Variation in antioxidant metabolism of young and mature leaves of Arabidopsis thaliana subjected to drought

Young and mature leaves of 4-week-old Arabidopsis plants were exposed to drought stress up to -2.54 MPa of water potential (psi(w)) by withholding water supply for 7 days. The efficiency of photosystem (PS) II photochemistry, F-v/F-m, and chlorophylls (Chls) remained unaltered and quantum yield of PSII electron transport (phi(PSII)) decreased slightly in drought-stressed young leaves, whereas F-v/F-m, decreased slightly and phi(PSN) and Chls decreased by 40 and 24%, respectively, in drought-stressed mature leaves. Both young and mature leaves exhibited a considerable increase in non-photochemical quenching (NPQ) and xanthophyll-mediated photoprotection capacity in response to drought stress, with a greater level of NPQ in mature leaves. Although the drought-induced increase in non-enzymatic antioxidants in young and mature leaves, enzymatic antioxidants including catalase, peroxidase (POD), superoxide dismutase (SOD) and glutathione reductase (GR) substantially increased only in drought-stressed mature leaves. Plants recovered rapidly 24 h after resupplying water, as indicated by that psi(w), F-v/F-m and pigment contents returned to well-watered control levels, however, the activities of POD, SOD and GR remained high. The fact that drought-stressed mature leaves suffer more stress than drought-stressed young leaves suggests that developmental stages of leaves might contribute to the differential prevention of oxidative damage in plants exposed to drought. (C) 2003 Elsevier Ireland Ltd. All rights reserved.