Johnson Jon D, Tognetti Roberto, Paris Piero
School of Forest Resources and Conservation, University of Florida, Gainesville, FL, USAPresent address: Intensive Forestry Program, Washington State University - Puyallup, 7612 Pioneer Way E., Puyallup, WA 98371, USA Present address: Dipartimento di Scienze Animali, Vegetali e dell'Ambiente, Università del Molize, Campobasso, Italy Present address: Istituto per l'Agroselvicoltura, Consiglio Nazionale delle Ricerche, Porano, Italy.
Physiol Plant. 2002 May;115(1):93-100. doi: 10.1034/j.1399-3054.2002.1150111.x.
Predictions of shifts in rainfall patterns as atmospheric [CO2] increases could impact the growth of fast growing trees such as Populus spp. and Salix spp. and the interaction between elevated CO2 and water stress in these species is unknown. The objectives of this study were to characterize the responses to elevated CO2 and water stress in these two species, and to determine if elevated CO2 mitigated drought stress effects. Gas exchange, water potential components, whole plant transpiration and growth response to soil drying and recovery were assessed in hybrid poplar (clone 53-246) and willow (Salix sagitta) rooted cuttings growing in either ambient (350 &mgr;mol mol-1) or elevated (700 &mgr;mol mol-1) atmospheric CO2 concentration ([CO2]). Predawn water potential decreased with increasing water stress while midday water potentials remained unchanged (isohydric response). Turgor potentials at both predawn and midday increased in elevated [CO2], indicative of osmotic adjustment. Gas exchange was reduced by water stress while elevated [CO2] increased photosynthetic rates, reduced leaf conductance and nearly doubled instantaneous transpiration efficiency in both species. Dark respiration decreased in elevated [CO2] and water stress reduced Rd in the trees growing in ambient [CO2]. Willow had 56% lower whole plant hydraulic conductivity than poplar, and showed a 14% increase in elevated [CO2] while poplar was unresponsive. The physiological responses exhibited by poplar and willow to elevated [CO2] and water stress, singly, suggest that these species respond like other tree species. The interaction of [CO2] and water stress suggests that elevated [CO2] did mitigate the effects of water stress in willow, but not in poplar.
随着大气中[CO₂]浓度升高，对降雨模式变化的预测可能会影响杨树属和柳树属等速生树木的生长，而这些树种中二氧化碳浓度升高与水分胁迫之间的相互作用尚不清楚。本研究的目的是描述这两个树种对二氧化碳浓度升高和水分胁迫的响应，并确定二氧化碳浓度升高是否能减轻干旱胁迫的影响。对生长在环境（350 μmol mol⁻¹）或高浓度（700 μmol mol⁻¹）大气二氧化碳浓度（[CO₂]）下的杂交杨树（53 - 246无性系）和柳树（箭叶柳）扦插生根苗进行了气体交换、水势组分、整株蒸腾作用以及对土壤干燥和恢复的生长响应评估。黎明前水势随水分胁迫加剧而降低，而中午水势保持不变（等水响应）。在高[CO₂]浓度下，黎明前和中午的膨压势均升高，表明存在渗透调节。水分胁迫降低了气体交换，而高[CO₂]浓度提高了两个树种的光合速率，降低了叶片导度，并使瞬时蒸腾效率几乎提高了一倍。高[CO₂]浓度下暗呼吸降低，水分胁迫降低了生长在环境[CO₂]浓度下树木的暗呼吸速率。柳树的整株水力传导率比杨树低56%，在高[CO₂]浓度下增加了14%，而杨树无响应。杨树和柳树对高[CO₂]浓度和水分胁迫单独表现出的生理响应表明，这些树种的反应与其他树种相似。[CO₂]浓度和水分胁迫的相互作用表明，高[CO₂]浓度确实减轻了柳树水分胁迫的影响，但对杨树没有作用。
