Abstract
SUMMARYGreenhouse tomato plants (Lycopersicon esculentum Mill. cv. Capello) were grown in a peal-moss based substrate and supplied with nutrient solutions of high (4.5 mS cm-1) or low (2.3 mS cm-1) electrical conductivity (EC) and under high (95 ± 5%) or low (55 ± 8% of capillary capacity) soil water content, to elucidate how EC and soil water status affect plant photosynthesis and related physiological processes. Two weeks after beginning the treatments, photosynthesis (Pn) was measured during changes of photo-synthetic photon flux (PPF) from 0 to 1200 u.mol m-2 s-1 using a gas exchange method. The rectangular hyperbolic model (Pn = Pmax KI (1-KI)-2 -r) provided a good fit for the photosynthetic light-response curve. High EC treatment changed the curve by increasing the initial slope (quantum yield) and decreasing photosynthetic capacity at high PPF. However, soil water deficit not only decreased the photosynthetic capacity, but also decreased quantum use efficiency. Depression of Pn was attributed to de...
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