Impact of chloride nutrition on nutrient uptake and physiological responses to drought stress in tomato plants

Resumen del póster presentado en el XVIII Simposio Hispano-Luso de Nutrición Mineral de las Plantas-NUTRIPLANTA2024 tendrá lugar en Badajoz, España, los días 22 a 24 de julio de 2024.

Water deficit is one of the primary environmental factors negatively affecting crop productivity and yield. Drought, besides disrupting plant water relations, photosynthesis and antioxidant capacity, can impact the nutrient uptake process, including essential macronutrients such as nitrogen (N), potassium (K), magnesium (Mg), and calcium (Ca). The presence of mineral nutrients in plant tissues is crucial for optimal plant development and growth. Their proper ionic gradient is considered essential for processes such as the regulation of enzymatic activities or signaling in response to abiotic stress (Yang et al., 2020, Plants 9:363). Although chloride (Cl¿) has been traditionally considered of little importance for agriculture and even a harmful ion for plants, because of its accumulation in photosynthetic organs under high salinity conditions, it has recently been recognized as a beneficial element for plants when accumulated at macronutrient levels. Our research has shown that Cl¿ is capable of improving plant development and growth, as well as the efficiency in the use of water, carbon, and N (Franco-Navarro et al., 2016, J Exp Bot 67:873; and 2019, Plant J 99:815; Rosales et al., 2020, Front Plant Sci 11:442). Additionally, we have recently demonstrated that plants treated with Cl¿ can develop better antioxidant response under N nutrient deficiency conditions (Lucas et al., 2024, Plant Physiol Biochem 212:108717). In this work, we investigated how Cl¿ applied at macronutrient levels (5 mM in the nutrient solution) affects growth, nutrition and different physiological aspects in mature tomato plants grown under both control and water deficit conditions. Our findings indicate that Cl¿ nutrition reduced the stress symptoms (i.e. efficiency of PS-II, SPAD and malondialdehide parameters), improving both growth and physiological status (i.e. photosynthesis rate, stomatal conductance, water use efficiency and antioxidant capacity) of tomato plants during sustained drought conditions. Furthermore, both ion fluxes and the efficiency in the use of N, Ca, Mg and K (NUE, CaUE, MgUE, and KUE, respectively) increased under drought conditions in plants treated with 5 mM Cl¿. Here we demonstrate that the more efficient nutrient uptake and use of Cl¿-treated tomato plants, in line with the better turgor maintenance previously showed in tobacco plants (Franco-Navarro et al., 2021, J Exp Bot 72:5246), participates in drought-resistant mechanisms improving photosynthesis and, consequently, crop growth and yield. Thus, we propose Cl¿ nutrition at beneficial macronutrient levels as a key tool for improving the ability of crops to withstand drought, promoting a more sustainable and resilient agriculture.