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.

摘要

Zoochoric 植物通常在外果皮中产生机械屏障，或在果肉（中果皮）或种皮（内果皮）中产生化学抑制剂以实现所需的休眠。Tamarindus indica L. 是一种这样的动物植物树种，但之前尚未探索可能的生物活性化学物质在其果实和种子传播的生态学中的作用。我们通过比较完整的籼稻和去果肉的籼稻的发芽情况，研究了籼稻果肉的萌发抑制作用种子。该实验表明，附着的果肉（包括外果皮）通过一种未经证实的机制延迟或减少了发芽。然后我们分析了果肉（包括外果皮）以找出是否存在主要的生物活性化学物质，通过使用酒精和水分馏创建提取物，然后使用 GLC-MS 分析进行分析。我们发现酒石酸是甲醇部分（但不是水溶液）中存在的主要生物活性化学物质，因此决定测试其对籼稻种子萌发的影响。我们将有活力的去浆的籼稻种子暴露于蒸馏水中不同浓度的纯酒石酸中，发现在 0.4 mg/ml 的浓度下观察到发芽抑制。因此，由于酒石酸是酒石酸的主要化学成分T. indica果肉，它可能在种子仍附着在树上或刚刚落到亲本树附近时抑制发芽，从而在种子的动物性传播中发挥关键作用，以便它们有机会到达距离较远的地方有利于发芽。