Pollination biology, breeding system and reproductive success of Adhatoda vasica, an important medicinal plant.

Adhaioda vasica Nees. (Acanthaceae) is an important and widely used medicinal plant. The flowers last for 3-5 days, they are protandrous and pass through three distinct phases: male, bisexual and female. Two spe�cies of carpenter bees, Xylocopa verticalis and Xylo�copa sp. are the effective pollinators. Pollen grains are deposited on the dorsal surface of the thorax during Xykeopa visit to the flowers in the male phase, and the stigma rubs the pollen-coated thorax and is pollinated when the bees visit the flowers in bisexual and female phases. There is a high level of geitonogamy. Pollination efficiency under field conditions is high (95%). However, fruit set is poor (6%). The species is self-incompatible. None of the self-pollinated flowers sets fruits, but over 50% of the cross-pollinated flowers sets fruits. The re�sults indicate that protandry does not prevent self-pollination, but reduces interference in export and import of pollen. Although the flowers have adapted well to achieve a high level of pollination, reproduc�tive success in terms of fruit set is low, largely due to the limitation of compatible pollen.