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E. V. Warm

Abstract

Seed vigor in sweet corn (Zea mays L.) was compared among cultivars with the triple recessive endosperm mutant gene combination amylose-extender (ae), dull (du) and waxy (wx), the shrunken-2 (sh2) gene, their sugary (su) counterparts and an open-pollinated cultivar of normal genotype. Dry weight was significantly lower for F2 kernels of the high-sugar genotypes ae du wx and sh2 than for their su counterparts or the normal cultivar. The endosperm:embryo dry weight ratio was also low in the high-sugar lines due primarily to their small endosperm. Seedling dry weight at 10 days was correlated with endosperm:embryo ratio. Comparisons were made among the cultivars for shoot, radicle, and seminal lateral root growth from intact seeds and from excised embryos on nutrient agar. The normal genotype showed superior seed vigor when evaluated by seedling growth from intact kernels, but not when embryos were grown on agar, suggesting that vigor in normal was due to large endosperms. Respiration rate (μl O2 uptake/kernel·hr) of the germinating seeds did not account for growth differences among the genotypes. Respiration at 24 hr after imbibition was negatively correlated with seedling dry weight at 10 days. Respiration at 48 and 72 hr showed no significant correlations with growth rates. Low seed vigor in high-sugar genotypes apparently was related to their small endosperms. The genotype of the embryo also was important in seedling vigor, but low vigor in high-sugar cultivars could not be attributed wholly to genetic inferiority of the embryo.

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Anwar A. Khan

ACC-derived ethylene production was used as an index of seed vigor of lettuce (Lactuca sativa L.), cabbage [Brassica oleracea (Capitata Group)], tomato (Lycopersicon esculentum Mill.), snap bean (Phaseolus vulgaris L.), and sweet corn (Zea mays L.) seeds. Seeds were aged at 40C and 93% relative humidity over saturated solution of KH2PO4 for various times to obtain seeds of differing vigor. Naturally aged lettuce seeds, differing in vigor, were also used. Depending on the seed type, 0.25 to 2 mm ACC (saturating dose) was needed to produce maximal amounts of ethylene. Seeds in the presence of ACC produced a much larger amount of ethylene than those in the absence of ACC, the ACC-derived ethylene could be detected before germination, and ACC had no adverse effect on germination. ACC-derived ethylene production paralleled vigor loss as determined by a decrease in percentage germination over a soak period required for complete germination of nonaged seeds (16 hours for lettuce, 24 hours for cabbage, and 48 hours for tomato and sweet corn), an increase in mean germination time (determined for lettuce only), and a decrease in seedling growth (determined for snap bean only). Second degree polynomial and logarithmic equations generated for the relationship of ACC-derived ethylene production to germination or growth parameters following seed aging, provided good to excellent fit. As a vigor test, the ACC-ethylene procedure has several advantages over the non-ACC ethylene procedure: It improves the sensitivity of the test by enhancing ethylene production, permits detection of small differences in vigor, and allows detection of ethylene before germination within a few hours of soaking. Chemical name used: 1-aminocyclopropane-1-carboxylic acid (ACC).

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

most important fresh vegetable in the country ( USDA, 2007 ). Lettuce seed quality is important because it affects seedling emergence and uniformity of growth, which is fundamental for attaining high yield and quality in a single harvest ( Smith et al

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Gokhan Hacisalihoglu and Anwar A. Khan

109 ORAL SESSION 28 (Abstr. 572–579) Fruit Set & Seed Quality–Vegetables

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David W. Wolff, Daniel I. Leskovar, Mark C. Black, and Marvin E. Miller

109 ORAL SESSION 28 (Abstr. 572–579) Fruit Set & Seed Quality–Vegetables

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Elaine M. Grassbaugh, Mark A. Bennett, and Andrew F. Evans

40 WORKSHOP 3 (Abstr. 656) Seed Quality Issues in Medicinal Herbs

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R.O. Nyankanga and H.C. Wien

109 ORAL SESSION 28 (Abstr. 572–579) Fruit Set & Seed Quality–Vegetables

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Yu Sung, Daniel J. Cantliffe, and Russell T. Nagata

109 ORAL SESSION 28 (Abstr. 572–579) Fruit Set & Seed Quality–Vegetables

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D.I. Leskovar, J.C. Ward, and A. Meiri

109 ORAL SESSION 28 (Abstr. 572–579) Fruit Set & Seed Quality–Vegetables

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Ming Zhang and Eric E. Roos

109 ORAL SESSION 28 (Abstr. 572–579) Fruit Set & Seed Quality–Vegetables