|Sampson, Blair - AUBURN UNIVERSITY, ALABAM|
Submitted to: American Journal of Botany
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 12, 1998
Publication Date: N/A
Interpretive Summary: Depletion of ozone in the upper atmosphere by is of concern because that ozone screens out most of the biologically harmful ultraviolet (UVb) wavelengths of sunlight. Intensified UVb is known to harm humans and photosynthesis in plants. We evaluate the potential harm of intensified UVb for floral resources used by bees. The two plant species we grew under rintensified UVb responded differently. Plants of one species, a newly commercialized oilseed crop, were less likely to flower at all. The other, a useful wildflower for "farming" new agricultural pollinators, responded with a delayed bloom, smaller flowers bearing less pollen, and a shorter flowering season. In the field, these effects may diminish a plant's abilities to attract pollinators as well as curtailing the reproductive success of its pollinators.
Technical Abstract: Intensified ultraviolet-B radiation or UV-B (wavelengths between 280-320 nm) can delay flowering and diminish lifetime flower production in a few plants. Here we studied the effects of enhanced UV-B on floral traits crucial to pollination and pollinator reproduction. We observed simultaneous flowering responses of a potential crop plant, Limnanthes alba a(Limnathaceae) and a wildflower Phacelia campanularia (Hydrophyllaceae) to five lifetime UV-B dosages ranging between 2.74 and 15.93 kJ m-2d-1. Floral traits known to link plant pollination with bee host preference, host fidelity and larval development were measured. Intensified UV-B had no overall effect on nectar and pollen production of L. alba and P. campanularia flowers. A quadratic relationship between UV-B and nectar sugar production of L. alba and P. campanularia and showed that even sub- ambient UV-B dosages can be deleterious for a floral trait. Other floral responses to UV-B were more dramatic and idiosyncratic. As UV-B dosage increased, L. alba plants were less likely to flower, but suffered no delays in flowering or reductions to lifetime flower production for those that did flower. Conversely, an equal proportion of P. campanularia plants flowered under all UV-B elicits idiosyncratic responses in flowering phenology and flower production from these two annual plants. Diurnal patterns in nectar and pollen production strongly coincided with fluctuating humidity and only weakly with UV-B dosage. Overall, our results indicated that intensified UV-B can alter some flowering traits that impinge upon plant competition for pollinator services, as well as plant and pollinator reproductive success.