Study On Magnesium Nutritive Physiology Of Grape (Vitis Vinifera L.)

Magnesium (Mg) which is un-substitutable by other cation plays an important role in the physiological process of plants. Its content affects not only the structure of plant cell, photosynthesis, enzyme activity & metabolism of active oxygen metabolism etc., but also the quality of fruit. In recent years, the deficiency of Mg in Sorthern grape planted soils has often been reported. In case of Mg deficiency, the whole physiological metabolic activity will be largely affected and the growth of plants will be influenced. To solve the problem of Mg deficiency in grape and to investigate the impact of Mg to the growth and the quality of grape, this study analyzes and estimated the Mg content of grape leaves in Hunan. In this study,’Red Globe’grape (Vitis vinifera L.), a great breed of Vitis vinifera which was planted widely in recent years in the south of China, was studied for growth and development, nutrition contents, physiological metabolism and fruit quality in different Mg treatments. The results are as follow:1. The contents of N, P, K, Cu all were in the appropriate range, the Ca content in the low range, the Mg content in the lack range, but the Zn content higher than the suitable range, the Fe, Mn contents in the suitable range or above it of leaves in 7 counties in Hunan Province (cities, districts) in 29 vineyards. Therefore, the widespread leaves yellow in Hunan vineyards was not caused by the deficiency of N、P、K、Fe、M、Cu、Zn, also not possible by the few Ca. But it was related with the Mg lack.2. The rational application of Mg fertilizer could promote the grape shoot, leaf, root growth and significantly stabilize and integrate ultrastructure of various organelles.The growths of new grape shoot elongation, the leaf area, dry weight and root activity, the main root section, the root fresh weight and dry weight were ascend in first and descend at last. When the Mg concentration is 0 mmol·L-1, the new shoots, leaf cells, root tip and root border cells were significantly damaged. New shoots, leaf and chloroplast structure were distortion, the leaf layers reduced and chloroplast membrane damaged, in contrast, no different was observed in other treatments. 3. Therefore, the offering Mg concentration affected the balance of nutrient elements in grapes. (1)In the level of lacking Mg, Mg content of grape organs decreased in the treatment period. As the Mg content increasing to normal, Mg content of all organs were increased with the processing time. If offering excessive Mg, it decreased in the late period of treatment. (2) At different levels of Mg nutrition, the influence was different to N, P, K, Ca, Fe in organs of grape. Mn content varyed degrees, but no obvious regularity. With the Mg2+ concentration increasing, Mg, Cu, Zn, S in different organs decreased first, but then increased. B content showed a downward trend, but there was a remarkable positive correlation between Mg content and Mg concentration, showing synergistic to each other. And there was a significantly positively correlation between Mg content and K, Ca, Mn, Zn showing an antagonism effect.(3) At different levels of Mg nutrition, the basic rules for nutritional elements the allocation in different grape seedling is:(N)leaf> root> petiole>stem, (K) petiole> root> stem> leaf, (Ca, Mn) leaf> petiole> root> stem,(Mg, B) petiole> leaf> stem> root, (Fe, S)root> leaf> petiole> stem, (Cu) leaf> root> stem> petiole, (Zn) leaf> petiole> stem> root.4. Suitable magnesium concentration could not only improve the light and CO2 utilization ability, but accelerated the growth of grape. (1) In the 3 mmol·L-1 Mg2+ treatment, numbers of normal chloroplasts were found that they contain lots of big starch grains, the grana and strom were observed obviously. The chloroplast ultrastructure was not obviously injured in the 5 mmol·L-1 treatment, while in the 0 mmol·L-1 and 1 mmol·L-1 treatment, a series of chloroplast configuration changed, and structure of grana and stroma lamellae were destroyed. (2) The diurnal variation of the photosynthetic rate (Pn)、transpiration rate (Gs) and stomatal conductance (Tr) of Mg fertilizer changed in the double- curve in daytime, indicating there were midday depression, and they decreased with the decrease of magnesium supply,and diurnal variation of intercellular CO2 concentration (Ci) was contrary to that of Pn and Gs. (3) The content of chlorophyll a(Chla), chlorophyll b(Chlb) and total chlorophyll(Chl(a+b)), the Pn, Tr, Gs, Ci, the light saturation point (LSP), the maximum net photosynthetic rate (Pnmax), apparent quantum yield (AQY) and carboxylation efficiency(CE) were significantly higher than other magnesium treatments, and they increased and then declined with the increasing of magnesium concentration. The change tendency of the ratio of Ch1 a/Ch1 b, light compensation point (LCP), CO2 compensation points (CCP) and CO2 saturation point (CSP) was opposite. There were non-linear positive correlations between Mg application rates and photosynthetic properties.5. Therefore, Mg nutrition affected the qsmotic adjustment, active qxygen metabolism and antioxidant enzymes in grape leaf. The suitable amount of Mg fertilizer (approximately 3 mmol·L-1) could protected the structure and function of cell membrane, and it was beneficial to resist lipid peroxidation and delayed leaf senescence. With the increasing of Mg2+ concentration, nitrate reductase (NR) activity, soluble protein (SP), soluble sugar (SS), superoxide dismutase (SOD) and peroxidase (POD) activity, catalase (CAT) activity in grape leaf were first increased and then decreased, showing a positive correlation with the concentration. But the contents of proline (Pro), malondialdehyde (MDA), superoxide anions (O2·) production rate, hydrogen peroxide (H2O2) were the opposite trend, showing a negative correlation with the concentration.6. The rational application of Mg fertilizer could promote fruit growth, increase fruit anthocyanins, resveratrol, fruit endogenous hormones and nutrient content, and improve fruit quality. (1) Under the appropriate Mg or excess Mg, The growth of Red Globe grape showed a typical double "S" curve, and under magnesium deficiency, the two fast growing periods were not clear. (2) Suitable amount of Mg inproved the content of anthocyanins and resveratrol (Res).The accumulation rate of Anthocyanin under fruit skin was faster with appropriate Mg than with lack and excess Mg. When the 92d after flowering, the content of Res with appropriate Mg was significantly higher than lack and excess Mg. (3) When the color of fruit was changed, GA3 and IAA in the three treatments were the highest in the 64d after flowering. But early fruit growth CTK and ABA were the highest in 50d after flowering. In the fruits with appropriate Mg, GA3, IAA、CTK、ABA were higher than lack or excess Mg treatment in the 50d,64d,92d after flowering. (4)In the three treatments, the content of N, P, Mg, Fe, Mn, Cu, Zn of the mature fruit was the highest in the 92d after flowering. K, Ca content was the highest in the 64d after flowering while the fruit was coloring. All nutrients were the highest in appropriate Mg, followed by high-magnesium treatment. Mg deficiency reatment was the lowest. (5) Suitable magnesium could increase the pH value of the fruit, sugar acid ratio, soluble solids, total sugar, vitamin C, total protein, free amino acid content, lower titratable acid.