| The phenomenon of stony desertification in Karst area of southwest China has become progressively serious.Soil in Karst areas is generally high in calcium,which makes vegetation restoration more difficult.Cerasus humilis has a high calcium content in the fruit,also known as"calcium fruit",which is likely to have the potential to adapt to high calcium soil.In order to determine whether economic species Cerasus humilis can adapt to the high calcium soil in the Karst region of Southwest China,pot experiments were designed to simulate the high calcium soil habitat in the karst region.The annual cuttings of Cerasus humilis seedlings were used as materials.Calcium acetate monohydrate was selected as the pure calcium source,and the exchangeable calcium content in the soil reached the high calcium level in the karst soil by adding calcium in fractions.The total mass of calcium added was 0 g,26.40 g,52.80 g,79.20 g and 158.40 g.After adding exogenous calcium,through the measurement of growth,photosynthesis,element absorption and storage and metabolites of Cerasus humilis seedlings,the adaptability of Cerasus humilis to high calcium soil was comprehensively analyzed and explored.The results show that:(1)In this experiment,the seedlings of Cerasus humilis could survive under all soil calcium conditions.According to Hou Xueyu's classification method,Cerasus humilis belongs to intermediate plants.When the quality of exogenous calcium does not exceed 52.80 g,that is,when the content of exchangeable calcium in soil does not exceed 4.20 g kg-1,calcium can promote the growth of Cerasus humilis seedlings;when the quality of exogenous calcium is 79.20 g,that is,when the content of exchangeable calcium in soil reaches 4.93 g kg-1,Cerasus humilis seedlings will be affected by high calcium stress and their growth will be inhibited.For the growth of Cerasus humilis seedlings,the optimum soil exchangeable calcium content was 3.34 g·kg-1.(2)From the perspective of photosynthetic characteristics,calcium can increase net photosynthetic rate and water use efficiency of Cerasus humilis seedlings and promote their growth when the quality of exogenous calcium does not exceed 52.80 g.When the quality of exogenous calcium reaches 79.20 g,Cerasus humilis seedlings will be affected by high calcium stress,and the net photosynthetic rate will begin to decrease,but Cerasus humilis seedlings can regulate its transpiration rate and maintain high water use efficiency.For the photosynthesis of Cerasus humilis seedlings,the optimum soil exchangeable calcium content was 3.34 g· kg-1.(3)According to the change rule of calcium content in different organs of Cerasus humilisy Cerasus humilis stored most of the calcium in stem,and stabilized the level of free calcium in cells by adjusting the content of calcium oxalate in cells.At the same time,Cerasus humilis could maintain very low calcium content in roots to adapt to high calcium soil.When the exchangeable calcium content in soil was 4.93 g·kg-1,the content of calcium phosphate and calcium carbonate in stems and leaves increased significantly under calcium stress.The optimum soil exchangeable calcium content was 4.93 g·kg-1 for the absorption and storage of calcium in Cerasus humilis seedlings.(4)In view of the changes of leaf enzyme activity and metabolites,Cerasus humilis scavenges reactive oxygen species and free radicals by regulating the activity of superoxide dismutase in leaves,and prevents the accumulation of malondialdehyde in cells from causing toxicity to plants.When the exchangeable calcium content in soil was less than 4.20 g·kg-1,the seedlings would not be affected by high calcium stress;when the exchangeable calcium content in soil reached 4.93 g· kg-1,the content of malondialdehyde in leaves increased slightly;when the exchangeable calcium content in soil was as high as 6.75 g· kg-1,the seedlings would be significantly stressed by high calcium.The activities of superoxide dismutase and the content of proline and soluble sugar in leaves increased significantly.Overall,Cerasus humilis can adapt to the high-calcium soil in the Karst area of Southwest China.When the exchangeable calcium content in soil does not exceed 4.20 g·kg-1,Cerasus humilis seedlings will not be affected by high-calcium stress.The optimum soil exchangeable calcium content for its growth is 3.34 g· kg-1.When the exchangeable calcium content in soil reaches 4.93 g· kg-1,Cerasus humilis is affected by slight high-calcium stress,and when the exchangeable calcium content in soil is higher than 4.20 g·kg-1.When the dosage reached 6.75 g ·kg-1,Cerasus humilis was significantly affected by high calcium stress.Cerasus humilis seedlings can survive under all soil calcium addition conditions and have potential as an introduced species for rocky desertification control in southwestern Karst region. |
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