Degree Type


Date of Award


Degree Name

Doctor of Philosophy




Field, growth chamber and laboratory studies were conducted in Iowa in 1982, 1983 and 1984 in order to determine the characters through which seed corn vigor is expressed, how long such influences persist and the relationship between the characters influenced. The influence of seed vigor on crop performance in uniform and reduced population due to seed vigor was investigated in 1983. Seed of two corn hybrids, A632 x (H99 x H95) and B73 x (H99 x H95) were dried at 35(DEGREES)C and 50(DEGREES)C to create high and low vigor. Twenty-one crop characters proposed to be influenced by seed vigor were measured in the field in 1982 and 1983. This was reduced to seven characters in 1984. In the field study, the characters measured were plant height and stem diameter at 4, 6 and 8 weeks after planting, shoot dry matter at 4 and 8 weeks after planting, penultimate and ear leaf lengths and width, numbers of tillers and ears per plant, days from planting to 50% tasseling and to 50% silking, fresh, dry weight and grain yield of harvested seeds. In the growth chamber plant height, stem diameter and shoot dry matter at 4, 6, 8 and 10 weeks after planting were measured;Results indicated that emergence, emergence rate, plant height, stem diameter, shoot dry matter at 4 and 6 weeks, penultimate leaf length and width were characters influenced by seed vigor. As the plant matured, the influence of seed vigor on initial vegetative growth diminished, however, yield was not influenced by seed vigor;In the 1983 study, the comparison was made between crop performance in uniform and reduced population due to seed vigor. Similar response as in the 1982 and 1984 study was observed but days to 50% tasseling and to 50% silking were delayed in the uniform population. There was no effect of population density on final grain yield. Plants were able to compensate completely for missing stands by producing shorter and thicker stem and heavier seeds. It can be concluded that seed vigor influcences stand establishment and initial vegetative growth but as the plant matures, the effect due to seed vigor diminished.



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Ebunade Akintorin-Adegbuyi



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152 pages