ABSTRACT
Detailed monitoring of the allelopathic expression and functional performance of leaves, roots and seeds of the tamarind tree was carried out, based on bioassay-guided investigation, physiological experimentation and pot culture observations using several common weed and edible crop species. Tamarind leaves induced strong growth inhibition of tested species as demonstrated by the application of aqueous extraction, physiological and pot culture experimentation. Most importantly, the tested species regenerated their growth upon removal of the blended tamarind leaves from the growth medium, suggested that tamarind leaves function as biologically active material. The roots of the tamarind tree caused severe growth suppression of the tested species in both laboratory and greenhouse conditions as demonstrated by the “plant-box method”, “soil-agar sandwich method” and physiological experiments. Interestingly, the magnitude of 298growth suppression was increased with the aging of tamarind seedlings, thus displaying strong competence of tamarind roots that exert function as a true growth regulator for plant growth regulation in the environment. Further studies on the seed and seed-coat of tamarind fruits to evaluate their functional capability as plant growth regulators revealed that these two parts possess species-specific expression through inhibitory and stimulatory effects. It is evident that the leaves and roots of the tamarind tree, as well as the seed and seed-coat of ripened tamarind fruits contain strong bio-active chemical(s) that function as true growth regulator(s) and are involved in plant-specific expression for growth regulation, particularly in weed species, thus, contributing significant importance in the environment. Differential allelopathic effects (inhibitory and stimulatory) of seed and seed-coat of ripened tamarind fruits are biologically important and could be utilized either as a bio-herbicide for weed control as well as bio-fertilizer for growth in agricultural production. The isolated bio-active molecules when chemically identified and characterized may yield excellent templates for use as plant growth regulators and/or bio-herbicide.
