American Journal of Botany 86(2): 261-268. 1999.
The Effects of Pollen Load Size and Donor Diversity on Pollen Performance, Selective Abortion, and Progeny Vigor in Mirabilis jalapa (Nyctaginaceae)
RICHARD A. NIESENBAUM

The influence of pollen competitive environment on pollen performance (pollen germination, stigmatic penetration, and pollen tube growth rate), the maturation or abortion of initiated fruit, seed size, and seedling vigor was explored by manipulating the size and diversity of stigmatic pollen loads on Mirabilis jalapa. All aspects of pollen performance significantly increased with the number of pollen grains on a stigma or pollen tubes in a style, but was not influenced by the diversity of pollen donors. Plants tended to mature single-ovulate fruits that came from flowers where pollen load size and diversity were greatest and aborted those where these were lowest. No plants from seeds resulting from pollinations with a single pollen grain survived, but other fitness measures were mostly determined by maternal plant. The data suggest that pollen performance is influenced by pollen competitive environment, and both the genetic diversity of the pollen load and number of competing pollen tubes are important determinants of seed/fruit abortion.


Fruit set, seed size, and seedling vigorThe maturation or setting of initiated fruit was related to both pollen load size and diversity, and was reduced when the level of competition was lower (Fig. 4). Fruit set was greatest with multiple donors and large numbers of pollen grains. Next greatest was single donor and large load size followed by multiple donors with small load size. Small size with low diversity and the single pollen grain respectively had lower proportions of flowers that set fruit (Fig. 4). All treatments were significantly different from each other (Fig. 4). The effects of maternal plant and the interaction of maternal plant and treatment were also highly significant (Table 3).

Treatment had no significant effect on seed mass, the number of days until emergence, height and leaf number at 90 d after planting, and height and leaf number at 120 d after planting (Table 4). However, all plants from seeds receiving treatment 5, a single pollen grain, died by 120 d. There was a significant maternal plant effect for seed mass and for height at 90 and 120 d, but not for the other variables considered (Table 4).

Mirabilis bibliography

Physiological Predetermination