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Grace Q. Chen, Louisa Vang and Jiann-Tsyh Lin

; Harry-O'kuru et al., 1999 ; Holser et al., 2000 ; Wu and Abbott, 1996 , 1999 ). Knowledge of seed development is essential to successful seed production and crop improvement. This work gives a broad description of L. fendleri seed development from

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Samuel Contreras, Mark A. Bennett, James D. Metzger and David Tay

L. ( Gutterman, 1973 ), and Polypogon monspeliensis L. ( Gutterman, 2000 ). Light quality, specifically the red to far-red (R:FR) ratio, during seed development affected the light requirements for seed germination in Arabidopsis thaliana L

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Yuting Zou, Yanan Wang, Mingwei Zhu, Shuxian Li and Qiuyue Ma

Seeds serve as a strong metabolic library, which is why seed development is an important stage for higher plants. During the process of seed maturation, substances such as starch, protein, and lipids are transformed and accumulated. Pavithra et al

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Gregory E. Welbaum

Seed production in the family Cucurbitaceae is more complicated than in dry-seeded grain crops because seeds mature within a moist fruit and are often held at high moisture content for several weeks before seed harvest. Muskmelon (Cucumis melo L.), a member of this family, was used as a model system to contrast seed development with crops that are dry at maturity. A detailed time course for `Top Mark' fruit and seed development is presented based on previous studies. In muskmelon fruit, precocious germination is inhibited osmotically by the low water potential of the surrounding fruit tissue. Muskmelon seeds exhibit primary dormancy that affects viability very early in development but has a greater effect on seed vigor and is removed by afterripening during dry storage. Osmotically distended or fish-mouth seeds are dead seeds that occur in cucurbit seed lots after aging kills the embryo without disrupting the semipermeable endosperm that completely surrounds and protects the embryo. Cucurbit seed crops should be harvested before the onset of fruit senescence to prevent aging of the seeds inside. Open-pollinated cucurbit seed crops are frequently once-over mechanically harvested. Mechanical harvesting combines seeds from many stages of development into a single seed lot, which may adversely affect quality and increase seed to seed variability. Hand harvesting cucurbit fruit at the optimal stage of development could improve seed quality in some instances but is more costly and time consuming and would increase production costs.

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Boris Andrés Bran Barrientos and Jong-Yi Fang

depth the influence of culture media and incubation conditions on the speed of seed germination and seedling development. For commercial and amateur growers, as well as future breeders of S. plicata , a tissue-culture protocol that ensures rapid

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David W. Still

Brassica crops have indeterminate growth and flower over an extended period of time. Harvested seed is therefore comprised of seed of varying degrees of physiological maturity and quality. Using population-based threshold models, broccoli (Brassica oleracea L. Group Italica), brussels sprouts (B. oleracea L. Group Gemmifera), red cabbage (B. oleracea L. Group Capitata), and rapeseed (B. napus L.) were characterized during seed development with respect to sensitivity to abiotic stress (reduced water potential) and shelf life. Using these models our data suggests that the physiological patterns of seed development are the same in all brassica crops we have tested to date. These population-based models can be used to provide a biological basis in which to evaluate cultural, postharvest and storage practices to ensure the production and maintenance of seed vigor.

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Mustafa M.A. Elballa and D.J. Cantliffe

The effect of temperature on seedstalk development, seed yield and quality in carrot (Daucus carota L.) was investigated in growth chambers at constant day/night temperatures of 33/28, 28/23, 25/20, 23/18, 20/15, and 17/12 °C. Days to flowering, seedstalk height, number of umbels, and seed yield decreased linearly with increasing temperature from 17/12 to 33/28 °C. Continuous high temperature (33/28 °C) had a detrimental effect on germination as measured by a standard germination test and an accelerated aging test. Optimum germination of the progeny occurred at 20/15 °C; however, germination rate was faster when seeds matured at 23/18 °C. Seeds that developed at 33/28 °C produced seedlings with the lowest vigor, while those which developed at 20/15 °C produced seedlings with the highest vigor. Brief exposure of plants to 33/28 °C during anthesis or early seed development was as detrimental to seed yield as continuous exposure to 33/28 °C. Exposure to high temperature (33/28 °C) during late seed development had less effect on seed yield, and seed quality was improved. Progeny vigor was reduced greatly by seed development at continuous high temperature (33/28 °C), but was unaffected by brief exposure to 33/28 °C at anthesis, early, or late in seed development. These results suggest that high (33/28 °C) day/night temperatures during pollination, fertilization, or early stages of seed development can greatly reduce carrot seed yield and seed quality.

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J.J. Steiner, R.B. Hutmacher, A.B. Mantel, J.E. Ayars and S.S. Vail

Abbreviations: ACLW, accumulated change in total leaf weight; AUM, average umbel maturity; DOY, day of year; ET c , crop evapotranspiration; PLS, pure live seed. 1 Research Agronomist. 2 Plant Physiologist. 3 Visiting Soil Scientist. 4 Agricultural

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Roel Rabara, Samuel Contreras, David Tay, Mark A. Bennett and Miller B. McDonald

Poster Session 34—Seed and Stand Establishment 30 July 2006, 12:00–12:45 p.m.

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David W. Still and Kent J. Bradford

141 POSTER SESSION 21 (Abstr. 833-841) Seeds and Seedlings