Abiotic Stress Research Papers - Academia.edu (original) (raw)

The evaluation of physiological and biochemical aspects is essential to identify clues that can assist breeders in selecting Persian walnut genotypes with considerable tolerance to drought stress. This objective can be obtained by analyzing seed biochemical compounds from diﬀerent genetic resources, e.g. seeds from individual trees that are commonly exposed to drought stress. In the current research, we evaluated the eﬀects of drought stress, as induced by PEG6000, on the germination of walnut seeds collected from six promising genotypes (i.e. 'SS2', 'TT2', 'TT1', 'ZM1','Haward' and'Chandler'). Aphotoperiod of12hwas provided duringtheexperiments, alongwithan average temperature of 25 ± 1°C. According to the diﬀerent indexes of germination, a greater tolerance was observed among three genotypes, namely, 'ZM1', 'Haward' and ‘Chandler’. In response to drought stress, the contents of proline and total soluble sugars increased, especially at intense levels of stress, whereas the amount of starch decreased. The levels of antioxidant activity signiﬁcantly increased by POD, APX, CAT, SOD and LOX enzymes in the radicle and plumule tissues as the water potential reached −1.5MPa. Three genotypes, namely, 'TT2', 'TT1' and 'SS2'were susceptible to cell wall damage(i.e. bylipid peroxidation). High levels ofSpdand Spm in tolerant genotypes were accompanied by signiﬁcant increases in the zeatin, endogenous IAA, zeatin riboside and ABA in the seeds. Our results suggest that, under drought stress, seed germination in walnuts can beneﬁt from the accumulation of free Spd in seeds during the phases of germination. However, the accumulation of free Put appeared to be an inhibitory factor which suppressed the germination of walnut seeds.