Enhanced tolerance of photosynthesis to high-light and drought stress in Pseudotsuga menziesii seedlings grown in ultraviolet-B radiation

• Published in: Tree physiology 2002-08, Vol.22 (12), p.829-838
• Main Authors: Poulson, Mary E, Donahue, Raymon A, Konvalinka, Julie, Boeger, M Regina Torres
• Format: Article
• Language: English
• Subjects: Dehydration; Light; Photosynthesis - physiology; Photosynthesis - radiation effects; Photosynthetic Reaction Center Complex Proteins - radiation effects; Photosystem II Protein Complex; Plant Leaves - anatomy & histology; Plant Leaves - physiology; Plant Leaves - radiation effects; Plant Transpiration - physiology; Plant Transpiration - radiation effects; Pseudotsuga - physiology; Pseudotsuga - radiation effects; Seedlings - growth & development; Seedlings - physiology; Seedlings - radiation effects; Trees - growth & development; Trees - physiology; Trees - radiation effects; Ultraviolet Rays
• ISSN: 0829-318X; 1758-4469
• DOI: 10.1093/treephys/22.12.829

We investigated the effects of an ambient dose of ultraviolet-B (UV-B) radiation on chamber-grown Pseudotsuga menziesii var. glauca (Beissn.) Franco (Douglas-fir) seedlings, to determine if the presence of UV-B radiation in the growth light regime induces tolerance to environmental stresses such as high light and drought. Douglas-fir seedlings were grown without UV-B radiation or with 6 kJ m-2 day-1 of biologically effective UV-B, which is ambient for the intermountain regions of Idaho. Non-stressed seedlings grown with UV-B radiation had 35% lower seedling dry mass, 36% higher concentrations of UV-B absorbing compounds per unit leaf area, 30% lower stomatal frequencies, 25% lower light-saturated photochemical efficiencies of Photosystem II and 45% lower light-saturated stomatal conductance than non-stressed seedlings grown without UV-B radiation. After 4 days of high-light stress, seedlings grown with UV-B radiation had 32% higher light-saturated carbon assimilation rates (A(CO2)) than seedlings grown without UV-B radiation. After water was withheld from the seedlings for up to 15 days, seedlings grown with UV-B radiation had 50% higher A(CO2) and 40% higher seedling water potentials than seedlings grown without UV-B radiation. The results support the hypothesis that UV-B radiation can act as an environmental signal to induce tolerance to high-light and drought stress in Douglas-fir seedlings. Possible mechanisms for the enhanced stress tolerance are discussed.