Effects of different pH environments on the growth,photosynthesis and physiological characteristics of Toona sinensis seedlings
[Objective]Provide reference for configuring the matrix of Toona sinensis seedling cultivation and selecting nursery and afforestation sites.[Method]Using 2-year-old T.sinensis seedlings as materials,potted experiments were conducted to investigate the effects of different pH environments(3.0,4.0,5.0,6.0,7.0,8.0,9.0,10.0)on the growth,photosynthesis,cell membrane permeability,osmotic regulation substance content,and antioxidant enzyme activity of T.sinensis seedlings.[Result]Strong acids(pH≤4.0)and strong alkalis(pH≥9.0)stress had inhibitory effects on the growth of young T.sinensis seedlings.The growth increments of stem diameter,seedling height,compound leaf length,and leaf area generally show a pattern of first increasing and then decreasing with increasing pH;the growth increments of stem diameter and seedling height were significantly lower at pH 3.0-6.0 and 9.0-10.0 than those at pH 7.0,8.0 treatments,and the control;compound leaf length and leaf area were not significantly affected at pH 6.0-8.0,but significantly lower in other treatments compared to the control.As the pH increased,the net photosynthetic efficiency,stomatal conductance,and transpiration efficiency of young T.sinensis seedlings showed a pattern of first increasing and then decreasing.At pH 3.0,4.0,and 10.0,these values were significantly lower compared to other treatments.The intercellular CO2 concentration of the leaves overall showed a trend of first decreasing and then increasing,with the lowest concentration at pH 7.0.The leaf cell membrane permeability,MDA content,SOD activity,POD activity,and osmotic regulation substance content all showed a trend of decreasing first and then increasing with increasing pH,but the magnitude of change varied among these indicators,and the impact of acid stress was greater than that of alkaline stress.In environments with pH≤5 and pH≥9,the cell membranes of T.sinensis seedlings were both damaged to varying degrees.The cell membranes were more severely damaged in strong acid and alkali environments.[Conclusion]The growth of T.sinensis seedlings is affected by the pH value of the environment.Acidic or alkaline conditions cause an increase in leaf cell membrane permeability,enhanced antioxidant enzyme activity,and weakened photosynthesis.Acid stress has a more significant inhibitory effect on the growth of T.sinensis seedlings compared to alkaline stress.T.sinensis seedlings have a certain tolerance to acidity and alkalinity,with the optimal pH range for growth being 6.0 to 8.0.
Toona sinensisacid-base treatmentstressgrowthphotosynthesisphysiological indexes
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