PHYSIOLOGICAL AND BIOCHEMICAL RESPONSES OF WHEAT VARIETIES TO HEAT STRESS

OZKAN, Fatma
M.S. in Biology
Supervisor: Prof. Dr. Meral YÜCEL
September, 1994, pages

In this study, the physiological and biochemical responses of wheat cultivars (Triticum durum and Triticum aestivum) under heat stress were investigated. Ten day old seedlings grown on perlite were used for all the tests. Physiological responses of the varieties to heat stress were measured by three different tests namely; Photosystem II activity, Membrane leakage, and TTC vital staining. On the other hand biochemical responses were evaluated at the level of heat shock induced protein synthesis by employing one and two dimensional electrophoretic techniques.
Intact seedlings were acclimated at 37 *C for 20 hours. The second lethal heat treatments were at 50 *C for 1 hour for membrane leakage and TTC viability assays while 40 *C for 10 minutes for PS-II activity test. The protection by preconditioning at 37 *C was obvious in these three tests and in all cultivars been used. As a result of these physiological tests Tosun and Karachia were found to be heat tolerant while others seem to be relatively sensitive to heat stress.
A total of 16 newly synthesized HSPs were detected in six cultivars of durum and bread varieties by 2-D electrophoresis, analyzed by silver staining. These proteins accumulated in the range of 15-18 kD and pI 6.0-7.0. There were qualitative differences in HSP induced protein synthesis among different cultivars. Some of these proteins were found to be cultivar specific, while a protein of 18 kD and pI 6 was observed in all cultivars.
We conclude that these changes in protein patterns upon heat treatment is both species and cultivar specific and that 18 kD protein may have a key role in heat response mechanism.
Keywords: Wheat, Triticum durum, Triticum aestivum L., Heat stress, Heat stress proteins, Membrane thermostability, PS II, TTC, Thermotolerance.