Degree Name

Master of Science (MS)

Semester of Degree Completion

1998

Thesis Director

Janice Coons

Abstract

Sweet corn (Zea mays L. var rugosa ) is the fourth most important fresh vegetable in the U.S.. Supersweet corn with shrunken-2 endosperm is more popular with consumers than traditional sweet corn with sugary endosperm because sh2 kernels have more sugars and retain this sweet flavor longer than su kernels. However, its acceptance by growers is hindered because of its inferior seed quality and poor seedling vigor, especially when temperature is low.

Seed vigor of four isoline pairs ( C68, Oh43, Il442a and Ia453 ) with two endosperm types ( sh2 and su ) was studied in this investigation. In a growth chamber, seeds were planted at 10, 15, 20 and 25°C. After two weeks, plants were harvested and the number of plants emerged, plant height, leaf number, fresh weight and dry weight were measured. Germination percentage and root length also were studied at four temperatures using envelope techniques. Ion and total sugar leakage from seeds imbibed in 10ml distilled water for 24hrs at four temperatures were evaluated using electrical conductivity and spectrophotometry.

All parameters measured in the seedling emergence and germination tests ( number of emerged plants, plant height, leaf number, fresh weight, dry weight, germination percentage and root length) decreased with decreasing temperatures. Low temperatures resulted in reduced germination, delayed emergence and delayed seedling growth of all sweet corn isoline pairs. Significant differences in response to temperature were found among isoline pairs. Ia453 is relatively tolerant and Il442a is relatively sensitive to low temperature of the four isolines based on the seedling emergence study. Traditional sweet corn ( su ) had higher emergence, higher germination and better seedling growth at all temperatures than supersweet corn ( sh2 ). Traditional sweet corn was more tolerant to low temperature than supersweet corn.

Shrunken-2 seeds had higher ion leakage and total sugar leakage than sugary seeds. Negative correlations between seed leakage and seed vigor were found in this study. The cultivars that had more seed leakage had poorer seed vigor. Of all parameters measured (percentage leakage, ions per gram seed and sugars per gram seed ), percentage ion leakage is the best indicator of seed quality and seedling vigor. Temperature did not significantly affect the ion and sugar leakage, although ion leakage increased constantly with the increasing of temperature.

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