Effect Of Calcium And Ca²⁺ Messenger On Physiological And Biochemical Characteristics Of Winter Wheet Seedlings Under Low Temperature Stress

Ca2+ plays an important role in plant as a second signal messeger. So this test study the resistance of cold and discuss the theory and technology of increasing the coldness,and a basis theory and technology for winter wheat.The main results were as follows:1.Under the cold stress,10 mmol/L Ca2+ could markedly increase the content of osmolytes in winter wheet seedlings leaves,including proline,soluble protein,and soluble sugar, which enhance osmotic adjustment ability; 10mmol/L Ca2+ can significantly improve the activity of superoxide dismutase(SOD),peroxidase(POD) and catalase (CAT) in winter wheet seedlings leaves and remain them at a relatively high level,and reduce content of malondialdehyde(MDA)and membrane permeability.This indicates 10mmol/L Ca2+ improve winter wheet's cold resistance,because it enhances the ability of aliminating active oxygen species(AOS)and maintenance of membrane stability.2.Winter wheet in experiment after being treated with CaCl2,LaCl3,EGTA and TFP, were grown hydroponically to investigate the change of photosynthetic and physiological parameters, chlorophyll content under the cold stress.The results showed that in comparison with LaCl3,EGTA and TFP,exogenous Ca2+ pretreatment decreased original fluorescence (Fo) during cold stress,but increased maximum photochemical efficiency (Fv/Fm),actual photochemical efficiency((?)PSâ…¡),electron transport rate (ETR) and photochemical quenching (qP) as well as chlorophyll contents. Moreover, exogenous Ca2+ pretreatment significantly increased net photosynthetic rate (Pn). CaCl2 and EGTA treatment did not dcrease intracellular CO2 (Ci),while LaCl3and TFP treatment dcreased Ci as well as stomatal conductance (Gs).It could be concluded that the decrease of Pn in both of CaCl2 and EGTA treatment was not resulted from stomatal limitation under the cold stress,but was true in both of LaCl3 and TFP treatment. So the photosynthetic system II (PS II)was protected efficiently and the recovery was faster.The result suggests that Ca2+-CaM messenger system plays an protective role against the damage to photosynthetic system caused by chilling stress.3.The results showed that the Ca2+-ATPase activities antioxidant system were increased higher,compared to LaCl3,EGTA and TFP, but content of active oxygen species(AOS)and malondialdehyde(MDA) were lower than that of others treatment. The result suggests that Ca2+ plays an protective role against the damage caused by chilling stress.It could be concluded that Ca2+-CaM and Ca2+-ATPase might be a cold signal transduction and one of physiology basic of enhancing the cold resistance.The Ca2+-ATPase activities in cell membrane systems under all the tretments showed the following pattern:plasma membrane>tonoplast membrane> mitochondrial membrane. The Ca2+-ATPase activity was the strongest on plasma membrane, regulating the Ca2+ source.