Positive Effects of Pollination on Subsequent Size, Reproduction, and Survival of Primula Veris

We conducted three experiments in which we applied additional hand pollination, flower removal, and leaf removal treatments in various combinations to Primula veris, a perennial spring—flowering rosette species. The purpose of the study was to determine whether the seed set of Primula veris was limited by pollen availability or by other resources, and whether there were measurable cost of reproduction. Hand pollination in the beginning of experiments significantly increased current seed set in only one of the three experiments. It also increased the next—year fruiting probability in that first experiment. In the second experiment, hand pollination did not significantly affect current seed set, but we nevertheless observed enhanced leaf growth in the treatment year and the two following years, and increased flowering frequency, fruiting frequency, and survival in the two following years. In the third experiment, after hand pollination we observed a higher net photosynthetic capacity of the leaves and, again, increased leaf growth in the treatment year and a higher flowering probability in the following year. The positive effect of hand pollination was even clearer when the leaves of the plants were removed at the beginning of the experiment. However, the treatment in which all the flowers were removed had effects on subsequent performance similar to those of the hand—pollination treatment, suggesting trade—offs. Thus, we did not observed any costs associated with reproduction after supplemental hand pollination; on the contrary, hand pollination resulted in increased survival, size, and reproduction of the plants in the subsequent years.