Genotypic variation in drought response of willows grown under ambient and enhanced UV-B radiation

The response of growth of willows to combinations of UV-B radiation and drought stress was studied in a 4-week greenhouse experiment. Eleven hybrid (Salix myrsinites L. × Salix myrsinifolia Salisb.) clones and four S. myrsinifolia clones were subjected to two UV-B (ambient; enhanced) and two water treatments (well-watered; drought-stressed). According to our results, enhanced UV-B radiation (twice the ambient level) or drought stress (50% less water than well-watered) decreased the growth of hybrid and S. myrsinifolia plantlets, but fast-growing S. myrsinifolia plantlets were more susceptible to drought stress than slower-growing hybrids were. Our results also suggest that enhanced UV-B radiation and drought stress have an additive negative effect on growth of willows. Within hybrid and S. myrsinifolia plantlets, the variation in growth between different clones and families was significant. Drought stress produced family- and clone-specific reactions, whereas the response of studied willow genotypes to enhanced UV-B and UV-B × drought was mostly similar.