Combined effects of water stress and salinity on growth, physiological, and biochemical traits in two walnut genotypes

Abstract

Due to its great economic value, walnut (Juglans regia L.) has received increasing attention during recent years. However, water stress and salinity limit walnut growth, production, and quality. We employed two walnut genotypes, precocious walnut, and late-bearing walnut, to investigate their growth, photosynthetic capacity, nonstructural carbohydrate contents, Cl − allocation, reactive oxygen species (ROS) accumulation, and osmotic regulation under water stress, salinity, and their combination.We found that late-bearing walnut showed higher total biomass and net photosynthetic rate, higher activities of antioxidant enzymes, higher osmoregulation, and lower ROS accumulation than precocious walnut under stressful conditions. In addition, late-bearing walnut restricted salt transport and allocated more Cl − into roots, whereas precocious walnut allocated more Cl − into leaves when exposed to salinity stress. These data collectively demonstrated that late-bearing walnut possesses better stress tolerance under water stress, salinity, and especially under their combination. Such knowledge of genotype-specific responses and tolerances to water stress and salinity is important for walnut plantation management under increasing drought and aggravated soil salinization occurring with climate change. | INTRODUCTIONWater is a crucial limiting resource of plant growth and production, and many areas are expected to experience decreased precipitation under climate change (Choat et al., 2018;Cook et al., 2015). Plants have different physiological and defense responses to lessen the damage under water stress, including changes in morphological and physiological traits to deal with water stress. For example, plants can change biomass allocation between roots and shoots under water-limited conditions

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