EFFECT OF AUXIN-LIKE PLANT GROWTH REGULATORS ON SALT STRESSED WHEAT VARIETIES

Mavituna, Ayşe Meltem

M.S., Department of Biotechnology
Supervisor: Prof. Dr. Meral Yucel
Co-supervisor: Assoc. Prof. Dr. Hüseyin Avni Öktem

September 1996, 95 pages

In this study, the effect of auxin-like plant growth regulators on salt stressed bread wheat (Triticum aestivum L.) varieties (Tosun and Bolal) were investigated. After surface sterilization, seeds were incubated within the plant growth regulators solution (either PSA-6 or 2,4-D) for eighteen hours in dark while the control seeds were incubated in distilled water for the same period of time. Seeds were inoculated to distilled water containing plastic trays and grown for 10 days at 25 * 2*C in growth chamber. At the 10th day of growth, stress treatment was started by replacing the distilled water with 2 % or 4 % NaCl solution. Fifteen days old seedlings with the last 5 days under salt stress were analyzed. Physiological responses of the seedlings grown from plant growth regulator treated seeds, to salt stress were determined by Photosystem II activity measurements. The proteins synthesized in root tissues under control, salt stress, after plant growth regulator treatment or both conditions were characterized by employing two dimensional electrophoretic techniques.

As a result of photosystem II activity measurements, Tosun has been determined to have a higher capacity of maintaining the PS II activity under 4 % salt stress for 5 days compared with Bolal, therefore can be referred as tolerant to salt stress on the basis of Photosystem II activity. The protective action of auxin-like plant growth regulators is more pronounced in the sensitive variety, Bolal. Moreover, this action was proved to be cultivar specific.

Quantitative and qualitative changes were observed in the root protein profiles of both Tosun and Bolal under salt stress and plant growth regulator treatments. A unique protein with a molecular weight of 54 kD was detected in Bolal in the presence of PSA-6 without any stress treatments. However, two other proteins (33 and 34 kD) were observed within the presence of both salt stress and PSA-6 in the same variety. On the other hand, two proteins with different molecular weights (15 and 23 kD) were observed in Tosun variety under salt stress conditions upon PSA-6 treatment.

Through the evaluation of the results, we conclude that the changes in protein patterns of the seedlings grown from plant growth regulator treated seeds and /or under salt stress are both cultivar specific.

Keywords: Wheat, Triticum aestivum L., Auxin-like plant growth regulator, PSA-6, 2,4-D, Salt stress, PS II, Salt stress proteins, PSA-6 induced proteins.