Intrapopulation variation in nectar secretion in Impatiens capensis.

Variation in nectar secretion rates within a population of Impatiens capensis was examined. There was no evidence for phenotypic variation between plants in nectar secretion rates. There was significant daily variation in secretion rates, which appeared to be caused by environmental factors. Individual flowers showed variable rates of secretion over consecutive hours, and these fluctuations in secretion occurred independently among the many flowers on any single plant. Time of day, plant size, and flower age (as indicated by sexual phase) showed no relationship to nectar secretion rates.