COSTS OF REPRODUCTION IN THE PINK LADYS SLIPPER ORCHID (CYPRIPEDIUM ACAULE) - DEFOLIATION, INCREASED FRUIT PRODUCTION, AND FIRE

An earlier experiment with the pink lady's slipper orchid demonstrated that plant leaf area was lowered only after successive years of incre ased fruit production. This result suggested that the cost of reproduc tion was small in relation to the energy budget of the plant. To test this idea, plants were subjected to experimental hand-pollination trea tments to increase fruit set as well as leaf removal treatments to dec rease the energy budget of plants. Changes in plant size in years 2 an d 3 and, to some extent, rate of flowering, were determined by a combi nation of initial plant size, leaf removal treatments in year 1, fruit production in year 1, and damage from an unplanned fire in year 2. Pl ants that had both leaves removed and produced a fruit in 1987 decreas ed in size in the following 2 years in comparison with other treatment groups. The cost of fruit production was not apparent in plants that had only one or no leaves removed. Plants apparently have to be put in to severe physiological stress in order for a cost of reproduction to appear in the following year. The cost of producing one fruit was a de cline of plant size in the following year of 30 cm(2), which is very s imilar to our previous experiment using a different design. An additio nal experiment failed to find evidence that these plants increase thei r photosynthetic rate to compensate for the loss of leaves or the cost of maturing fruit. Published experiments in both the greenhouse and t he field that failed to find a cost of reproduction should be reevalua ted in terms of the intensity of treatment imposed and the overall ene rgy budget of the plant in field situations.