AN EPR STUDY OF WHEAT SEEDS BY THE USE OF NITROXIDE SPIN PROBES

The viability of a variety of wheat seeds Mas investigated by use of t he EPR technique, Three different types of spin probes (4-Hydroxy-TEMP O (TANOL), -Carbamoyl-2,2,5,5-tetramethyl-3-pyrrolin-1-yloxy, 3-Carbam oyl-PROXYL) were utilized in examining the viability of embryo cells. The penetration of the spin probe across the membrane was observed via the change in signal intensity against time for dry embryos of the va riety of wheat seeds soaked in aqueous solutions of spin probe and lin e broadening agent. From the analysis of the signal intensity-time cur ves (i.e. rehydration curves) it was observed that the two kinds havin g different genetic roots (Bezostaya, Kunduru) exhibit similar saturat ion behaviour whereas Gerek saturates much more easily. The rehydratio n curves for naturally aged seeds indicates that aging causes rapid sa turation and an important decrease in the signal intensity. In order t o get better insight on the effect of the signals from polar and nonpo lar regions on the experimental spectra, these spectra were simulated by the use of the theoretical models developed.