Abstract
We collected seeds of Solidago virgaurea plants growing at different altitudes in the Mt. Hakusan area of Japan and cultivated them in a naturally-lit green house. Three-week-old seedlings were irradiated with supplemental UV-B for 12 h each day for 1 and 2 weeks. After a week of irradiation seedlings from the higher altitude population at Oh-nanjiho (ON) had accumulated more anthocyanins than those from the lower altitude population at Bettoh-deai (BD). Levels of anthocyanins in the ON seedlings were highly correlated with the dose of UV-B radiation and this correlation was also observed after 2 weeks. The growth of third leaves was retarded by UV-B radiation in both populations. The extent of growth retardation in third leaves was correlated with the dose of UV-B radiation in both populations. However, no significant difference in the extent of leaf area growth was observed between the ON and BD populations. The increase in plant fresh weight was extensively inhibited in the ON seedlings after 1 week of UV-B radiation. The inhibition recovered to the levels of those in the BD population following a week of irradiation. These results indicate that the two populations respond differently to supplementary UV-B radiation during the fi rst week. Because flavonoids such as anthocyanins play an important role in protection against UV-B radiation in many plants, populations growing at higher altitudes may be better able to adapt to increased global levels of UV-B radiation.
