Degree Type


Date of Award


Degree Name

Doctor of Philosophy




Some of the most widely grown public corn (Zea mays L.) inbreds were tested for tolerance to dryer induced injury. Inbred parent B37 was grown in 1979, and A632, B73, and Mo17 were grown in 1979 and 1980. The single cross H99 x H95 was used as a pollinator both years. Random ear samples were then collected, to obtain ears with moisture percentages ranging from approximately 50 to 20%, and dried to 12% moisture at 35, 40, 45, and 50 C;Maternal parent A632 showed the most tolerance to high drying temperatures while both B73 and Mo17 proved to be relatively intolerant. In both years, however, anomalous declines in cold-test emergence were noted for A632 when harvested at 30 to 35% moisture and dried at 45 and 50 C. Based on only one year of data, B37 was intermediate in tolerance. Combined analyses yielded significant inbred-parent by harvest-moisture by drying-temperature interactions for both germination and cold-test emergence percentages. Those interactions alone do not allow for simple recommendations of safe harvest moistures and drying temperatures. Specified components from the combined analyses were then used to predict values for seed quality parameters that would be useful to seed producers. Field performance of 1979 seed in 1980 was similar to that observed in laboratory tests;To elucidate the basic physiology of dryer-induced injury, other additional studies were undertaken. A preliminary comparison of drying rates among inbred parents A632, B73, and Mo17 generally showed that A632, the tolerant genotype, dried at the fastest rate in both the laboratory and the field. Results from seed that had been dried to approximately seven percent moisture indicated that overdrying at higher temperatures may have detrimental effects on seed quality. However, the performance of seed overdried at 35 or 40 C, and maintained in that state, was comparable to seed that had been dried to 12% moisture. Finally, a study of dry matter transfer from kernels to shoots and roots showed that root growth of intolerant genotypes was more susceptible to drying injury than was shoot growth. Casual observations indicated that reduced transfer to roots was associated with little or no primary root development.



Digital Repository @ Iowa State University,

Copyright Owner

Robert Joel Navratil



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78 pages