The Growth Physiological Characteristics of Haloxylon ammodendron Seedlings under Different Drought Gradients
In order to explore the dynamic response characteristics of the growth physiology of Haloxy-lon ammodendron seedlings under different drought gradients and drought time in the Qitai desert area of Xinjiang,biennial potted seedlings were used as materials to simulate the natural moisture changes in the desert soil during the high temperature period in summer,and the soil field water capacity was used as the benchmark to set up normal(field water capacity 80%),mild(field water capacity 60%),moderate(field water capacity 40%)and severe drought(field water capacity 20%)treatments,and the stress continued for 40 days.The growth and physiological indicators of the seedlings were monitored every 10 days using a tape measure and a portable photosynthetic instrument,and the multiple comparison method was used for evaluation and analysis.The results revealed that as the drought intensity of the habitat intensified,the increases in seedling plant height and crown area showed a decreasing trend,and the net increase in plant height decreased after 10,20,30,and 40 days of seedling stress under the field water capacity treatment of 60%,which were 58.60%,38.18%,22.39%and 7.49%lower than the 20%decrease in field water capaci-ty.The net decrease in the net photosynthetic rate of seedlings under different durations of stress from the largest to the smallest was on the 40th day,the 30th day,the 20th day and the 10th day.The net decreases in the net photosynthetic rate after 20 days of stress in each drought treatment were relatively at lowest level,which were 54.00%,61.00%and 74.00%lower than that after 40 days of stress.The differential characteristics of the growth physiological responses of seedlings under different drought conditions were as follows:the changes in the main growth and physiological indicators of seedlings after 10 days of stress in the field water capacity treatment of 60%were significantly lower than those of other drought treat-ments.
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