Pollination thoroughness and maternal yield regulation in wild radish, Raphanus raphanistrum (Brassicaceae)

Abstract

Under conditions where resources are limited, there are often negative correlations between components of maternal yield, or between fruit and flower production. Pollination, in turn, may vary among individuals and influence total maternal expenditure. We examined the impact of variation in pollination thoroughness upon yield components and overall plant growth in wild radish (R. raphanistrum) plants grown in the greenhouse. Plants received different pollination treatments in which 0% to 100% of all flowers produced were hand-pollinated. Fruit set was increased by hand-pollination, but rarely exceeded 30%, even when more than 50% of the flowers were pollinated. Plants receiving more thorough pollination or having greater proportion fruit set produced significantly smaller seeds. Seed number per fruit was not influenced by pollination treatment. Mean values of yield components and interactions between components often varied among plants from different maternal families. Increasing pollination thoroughness also resulted in dramatic decreases in flower production. If male fitness is related to flower number, there may be a tradeoff between maternal fecundity and successful pollen export operating at the whole-plant level in this species.

Genetics of sex allocation in Mimulus (Scrophulariaceae)

“…Thus a more general result may have been generated if we had examined the trade-off between seed production and pollen production. At the phenotypic level, fruit production has been shown to decrease subsequent pollen production in a number of hermaphroditic species (e.g., Silvertown, 1987;Stanton et al, 1987) including M. guttatus (Macnair and Cumbes, 1990). Similarly, trade-offs between pollen and fruit production are suggested by reports that females have higher seed-set than hermaphrodites in gynodioecious species (e.g., Kohn, 1989;Delph, 1990;Eckhart, 1992;Ashman, 1994).…”

Pollen grain numbers, ovule numbers and pollen-ovule ratios in Caryophylloideae: correlation with breeding system, pollination, life form, style number, and sexual system

“…In the study of Gross and Soule (1981), male flower production ranged from 3 to 4.2 times that of similar-sized females. As proposed by Gehring (1993) for S. latifolia, high male flower numbers probably evolved after the evolution of dioecy in response to sexual selection for a large male inflorescence (Eckhart 1991) or to selection for increased pollen output (Charlesworth et al 1987;Stanton et al 1987). …”

The biology of Canadian weeds. 132. Raphanus raphanistrum L.

“…Stanton (1985) found that larger seeds generally produce larger plants with more flowers than do smaller seeds, a conclusion supported by Choe et al (1988) who found that the weight of a radish plant at any given period of early growth is proportional to the original seed weight, and that relative growth rate is not influenced by initial seed weight. In a greenhouse pollination study, fruit set remained relatively stable, rarely exceeding 30% regardless of pollination thoroughness (Stanton et al 1987). Differences among maternal plants for seed number, size, and weight traits far exceeded differences among pollen donors (Mazer 1987a, b).…”