Stress Tolerance and Stress-Induced Injury in Crop Plants Measured by Chlorophyll Fluorescence In Vivo1: Chilling, Freezing, Ice Cover, Heat, and High Light

摘要

The proposition is examined that measurements of chlorophyll fluorescence in vivo can be used to monitor cellular injury caused by environmental stresses rapidly and nondestructively and to determine the relative stress tolerances of different species. Stress responses of leaf tissue were measured by FR, the maximal rate of the induced rise in chlorophyll fluorescence. The time taken for FR to decrease by 50% in leaves at 0°C was used as a measure of chilling tolerance. This value was 4.3 hours for chilling-sensitive cucumber. In contrast, FR decreased very slowly in cucumber leaves at 10°C or in chilling-tolerant cabbage leaves at 0°C. Long-term changes in FR of barley, wheat, and rye leaves kept at 0°C were different in frost-hardened and unhardened material and in the latter appeared to be correlated to plant frost tolerance. To simulate damage caused by a thick ice cover, wheat leaves were placed at 0°C under N2. Kharkov wheat, a variety tolerant of ice encapsulation, showed a slower decrease in FR than Gatcher, a spring wheat. Relative heat tolerance was also indicated by the decrease in FR in heated leaves while changes in vivo resulting from photoinhibition, ultraviolet radiation, and photobleaching can also be measured.