210 Effects of Salt and Water Stress on the Growth and Photosynthesis Rate of Bell Pepper (Capsicum annuum L.)

Salt and water stress affect in a significant way most common horticultural crops in northwest Mexico, where bell pepper, hot pepper, and tomato are the most important vegetable crops. Growth rate (GR) and physiological traits in bell pepper were analyzed under salt and drought stress. Two cultivars of bell pepper, `Hungarian Yellow' (HY) and `Sta. Fe Grande' (SG), were evaluated. GR in both cultivars was decreased by salt and drought stress interaction. Salt concentration in the irrigation water affected the amount of dry matter in the plant tissue. Relative growth ratio (RGR), net assimilation ratio (NAR), leaf area ratio (LAR), and photosynthesis rate (P n ) decreased in a correlated amount to the salt NaCl content in the experiment (0, 80, and 160 m m ). Differences in the RGR under salt and drought stress between SG and HY were significant. The observed decrease in RGR was explained by NAR and LAR, where RGR was more affected by NAR than LAR. Similarly, the decrease in NAR was explained by C/F and Pn, indicating that NAR was more affected by Pn than C/F. The difference in observed NAR between both cultivars was understood by difference in C/F. Finally, a high relation of C/F in SG cultivar under salt and drought stress was caused by a physiological use of photosynthetic products, causing a significant decrease in NAR in the cultivar HY. This difference in NAR was found to be the factor that affected RGR in both cultivars.