Effect Of Calcium On Growth And Physiological Metabolism Of Pepper Seedlings Under Root-zone Flood Stress

Under natural condition, after having the flood or the rainstorm, certain low-lying soil and bog region of imperfectly drained or high subsoil water level, because of the excessive water contents are often leading to harm to the plant, and affecting the normal growth of plants, and becoming the restrictive factor. So it is very significant to enhance plant's patience and the resistance under flooding stress to the agricultural production. As a major element necessary for plant growth and a second messenger of coupling extra-cellular signal and intracellular physiological reactions, calcium (Ca²⁺) plays a crucial role in regulating physiological reactions under environment stress. It has been known that [Ca²⁺]_cyt increase rapidly under environmental stress and Ca²⁺·CaM compound formation after Ca²⁺ combined with target enzyme CaM. It could relieve the harm of stress to the crops by regulating gene expression and inducing change of physiological and biochemical metabolism under environmental stress. Plants have evolved mechanisms for flood stress and adjusting their cellular metabolism to adapt for environmental stress. Therefore, it has the important theory value and the practice significance to research the effect of calcium on growth and physiological metabolism of pepper seedlings under root-zone flood stress.The research used HuaxiDangwu hot pepper of Guizhou Province as the material, through soaking seeds and spurting the leaf of the different consistence Ca²⁺, researching the effect of Ca²⁺ on growth of pepper seedlings under root-zone flood stress, exploration the best Ca²⁺ processing method, reduced the injury of pepper seedling under flooding stress . Then useing the best processing method of Ca²⁺ (10mmol·L^-1 Ca²⁺ soaking seeds), studing the influence about Ca²⁺ to the hot pepper seedling root system respiratory metabolism, leaf ROS metabolism, the carbohydrate metabolism of roots, stems, leaves and the relation under the flood stress, discussing the physiological regulation function about Ca²⁺ in the adaptation flooding stress process of pepper plant. Main research results were as follows:The regulative effect of calcium element to pepper seedling under flood stress has tow sides. On the one hand it is advantage in the certain consistence scope; on the other hand it is negative when the consistence is excessively high. This test result indicated: the best processing method of Ca²⁺ reduces the injury of flood to the hot pepper seedling is: 10mmol·L^-1 Ca²⁺ soaking seeds processing.The measuration's result indicated that the extraneous Ca²⁺ processing can suppress effectively to the chlorophyll destruction, membrane penetrable elevation and root activity being weaken under flood stress, and relatively enhanced the fresh weight and dry weight of seedling, reduced root system's damage. These indicated the extraneous Ca²⁺ processing could enhance the resistance of hot pepper seedling to overhead flooding injury.The measuration about oxidation resistance enzyme activity and the non-enzyme oxidation inhibitor content demonstrate that after the Ca²⁺ processing, the hot pepper seedling leaf has the function maintain high level ROS metabolism, its mechanism possibly is advantageous to induce biosynthesis and keep activity about anti-oxidase enzyme of SOD et al., and non-enzyme oxidation inhibitor of ASA and GSH. Thus enhances the ability of plant to eliminate the free radical, reduced the membrane system's peroxidation damage. This possibly is a physiology biochemistry foundation of Ca²⁺ could enhance the resistance of hot pepper seedling to overhead flooding injury.Exogenous Ca²⁺ application in nutrient solution could relieve the harm caused by flood stress and result in improved growth of roots, increased fresh and dry weight of pepper seedlings. Compared with the seedlings with flood alone treatment, the activities of SDH, MDH and ADH were promoted, while LDH activity was inhibited, accumulations of lactate and acetaldehyde in pepper seedling roots under exogenous application Ca²⁺ treatment. It indicated that Ca²⁺ could relieve the harm of flood stress, through regulating respiratory metabolism of roots.Exogenous Ca²⁺ application treatment could increase the contents of and solubility sugar, cane sugar and fruit sugar in roots, stems and leaves of pepper seedlings, decreased the content of starch and glucose in pepper seedling roots, which could improve in the ratio of root carbohydrate concentration to leaves carbohydrate concentration, and promote the appearance of carbohydrate metabolism; adapting the flood stress. It indicated that Ca²⁺ could adjust carbohydrate contents and relieve the harm of flood stress.