The question of which resource allocation patterns will be selected to ensure male and female reproductive success has attracted many researchers, especially in reference to plants of alpine environments. This study investigated the pattern of reproductive allocation within inflorescences of Aconitum gymnandrum Maxim, a common species of the Qinghai-Tibet Plateau, and experimentally explored the potential mechanism underlying this pattern.
Data on floral allocation and seed production in bottom, middle, and top flowers in racemes of A. gymnandrum were gathered in a variety of sub-alpine and alpine meadows, and their maternal plants were collected. A flower-removal experiment also was performed, to determine whether allocation was affected by within-raceme competition. These data were analyzed with repeated-measures analysis of variance and two-way analysis of variance.
Results showed that there was a marked decline in carpel number, female mass, seed number, and seed mass per fruit with flowering sequence within a raceme, while anther number, male/female mass ratio and pollen/ovule ratio increased. Floral sex allocation was male-biased in top flowers, while seed set was constant among positions. Variation in the amount of pollen received cannot explain the observed results, and the flower-removal experiment did not improve the seed set of the remaining flowers, indicating that an unavoidable architectural effect has led to the position-dependent pattern of sex allocation with raceme.