Effects Of Exogenous Calcium On Physiological And Biochemical Characteristics Of Pinus Sylvestris Var.mongolica Seedlings Under Drought Stress

Pinus sylvestris var.mongolica is an important tree species for afforestation in sandy land of China.But in recent years due to the lack of water and soil nutrients and other reasons,Pinus sylvestris var.mongolica withered and yellow,growth decline and other phenomena.A large number of studies show that drought stress caused by water loss is one of the important reasons for the decline of Pinus sylvestris var.mongolica in sandy land.Calcium is one of the essential nutrients for plant growth and plays an important physiological role.This test by Pinus sylvestris var.mongolica seedlings 3 years as the research object,design 2 water treatment and 3 calcium treatment on control test,determination of Pinus sylvestris var.mongolica seedlings under drought stress of the growth,photosynthetic characteristics and water use efficiency(WUE)for a long time and antioxidant enzyme activity indicators,such as study of exogenous calcium on Pinus sylvestris var.mongolica seedlings under drought stress the influence of the physiological and biochemical characteristics.The results can provide scientific basis for the rational management of Pinus sylvestris var.mongolica.The research results show that:(1)The biomass of Pinus sylvestris var.mongolica seedlings decreased significantly under drought stress(p<0.05),while the biomass of Pinus sylvestris var.mongolica seedlings increased under drought stress under exogenous calcium(p<0.05).Under drought conditions,the biomass of 5 and 10 mmol Ca Cl2 seedlings of Pinus sylvestris var.mongolica was significantly increased by 20.17 % and 16.31 %,respectively,compared with that without calcium treatment.The results showed that the growth of Pinus sylvestris var.Mongolica seedlings could be improved by adding exogenous calcium.(2)The net photosynthetic rate of Pinus sylvestris var.mongolica seedlings decreased by 29.19%(p < 0.05)and water use efficiency increased by 38.17%(p < 0.05).Under drought conditions,the net photosynthetic rate of Pinus sylvestris var.mongolica seedlings treated with 5 mmol Ca Cl2 increased by 33.83%(p < 0.05)and WUEi was 47.16%(p < 0.05)higher than that of the control group.However,the net photosynthetic rate of Pinus sylvestris var.mongolica seedlings treated with 10 mmol Ca Cl2 was lower than that of the untreated group,and the WUEi difference was not significant.The results showed that the photosynthesis of Pinus sylvestris var.mongolica seedlings could be enhanced by applying exogenous calcium at 5 mmol Ca Cl2 concentration.(3)Under drought stress,SOD,CAT and POD activities of Pinus sylvestris var.mongolica seedlings showed a significant increase trend(p<0.05),while MDA content showed no significant change.Under drought conditions,SOD,CAT and POD activities of 5 and 10 mmol Ca Cl2 seedlings were significantly increased(p<0.05),and MDA content was significantly decreased(p<0.05).The results showed that exogenous calcium could increase the antioxidant enzyme activity and decrease the MDA content of Pinus sylvestris var.mongolica seedlings under drought stress.