EFFECT OF SOIL APPLIED L-METHIONINE ON GROWTH, NODULATION AND CHEMICAL-COMPOSITION OF ALBIZIA-LEBBECK L

A pot experiment was conducted to evaluate the influence of an ethylene (C2H4) precursor, L-methionine (L-MET) added to soil on the growth, nodulation and chemical composition of a leguminous tree, Albizia lebbeck L. Benth (black ciris). L-Methionine (10(-9) to 10(-1) g kg-1 soil) was applied as a soil drench to established uniform seedlings of Albizia lebbeck L. L-MET treatments had significant effects on all the plant growth parameters monitored. Plants responded positively to low to medium L-MET concentrations (10(-9) to 10(-3) g kg-1 soil) while high levels of L-MET had either negative or no effects. An L-MET treatment of 10(-6) g kg-1 soil was the most effective in increasing shoot height, plant girth, dry weights of shoot and roots, number and dry weight of nodules and total biomass. The chemical analysis of the plant material revealed that the highest N, P and K contents were present in plants exposed to 10(-6) g L-MET kg-1 soil, while Ca and Mg contents were maximum with 10(-5) g L-MET kg-1 soil. A similar trend was observed with the uptake of these elements by the plant. A significant quadratic dose-response relationship was found in all cases when each individual parameter was regressed against log [L-MET] excluding the control. Since, attempts were made to prevent any nutritional and water stress, the plant response to L-MET was most likely caused by substrate-dependent microbial production of ethylene in the rhizosphere.