Role of Tartaric Acid in the Ecology of a Zoochoric Fruit Species, Tamarindus indica. L

Abstract

ABSTRACT Zoochoric plants usually produce fruits with a mechanical barrier in the exocarp, or chemical inhibitors in the fruit pulp (mesocarp) or seed coat (endocarp) to achieve required dormancy. Tamarindus indica L. is one such zoochoric tree species, but the role of possible bioactive chemicals in the ecology of its fruit and seed dispersal has not been explored before. We investigated the germination inhibitory effects of T. indica fruit pulp by comparing germination of intact T. indica fruits with depulped T. indica seeds. This experiment revealed that attached pulp (including exocarp) delayed or decreased germination via an unverified mechanism. We then analyzed the pulp (including exocarp) to find out if there was a dominant bioactive chemical, by creating extracts using both alcohol and aqueous fractionation, and then analyzed them using GLC-MS analysis. We discovered that tartaric acid was the main bioactive chemical present in the methanol fraction (but not aqueous), so decided to test its effect on T. indica seed germination. We exposed viable depulped T. indica seeds to varying concentrations of pure tartaric acid in distilled water and found germination inhibition was observed at a concentration of 0.4 mg/ml. Therefore, since tartaric acid is the major chemical component in T. indica fruit pulp, it is possible that it could play a crucial role in the zoochoric dispersal of seeds by inhibiting germination while they are still attached to the tree or have just fallen close to the parent tree so that they have an opportunity to reach distant sites favorable for germination.