Ghannoum Oula, Conroy Jann P, Driscoll Simon P, Paul Matthew J, Foyer Christine H, Lawlor David W
Centre for Horticulture and Plant Sciences, University of Western Sydney, Locked Bag 1797, South Penrith DC, NSW 1797, Australia.
Present address: Molecular Plant Physiology Group, Research School of Biological Sciences, Australian National University, GPO Box 475, Canberra, ACT 2601, Australia.
New Phytol. 2003 Sep;159(3):599-608. doi: 10.1046/j.1469-8137.2003.00835.x.
• Here, the contribution of stomatal and nonstomatal factors to photosynthetic inhibition under water stress in four tropical C grasses was investigated (Panicum coloratum, Bothriochloa bladhii, Cenchrus ciliaris and Astrebla lappacea). • Plants were grown in well watered soil, and then the effects of soil drying were measured on leaf gas exchange, chlorophyll a fluorescence and water relations. • During the drying cycle, leaf water potential (Ψ ) and relative water content (RWC) decreased from c. -0.4 to -2.8 MPa and 100-40%, respectively. The CO assimilation rates (A) and quantum yield of PSII (Φ ) of all four grasses decreased rapidly with declining RWC. High CO concentration (2500 µl l ) had no effect on A or Φ at any stage of the drying cycle. Electron transport capacity and dark respiration rates were unaltered by drought. The CO compensation concentrations of P. coloratum and C. ciliaris rose sharply when leaf RWC fell below 70%. In P. coloratum, 5% CO did not prevent the decline of O evolution rates under water stress. • We conclude that inhibition of photosynthesis in the four C grasses under water stress is dependent mainly on biochemical limitations.
• 本文研究了四种热带C4禾本科植物（巴哈雀稗、孔颖草、狗尾草和无芒虎尾草）在水分胁迫下气孔和非气孔因素对光合作用抑制的贡献。
• 植株种植于水分充足的土壤中，随后测定土壤干燥对叶片气体交换、叶绿素a荧光和水分关系的影响。
• 在干燥周期中，叶片水势（Ψ）和相对含水量（RWC）分别从约-0.4兆帕降至-2.8兆帕，从100%降至40%。随着RWC的下降，所有四种禾本科植物的CO2同化率（A）和PSII量子产率（Φ）均迅速降低。在干燥周期的任何阶段，高CO2浓度（2500微升/升）对A或Φ均无影响。干旱并未改变电子传递能力和暗呼吸速率。当叶片RWC降至70%以下时，巴哈雀稗和狗尾草的CO2补偿浓度急剧上升。在巴哈雀稗中，5%的CO2并不能防止水分胁迫下O2释放速率的下降。
• 我们得出结论，水分胁迫下四种C4禾本科植物光合作用的抑制主要取决于生化限制。
