Kinetin and arbuscular mycorrhizal fungi: vital regulators of Vicia faba plantsʼ response and tolerance to drought stress

In light of the detrimental consequences of climate change and global warming, drought (water deficit) has emerged as a major abiotic stressor that adversely affects plant development, productivity, and sustainable agriculture globally. Vicia faba L. (faba bean), a highly nutritious leguminous crop, is especially vulnerable to water scarcity. As a possible solution, this study highlighted the recent advances in plant stress physiology regarding the role of kinetin (20 mg/L) and arbuscular mycorrhizal (AM) fungi in enhancing V. faba resilience to drought (30% water holding capacity) with emphasis on their growth, physiological and biochemical mechanisms. Under controlled conditions, drought markedly decreased plant growth, photosynthetic pigments (chlorophyll a + b and total pigments), and relative water content (RWC), while increasing stress markers (hydrogen peroxide and electrolyte leakage). Nevertheless, these negative effects were considerably lessened by AM fungi and kinetin application. Their application led to the improvement of V. faba growth parameters, maintaining cellular hydration (high RWC), higher activity of antioxidant enzymes (superoxide dismutase, catalase, peroxidase, ascorbate peroxidase, and polyphenol oxidase) and organic adjustments which include total soluble protein, proline and total soluble carbohydrate. The most surpassing effect is that AM fungal inoculation enhanced the soil-rich glomalin content, both easily and total extractable. Regarding the effect of drought stress on mycorrhizal colonization; microscopic observation showed a noticeable reduction in the formation of arbuscules and vesicles under drought. Although reduced colonization, AM fungi can nevertheless benefit host plants. These findings highlight the potential of integrating AM fungal inoculation or kinetin treatment as an eco-friendly strategy to enhance drought resilience in V. faba cultivation.