## 2 Abiotic Stresses of Agricultural Importance  
Crop stress poses a significant threat to food security worldwide by lowering agricultural output and restricting yield potential [10]. Abiotic stresses, exacerbated by climate change, have a major effect on food production and need to be further investigated. Environmental factors, such as water stress, high soil salinity, and pollution have also been shown to hinder plant growth and productivity by imposing physiological and biochemical constraints [10]. These pressures threaten plant resilience, can result in yearly agricultural losses of over USD 170 billion [11], and yield 60% below ideal conditions [12]. Drought is among the most damaging abiotic stresses affecting agricultural systems, accounting for a significant portion of agricultural losses and severely impacting essential crops, such as wheat, maize, rice, and soybeans, with estimated annual losses of approximately USD 44 billion [5]. However, other studies suggest that these losses may reach as high as USD 80 billion annually [11]. Approximately 11% of total croplands and 14% of pastures are affected by recurrent droughts, while more than 60% of irrigated croplands experience high water stress [5]. Heat waves affect plant growth differently depending on the species; however, they are undeniably a highly disruptive factor in crop development worldwide [13], with their frequency projected to increase fourfold by 2040 [14]. Climate-related events have tripled in severity in Europe, reducing cereal yields by 9% and non-cereal crops by 3.8% [15]. Southern Europe is particularly vulnerable, as wheat and corn production are expected to decline sharply due to water shortages and rising temperatures driven by climate change [16]. Heat waves in Africa and Asia have caused yield losses of 15-35% [14]. Soil degradation is a growing concern in agriculture, with salinity affecting approximately 10% of arable land, including both irrigated and rainfed areas, resulting in an estimated global economic cost of USD 30 billion per year [11; 17]. Some authors claim that salinity affects 1100 Mha of soil, which represents a total of 7% of the world's surface [18]. Additionally, heavy metal contamination further accelerates soil degradation, impacting over 20 million hectares of land with pollutants [19]. In Europe, an estimated 2.5 million locations may be contaminated with organic pollutants and heavy metals, while in the United States, between 235,000 and 355,000 sites are considered in need of remediation. In China, by contrast, approximately 16% of the territory is thought to harbor heavy metals and other pollutants above soil quality levels [20]. Mitigating the consequences of abiotic stress on plants and improving their resistance to environmental changes largely depends on biological and chemical approaches. Among the chemical methods, the application of exogenous abscisic acid (ABA), since it controls stomatal closure and hence lowers water loss under drought and salt stress, and also regulates toxic metal transport, minimizes damage from heavy metal stress [21; 22]. A novel strategy involves the use of nanotechnology, such as zinc oxide nanoparticles, which have shown promise in enhancing antioxidant defenses and reducing oxidative stress under extreme conditions [23]. Also, certain plant polymers, such as lignin, are less sensitive to environmental relative humidity [24], which enables plants to better withstand the effects of drought [25]. From a biological perspective, leveraging plant-microbe interactions offers a promising and sustainable strategy for stress mitigation. Beneficial microorganisms, such as endophytic fungi, arbuscular mycorrhizal fungi (AMF), plant growth-promoting rhizobacteria (PGPR), or cyanobacteria, enhance plant resilience by improving nutrient and water uptake, stimulating stress-related hormone production, and regulating reactive oxygen species (ROS) to limit cellular damage [26; 27; 28].