss of viability of seeds stored at 75% RH
after 3 to 12 months storage. Regression equations used to generate these plots are listed in Appendix
Table A12.
ii i ii i: i iii
''' .. .. i
1i:::.
2:::::
2.:::::
2
2- 2.2
storage (Fig. 12A, B, C).
The rate (To5) and uniformity (T90 T1) of germination were similar after seed storage at 11%,
32%, or 52% RH and 50C, 159C, or 259C temperatures (Fig 12 D-I). At 59C, the lowest T50 (< 2.1 days)
and T90 T10 (< 1.0 day) occurred after 12 months storage at 11% to 52% RH (Fig. 12 D and G), while
at 152C or 259C values similar to those at 59C occurred after all storage durations (Fig 12 E,F, H, I).
Recommendations for best seed storage:
52C at 11% to 52% RH for up to 12 months
159C at 11% to 52% RH for up to 12 months
259C at 11% to 52% RH for up to 12 months
SUMMARY
Seed Moisture content during storage. Moisture in seeds is in equilibrium with the ambient
relative humidity of the storage container. Seed moisture percentage at a given RH depends on the
species storage reserves (Atwater, 1980). Seeds of most bedding plant species are desiccation-tolerant
and require low moisture levels for long-term storage (Table 2). A 4% to 6% seed moisture content is
considered favorable for the prolonged storage of these species (Hartmann et al., 1990). Bewley and
Black (1982) reported that some species lose viability during storage at seed moisture levels below 4%,
causing delayed germination (T50) and irregular germination (T90 T10). Delphinium seed stored at 50C
were found to have reduced total germination at below 6% moisture content (Fig. 3A). Ageratum,
impatiens, marigold, pansy, phlox, salvia and vinca seed were tolerant of storage at below 4% seed
moisture at 59C, but less tolerant at 152C or 259C storage. Significant delay in germination of these
species after storage at 11% RH frequently occurred, which probably was due to excessive seed
desiccation. Come (1980) found that the harmful effects of excessively low seed moisture level during
storage could be mitigated by slow rehydration with saturated vapor before sowing.
Seed moisture content during storage affects the rate of seed deterioration. Bradbeer and Pinfield
(1967) reported that the minimal loss in seed viability of many species occurred when seeds were stored
Table 2. Average percent moisture contents of bedding plant seeds after 12-months storage at
11% to 75% relative humidity and 5C to 250C temperature, and from fresh seed packet.
Averages are of four replications of 100-seeds.
% Moisture Content of Seeds
Storage Relative Humidity (%)
Storage Seed
Species Temp. (*C) 11 32 52 75 Packet
Ageratum
Coreopsis
Delphinium
Geranium
Gerbera
Impatiens
Marigold
Pansy
Phlox
Salvia
Vinca
5
15
25
5
15
25
5
15
25
5
15
25
5
15
25
5
15
25
5
15
25
5
15
25
5
15
25
5
15
25
5
15
25
2.0 3.3
2.3 4.1
2.7 5.0
4.6 6.3
5.3 6.8
5.8 7.6
4.9 6.8
6.3 7.4
6.9 7.9
5.1 6.0
6.4 7.0
6.8 7.3
4.5 5.8
5.1 6.4
5.6 6.4
2.2 2.5
3.2 4.1
3.4 4.9
3.5 5.2
3.9 6.0
4.9 6.9
2.7 4.0
3.0 5.9
4.2 5.9
6.5 7.7
6.7 8.0
7.0 8.2
3.4 5.0
4.1 5.8
4.3 6.0
3.0 5.1
3.6 5.8
3.8 5.7
4.7 7.3
5.2 8.1
5.9 9.2
9.2 13.1
9.8 13.1
10.7 14.9
8.3 11.1
9.1 12.7
9.5 13.7
8.3 13.2
9.0 14.2
10.5 15.8
6.7 7.9
7.0 8.2
7.6 8.4
3.2 5.6
5.0 7.5
6.0 7.8
5.8 9.4
6.3 9.8
7.4 10.2
4.5 8.2
6.1 10.0
6.8 10.7
9.7 11.2
10.0 11.6
10.4 12.0
7.2 10.6
7.4 11.5
7.5 12.3
6.7 9.2
7.1 9.5
7.5 9.7
at 20% to 25% RH. The statistical analyses of the storage data for the bedding plant species in our
studies indicated that the slowest rate of seed deterioration occurred at 5QC between 25% and 40% RH.
At this range in relative humidity, seed moisture levels during storage generally were 5% to 6% (Table 2).
An accelerated rate of decline in total germination and delay in germination frequently resulted when seed
had moisture contents exceeding 7%, with faster decline at higher storage temperatures. Seeds stored
at 75% RH, had moisture contents from 8% to 16% and generally total germination was greatly reduced
or totally lost at all temperatures after 3 months of storage. Hartmann et al. (1990) reported that seeds
stored at high moisture levels had increased enzymatic activity and respiration, which hastened
physiological deterioration.
Other factors affecting seed viability during storage. Besides the interrelationships between
temperature, seed moisture content, and storage duration, other factors must be recognized that can
influence the results found in developing the recommended storage conditions for a particular species.
Only one cultivar was used for each species in our seed storage studies, although we recognize that
different cultivars of a particular species may show different viability characteristics under the same
storage conditions. Six commercial wholesale producers of seeds for the bedding plant industry, located
in Europe, Japan and the United States, donated seeds for our research. Although all seeds were
received within 2.5 months after harvest, differences existed in production areas, and possibly in harvest
and storage procedures employed. It was assumed that differences among production and harvest
locations would be relatively small under favorable conditions, although under unfavorable conditions
(moisture stress, low RH or high temperature) they could be quite large.
Seeds were not stored in hermetic (airtight) containers in this study. Rather, seeds were stored
in 15 x 2.5 cm plastic petri dishes sealed with parafilm tape. No measurements were made to determine
if in the enclosed atmospheres the oxygen levels decreased or the carbon dioxide levels increased. It
is not believed that an important change occurred in the levels of these gases, since the quantities of
seeds were small in relation to the volume of air in each dish.
All seeds were dusted with the fungicide captain prior to storage. Hartmann et al. (1990) reported
that fungi will not grow on seed having moisture contents in equilibrium with an ambient RH below 68%,
or below 13% seed moisture content for seeds having starchy endosperm tissue. Bacteria do not cause
significant seed deterioration during storage, since bacteria require free water to grow and seeds are
stored dry. In our study, no signs or effects of deleterious storage fungi were found on any seed
treatment after storage or during germination. Although few or no seeds germinated following storage
at 75% RH, no field or storage fungal organisms developed on the seed during germination.
COMMERCIAL APPLICATION
The term "seed viability" to a commercial bedding plant producer means the seed is alive and
capable of germinating and producing a "normal" seedling under the proper environmental conditions.
Seed viability is highest at maturity, but seed dormancy usually does not permit germination for 1 to 4
months. After physiological maturity the viability of seeds gradually declines; with their longevity
depending on the environmental conditions received in the field, after harvest, and during seed storage.
Seed vigor includes the total germination percent, speed of germination, uniformity of germination and
seedling development, normal seedling morphological development, and capacity for storage of seed
under favorable or adverse environmental conditions (APSA, 1978). In our study, many of these factors
were evaluated.
Previous research has shown that the vigor and viability of seeds decline as seeds age, with the
slowest declines occurring for seeds at low moisture contents stored at low temperatures. In our study,
seeds of each bedding plant species were stored at relative humiditities ranging from 11% to 75% and
temperatures from 41 to 771F, and the seed moisture levels were measured at numerous combinations.
The results have permitted us to make recommendations for each of the bedding plant species, including
the best RH range at each storage temperature. These recommendations should assist plant breeders,
seed distributors, and commercial growers to better understand the best environment for each species.
Commercial growers have limited storage facilities for keeping surplus seed from one season or
year to the next. Home refrigerators that maintain 59C (419F) and 40% to 45% RH levels can be used
for storing seeds. Seeds stored in home refrigerators in non-sealed containers generally have 7% to 12%
moisture contents, which Table 2 shows is excessive for long-term storage of seed for many bedding plant
species. Seeds of ageratum, impatiens, marigold, pansy, salvia, or vinca should be dried to 4% moisture
and placed in glass or plastic vials with screw caps before storing in a home refrigerator. Never store
seed in the greenhouse or headhouse without placing them in a refrigerator, since changing temperatures
and humidities cause the rapid aging of seed. Growers using old seed should conduct germination tests
prior to sowing. If the seed has below 60% germination and germination is slow and irregular, then the
seed should be discarded.
LITERATURE CITED
Association of Official Seed Analysts. 1978. Rules for testing seeds. J. Seed Technol. 3(3): 1-126.
Atwater, B.R. 1980. Germination, dormancy and morphology of the seeds of herbaceous ornamental
plants. Seed Sci & Tech. 8:523-573.
Ball, V. 1991. Ball red book: Greenhouse growing. 15th ed. Geo. J. Ball Publishing, West Chicago, II1.
Bewley, J.C. and M. Black. 1982. Physiology and biochemistry of seeds. Springer-Verlag, New York.
Bradbeer, J.W. and N.J. Pinfield, 1967. Studies in seed dormancy. III. The effects of gibberellin on
dormant seeds of Corylus avellana L. New Phytol. 66:515-523.
Carpenter, W.J. 1989. Salvia splendens seed pregermination and priming for rapid and uniform plant
emergence. J. Amer. Soc. Hort. Sci. 114:247-250.
Carpenter, W.J. and J.F. Boucher. 1991. Proper environment improves the storage of primed pansy
seed. Hort Science 26: 1483-1485.
Carpenter, W.J. and J.F. Boucher. 1992a. Temperature requirements for the storage and germination
of Delphinium x cultorum seed. HortScience 27:989-992.
Carpenter, W.J. and J.F. Boucher. 1992b. Germination and storage of vinca seed is influenced by light,
temperature, and relative humidity. HortScience 27:993-996.
Carpenter, W.J. and E.R. Ostmark. 1992. Growth regulators and storage temperature govern germination
of coreopsis seed. HortScience 27:1190-1193.
Carpenter, W.J., E.R. Ostmark, and J.A. Cornell. 1993. Temperature and seed moisture govern storage
duration and germination of Phlox drummondii Hort Science 28:185-188.
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APPENDIX TABLES
Table A 1. Ageratum coefficient estimates, R2 values, and figure designations for fitted regression models.
Estimated Response =
bo + b, SP + b, RH + b, SPx RH + b4 SP2 + b, RH2 + by SP x RH2 + by SP2 x RH
Coefficient Estimates
Temp
Response (*C) bo b b2 b3 b3 bs b6 b7 R2 Figure
G 5 105.03 -3.59 -0.06 0.05 0.23 -1.3x103 -3.6x103 0.692 1A
15 112.28 -5.54 -0.69 0.25 0.26 4.9x103 -1.9x103 -9.1x10"3 0.797 1B
25 112.95 -6.74 -0.54 0.23, 038 3.7x103 -1.7x10-3 -9.8x103 0.751 1C
Tso 5 1.92 -0.03 3.4x10-3 -1.0x10-3 1.2x103 -4.0x105 13x10-5 0.592 1D
15 1.92 -6.5x103 -1.6x10-3 -2.1x103 6.9x104 -1.7x105 4.2x10-5 0.868 IE
25 2.11 -0.02 -0.02 9.9x104 3.2x104 0.478 1F
Tgo-Tio 5 1.41 0.04 -0.02 2.6x103 -3.6x103 2.4x104 -2.9x10-5 0.597 1G
15 0.95 0.13 0.02 -5.3x103 -4.6x103 -1.5x104 4.7x10-5 15x104 0.852 1H
25 0.53 0.16 0.07 -1.2x10-2 -6.7x103 -8.9x104 9.4x10-5 4.9x104 0.745 1II
Table A 2. Coreopsis coefficient estimates, R2 values, and figure designations for fitted regression models.
Estimated Response =
bo + b,SP + b2RH + bySPxRH + b SP2 + byRH2 + b SPx RH2 + bSP2x RH
Coefficient Estimates
Temp
Response (C) bo bI b2 b3 b4 bs b6 by R2 Figure
G 5 26.08 12.71 0.11 9.8x103 -0.93 -3.3x10- 0556 2A
15 5.77 21.82 0.75 -0.17 -1.78 -2.6x103 2.9x102 0.812 2B
25 19.71 10.63 1.70 -4.2x103 -0.94 -3.1x10-2 0.606 2C
T50 5 5.97 0.83 0.44 -0.11 -2.4x10-3 4.7x10"4 5.7x103 0.779 2D
15 22.17 -3.93 -0.18 1.5x10-2 031 2.4x103 0.901 2E
25 14.45 -0.30 -0.30 1.7x10-2 93x10-2 5.2x103 0.951 2F
Tgo-TIo 5 5.79 156 9.5x10"2 -2.7x10-2 -0.12 2.52x10(3 0.715 2G
15 9.87 0.23 -1.5x103 4.5x104 0.836 2H
25 16.52 -1.20 -8.0x10-2 1.1x10-2 0.11 1.1x103 0.878 21
Table A 3. Delphinium coefficient estimates, R2 values, and figure designations for fitted regression models.
Estimated Response =
b + b,SP + b2RH + b, SP x RH + b, SP2 + b RH2 + b SP x RH2 + b SP x RH
Coefficient Estimates
Temp
Response (*C) b0 b, b2 b3 b4 bs b6 b7 R2 Figure
G 5 62.40 -3.24 1.71 33x10"2 -2.5x10'2 0.772 3A
15 92.21 -7.90 0.97 1.1xl02 0.36 -1.9x10'2 0.720 3B
25 66.93 -1.74 0.72 -2.5xl0"2 -1.4x10-2 0.737 3C
Tso 5 9.07 0.26 -0.12 -1.1x10-2 1.4x103 0.604 3D
15 9.77 0.58 -0.24 22x10-3 -3.9x10-2 35x103 0.720 3E
25 12.42 0.22 -0.25 -1.4x10-2 4.1x103 2.6x104 0.861 3F
T90-TIo 5 10.73 -0.37 -0.14 1.8x10-2 2.6x10-2 1.0x103 -1.1x10-3 0.494 3G
15 8.90 0.53 -0.16 3.0x103 -3.2x10-2 2.4x103 0.588 3H
25 11.00 0.64 -0.16 -3.2x10-2 -3.1x10-2 4.9x103 1.9x10-3 0.768 31
Table A 4. Geranium coefficient estimates, R2 values, and figure designations for fitted regression models.
Estimated Response =
bo + b,SP + b2 RH + bSP x RH + b4SP2 + b, RH2 + be SP x RH2 + b SP2 x RH
Coefficient Estimates
Temp
Response (*C) bo i b2 b3 b4 bs b6 b7 R2 Figure
G 5 89.82 2.70 0.02 -0.24 0.551 4A
15 91.13 2.34 -0.30 73x10-2 -0.26 4.6x10-3 -1.1x103 0.734 4B
25 87.96 2.82 0.13 -21x10-2 -0.20 0.547 4C
Tso 5 1.66 9.8x10-2 -1.2x10-2 9.0x10-5 0.455 4D
15 1.43 0.04 1.1x10-3 -4.2x103 1.7x10- -1.5x10 7.6x10-5 0.886 4E
25 1.30 0.16 -3.8x10-2 -5.6x103 5.5x104 0.834 4F
T90-Tlo 5 1.65 -6.8x103 1.2x10-2 -2.3x103 3.0x103 -2.1x104 3.2x10- 0.572 4G
15 2.44 -0.13 -5.3x102 7.8x103 8.3x103 2.6x104 -3.7x104 0.783 4H
25 3.08 -0.16 -0.13 1.6x102 8.1x10-3 13x103 -9.0x10-5 -5.3x104 0.836 41
Table A 5. Gerbera coefficient estimates, R2 values, and figure designations for fitted regression models.
Estimated Response =
b, + b, SP + b2RH + b SP x RH + b SP2 + by RH + bSP x RH
Temp
Response (*C)
G 5
15
25
Tso 5
15
25
To-Tio 5
15
25
bo
76.79
87.55
79.26
3.44
4.29
3.37
3.54
5.61
1.98
b,
-0.31
-2.02
-3.12
-0.12
-0.21
-0.08
-0.20
-0.63
-0.09
b2
-0.03
-0.76
-0.07
-0.02
-0.06
-9.9x1
-0.06
-0.18
0.05
Coefficient Estimates
b3 b4
0.09
0.17
0.21
-1.1x10-3 4.5x1l
-2.1x103 8.6x11
0-3 -5.3x10-3 8.1xl1
6.1x103 2.3x1l
-2.8x10-2 2.1xl
-9.5x10-3 1.2xl1
Table A 6. Impatiens coefficient estimates, R2 values, and figure designations for fitted regression models.
Estimated Response =
bo + b, SP + b RH + b SPx RH + b SP2 + b RH2 + b6 SPx RH2
Coefficient Estimates
b,
-2.33
-0.34
b2
-0.27
0.60
b3
0.09
0.04
bs b6
4.2x10-3 -1.2x10-3
-9.4x10-3
R2
0.539
0.472
Figure
6A
6B
25 99.34 -3.25 -0.17 0.25 0.05 6.4x103 -5.7x10-3 0.900 6C
TSo 5 4.26 -0.24 5.6x10-3 -2.8x103 1.7x10-2 -1.2x104 3.9x10- 0.642 6D
15 4.22 -0.23 -5.6x103 1.3x10-2 0.673 6E
25 4.05 -0.20 0.20 -8.4x10-3 1.9x10-2 -3.6x104 1.5x104 0.810 6F
Tso-To 5 230 -5.0x104 -0.31 0.02 0397 6G
15 2.12 -0.25 3.4x103 -1.4x10-3 2.0x10-2 0.443 6H
25 2.28 -0.19 -0.04 15x10-2 73x104 0.569 61
I
bs
7.2x104
1.3x10-2
2.0x10-
2.3x104
8.2x104
3.4x104
5.6x104
-1.9x104
-6.9x104
b6
-1.9x10-3
-3.3x10-3
-5.2x103
1.1x104
-5.2x10-s
-1.9x104
1.9x104
R2
0.872
0.659
0.878
0.700
0.806
0.900
0.458
0.611
0.844
Figure
5A
5B
5C
5D
5E
5F
5G
5H
51
Response
G
Temp
(C)
5
15
bo
99.84
89.29
b3
I
0-3
04
0-4
03
0-3
0-2
b4
--
Table A 7. Marigold coefficient estimates, R2 values, and figure designations for fitted regression models.
Estimated Response =
bo + b, SP + b, RH + b SPxRH + b SP2 + b RH2 + b6 SPx RH2 + b, SP2 RH
Coefficient Estimates
Temp
Response ('C) bo bI b2 b3 b4 bs b b7 R2 Figure
G 5 85.13 1.54 0.25 -0.09 -3.5x103 0.742 7A
15 83.88 3.21 0.02 -0.21 0.694 7B
25 84.27 0.95 0.51 -0.04 0.07 -0.01 2.1x10-3 -8.1x103 0.726 7C
Tso 5 0.34 030 9.7x10-3 -6.4x103 -1.6x10-2 2.0x10-6 4.1x10-5 2.8x104 0.908 7D
15 0.79 0.10 -2.7x10-3 6.7x104 -4.6x103 0.839 7E
25 1.10 -0.01 -0.02 8.6x103 -2.5x103 2.5x104 -9.9x10-5 0.952 7F
Tgo-T1o 5 -0.15 0.49 5.7x103 -9.2x103 -0.03 2.8x104 7.2x104 0.846 7G
15 0.44 0.19 -5.8x10-3 1.5x103 -7.6x10-3 0.847 7H
25 032 0.21 -1.2x10-3 1.2x103 -7.9x103 0.922 71
Table A 8. Pansy coefficient estimates, R2 values, and figure designations for fitted regression models.
Estimated Response =
bo + b, SP + b2 RH + b SPx RH + b4 SP2 + b1 RH2
Coefficient Estimates
Temp
Response (*C) bo bI b2 b3 b4 bs R2 Figure
G 5 87.15 0.07 033 -0.02 -2.9x103 0.708 8A
15 97.76 -1.88 -0.11 0.03 0.597 8B
25 88.99 -1.49 0.45 -5.3x10-3 0.731 8C
T5o 5 3.65 -0.02 -3.6x104 0.289 8D
15 3.56 3.6x10-3 -2.3x103 0.243 8E
25 4.24 -0.13 -0.03 -1.1x103 1.3x10-2 5.7x104 0.783 8F
T90-Tio 5 1.98 0.03 -1.3x10-3 0342 8G
15 1.48 0.11 45x104 0.736 8H
25 2.89 -0.28 -0.02 -1.9x10"3 0.03 4.8x104 0.737 81
Table A 9. Petunia coefficient estimates, R2 values, and figure designations for fitted regression models.
Estimated Response =
bo + b, SP + b, RH + by SPx RH + b SP2 + b6 RH2 + b6 SP x RH + b, SP2 x RH
Coefficient Estimates
Temp
Response (C) be b, b2 b3 b4 bs b6 by R2 Figure
G 5 86.35 -0.06 0.17 -2.6x103 0342 9A
15 80.93 -0.34 054 -6.7x10-3 0.472 9B
25 101.74 -5.5 -1.00 032 0.33 8.7x103 -2.2x103 -1.5x10-2 0581 9C
Tso 5 3.67 -0.01 -0.01 1.8x104 0.472 9D
15 4.46 -0.23 -0.05 7.0x10-3 13x102 4.2x104 -4.6x104 0.826 9E
25 353 0.02 0.01 -5.0x103 -6.9x104 -2.1x104 1.1x104 0.852 9F
To-Tio 5 1.94 -0.05 -1.8x10-3 7.7x104 0392 9G
15 2.40 -0.20 -0.02 3.9x103 1.3x102 1.7x104 -2.9x104 0596 9H
25 1.84 0.13 -0.04 -8.8x103 7.5x104 0.682 91
Table A 10. Phlox coefficient estimates, R' values, and figure designations for the fitted regression models.
Estimated Response =
bo + b, SP + b RH + b, SP x RH + b SP2 + b, RH2 + b6SPx RH2 + b7 SP2 x RH
Coefficient Estimates
Temp
Response ('C) bo b, b2 b3 b4 b5 b6 by R2 Figure
G 5 96.47 -0.31 -0.05 0.03 8.1x104 -5.8x104 0.670 10A
15 102.53 -1.91 -0.61 0.20 6.9x103 -2.4x10-3 -5.1x103 0.945 10B
25 106.62 -3.18 -0.53 0.12 6.5x102 95x103 -2.6x103 0.851 10C
To 5 3.83 -2.4x10-3 -3.1x102 2.7x104 4.8x10-5 0.865 10D
15 334 9.9x10-2 4.0x103 -4.1x103 -9.0x10- 9.5x105 0.915 10E
25 2.94 031 -1.3x10-2 -3.5x10-3 -1.1x102 9.3x10-5 1.8x104 0.946 10F
To-T1o 5 1.82 038 -0.07 2.7x10-3 -2.5x10-2 9.7x104 0.780 10G
15 0.74 0.61 -3.6x10-2 3.8x10-3 -3.6x10-2 5.0x104 0.905 10H
25 132 1.21 3.1x10-2 5.7x10-3 -7.0x10-2 -3.9x104 0.890 10I
Table A 11. Salvia coefficient estimates, R2 values, and figure designations for fitted regression models.
Estimated Response =
bo + b,SP + bRH + b3SP x RH + b4SP2 + b6RH' + bSPx RH2 + bSP x RH
Coefficient Estimates
Response
G
Temp
(C)
5
15
25
bo
74.62
64.61
70.07
bi
-0.99
031
-9.21
b2
0.31
0.42
1.93
b3
0.05
-3.4x104
0.11
b4
-0.11
-0.10
0.57
bs
-1.5x10-
2.4x103
-0.03
b6
-2.3x10-3
-2.6x10-3
-3.7x10-3
b7
7.2x103
8.8x103
R2
0.894
0.602
0.951
Figure
11A
11B
11C
Tso 5 3.78 0.13 -3.2x103 -3.5x103 -6.8x103 -2.3x10-5 6.8x10-5 0.860 11D
15 3.43 0.20 -0.02 1.2x103 -1.2x102 2.8x104 0.766 11E
25 3.48 0.26 -0.02 -5.1x103 -1.1x10-2 2.4x104 1.4x104 0.931 11F
T9-T1o 5 3.69 -0.35 -0.05 6.5x103 0.02 3.1x104 -3.3x104 0.522 11G
15 1.66 0.04 2.7x103 0.491 11H
25 2.32 -0.24 0.03 -2.1x103 0.03 -1.2x103 2.4x104 6.4x104 0.814 111
Table A 12.
Vinca coefficient estimates, R2 values, and figure designations for the fitted regression models.
Estimated Response =
b0 + b,SP + b2 RH + b SPx RH + b4 SP + b6 RH2
Coefficient Estimates
Temp
Response (C) b0 b, b2 b3 b4 bs R2 Figure
G 5 99.31 -1.93 -0.01 0.11 0.342 12A
15 91.30 -0.37 0.30 -4.5x10-3 0376 12B
25 94.15 -0.46 0.02 0317 12C
Tso 5 2.19 0.05 -7.4x103 1-4.6x10" 1.0x104 0.535 12D
15 2.07 0.08 -1.0x10-2 6.9x10 -4.2x103 2.2x104 0.662 12E
25 2.22 0.03 -1.4x102 -2.3x103 2.2x104 0.405 12F
Tgo-T1o 5 136 0.15 -0.02 75x10' -1.5x10-2 2.2x104 0.734 12G
15 0.90 0.21 -0.02 -2.0x103 -1.2x10-2 5.2x104 0.666 12H
25 139 0.11 -0.04 -8.3x10" 6.7x104 0.577 121
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