Growth and stomatal responses of temperate meadow species to enhanced levels of UV-A and UV-B+A radiation in the natural environment.

Some responses of various meadow species to enhanced UV-radiation of the natural daylight spectrum are described together with the experimental protocol employed. Growth responses to supplementary UV-B+A are mostly inhibitory when compared to the ambient daylight treatment for Bellis perennis, Cardamine pratensis, Cynosurus critatus and Ranunculus ficaria. However, the response of UV-A treatment compared to that of the UV-B+A varies in significance according to the species and parameter investigated. The pertinence of the ambient and UV-A treatment to data interpretation is discussed. Stomatal conductance of B. perennis was measured throughout the 24 h cycle. Although no significant difference could be found between the stomatal conductance of UV and ambient treated plants during the hours of daylight, at night it was found that the UV-B+A treated plants were unable to achieve the same degree of closure as the ambient treated plants. UV-damage and growth responses could alter the diversity of the meadow ecosystem and these effects could be exacerbated by water loss.