The effects of long-term drought stress on chlorophyll, proline, protein and hydrogen peroxide (H₂O₂) contents, malondialdehyde (MDA) in terms of lipid peroxidation and on the changes in the activities of antioxidant enzymes such as superoxide dismutase (SOD, EC 1.15.1.1), ascorbate peroxidase (APX, EC 1.11.1.11), catalase (CAT, EC 1.11.1.6) and peroxidase (POX; EC 1.11.1.7) in the leaves of pea ( Pisum sativum L.) were studied in field conditions. Chlorophyll and protein contents in leaves decreased significantly with increased drought stress. The proline content increased markedly under water deficit. MDA amounts were elevated as a result of water shortage, whereas H₂O₂ content changed slightly in pea leaves exposed to drought stress. Drought stress markedly enhanced the activities of SOD, CAT and POX but slightly changed the activity of APX. We conclude that in field conditions, long-term water shortage increased the susceptibility to drought in peas.

The effects of irrigation water salinity on growth, yield, and water consumption of okra was investigated with a pot experiment. For this purpose, five irrigation water salinity levels with electrical conductivities of 1.5, 2.5, 3.5, 5.0, and 7.0 dS∕m and tap water as a control treatment were used in a randomized design with five replications. Irrigation practices were realized by considering the weight of each pot. Threshold soil salinity and slope values of the yield response to soil salinity level were determined to be 3.48 dS∕m and 4.2%, respectively, for fruit yield, 4.24 dS∕m and 7.0% for vegetative dry weight, and 6.0 dS∕m and 7.9% for root dry weight. The results revealed that okra was moderately tolerant to salinity. Increasing soil salinity levels caused significant decreases in plant water consumption. Plant water consumption decreased by 2.43% per unit increase in soil salinity. Plant coefficient ( Ky ) was 1.26. Saline irrigation water treatments altered Cl, Mg, Ca, and Na accumulations in le...

BACKGROUND: Salinity and drought stresses have become widespread in many regions of the world. Although there are several studies, their findings about the response of lettuce to water and salinity stresses are contradictory. This paper therefore aims to evaluate the effects of water deficit and irrigation water salinity on growth, yield, and water consumption of iceberg lettuce. For these purposes, two experiments were carried out under Mediterranean conditions.RESULTS: The water yield response factors (K_y) determined for the lettuce plant grown under stress conditions caused by water (K_y = 1.69) and irrigation water salinity (K_y = 2.62) were quite different from each other. The classical salinity tolerance model did not reflect the results accurately because the fresh yield and plant water consumption of lettuce increased sharply with increasing soil salinity up to 2.17 dS m⁻¹ and then decreased slightly after this value. Thus, a new model was created to reflect both the increase and decrease in fresh yield. The actual salt tolerance model for iceberg lettuce plant showed that the optimum salinity is 1.84 dS m⁻¹ with relative yield decreases of 8.26 and 22.7% per unit salinity increase above and below the optimum salinity level, respectively.CONCLUSION: Lettuce fresh yield at soil salinity below the optimum salinity experienced greater reduction than at soil salinity above the optimum value. The results reveal that the use of low‐salinity irrigation water should be preferred to increase fresh yield in iceberg lettuce cultivation. © 2021 Society of Chemical Industry.