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

), we observed that the maternal light environment during ‘Tango’ lettuce seed development significantly affected seed weight, germinability, and longevity. Seeds produced under a light environment consisting of 8 h fluorescent light were lighter and

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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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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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Neil O. Anderson, Peter D. Ascher, Richard E. Widmer and James J. Luby

The generation time (0.75 to 1.5 years) in perennial, hexaploid chrysanthemums [Dendranthema grandiflora Tzvelv. (Chrysanthemum morifolium Ramat.)] impedes the rate of progress for sexual breeding programs in creating new clonal cultivars, inbred lines for hybrid seed production, and genetic studies. Modifications to the crossing environment and embryo rescue were evaluated to minimize the chrysanthemum generation cycle. One greenhouse chrysanthemum clone was outcross-pollinated using a bulk pollen source. Following emasculation, inflorescences were either left in situ or the peduncle bases were placed in styrofoam boards floating on a solution of 1% sucrose and 200 ppm 8-HQC under laboratory conditions. Embryogenesis occurred at a faster rate under laboratory conditions as tested with histological techniques; the heart stage appeared as early as the second day after pollination, compared with 11 days using in situ methods. Total embryogenic development time ranged from 25 (laboratory seed development) to 52+ days (in situ ripening). In a second test, embryo rescue (ER) significantly improved percent seed set, percent germination, and percent of progeny reaching anthesis relative to normal development. ER progeny from both garden parents were significantly earlier in total generation time than corresponding non-ER siblings. Laboratory seed development and ER were then used sequentially to obtain an average progeny generation time of =100 days, thus allowing for three generations per year. The potential impact of these two techniques on breeding chrysanthemums and other perennial crops with long generation times is discussed.

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Samuel Contreras, David Tay and Mark A. Bennett

Among the factors affecting germinability of a seed lot are the environmental conditions under which the seeds are produced. The objective of this study was to determine the effects of temperature during seed development on seed quality of two Asteraceae species. Seeds of lettuce cv. Tango and Helianthus debilis cv. Vanilla Ice and sp. cucumerifolius were produced in a greenhouse under one of two treatments: i) hot (27, 40, and 20 °C temperatures average, max, and min, respectively), and ii) cool (23, 33, and 18 °C temperatures average, max, and min, respectively). In both species, heavier seeds were produced under the cool conditions and no differences were observed in standard germination. In lettuce, germination percentage and rate were both affected by increased levels of exogenous ABA concentrations and reduced water potential (PEG solutions), and, in both cases, seeds from cool treatments were more affected. Germination at 30 °C and constant light was higher for seeds from the hot treatment. Lettuce seed showed a strong light requirement for germination. However, seeds from the hot treatment gave better dark germination at 13 and 19 °C. Seeds of H. debilis did not required light for germination, and the germination percentage and rates were evaluated at 13, 21, and 29 °C. For both lines, seeds from each treatment behave similarly; however, the germination of H. debilis cv. Vanilla Ice at 29 °C was higher when seeds were produced in the hot conditions. The results showed that temperature during seed development affected aspects of seed quality that are not detectable by the standard germination, but by germination at suboptimal conditions. Within the Asteraceae family, differences varied among and within species.

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Shengrui Yao, Junxin Huang and Robert Heyduck

breeding/cultivar selection process, they mentioned the need for a complete understanding of flowering, pollination, self-sterility, and seed development and conducted some preliminary research on these topics ( Ackerman, 1961 ). Yan et al. (2009 , 2010

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Zhenhua Li, Yiling Liu and RenXiang Liu

Seed development is normally divided into three stages: morphogenesis, reserve accumulation, and maturation drying ( Kermode et al., 1985 ). At the morphogenetic stage, the seeds do not possess germination ability, which is gradually obtained with

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Rebecca C.-C. Hsu and Yung-I Lee

germination percentage than immature seeds. This is contrasting to the germination profiles of most Cypripedium species ( De Pauw and Remphrey, 1993 ; St. Arnaud et al., 1992 ). Currently, little is known about the seed development and the characteristic of