Heteromorphic stamen: a strategy in nectarless entomophilous plants to increase pollination efficiency? An investigation with regard to three species of Commelinaceae

Abstract

Entomophilous plants produce flowers with bright colours, patterns, and rewards like nectar, pollen, etc. for self-advertising. Many such plants only have pollen as a reward, so they deceive pollinators by appearing to offer more reward than is actually present. This is accomplished by hairy filaments, broad anther connectives, variously modified staminodes, etc. More than 20 angiosperm families have heteromorphic stamens, the significance of which has not been adequately studied. Their role with regard to Commelina diffusa, Dictyospermum montanum and Rhopalephora scaberrima of Commelinaceae is investigated here. These plants, apart from being nectarless, produce short-lived flowers and are an excellent system for studying the relevance of morphological adaptations in reproductive success. It has been suggested that the dimorphic anthers address the conflict of using pollen, the carriers of male gametes, as a reward to lure pollinators, thereby reducing the available gametes for fertilization. This is accomplished by functionally separating the anthers for ‘feeding’ and ‘pollinating’ purposes. Our study showed that while the feeding anthers infatuate the insects and are manipulated by them, the pollinating anthers succeed in maximizing pollen exports by using specific un-groomed ‘safe sites’ on the body of the insect to solve the conflict by using pollen as a reward.