Thresholds for chickpea leaf expansion and transpiration response to soil water deficit

This study determined the thresholds (the onset of decline) for leaf expansion (C-L) and transpiration (C-T) responses to soil water deficit in chickpea (Cicer arietinum L.) and evaluated their importance to crop performance under rainfed conditions using a chickpea simulation model in two contrasting locations. Two pot experiments were conducted to determine the thresholds during adrying cycle, when plant responses were monitored as the soil dried progressively. Leaf area expansion and transpiration did not change until the fraction of transpirable soil water (FTSW) reached 0.48 (C-L) and 0.34 (C-T), respectively, and then decreased linearly to FTSW of 0.03 for leaf expansion and 0 for transpiration. Simulation results of sensivity test showed that for long and intensive terminal droughts, high C-L and C-T and for short and intermittent droughts, low C-L and C-T favor grain yield but the yield increases with best combinations of C-L and C-T do not exceed 1% (20 kg ha(-1)) and 5% (40 kg ha(-1)), respectively. Thus, the contribution of C-L and C-T differences in crop performance under water deficit conditions seems limited. (C) 2000 Elsevier Science B.V. All rights reserved.