Effects of elevated ultraviolet radiation and endophytic fungi on plant growth and insect feeding in Lolium perenne, Festuca rubra, F. arundinacea and F. pratensis.

Plants of perennial ryegrass (Lolium perenne L.), red fescue (Festuca rubra L.), tall fescue (F. arundinacea Schreb.) and meadow fescue (F. pratensis Huds) were exposed at an outdoor facility located in Edinburgh, UK to modulated levels of UV-B radiation (280-315 nm) using banks of cellulose diacetate filtered UV-B fluorescent lamps that also produce UV-A radiation (315-400 nm). The plants were derived from a single clone of each species and were grown both with and without colonization by naturally-occurring fungal endophytes. The UV-B treatment was a 30% elevation above the ambient erythemally-weighted level of UV-B during July to October. Growth of treated plants was compared with plants grown under elevated UV-A radiation alone produced by banks of polyester filtered lamps and with plants grown at ambient levels of solar radiation under banks of unenergized lamps. At the end of the treatment period, sample leaves were collected for feeding trials with the desert locust Schistocerca gregaria (Forsk). The UV-B treatment produced no effects on the aboveground biomass of any of the four grasses. The UV-B treatment and the UV-A control exposure both increased plant height and the number of daughter plants formed by rhizome growth in F. rubra. There were significant effects of endophyte presence on the total fresh and dry weights of F. arundinacea and F. rubra, on fresh weight only in F. pratensis, and on the fresh and dry weights of inflorescence in F. arundinacea and L. perenne. There were no effects of UV treatments on the absolute amounts of leaf consumed or on the feeding preferences of locusts for leaves with or without endophyte in three species: F. rubra, F. arundinacea and L. perenne. In F. pratensis there was no effect of UV treatment on the weight of leaves consumed but a significant UV x endophyte interaction caused by a marked change in feeding preference between leaves with and without endophyte that differed between the UV-B treatment and UV-A control exposures. The alkaloid compounds known as lolines were analysed in leaves of F. pratensis and were only found in plants grown with endophyte. However, there was no significant relationship between total loline content and insect feeding preference. These effects illustrate the potential complexities of species interactions under increasing levels of UV-B. The experiment also demonstrates the importance of appropriate controls in UV lamp supplementation experiments for interpretation of both plant growth and insect feeding effects.

Effects of sulphur dioxide and ozone on lichen colonization of conifers in the Liphook Forest Fumigation Project.

In the Liphook Forest Fumigation Project the conifers Picea abies(L.) Karst., P, sitchensis (Bong-) Carr. and Pinus sylvestris L. were grown from the seedling stage and subjected, by open-air fumigation, to three regimes of SO2 (ambient, 4 ppb (parts in 109 by volume); low, 12 ppb; high, 20 ppb) and two regimes of O3 (ambient, 25 ppb; high, 30 ppb) in factorial combination, between 1987 and 1990. We determined the abundance of three lichens, Evernia prunastri (L.) Ach., Hypogymnia physodes (L.) Nyl. and Lecanora canizaeoides Nyl. ex Crombie, which colonized the trunks and branches of the saplings, at the end of the experiment between May-July 1991. All three species showed a marked preference for P. abies and were scarcest on P, sylvestris which had the most acidic hark. E. prunastri was the rarest of the three lichens and only colonized plots exposed to ambient SO2 (4 ppb). Diminutive thalli of H. physodes were relatively numerous in the ambient SO2 , plots, much scarcer in those receiving low SO2 (12 ppb) and rare in those with high SO2 (20 ppbl. Coverage by L. conizaeoides was very low in the ambient SO2 , plots but appreciable in the low and high SO2 treatment plots. The results indicate directly beneficial effect of SO2 on L. conizaeoides colonization rather than an indirect benefit through competitor release. The O3 treatment (1.3 times ambient during Spring-Autumn) did not influence the abundance of the lichens. All three lichen species appeared to be more sensitive (positive and negative effects) to SO2 , than mapping studies have suggested. Possible reasons for the high SO2 -sensitivity of the lichens are discussed. These include the high acidity of conifer bark and the fact that growth from diaspores and development of immature thalli is involved rather than survival of established populations.