Biology Department, Boston University, 5 Cummington Street, Boston, Massachusetts 02215.
Am J Bot. 1998 Dec;85(12):1672-9.
An 11-yr experimental study of the cost of reproduction in three wild populations of the perennial orchid Cypripedium acaule contrasted experimental plants that were repeatedly hand-pollinated and often made fruits with control plants that were not hand-pollinated and only rarely made fruits. Repeated flowering without subsequent fruit production resulted in no detectable reduction in either plant size or probability of flowering in subsequent years. A cost of fruit production was evident in experimental plants in all three populations in terms of a reduced probability of flowering and smaller leaf area in subsequent years, but was not evident in terms of mortality rate. Experimental effects of fruit production reached maximum values at 3-7 yr, depending on the population. The probability of remaining dormant below ground in a given year was strongly dependent on plant size in the previous year. Furthermore, the length of the dormancy period (one to several years) was a significant and inverse function of plant size just prior to dormancy. Sample sizes and the consequent ability to detect experimental effects declined over time as more plants died or stopped flowering. Four to seven years appears to be an optimal duration for studies of the cost of reproduction in perennial herbs similar to this species. Studies lasting less than 4 yr may be too brief to reveal experimental effects, whereas those lasting more than 7 yr may fail to reveal new insights.
一个 11 年的实验研究，比较了三个野生地区的多年生兰花 Cypripedium acaule 的繁殖成本，实验植物是经过多次人工授粉并且经常结果的，而对照植物未经人工授粉且很少结果。反复开花而不结果实，不会导致植物大小或来年开花的可能性有任何可察觉的降低。在所有三个种群的实验植物中，果实生产的成本都表现为来年开花的可能性降低和叶片面积减小，但死亡率方面没有表现出来。果实生产的实验效应取决于种群，在 3-7 年内达到最大值。在给定的一年中，在地下休眠的可能性强烈取决于前一年的植物大小。此外，休眠期的长度（一到几年）与休眠前的植物大小呈显著的负相关。样本量和随之而来的检测实验效应的能力随着更多的植物死亡或停止开花而随时间下降。对于类似于该物种的多年生草本植物的繁殖成本研究，4 到 7 年似乎是一个最佳的持续时间。持续时间少于 4 年的研究可能太短而无法揭示实验效应，而持续时间超过 7 年的研究可能无法揭示新的见解。
