Water use efficiency response of field-grown muskmelon and pepper to environmental water status.

The effect of water deficit on muskmelon and pepper leaf water potential, gas exchange and water use efficiency was evaluated. Both species were submitted to three watering treatments in open field conditions: irrigation only at transplanting (the control), irrigation at transplanting and fruit-setting, and full irrigation restoring 100% maximum crop evapotranspiration (ETc). Leaf water potential (?l) in pepper markedly decreased with increasing evaporative demand during the day and it was lower in the stressed than in well-watered plants. In contrast, muskmelon maintained a near constant ?l from 10:00 h to 16:00 h both in stressed and in well-watered plants. Muskmelon exhibited greater net assimilation and leaf water use efficiency than pepper. With varying air vapour pressure deficit, stomatal conductance of muskmelon markedly changed while it varied slightly in pepper. Above-ground total dry biomass was much higher in muskmelon than in pepper and total biomass water use efficiency in muskmelon was about 2-fold higher than in pepper (on average 1.6 and 0.82 kg/m-3, respectively), demonstrating a greater efficiency of the former in using water.