Role of growth regulator on soil of mango plantation

Mango (Mangifera indica) belong to the family Anacardiaceae: 40 species are found in South Asia and 13 of them are cultivated for edible fruits. The Sindh varieties are: Sindhri, Baganpali, Swarnarika, Neelum, Dasheri, Langra, Alphonso. The large number of microorganism produce auxin, cytokinins, ethylene and GA like substances. Effect of growth regulator on soil, -Production of auxin by microorganisms in soil and in plants -Cytokinin production by microorganisms -Ethylene in soil -GA production by soil microorganisms -Growth regulators modulate the plants root system -Growth regulators and mycorrhizae -Growth regulators encourage development of soil microorganisms -Growth regulator increase the nitrogen fixing bacteria or which rapidly mineralise insoluble ingredient in soil -Microorganisms are antagonistic to soil parasites and reduce the number of the latter. Auxin, auxin present in rhizosphere and has favourable effect on seed germination. Auxin alter the permeability o leaf and root surface and permits the out flow of nutrients, which might habour microorganism both unfavourable and favourable especially pathogenic forms. Biotin antagonises the activity of IAA if present in the soil and it interfers with auxin activity. Tryptophan is the obligate requirement of auxin synthesis. The presence of auxin is detected by chemical and biological means. Cytokinin, cytokinin were detected in root exudates of many plants. Cytokinin are produced by the soil micro-organism although their exact role is unknown. Cytokinin in soil helps in germination of parasites and selectively favour soil microorganism. Cytokinin bioassays are chlorophyll retention test and radish cotyledon assay. Gas chromatography is used for separating and detecting cytokinin. Leachates from plants contain growth substances. Ehylene, the microbial synthesis in the soil results in to ethylene production which is directly linked with the presence of water in the soil. Soil containing high water potential produces largest amount of ethylene. Bacteria contributes more to ethylene production than fungi. Oxygen availability in the root zone is important in regulating ethylene production. Ethylene in soil affects both plants and micro-organisms. Ethylene stimulate the growth of fungi in soil. Gas-liquid chromatography is used for detection of Ethylene. GA production by soil microorganisms, a variety of soil microorganisms produce gibberllin-like substances e.g. GA3 and GA9. GA improves the fertility of soil and growth of plants.