Comparison Of Growth Response And Stress Resistance Among Three Varieties Of Morus Alba L. Under Drought And Salt Stress

Drought and salinization are main factors that limiting the development of agriculture and forestry,in order to explore the impacts of salt and drought stress on physiological-biochemical characteristics and tolerance of Morus L.,three mulberry varieties of Nongsang 14,Nongsang 12 and Qiangsang 1 were subject to salt and drought stress,which to provide the guidance of mulberry cultivation,breeding and planting.We weighting the pots to simulate drought stress(CK,30%FC)and pouring Na Cl solution to simulate sail stress(CK,T0.1 and T0.3),meanwhile,the morphologic changing and physiologicalbiochemical characteristics were investigated,the results showed that:(1)The drought treatment significantly decreased the relative height growth rate(RHG),net photosynthetic rate(Pn),stomatal conductance(Gs),transpiration rate(Tr)and intercellular CO2 concentration(Ci),however it improved water-use efficiency(WUE)and increased limiting value of stomata(Ls).The root dry mass(RDM),steam dry mass(SDM),leaf dry mass(LDM)and total dry mass(TDM)of Nongsang14 and Nongsang 12 had a significant decline,however these decline were not found on Qiangsang 1.The SOD activity of Nongsang 14 decreased,while the POD activity of Nongsang 14 increased.Drought lead to a significant higher MDA content in Qiangsang 1.The stomatal limitation decreased the Pn significantly in three variety of potted Morus L.seedlings,meanwhile the non-stomatal limitation also exist in Nongsang 14 and Qiangsang 1.Nongsang 14 and Nongsang 12 responsed to heavy drought stress by efficient morphological adjustment combined with strong stomatal conductance to control water use efficiency under the drought stress,and this water-using strategy maybe more suitable cultivating in humid regions.While Qiangsang 1 water-using strategy were by controlling the biomass allocation,especially control above ground biomass,contrast to Nongsang 14 and Nongsang 12,it maybe more suitable cultivating in arid regions.(2)The photosynthetic pigment content of Nongsang 14 and Nongsang 12 increased under T0.1 treatment,but T0.3 treatment decreased pigment content among all three mulberry varieties,which Nongsang 14 decreased significantly.The Pn,Gs and Tr of three mulberry varieties decreased under salt stress,T0.3 treatment restricting the leaf gas exchanging more intensely and the stomatal limitation decreased Pn signicantly.The Ci of Nongsang 14 increased on the seventh day of T0.3 treatment and fourteenth day of T0.1 treatment,which means the non-stomatal limitation also exist in Nongsang 14.T0.3 treatment increased Fo and decreased Fm,Fv/Fo,Fv/Fm,q P and YⅡ,which means that the capacity of PSⅡ reaction center of photosynthetic electron transport chain reduced.Effciency of photochemical conversation decreased,oxidation side of PSⅡand primary electron acceptor was suffering damage,electron transfer was restrained among three species during subject to salt stress.T0.1 treatment enhanced the NPQ of Nongsang 14 and Nongsang 12,but their NPQ decreased and YNO increased signicantly on the seventh day of T0.3 treatment,it reflected that light energe was overflowing.T0.3 treatment increased NPQ of Qiangsang 1,which means the distribution of excitation energy was changed and Qiangsang 1 has a better thermal dissipation.The SOD,POD,SS and MDA of three mulberry varieties increased under salt stress,meanwhile the POD and SS accumulated significantly on T0.3 treatment;The MDA content of Nongsang 12 increased significantly on the seventh day of salt stress,which means the cell had a severe membrane lipid peroxidation.(3)Three mulberry varieties had already damaged on the seventh day of salt stress.Three mulberry varieties accumulating SS to resist osmotic stress,enhancing thermal dissipation capability to protect photosynthetic apparatus,improving the POD activity to remove reactive oxygen species.Nongsang 14 is salt-sensitive,it’s photosynthetic pigment degraded heavily,the efficiency of PSⅡenergy transfer was restrained,the restriction of Pn existing the non-stomatal limitation and their leaf dropped down entirely;Nongsang 12 have a better salt tolerance,it improved photosynthetic pigment content to adapt the mild salt stress(T0.1),but the results of MDA reflects Nongsang 12 had a severe membrane lipid peroxidation.The results of pigment content,photochemical efficiency and thermal dissipation capacity suggesting that Qiangsang1 have a strong resistance to salt stress.After analyzing and comparing,we drew to a conclusion that the capacity of stress resistance: Qiangsang1>Nongsang 12>Nongsang 14.What’s more,Nongsang14 and Nongsang 12 growing faster,they will growing better on fertile soil which means they have a greater vegetative potential,we suggesting that they can be cultivating on fertile soil to expand the economic value.Since Qiangsang 1 has a better stress resistance,we can planting Qiangsang1 into arid and saline inland areas to use it’s ecological functions including preventing and controling desertification,water and soil conservation.