| The healthy and sustainable management of plantations in semi-arid areas of China is of great significance to the ecological security of the region.Calcium,as a symbolic element of soil migration in semi-arid areas,plays an important role in alleviating drought stress and regulating tree growth.So taking Pinus tabuliformis seedlings as the research object,through the study of the different calcium treatment of Pinus tabuliformis seedlings(0,50,100,200,400,600,800 mg·kg-1),to the growth of Pinus tabuliformis seedlings,photosynthesis,water use efficiency and chlorophyll fluorescence,enzyme activity measurement analysis,it is concluded that the optimal calcium concentration of Pinus tabuliformis seedlings,and the mechanism of the calcium of the seedlings of Pinus tabuliformis.The results provide a scientific theoretical basis for the rational cultivation and healthy and sustainable management of Pinus tabuliformis plantation in semi-arid areas.The results are as follows:(1)The growth of Pinus tabuliformis seedlings was significantly promoted by the addition of an appropriate amount of calcium.The plant height,basal diameter,root,stem,leaf and total biomass of Pinus tabuliformis seedlings were significantly increased(p<0.05),and the growth amount of Pinus tabuliformis seedlings was significantly reduced when calcium deficiency and calcium excess were observed(p<0.05),and the optimal calcium concentration of Pinus tabuliformis seedlings was between 50?100 mg·kg-1.(2)Applying adequate calcium to Pinus tabuliformis seedlings can promote the synthesis and accumulation of photosynthetic pigments(chlorophyll and carotenoids),and promote the synthesis and accumulation of soluble sugars,starches and soluble proteins,and significantly improve the photosynthesis of Pinus tabuliformis seedlings(p<0.05).When calcium deficiency or calcium concentration is too high,the synthesis and accumulation of photosynthetic pigments,the improvement of photosynthetic rate and the synthesis of photosynthetic products will be adversely affected,and the optimal concentration of photosynthetic characteristics and product accumulation of Pinus tabuliformis seedlings will be between 50?100 mg·kg-1.(3)The water use efficiency of Pinus tabuliformis seedlings was significantly improved after calcium application(p<0.05).The instantaneous water use efficiency(iWUE)at 400mg·kg-1 calcium treatment was significantly higher than that of calcium deficiency and high calcium treatment.(4)The addition of calcium had a great influence on the change of chlorophyll fluorescence in Pinus tabuliformis seedlings.Fv/Fm calcium concentration in more than 400 mg·kg-1 significantly reduced,the Fv/Fo of Pinus tabuliformis were significantly lower than that of other treatments(p<0.05)when the calcium concentration was over 200 mg·kg-1.When the calcium concentration was over the range of 0?100 mg·kg-1,Vj was significantly increased,and ETO/TRO and ETO/ABS were significantly increased when the calcium concentration was over 200 mg·kg-1.Fo/Fm increased significantly over 0?200 mg·kg-1(p<0.05).This indicates that when the concentration of calcium is in high calcium concentration range(more than 200 or 400 mg·kg-1),the effect of calcium on chlorophyll fluorescence is more significant.At this time,the primary reaction effect of photosynthesis was significantly reduced,and calcium had a stress effect on Pinus tabuliformis seedlings.(5)Based on different calcium treatment of Pinus tabuliformis seedling of POD,SOD,CAT,it is concluded that the calcium concentration of 50?100 mg·kg-1 the highest SOD activity,within the scope of calcium concentration of 0?100 mg·kg-1 is the highest CAT activity Pinus tabuliformis,calcium concentration of 50 mg·kg-1 when the highest POD activity,combined calcium concentration of 50?100 mg·kg-1 is within the scope of the highest resistance of Pinus tabuliformis seedlings.According to the above results,the optimal calcium concentration for the growth and development of Pinus tabuliformis seedlings was 50?100 mg·kg-1.The growth of Pinus tabuliformis seedlings is disadvantageous if the calcium concentration is too high or too low. |
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