UV-B radiation and acclimation in timberline plants.

Research has shown that some plants respond to enhanced UV-B radiation by producing smaller and thicker leaves, by increasing the thickness of epidermis and concentration of UV-B absorbing compounds of their surface layers and activation of the antioxidant defence system. The response of high-altitude plants to UV-B radiation in controlled conditions is often less pronounced compared to low-altitude plants, which shows that the alpine timberline plants are adapted to UV-B. These plants may have a simultaneous co-tolerance for several stress factors: acclimation or adaptation to the harsh climate can also increase tolerance to UV-B radiation, and vice versa. On the other hand, alpine timberline plants of northern latitudes may be less protected against increasing UV-B radiation than plants from more southern latitudes and higher elevations due to harsh conditions and weaker preadaptation resulting from lower UV-B radiation exposure. It is evident that more long-term experimental field research is needed in order to study the interaction of climate, soil and UV-B irradiance on the timberline plants.