Analysis of available-phosphate and alkaline phosphatase (Apase) activity during a rice cultivation cycle in rice agroecosystem

Rice-fields constitute a very interesting habitat for the study of phosphatase activity as they are dominated by cyanobacteria and contribute significantly to maintain soil fertility. The enzyme phosphatase can be classified according to the substrate on which it acts such as phosphomonoesterase (PMEase), which catalyzes the hydrolysis of monoester bonds and phosphodiesterase (PDEase) which acts on diester bonds and so on. Phosphatases are classified as acid (pH 4.0–5.0) or alkaline (pH 9.0–10.5) phosphatases-ACP (acidic phosphatase) and ALP (alkaline phosphatase), respectively depending on the pH at which the maximum activity occurs. Since alkaline phosphatases participate in the production of orthophosphate ions and their transportation into the cytoplasm, a negative correlation has been found between intracellular alkaline phosphatase activity and orthophosphate concentration in the growing microorganisms. The purpose of this study is to perform an empirical analysis and reveal the pivotal role of available-phosphate and alkaline phosphatase (APase) activity on the growth of rice crops during the course of cultivation. In this study, the scientific data has been collected and refined through the field as well as laboratory work. Moreover, in order to analyze the total availability and absorbability of phosphorus in the soil, the very popular Olsen method has been used. The result is revealing a comparative account of available-P of soils & water collected from surface and sub-surface regions during a rice cultivation cycle as well as average PMEase activity of filtered and unfiltered water in relation to total-P of unfiltered water during a rice cultivation cycle. The maximum content of available-P in both soil and water was recorded in the deep water region in the month of November and then further decreased at the end of crop cycle. Maximum total P in water was detected in July-August and minimum in November. Photosynthetic N₂-fixation has an absolute requirement of ATP and its requirement is specifically met through the process of photosynthetic phosphorylation. This important function cannot be realized in the phosphate deficient condition. The concentration of available P in water seems to be non-inhibitory concentration for extracellular/cellular enzymatic activities.