effect of water stress and elevated ambiEnt CO₂ on Gas exchange, photochemical efficiency and leaf water potential of The Négrette (Vitis Vinifera L.)

F. Attia, F. Garcia, C. Baduca Cimpeanu, F. Ben Mariem,

M. F. Kasraoui, T. Lamaze, M. Garcia

KEY WORDS: chlorophyll fluorescence, diurnal courses, net photosynthetic rate, water use efficiency, elevated ambient CO₂ level

ABSTRACT

Diurnal courses of gas exchange, photochemical efficiency, and leaf water potential (Ψ_L) of the red wine grape cultivar Négrette (Vitis vinifera L.) were studied under water stress and elevated ambient CO₂ level. For severe water stress (SS) treatment Ψ_L decreased from 06:00 to 16:00 and increased afterwards. The control (To) showed higher net photosynthetic rate (An) and stomatal conductance (g_s) than the severe stressed vines. Under elevated ambient CO₂ (800 ppm) both the control and the stressed vines showed a higher net photosynthetic rate and a higher true quantum yield for CO₂ assimilation. Transpiration and stomatal conductance were affected by water limitation and CO₂ variation. Water use efficiency (WUE) was higher under water stress conditions than for the well-watered vines and was also higher is the CO₂ level is important. Significant correlations were established between An and gs at air ambient and elevated CO₂ levels.