Growth and protection against oxidative stress in young clones and mature spruce trees (Picea abies L.) at high altitudes

Clones of Norway spruce (Picea abies L.) were grown for several years on an altitudinal gradient (1750 m, 1150 m and 800 m above sea level) to study t he effects of environmental x genetic interactions on growth and foliar met abolites (protein, pigments, antioxidants). Clones at the tree line showed 4.3-fold lower growth rates and contained 60% less chlorophyll (per gram of dry matter) than those at valley level. The extent of growth reduction was clone-dependent. The mortality of the clones was low and not altitude-depe ndent. At valley level, but not at high altitude, needles of mature spruce trees showed lower pigment and protein concentrations than clones. In gener al, antioxidative systems in needles of the mature trees and young clones d id not increase with increasing altitude. Needles of all trees at high alti tude showed higher concentrations of dehydroascorbate than at lower altitud es, indicating higher oxidative stress. In one clone, previously identified as sensitive to acute ozone doses, this increase was significantly higher and the growth reduction was stronger than in the other genotypes. This clo ne also displayed a significant reduction in glutathione reductase activity at high altitude. These results suggest that induction of antioxidative sy stems is apparently not a general prerequisite to cope with altitude in clo nes whose mother plants originated from higher altitudes (about 650-1100 m above sea level, Hercycnic-Carpathian distribution area), but that the gene tic constitution for maintenance of high antioxidative protection is import ant for stress compensation at the tree line.