Effect of cold stress on chlorophyll content, chlorophyll fluorescence and activity of oxidative enzymes of barley cultivars (Hordeum vulgare L.)

Cold is one of the most important abiotic stresses that limits crop growth and yield worldwide. In order to investigate how 20-day-old barley seedlings adapt to short-term cold stress, the present study was carried out in a factorial experiment with four replications in the seed laboratory of Karaj Seedling and Seed Breeding Research Institute. The experimental factors included barley cultivars (cold-sensitive Karon, semi-cold-tolerant Fasih, and cold-tolerant Makoi) and cold stress with three levels of 4, 8, and 22 oC (control). Temperature treatments were applied to barley seedlings for 48 hours. The results of analysis of variance showed that the interaction of cold and cultivar was significant on most of the measured traits in this study. The mean comparison also showed that the highest value of F0 was observed in Karun and Fasih cultivars at 8 oC and in Makoi cultivar at 4 oC, while in all three cultivars, Fv value and chlorophyll a content decreased with decreasing temperature. The ratio of Fm/Fv in Makoui and Fasih cultivars decreased with decreasing temperature, however no significant change was observed in Karon cultivar. In addition, with decreasing temperature, malondialdehyd (MDA) and H2O2 concentration and peroxidase (POX) activity increased in all three cultivars, especially Karon cultivar, but catalase (CAT) and super oxid dismutase (SOD) activity were not affected by the cultivar, and the highest CAT and SOD activity were obtained at 8 and 4 oC, respectively. The obtained results showed that the cultivars more tolerant than the sensitive cultivar (Karon) at low temperatures by limiting the production of compounds such as H2O2 and MDA, had higher chlorophyll content and photosynthetic efficiency, which probably reflects greater adaptation to cold.