Phosphatase containing and phosphate solubilizing bacteria from soils under tea cultivation and their response to some phosphorothioate type of pesticides

Abstract

Phosphorus is a fascinating plant nutrient and it occupies a critical position both in plant growth and biology of soil. It is a constituent of ADP and ATP, which are two of the most important substances in life processes. Plants can absorb phosphorus from soil only in a soluble form. This transformation of phosphorus is carried out by a number of microorganisms present in soil. Organically bound phosphorus enters in soil during the decay of natural vegetation, dead animals and from animal excretions. Assimilation of phosphate from organic compounds by plants and microorganisms takes place thorough the enzyme quotphosphatasesquot which is present in a wide variety of soil microorganisms. They can bring out a number of transformations of phosphorus by either mineralizing or immobilizing organic phosphorus. Inorganic phosphorus generally enters into the soil by means of fertilizer application. Among all forms of phosphorus present in soil only the movovalent anion (H2PO4-) is considered available, for the growing plants. Soil microorganisms play an important role in sypplying growing plants with available forms of phosphorus. In soil under tea cultivation various forms of phosphatic fertilizers are used. The fate of applied phosphorus in tea soil was studied by Bhattacharya and Dey (1984 and 1983) and found that the availability of phosphorus depend upon a series of chemical and biological factors. In acid tea soil of North East India abundant quantities of soluble aluminium and iron are present. When phosphatic fertilizers are added in this type of soil, a large portion of it is converted into the insoluble aluminium phosphate and ferric phosphate. Therefore, in these soils, microorganisms responsible for the transformation of phosphorus, is very important in agronomical point of view. Moreover tea soil is very frequently exposed to various types of pesticidal chemicals which may influence the soil microflora. In this thesis an attempt was made to isolate, characterize and identify the phosphatase containing and...