Greenhouse Tomato Growth and Physiological Responses to High Nutrient Solution Electrical Conductivity and Low Substrate Water Content

摘要

The ionic concentration of a nutrient solution, shown by its electrical conductivity (EC), has profound effects on tomato plant growth and fruit yield in the greenhouse. However, high EC effects cannot be simply attributed to restricted water uptake by rhizosphere salinity as usual. To understand the differences in effects of high EC and substrate water deficit, tomato plants were grown in peat-moss based substrate with a nutrient solution of high (4.5 dS m ) or low (2.3 dS m~(-1)) EC under high (95%of capillary capacity) and low (55%) substrate water content (SWC), and examined were the effects on growth, yield, photosynthesis, and plant water relations. Salts were intentionally allowed to accumulate in the substrate for seven weeks by placing thepot in a dish without leaching. Both high EC and low SWC significantly decreased plant growth, dry matter production and fruit yield as well as photosynthesis, leaf water and turgor potentials, stomatal conductance and transpiration. However, blossom-end rot of fruit was more severe in high EC than in low SWC although the leaf Ca content was similar in these two stress treatments. Moreover, soluble protein content and Rubisco activities on a leaf area basis were not decreased by high EC but decreased by low SWC. Results suggested that high EC was different from substrate water deficit in effects on some physiological processes. Further research is needed to elucidate the detailed mechanism of high EC effects.