A garden study of the effects of ultraviolet-B radiation on pollination success and lifetime female fitness in Brassica

While a large number of studies have examined the effects of increased ultraviolet-B radiation (UV-B) on growth and physiological function of plants, UV-B effects on pollination success and fitness are poorly understood. To examine this question, we measured growth, timing of flowering, pollination success, production of pollen, ovules, flowers, fruits, and seeds, and quality of offspring produced by Brassica nigra and B. rapa in a garden experiment. A total of 313 plants of the two species were randomly divided into two treatment groups. One group received only natural ambient levels of UV-B, while the other received an artificially enhanced UV-B dose. Fitness of B. nigra declined at the higher UV-B dose while B. rapa fitness did not change. One possible cause of this result was a shift in the relative attractiveness of the two species to pollinators: visitation to B. nigra declined at the high UV-B dose while B. rapa visitation increased. Received: 25 October 1996 / Accepted: 27 March 1997