Adaptability of Crop Plants to High Temperatures Stress1
- Hwei-Hwang Chen,
- Zheng-Yan Shen and
- P. H. Li2
The ability of crop plants to adapt to heat stress is potentially an important component of tolerance to heat stress under field conditions. Two genotypes each of bean, potato, and soybean and tomato, with known differences in heat sensitivity as evaluated by their yield and fruit set under high temperature conditions, were used in a study of adaptability of leaf tissues to heat stress. Heat tolerance was measured by 2,3,5-triphenyl tetrazolium chloride (TTC) reduction and conductivity tests; both methods gave similar results. The degree of heat tolerance could be expressed by either the heat killing temperature or the heat killing time, the latter being the more sensitive indicator.
Heat tolerant and susceptible genotypes did not differ in heat killing time when the plants were grown at 20/15 C day/night temperature; however, the differences became dramatic after the plants were acclimated at temperatures above 30 C for 24 hours. Heat killing time was a function of the acclimating temperature with the optimum acclimating temperature found to be 35 to 37 C. Rate of heat acclimation was very fast, and a continuous high temperature treatment appeared to be necessary to retain the high level of heat tolerance. Heat tolerance of leaves was not affected by age when the plants were grown under 20/15 C condition. At 35/35 C, however, the heat tolerance of leaves was lower at the earlier stages and reached a level similar to fully grown plants after 30 days growth.
The results suggest that I) the TTC reduction test in addition to the conductivity test can be used to test heat tolerance in crop plants, and 2) screening genotypes that perform well in high temperature environments is feasible at the early stage of growth by testing leaf tissue heat tolerance after the plants have been subjected to a high acclimation temperature, such as 35 C for 12 to 24 hours.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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