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 exami ned from spore germination to colony sporulation across a series of environ mentally relevant UV-B doses. For the litter fungi all aspects of fungal de velopment and morphology studied were affected. On the basis of the respons es of mycelial extension rate and spore germination to increasing UV-B, the 12 litter fungi were divided into two groups. Group A (Aspergillus fumigat us, 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 ra te on the agar surface was similarly affected, with reductions ranging from 15 to 25%. In contrast group B (Mucor hiemalis, Cladosporium cladosporioid es, Leptosphaeria coniothyrium, Trichoderma viride, Ulocladium consortiale, the Verticillium state of Nectria inventa and Marasmius androsaceus) were relatively insensitive to UV-B, with significant, but small, reductions in mycelial extension rate (<5%) and spore germination (0-22%). Spore producti on 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 W-B dose. In contrast, in all seven phylloplane species, spore germination was unaffected by increasing d ose. Mycelial extension rate was slightly (2-12%), but significantly, inhib ited by UV-B for the four phylloplane fungi tested. The contrasting respons es of phylloplane and litter fungi to UV-B are discussed along with the imp lications for resource capture by competing fungal species and the possible effects of UV-B on decomposition processes.