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Christian Andreasen, Andrius Hansen Kemezys, and Renate Müller

temperate zones, seed production for Gerbera hybrids must take place in heated glasshouses, but in a subtemperate climate, production may take place in fields or under partly protected field conditions ( Dufault et al., 1990 ). High seed quality and uniform

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Luther Waters Jr. and Bonnie L. Blanchette

Abstract

Field-emergence trials and laboratory seed-quality tests were conducted on 45 seed lots of 13 sweet corn (Zea mays L.) hybrids. Results from standard laboratory germination tests were not correlated with field emergence in 4 field trials. Cold tests conducted in sterile sand and on rolled towels were correlated highly with field emergence. Electrolyte leakage tests conducted on individual seeds with the ASA-610 Automatic Seed Analyzer were superior to bulk-seed measurements with a conductivity meter. By combining the seedling-growth cold test (total seedling dry weight) with the Automatic Seed Analyzer test, multiple correlation values with field emergence ranged from 0.70 to 0.80.

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Eulogio Pimienta-Barrios and Park S. Nobel

Flower and fruit production by the columnar cactus, Stenocereus queretaroensis (Weber) Buxbaum, occurred during the dry season in the late winter and spring, and the relatively small annual stem extension occurred primarily during the fall. Thus, reproductive growth does not directly compete with vegetative growth for resources such as reducing sugars, which increased during the wet summer season, a period when total sugars were decreasing. Stem extension, reproductive demography, fruit quality, seed size, and seed quality were not influenced by irrigation. Final fruit size and seed germination, however, were enhanced by applying water. The times from flower bud differentiation to flower opening and from anthesis to fruit ripening were relatively short and unaffected by irrigation.

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M.D. Edwards, R.L. Lower, and J.E. Staub

Abstract

Three cucumber (Cucumis sativus L.) populations were evaluated to determine the effects of several seed harvesting and handling procedures on seed quality. Fruit maturity at seed harvest, fermentation duration in seed extraction, seed storage time, and germination temperature all significantly influenced germination percentage and rate. About 30% of the observed variation in germination percentage was due to interactions between handling factors rather than to main effects of factors. Although germination in excess of 90% was observed for some combinations of factors with as little as 28 days of fruit maturity (post-pollination), the advantages of greater seed maturity at harvest were evident for rate of germination and tolerance to long fermentation times. Positive responses to short fermentation durations (≤4 days) occasionally were observed, but longer fermentation durations were markedly deleterious under some conditions. Six months of seed storage were effective in improving germination of seed at 15° and 20°C, but had little effect on germination at 25°. The 3 cucumber populations were markedly different in response to some seed handling factors.

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Victor M. Sanchez, F.J. Sundstrom, and N. Suzanne Lang

This study investigated the influence of plant size, as determined by plant density, and fruit load variation on the production and quality of bell pepper (Capsicum annuum L.) seeds. Six-week-old `Resistant Giant no. 4' bell pepper seedlings were transplanted 15, 30, 45, and 60 cm apart. Plants spaced 45 cm apart were not thinned or were thinned to one or three fruit per plant. Pepper plants grown at low plant densities produced larger fruit and seeds that germinated faster and at higher percentages than plants grown at higher densities. Assimilate export rate (AER) increased linearly with plant spacing. At harvest, C exchange rate (CER) and AER of plants with nonthinned fruit loads were ≈ 300% and 500% higher, respectively, than those of plants with one or three fruit. Fruit thinning decreased CER and AER; however, seeds produced by plants with one or three fruit had significantly higher germination percentages than plants with full fruit loads. These observations suggest that the high CERS of smaller plants with nonthinned fruit loads may have been insufficient to compensate completely for the higher sink demands. Therefore, crop cultural practices that increase the ratio of pepper plant size to total fruit count may increase the quality of seeds produced by those plants.

Open access

Bill B. Dean, Thomas Noland, and James D. Maguire

Abstract

Two surveys were conducted to evaluate the problem of low germination of carrot (Daucus carota L.) seed grown in the Columbia Basin area of Washington and Oregon. Analyses of weather data via a heat unit model demonstrated that the major difference in growing environment was the number of heat units (10C base) occurring before or during early bloom. The correlation between pre-bloom period heat units (May + June) and final percent germinability of seed lots from survey number one resulted in an r 2 of 0.42 with the probability of F > 0.12. The second survey showed that the greatest reason for low seed germination among seed lots in 1984 was an increased percentage of abnormal germinants compared to 1983. This indicates that the seed germination problem in carrots may be due to seed being harvested at an immature stage, which resulted in low seed germination percentage.

Open access

A.G Taylor and T.J. Kenny

Abstract

Germinated seeds of ‘King Cole’ cabbage (Brassica oleracea L. ‘Capitata’) were separated on a float-sink basis from nongerminated seeds by density differences. Aqueous solutions of varying densities were prepared from Maltrin 250. Brief exposures (<2 min) of the germinated seeds to 1.10 g cc−1 solution did not affect the percentage of seedling growth. The percentage of recovery of germinated seeds increased, and the percentage of germinated seeds decreased as the solution density increased from 1.06 to 1.09 g cc−1. Sowing density-separated germinated seeds improved both the percentage of emergence and time to 50% emergence for nonaged and artificially aged seeds. The greatest improvement in emergence was observed from the aged seeds. Dry seeds were separated into density lots of 0.95 to 1.05 g cc−1 in 0.05 increments with solutions of hexane and chloroform. Each dry seed density lot then was germinated and separated. The dry seed density separation did not improve the percentage of germinated seeds or recovery. No correlation was found between the densities of dry and imbibed seeds.

Open access

Hillel Soffer and O. E. Smith

Abstract

Lettuce, Lactuca sativa L., plants were grown in soil irrigated at various intervals with nutrient solution and in hydroponics culture. Increased nutrient level added to the soil increased seed yield but did not give a corresponding increase in seedling performance.

Hydroponically propagated seed, although heavier than soil propagated seed, were relatively poor in vigor and germinability. A positive linear correlation was found between N levels (5-15 meq) and seed yield, weight per seed, and seedling vigor. Amounts of amino acids and lipids were not positively correlated with nutrient supply, N level, or seedling vigor. Lettuce seed weight was a useful parameter in predicting seedling vigor only within a seed lot obtained from plants grown under the same environmental and nutritional conditions.

Open access

Eric E. Roos

Abstract

Seldom are seeds harvested and immediately planted without undergoing at least a brief storage period. Exceptions would be certain seeds designated as “recalcitrant” (not readily storable) (45) which must be planted immediately, or viability is soon lost. Examples include many tropical plants as well as many of our temperate trees. The life span of these recalcitrant seeds may be of the order of a few days to several months (22). Another case where freshly harvested seeds may not undergo storage would be breeding materials where the object is to produce as many generations a year as possible. In this case, seeds are often harvested in an immature state and planted immediately. However, normally most seeds are stored several weeks or months before being planted. Longer storage periods, 1 to 5 years, are necessary for seeds which may be expensive or difficult to produce, or for those cultivars which are not produced every year due to lower demand by growers. Finally, germplasm banks, such as the USDA National Seed Storage Laboratory, may wish to preserve seeds for decades or even centuries (26).