effect of water stress and elevated ambiEnt CO₂ on Gas exchange, photochemical efficiency and leaf water potential of The N�grette (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 N�grette (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.