Effects Of Putrescine On The Physiological And Biochemical Characteristics In Different Cultivars Of Hulless Barley Seedlings Under UV-B Radiation Stress

More and more UV-B radiation reaches to the ground and enhances the impact of plants due to thinning of the ozone layer which has caused widespread concern in the whole society. Now it has become main research topics in the academic field. It has been indicated that polyamines play an important role in the plant response to adverse environmental conditions. In the present study, two varieties of hulless barley (Dulihuang and Kunlun-12) were used to investigate the effects of putrescine (Put) pretreatment on the physiological indexes and photosynthetic indexes under UV-B radiation. The main results were summarized as follows:1. The content of the malondialdehyde (MDA) in both hulless barley leaves markedly increased and relative water content (RWC) markedly decreased in 3μmol m-2S-1 UV-B radiation treatment for 24h. The MDA content was higher in Dulihuang than that in Kunlun-12, and RWC was lower in Dulihuang than that in Kunlun-12. This found showed that Kunlun-12 was more tolerance to UV-B radiation stress.2. Under UV-B radiation, the MDA content in the pretreatment with Put reduced compared to the UV-B radiation only. We also found that the effect of Put was more obvious to Dulihuang. Moveover, D-Arg application (an inhibitor of Put biosynthesis) could remove the effect of Put. This data show that Put pretreatment could relieve the damage of UV-B radiation to the hulless barley leaves. Further study showed that Put could promote accumulation of flavonoids and anthocyanidin, increase the activities of antioxidant enzymes (APX, CAT, POD, SOD, GR), enhance the GSH level and decrease the H2O2 content leading to reduce the oxidative damage induced by UV-B radiation in hulless barley leaves.3. The Put pretreatment could increase the values of Fv/Fm, Yield, ETR, NPQ and qP in the hulless barley leaves under UV-B radiation, leading to reduce the damage of photosynthetic organ and photosynthesis induced by UV-B radiation in the hulless barley leaves.Taken together, UV-B radiation stress could cause oxidative damage in two species of hulless barley leaves. The exogenous Put could reduce the oxidative damage induced by UV-B radiation through increasing the absorption compounds including flavonoids, anthocyanidin, GSH, increasing the activities of antioxidant enzymes and decreasing the H2O2 content, and improving electronic transfer rate, increasing open proportion of PS II response center and protecting heat dissipation and so on.