Effects of drought stress on early seedling growth and ecophysiology of beans, pepper, tomato and watermelon grown in screenhouse-potted soil

Abstract

With changing rainfall patterns, deforestation and degradation of arable land, freshwater resources for irrigation are reducing, increasing the potential for drought stress on crops. The aim of this research was to study the growth and ecophysiological responses of beans, pepper, tomato and watermelon potted and grown in screenhouse under varied irrigation, for 14 days. There were three treatments: zero irrigation after seedling establishment, 0.1 L/pot/week, 0.2 L/pot/week and 0.3 L/pot/week respectively, each pot with three plants, in a completely randomized design with 3 replicates. Growth and ecophysiological measurements were recorded for the first three weeks of growth. ANOVA and Pearson Correlation were conducted, with significance at α 0.05. Plants with zero irrigation had the least growth in all parameters measured; growth was stimulated by irrigation, with a threshold at 0.2 L/week (corresponding to 2200 mm, the mean annual rainfall for the region) for pepper, tomato and watermelon seedlings. Biomass accumulation in all species increased with irrigation but WUE decreased. The quantum efficiency of photosystem II photochemistry of beans and watermelon increased to 0.8 as irrigation increased, while pepper and tomato remained low in all treatments, indicating stress. These results show that early seedling stages are sensitive to drought; however, beans and watermelon seedlings were more resistant to soil moisture deficit than tomato and pepper seedlings. Early farm management should consider appropriate irrigation volumes for better and more vigorous crops in the field. This is essential in a future where irrigation water deficits are predicted to increase during the cropping seasons.