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.
ultimate seed lot quality and germination performance. Seed quality is a multidimensional property composed of factors such as seed fill and viability, seed vigor, and seed health. Germination performance comprises the percentage and rate of germination
pressure. Seed quality is a critical factor for producing plants with normal and uniform seedling establishment, high-yielding capacity, and tolerance to stressful field conditions. Florida is a major global agricultural epicenter with vegetable
Abstract
Flooding of bell pepper (Capsicum annuum L.) for 96 hr at anthesis adversely affected plant growth. Average leaf size of the flooded plants was significantly less than that of nonflooded controls. Ratios of leaf dry weight to root dry weight indicated that flooding reduced root development more than leaf development. Mean photosynthetic rate over the 96-hr flooding period and the 72-hr post-flooding period was decreased by 62%. Viability, germination percentage, and average weight of seeds from flooded plants were significantly less than those of control plants. Pepper photosynthetic rate was correlated with seed weight, seed viability, and germination percentage. Reductions in seed viability as a result of soil flooding may, therefore, be attributable to reductions in the supply of photosynthates to the seed.
High-quality seed lots are required for successful establishment of horticultural crops. Testing methods are needed that can detect the early phases of aging prior to a significant loss in germination. Quality was assessed using both germination speed and uniformity on non-primed and primed, as well as non-aged and aged, lettuce (Lactuca sativa L.) seed. Speed and uniformity were quantified using time to 50% (T50) germination and one standard deviation (Tsd), respectively. Embryo elongation was developed as a rapid test by first soaking seeds for 2 hours, then cutting and removing the distal one-third of the seed, and finally observing the percentage of visibly elongated embryos from the seed coverings over time. The mild aging conditions employed in this study (45 °C and 50% relative humidity for up to 21 days) had little influence on viability (germination in all treatments was >98%), but reduced germination rate (increased the time for T50 and Tsd). Primed seeds aged faster than non-primed seeds under the same aging conditions. The percentage of elongated embryos was calculated at hourly intervals after cutting, and treatment differences were observed after a total hydration period of 5 hours. The embryo elongation test detected aging in both primed and non-primed treatments.
Abstract
‘Miragreen’ garden pea seeds from individual seed lots were sorted into bleached, partially-bleached, and non-bleached categories. Seeds were either soaked for 48 hours in aerated water at 22°C, coated with thiram fungicide, or received no treatment. Seeds were planted in Conover loam soil where damping-off and seedling rot were primarily caused by Pythium ultimum Trow and Fusarium solani (Mort.) Sacc f. sp. pisi (Jones) Snyd. & Hans. No differences in germination in vitro were found among bleached, partially bleached, and non-bleached seeds. However, seedling emergence in the field was greater from untreated non-bleached seeds (69%) than from untreated bleached seeds (30%); emergence from partially bleached seeds (58%) was intermediate. Regardless of degree of bleaching, all seedlings were a normal green color after emergence, and appeared equal in vigor. Pea yields from untreated bleached seeds were less than from untreated non-bleached seeds, apparently because pea-emergence damping off was so much greater with bleached than with non-bleached seeds. No yield differences occurred with fungicide-treated seeds. Soaking partially bleached seeds for 48 hours in aerated water at 22°C prior to planting in April was as effective in improving emergence in artificially infested soil as coating seeds with thiram. However, when seeds were planted in mid-June, the thiram treatment gave higher seedling emergence than the soaking treatment. In general, high yields were achieved by early planting of seeds and minimum root rot.
Abstract
In the paper by O. E. Smith, N. C. Welch, and T. M. Little in J. Amer. Soc. Hort Sci. 98(6):529-533, November 1973, the following changes should be made on page 529, column 2, lines 28 and 35:
Line 28: change “transferred to a 1/15 M” to read “transferred to a 20-fold dilution of a 1/15 M”
Line 35: change “of the pH 7.0 phosphate” to read “of the pH 7.0 dilute phosphate”
If the buffer is used at 1/15 molar, the roots of the young plants will be injured due to the high osmotic strength of the buffer.
Abstract
Seed weight in lettuce was more important than seed width or thickness in predicting vigor. An air column separator was an effective way to separate seeds varying in weight. A biological assay called the slant test was developed to test vigor. The average root length after 3 days was used as a measure of vigor.
Lycopersicon esculentum cv. UC82b cotyledons were co-cultivated with A. tumefaciens carrying vectors with modified isopentenyl transferase (ipt) genes. The ipt gene was placed under the control of the RUBISCO promoter in both the sense and antisense orientation. Over 50 transformants were recovered on kanamycin-containing media. Seeds from RO plants were germinated on selective media and R1 plants transformed with the ipt gene identified by PCR and Southern blot hybridization. Phenotypes of the R1 plants, whether transformed with the ipt gene in the sense or antisense orientation, were comparable to the control plants transformed with an inactive cytokinin gene. Fruit weights from both were similar to those from control plants, however, yields were reduced and ripening delayed. Most fruit had no seeds or very few small seeds. Cytokinin levels are being determined in order to correlate them to the observed phenotypes.
Abstract
Several lots of lettuce seed were separated into fractions varying in seed width and weight per seed. Seed vigor, as measured by the slant test, was found to vary in relation to seed weight. In field trials low vigor seeds emerged slower with less total emergence and produced smaller seedlings at thinning time than high vigor seeds. Head size at harvest and percent marketable heads were greater from high vigor seeds. It is suggested that seed vigor can be used to evaluate potential field performance of lettuce.