Variation in the responses of litter and phylloplane fungi to UV-B radiation (290-315 nm)

The development of 12 litter and seven phylloplane fungal species was examined from spore germination to colony sporulation across a series of environmentally relevant UV-B doses. For the litter fungi all aspects of fungal development and morphology studied were affected. On the basis of the responses of mycelial extension rate and spore germination to increasing UV-B, the 12 litter fungi were divided into two groups. Group A {Aspergillus fumigatus, Penicillium hordei, P. janczewskii, P. spinulosum and P. purpurogenum) were sensitive to UV-B, with the predicted effects of a 15% ozone depletion resulting in 22-44% reductions in spore germination. Mycelial extension rate on the agar surface was similarly affected, with reductions ranging from 15 to 25%. In contrast group B {M.ucor hiemalis, Cladosporium cladosporioides, Leptosphaeria coniothyrium, Trichoderma viride, Ulocladium consortiale, the Verticillium state of Nectria inventa and Miamsmius androsaceus) were relatively insensitive to UV-B, with significanAt, but small, reductions in mycelial extension rate (< 5%) and spore germination (0-22%). Spore production in response to UV-B in the litter species was very variable, reductions ranging from 5 % to complete inhibition. Only P. hordei showed a significant increase in spore production in response to UV-B dose. In contrast, in all seven phylloplane species, spore germination was unaffected by increasing dose. Mycelial extension rate was slightly (2-12%), but significantly, inhibited by UV-B for the four phylloplane fungi tested. The contrasting responses of phylloplane and litter fungi to UV-B are discussed along with the implications for resource capture by competing fungal species and the possible effects of UV-B on decomposition processes.