Effects Of Drought Stress On Water Physiology And Expression Of AQPs Geans To Malus Zumi

The apple production area in the northwest Loess Plateau is the largest apple producing area in China.The annual output accounts for more than 50%of the total apple production.It has the natural environmental conditions necessary for the production of high-quality apple such as deep soil,long sunshine hours and large temperature difference between day and night.At the same time,the environmental conditions such as low annual rainfall,uneven precipitation,high evaporation,and severe seasonal drought in the production area have severely restricted the development of the apple industry in this area.In this experiment,two-year-old Malus zumi Mat.potted seedlings were used as test materials,and they were treated with severe drought stress?relative soil moisture:35±5%?for different duration?0d,20d,40d,60d?.The study of water distribution by isotope labeling,determine the water content of different organs in different parts,mature leaf water content?total water content,bound water content,free water content?,malonaldehyde content,osmotic adjustment substance?soluble sugar,soluble protein,free proline?content and the relative expression of aquaporin AQPs gene in roots under different conditions of drought stress.At the same time,the changes of water potential of mature leaves in different soil relative water content,air humidity and temperature were measured to study the integrated effects of the above three environmental conditions on the water potential of mature leaves.The results show that:1.With the prolongation of drought stress,the dD of the shoot apex,middle stem,middle leaf,base stem and base leaf decreased,while the dD increased in the underground parts such as the main root and lateral roots.It indicates that the water transport of Malus zumi in the condition of drought stress shifted from the shoot tip,stem and leaf to the underground part such as the main root and lateral root.2.With the prolongation of drought stress,the water content in the shoot tip,middle stem,middle leaves,base stem,base leaves,main roots and lateral roots of Malus zumi was decreased.3.With the time of drought stress extended from 0 days to 60 days,the total water content and free water content in the mature leaves of the Malus zumi decreased from 75.26%and 51.99%to 58.49%and 22.72%,respectively,while the bound water content increased from 23.27%to About 34.05%.4.With the drought stress time extended from day 0 to 60 days,the malondialdehyde content increased from 16.52 umol/g FW to 52.85 umol/g FW,and the free Pro content increased from 81.29 ug/g FW to 183.38 ug/g FW.The soluble sugar content increased from 2.28%to 2.82%.Under normal water supply conditions,the soluble protein content in the mature leaves of Malus zumi was 34.02 ug/g,which rose to a maximum of 43.58 ug/g after 20 days of drought stress,and then gradually decreased to 30.54 ug/g.5.The relative water content of soil,air humidity,and temperature all affect the water potential of the mature leaves of Beaded Sea Begonia.The regression analysis shows that the quantitative relationship is:y=-6.63+0.002x₁+0.398x₂-0.023x₃-0.01x₂²,where y indicates the water potential of the mature leaves in Malus zumi?MPa?,x₁ indicates the relative soil moisture content?%?,x₂ indicates the temperature?°C?,and x₃ indicates the air humidity?%?.6.The relative expression levels of aquaporin-related genes MzPIP1;4,MzTIP1;2,MzTIP1;4,MzTIP1;6,and MzTIP3;2 in the roots of Malus zumi were decreased as the duration of drought stress prolonged,While the relative expression levels of MzTIP1;1,MzTIP1;3,MzTIP1;5,MzTIP2;2,MzNIP5;1 and MzNIP6;1showed a trend of increasing first and then decreasing with the prolongation of drought stress.