The Optimum Concentration Of Calcium Of Q.acutissima Seedlings And Its Effect On Growth And Physiology

Calcium,as a large mineral element of plant growth,is not conducive to normal growth of plants when the content of calcium is too little or too much.In nature,the heterogeneity of soil calcium is very high,therefore it is of great significance to study the appropriate calcium concentration of the tree species under specific conditions to guide the appropriate tree.In this study,Quercus.acutissima seedlings were used as test materials,seven calcium gradients(0,50,100,200,400,600,and 800 mg?kg^-1)were set under sand culture conditions to investigate the differences.The effect of different calcium concentrations on the growth,photosynthetic characteristics,water use efficiency,nutrient uptake and distribution of Q.acutissima seedlings,in order to clarify the optimal growth threshold of Q.acutissima seedlings.On this basis,LaCl₃ was selected as a calcium channel blocker,five gradients(0,1.5,3.0,4.5,and 6.0mmol?L^-1)were used to study the physiological and biochemical responses of Q.acutissima seedlings to calcium in the presence of La³⁺inhibition in order to provide scientific basis for the rational management of Q.acutissima forest.The test results are as follows:1.Optimum calcium concentration in the growth of Q.acutissima seedlings:?1?Moderate calcium treatment significantly promoted the growth of Q.acutissima seedlings.The plant height and base diameter increased after aplying a proper amount of calcium,as well as root biomass,stem biomass,leaf biomass and the total biomass The growth of Q.acutissima seedlings decreased when calcium deficiency and calcium excess occurred.The optimum calcium concentration of growth of Q.acutissima seedlings is between 200 and 400 mg kg^-1.?2?Appropriate amount of calcium treatment can significantly promote the accumulation of photosynthetic pigments?chlorophyll and carotenoid?of Q.acutissima seedlings,and increase the photosynthetic parameters?net photosynthetic rate,stomatal conductance,transpiration rate?and the content of Photosynthate?soluble sugar,starch,soluble protein?.The optimum calcium concentration,increasing the content of photosynthetic pigments and photosynthates,is between 200 and 400 mg kg^-1,and the optimum calcium concentration to promote photosynthetic parameters is 200 mg kg^-1.When calcium deficiency and calcium concentration are too high,they are not conducive to synthesis and accumulation of photosynthetic pigments,the increase of photosynthetic rate and the synthesis of photosynthates.The optimum calcium concentration for promoting photosynthesis of Q.acutissima seedlings is between 200 and 400 mg kg^-1.?3?There is no significant improvement in the water use efficiency of Q.acutissima seedlings.The instantaneous water use efficiency is significantly higher than that of calcium Deficiency and high calcium treatment in 200 mg?kg^-11 calcium treatment,and the optimum calcium concentration is between 100 and 600 mg?kg^-1.?4?The content of N,P,K and Mg in the roots,stems and leaves of Q.acutissima seedlings increased with appropriate amount of calcium.The optimum calcium concentration for the absorption distribution of N and P is between 200 and 400 mg kg^-1,while the optimum calcium concentration for the absorption distribution of K and Mg is between 100 and 400 mg kg^-1.Calcium deficiency and calcium excess are not conducive to the absorption and utilization of N,P,K and Mg by Q.acutissima seedlings.2.Physiological and biochemical characteristics of Q.acutissima seedlings treated with blocking calcium chloride?with LaCl₃?:?1?Photosynthetic characteristics of Q.acutissima seedlings was changed under blocking calcium treatment,chlorophyll-a,chlorophyll-b,chlorophyll?a+b?and carotenoids are all significantly decreased after applying calcium channel blockers;net photosynthetic rate,stomatal conductance and transpiration rate are also significantly decreased;and the contents of soluble sugar,starch and non-structural carbohydrate decreased significantly,while the content of soluble protein reduced.?2?The water use efficiency and instantaneous water use efficiency of Q.acutissima seedlings are significantly reduced under blocking calcium treatmen,and reached a minimum at 6.0 mmol?L^-1.?3?The contents of POD and CAT in leaves of Q.acutissima seedlings significantly decreased,the content of MDA increased after blocking calcium treatment,and all of them reached the extreme value at 6.0 mmol?L^-11 treatment.?4?After applying of calcium channel blockers,the contents of N,P and Mg in roots,stems and leaves of Q.acutissima seedlings decreased significantly,and content of K increased.Through comparison and analysis of growth,photosynthetic characteristics,water use efficiency,absorption and distribution characteristics of nutrient elements N,P,K,and Mg of Q.acutissima seedlings under different calcium treatments,the optimum calcium concentration for the growth is between 200⁴00 mg?kg^-1.At the optimum calcium concentration,the photosynthetic characteristics,water use efficiency and content of N,P and Mg of Q.acutissima seedlings all decreased significantly,the resistance of plants is weakened,and the calcium has a significant effect on the growth of Q.acutissima seedlings.