XVI International Botanical Congess

A previous study of Campanula punctata pollinated by Bombus diversus showed greater male reproductive success in plants with wider corollas. We examined the effect of corolla width on (i) the number of pollen grains which fell on the petal or off the flower and were lost at the first visit of Bombus (pollen fall) and (ii) the number of pollen grains deposited onto the pollinator (pollen deposit). Pollen fall decreased with increasing corolla width, while pollen deposit remained constant, so that most pollen grains removed (= pollen fall + pollen deposit) from a wide flower were deposited onto the pollinator. Wide corollas of Campanula served as a pollen dispensing mechanism in that they enhance the efficiency of pollen transfer by reducing the number of pollen removed per visit.