Studies On Magnesium Nutrition Physiology Of Balsam Pear

Balsam pear cultivars "Taiwancuiyu","Lanshanchangbai" and "Guangdongqingpi" grown in pots containing sand were used to study for the growth,antioxidant systems and photosynthetic system under Mg concentration of 0mg/L,20mg/L,40mg/L,80mg/L,160mg/L. The main results were as follows:(1) The optimum Mg consistence balsam pear cultivars "Taiwancuiyu","Lanshanchangbai" and "Guangdongqingpi" was 40mg/L, when the Mg consistence was <20mg/L, it affected the the growth of balsam pear,when the Mg consistence was >80mg/L, it also affected the the growth of balsam pear. The height of Mg efficiency of three balsam pear was "Taiwancuiyu">"Lanshanchangbai" > "Guangdongqingpi".(2) Under the stress of Mg,the growth of balsam pear roots and shoots were subject to varying degrees Mg inhibited the shoot growth of balsam pear ,such as the size of leaf, plant height and the cumulation of shoot dry weight ;it also inhibited the normal growth , dry weight of balsam pear root, Mg deficiency stress had agreater effect on agronomy indexes than that of high Mg stress of three balsam pear.(3) The time of symptom of Mg deficiency stress and high Mg stress were different. The time of deficiency of Mg stress was earlier than that of high Mg stress,and the symptom was more serious. Balsam pear under Mg deficiency stress did not reveal obvious symptom in the early growth stage. before 30 days treatment. Mg deficiency stress and high Mg stress firstly acted on bottom leaves.(4) Mg deficiency stress decreased the content of chlorophyll and the activity of balsam pear leaf nitrate reductase(NR),and it embarrassed carbon and nitrogen metabolism,and decreased the content of soluble sugar and protein . Application Mg proper could increase the rate of photosynthetic,the content of chlorophyll, the synthesis andaccumulation of carbohydrate soluble sugar.(5) The generation of H2O2 and O2.- content increased under the stress of Mg,it damaged the structure and function of cell membrane, arosed MDA accumulation, led to the increase of cell membrane permeability, it was indicated that balsam pear was damaged by Mg stress.(6) Proper Mg application significantly increased activities of superoxide dismutase(SOD), catalase(CAT) and peroxidase(POD), raised the ability of anti-oxidant of balsam pear and could postpone the senescence of plants.(7) Under the deficiency stress and high Mg stress , the content of free proline in balsam pear was cumulated,and it protected balsam pear leaves. The increase was lower in the high concentration and further stress of Mg.(8) Under the stress of Mg, balsam pear clear up superfluous active oxygen by dint of GSH-AsA cycle. Under the stress of Mg ,balsam pear leaf's ascorbate peroxidase(APX) activity was active ,and it protected the balsam pear .(9) Under the stress of Mg, the activities of balsam pear leaf's dehydroascorbate reductase(DHAR) enhanced in the increased concentration stress of Mg,it got the maximum under the concentration of 40mg/L,and decreased in the increased concentration stress of Mg.(10) Under the stress of Mg, the activities of balsam pear leaf's ascorbate peroxidase(APX) activity glutathione reductase(GR) decreased in the increased concentration stress of Mg,it got the minimum under the concentration of 40mg/L,and enhanced in the increased concentration stress of Mg.(11) Under the deficiency stress and high Mg stress, the content of flavonoid in balsam pear was cumulated, and the resistibility in balsam pear enhanced.