Drought increases heat tolerance of leaf respiration in Eucalyptus globulus saplings grown under both ambient and elevated atmospheric [CO2] and temperature

• Published in: Journal of experimental botany Vol. 65; no. 22; pp. 6471 - 6485
• Main Authors: Gauthier, Paul P. G, Crous, Kristine Y, Ayub, Gohar, Duan, Honglang, Weerasinghe, Lasantha K, Ellsworth, David S, Tjoelker, Mark G, Evans, John R, Tissue, David T, Atkin, Owen K
• Format: Journal Article
• Language: English
• Published: England Oxford University Press [etc.] 01.12.2014; Oxford University Press
• Subjects: Acclimatization; Adaptation, Physiological - drug effects; Analysis of Variance; Atmosphere; Australia; Carbohydrates - analysis; carbon dioxide; Carbon Dioxide - pharmacology; Cell respiration; Cell Respiration - drug effects; climate change; Darkness; Drought; Droughts; elevated atmospheric gases; Eucalyptus - drug effects; Eucalyptus - growth & development; Eucalyptus - physiology; Eucalyptus globulus; heat tolerance; High temperature; Hot Temperature; leaves; Phenotype; Photosynthesis; Plant cells; Plant growth; Plant Leaves - anatomy & histology; Plant Leaves - drug effects; Plant Leaves - physiology; RESEARCH PAPER; saplings; Solubility; Starches; Sugars; temperature; Australia; temperature response; Q10; drought; elevated CO2; Eucalyptus globulus; Dark respiration
• ISSN: 0022-0957; 1460-2431
• DOI: 10.1093/jxb/eru367

This study highlights the dynamic nature of the temperature dependence of leaf respiration in plants experiencing future climate change scenarios, particularly with respect to drought and elevated [CO2]. Climate change is resulting in increasing atmospheric [CO2], rising growth temperature (T), and greater frequency/severity of drought, with each factor having the potential to alter the respiratory metabolism of leaves. Here, the effects of elevated atmospheric [CO2], sustained warming, and drought on leaf dark respiration (R dark), and the short-term T response of R dark were examined in Eucalyptus globulus. Comparisons were made using seedlings grown under different [CO2], T, and drought treatments. Using high resolution T–response curves of R dark measured over the 15–65 °C range, it was found that elevated [CO2], elevated growth T, and drought had little effect on rates of R dark measured at T <35 °C and that there was no interactive effect of [CO2], growth T, and drought on T response of R dark. However, drought increased R dark at high leaf T typical of heatwave events (35–45 °C), and increased the measuring T at which maximal rates of R dark occurred (T max) by 8 °C (from 52 °C in well-watered plants to 60 °C in drought-treated plants). Leaf starch and soluble sugars decreased under drought and elevated growth T, respectively, but no effect was found under elevated [CO2]. Elevated [CO2] increased the Q 10 of R dark (i.e. proportional rise in R dark per 10 °C) over the 15–35 °C range, while drought increased Q 10 values between 35 °C and 45 °C. Collectively, the study highlights the dynamic nature of the T dependence of R dark in plants experiencing future climate change scenarios, particularly with respect to drought and elevated [CO2].