| Low temperature is an important abiotic stress that limits plant growth and development,geographic distribution and crop productivity,especially in high altitude areas.It is estimated that crop losses due to cold stress?0-12??can reach hundreds of One billion dollars.Therefore,methods for improving cold resistance of plants through different technologies have attracted worldwide attention.The low temperature adaptation mechanism of plants and improving their low temperature adaptation ability not only have very important scientific and theoretical significance,but also have more important application value.In particular,improving the low-temperature tolerance of low-temperature-sensitive pastures and crops has become an urgent problem.Elymus nutans Has rich nutritional value and good palatability.It has the advantages of lush stems and leaves,well-developed roots,good adaptability,and strong resistance to stress.Vegetation restoration on artificial grasslands and the Qinghai-Tibet Plateau.Many studies in recent years have found that the use of plant growth regulators can improve various biotic and abiotic resistance in plants.Brassinolides?BRs?and proline?Pro?can regulate plant growth and development,and can also improve plant resistance to low temperature and other resistance.However,the mechanism of BRs and Pro regulating low-temperature adaptation of Elymus nutans is unclear.In this study,we used Tibetan wild Elymus nutans as the research object,and applied exogenous BRs and Pro to the leaves to systematically explore the mechanism of BRs regulating the low-temperature adaptation of Tibetan wild Elymus plants at seedling growth and physiological levels.It aims to provide a new theory for BRs to regulate the low temperature adaptability of plants and further lay the foundation for improving the cold resistance of wheat crops in agricultural production.The main results and conclusions are as follows:?1?Low temperature stress significantly affected the growth and physiological characteristics of Elymus nutans seedlings.Exogenous spraying with different concentrations(0,0.001,0.01,0.1,1?mol·L-1)of EBR could not only improve the Elymus nutans seedlings.Fresh weight,and can reduce the relative conductivity in the leaves,of which the treatment with 1 mol·L-1EBR has the best cold resistance effect.Therefore,exogenous EBR can improve the active oxygen scavenging ability,thereby enhancing the cold resistance of Elymus nutans.?2?Cold stress resulted in the significant induction of SOD,GR,and APX activity,as well as in the slight suppression of POD and CAT activity,as compared with control.EBR-pretreated stressed plants displayed significantly higher CAT,APX,and GR activities,while SOD activity displayed no significant change among cold treatments.In addition,exogenous EBR caused a significant increase in As A,GSH,and free proline concentrations under cold stress,whereas reduced the accumulation of malondialdehyde?MDA?and superoxide anion radical.?3?Spraying EBR can promote the accumulation of proline content in Elymus nutans leaves under low temperature stress,increase the activities of biosynthetic enzymes P5CR and P5CS and the expression of P5CS and P5CR genes.?4?Low temperature inhibited the normal growth of Elymus nutans seedlings.Under low temperature?4??stress,spraying 10 m M proline can increase root length,fresh and underground weight,dry weight above and below ground of Elymus nutans seedlings,compared with low temperature?4??stress.Increased by 27.11%,48.80%,48.83%,51.74%and 38.87%respectively;the content of Pro and soluble sugar increased by 42.96%and22.98%?P<0.05?;meanwhile,APX,CAT,Ch ICu/Zn SOD,Cyt Cu/Zn SOD were increased Gene expression and POD,CAT,SOD,and APX activities?P<0.05?;MDA and relative conductivity contents decreased by 47.84%and 20.87%?P<0.05?.In short,exogenous EBR and Pro can regulate the cell osmotic potential of Elymus nutans seedlings,protect the stability of the cell membrane structure,enhance the ability of osmotic adjustment and increase the activity of antioxidant enzymes,up-regulate the expression of antioxidant enzyme genes,and thereby increase the Cold resistance. |
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