Abstract
Tomato plants were grown in peatmoss-based substrate and supplied with nutrient solution of high (4.5 mS·cm–1) or low (2.3 mS·cm–1) electrical conductivity (EC) under high (95%) or low (55% of capillary capacity) substrate water content (SWC) to examine the effects of high EC and low SWC on growth and physiology. Salts were allowed to accumulate in the substrate for 7 weeks. Both high EC and low SWC significantly decreased dry matter production (DMP) and fruit yield (FY). Fruit harvest index was lower in high EC- or low SWC-treated plants. Decrease in marketable FY was attributed to both the decrease in total FY and the increase in small and abnormal (cracked and rot) fruits. Both high EC and low SWC decreased photosynthesis (PN) and leaf water potential (ΨL). However, chlorophyll content and respiration were increased by high EC under both high and low SWC. Water consumption based on both whole plant and unit of leaf area was decreased by high EC and low SWC. ΨL and transpiration were depressed by high EC and low SWC, especially at midday. There was a significant positive correlation between fruit yield and water consumption. The effects of high EC and low SWC were additive on most of the variables. Decreases in ΨL might ultimately account for water consumption reduction, PN depression, and FY decrease.
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