Effect of cold stress on some physiological characteristics and antioxidant systems in (Linum usitatissimum L.) genotypes at seedling stage

In order to study the effects of cold stress on some physiological characteristics of three pre-selected of linseed, a factorial experiment based on completely randomized design with two factors and three replicates was carried out in growth chamber of Faculty of Agriculture, Vali-e-Asr University of Rafsanjan, IRAN. The First factor was cold treatment at three levels (25, 0 and -2.5 ℃) and the second factor was genotype including three accessions named MAR778b, CYP706 and IND1257 selected based on preliminary test as tolerant, semi tolerant and sensitive to cold, respectively. The results showed that temperature decrease from 25 to 0OC did not induce any significant change in any trait. On the contrary, -2.5 ℃ treatment significantly increased content of total soluble sugars, proline and malondialdehyde IND1257 (susceptible) much more, and chlorophyll content, much less than two other genotypes. Also, total leaf carotenoids content of tolerant genotype (MAR778b) at -2.5 OC was significantly lower than control (25 OC), though those of two other genotypes were not different. Finally, poly phenol oxidase activity decreased by 0 and -2.5 OC in all three genotypes but phenyl alanine amonialyase increased at -2.5 OC compared to 0 and 25 OC only in tolerant cultivar (MAR778b). Correlation analysis revealed a significant association of PAL activity with stress susceptibility index