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Thesis (M.S.)—University of Nebraska—Lincoln, 1973. Department of Agronomy.


Copyright 1973, the author. Used by permission.


In 1971 grain sorghum (Sorghum bicolor (L.) Moench) ranked second in production among &. S. feed grains with a record 6.72 million hectares harvested for grain. Most of the production is confined to Great Plains an Southwestern U. S. states where the crop is frequently subject to temperatures of 35 to 40 C at various times during the growing season. Although drought stress is generally considered the most critical factor in determining sorghum yields in these areas, little progress has been made toward differentiating between the separate effects of heat and drought stress on plant development and grain production.

The investigations reported here were designed to study various aspects associated with heat tolerance in grain sorghum, especially as they relate to heat hardening. References to heat tolerance will follow the terminology of Levitt, Sullivan, and Krull (1960) in that heat tolerance will refer to the ability of plant tissues to live and function when at high temperatures.

Experiments were conducted in 1971 to study heat tolerance in grain sorghum. Results of three separate studies are reported her including the effect of heat hardening on grain yield, variation in heat tolerance of sorghum at different ambient temperatures, total energy levels, and relative humidities, and the effect of an antitranspirant on heat tolerance. Experiments I and II were conducted in field plots at Lincoln, Nebraska, and Experiment III was conducted in field plots at the University of Nebraska field laboratory, Mead, Nebraska.

Advisors: Charles Y. Sullivan and Jerry D. Eastin