Effects Of Water Stress On Physiological-biochemical Characteristics Of Four Walnut Varieties

Walnut is rich in nutrients,easy to store,and fullof high health and medicinal value,which serves as one of the most favorednuts foods.Nowadays,the quality and production of walnut have been seriously threatened by floods frequently happened around the world.Thus,it is of great significance to filter new flood-resistive breeds as graft stockto accelerate the development of walnut industry and cutthe loss caused by floods events.In order to study the response of different walnuts to waterlogging stress to help the filtering of flood-resistive breeds and provide basis for waterlogging resistance mechanism,screen flooding-resistant,this paperis based on annual Juglans nigra,Sichuan native walnuts,Juglans sigillata Dode and Carya illinoinensis seedlings,addresses the method of flooding simulation experiment and the method of comprehensive evaluation,observes the morphological characteristics,photosynthesis and related physiological and biochemical indexes of the four walnut varieties in the control group?no flooding treatment?,T₁₀?flooded depth 10cm?,T₂₀?flooded depth 20cm?and T₃₀?flooded depth 30cm?.Main conclusions are as follows:?1?Under T₁₀ condition,American Black walnuts and Juglans sigillata were founded with foliage yellowing and wilting in 7^thday,while Sichuan native walnuts happened in 9^thh day and American pecans remain normal.Under T₂₀ and T₃₀,some of American black walnuts,Sichuan native walnuts and Juglans sigillata showed foliage yellowing,wilting and being dried up in 5^th,5^th and 6^th day,while some of American pecans showed foiled crimped and dried up in 5^th and 7^th day.The sequence of damage degree of four varieties is T₃₀>T₂₀>T₁₀>CK.?2?Under the stress of flooding,the net photosynthetic rate and soluble sugar content of four walnut varieties under T₁₀ stress showed a tendency to increase first and then decrease,in the 12^rd day,the sequence of the max net photosynthetic rate within the four category shows:Sichuan native walnuts>Carya illinoinensis>Juglans nigra>Juglans sigillata Dode,under T₂₀ and T₃₀ water-stressing condition,American black walnut,Sichuan native walnuts and Juglans sigillata showed an integral decline tendency in net photosynthetic rate.The net photosynthetic rate of American pecans displayed no distinct difference compared to CK group?p>0.05?,and decreased to min level as 1.03?mol·m^-1·s^-2in 4^rd day then fluctuate around 3.40?mol·m^-1·s^-2 under T₃₀ condition.?3?As the time of flooding goes,the content of soluble sugar of four varieties presented an increasing first and decreasing after tendency,while the relative water content,relative conductivity,soluble protein SOD and MDA remained almost unchanged and no difference between CK group?p>0.05?.Black walnuts,native walnuts,and Juglans sigillata showed a decline of relative water content,an increasing tendency of leaf relative conductivity,an increasing followed by decreasing tendency of soluble sugar,soluble protein and MDA,a decreasing tendency of SOD.American pecans stayed the same with CK group in all indexes above under T₂₀ and T₃₀ conditions.?4?According to the above indexes,it was evaluated by the membership function method that the waterlogging resistance of four walnut varieties was from strong to weak,which was Carya illinoinensis?8.85?>Sichuan native walnut?7.65?>Juglans nigra?7.36?>Juglans sigillata?7.32?.