Can biostimulants enhance plant resilience to heat and water stress in the Mediterranean hotspot?

Abstract

Heat and water stress are imposing significant constraints on agricultural systems, particularly in Mediterranean regions experiencing prolonged droughts, rising temperatures, and increasing aridity. These abiotic stresses trigger secondary effects, including osmotic and oxidative stress, simultaneously influencing multiple plant traits. Under drought conditions, stomatal closure limits CO₂ uptake, interfering with photosynthetic electron transport and increasing the production of reactive oxygen species (ROS). Elevated ROS determine oxidative stress, damaging cell membranes, causing genotoxicity, and disrupting key metabolic processes like nutrient transport, cell division, and expansion. Plants activate natural defence mechanisms to counter these stresses, but these responses are energetically costly. The diversion of carbon skeletons and energy from growth and biomass accumulation to stress responses results in reduced yields, especially in key Mediterranean crops such as wheat, tomato, grapevine, and olive trees, which are highly vulnerable to extreme climatic events. Biostimulants hold significant potential as an innovative approach to strengthening plants' natural defences and enhancing their capacity to endure heat and drought stress. By modulating stress-related pathways, enhancing antioxidant defence mechanisms, and promoting the accumulation of osmolytes, these products help maintain water use efficiency (WUE), sustain photosynthetic activity, and reduce stress-induced yield losses. In areas where water scarcity is a major limiting factor for agriculture, biostimulants offer a promising strategy to enhance plant adaptation to increasingly unpredictable precipitation patterns and higher temperatures. Beyond their immediate benefits, biostimulants offer a sustainable solution for supporting crop productivity amidst climate change. Further research into their biochemical, physiological, and metabolic impacts, specifically focusing on Mediterranean cropping systems, will be essential to optimise their application and integrate them effectively into modern, sustainable farming strategies.