Physiological and Biochemical Responses of Stylosanthes spp. Under Water Deficit Conditions

Studies aimed at identifying genotypes tolerant to water deficit are essential for the development of superior plant materials adapted to regions with limited water availability, such as the Brazilian Semi-Arid. This study evaluated the physiological, biochemical, and enzymatic responses of Stylosanthes spp. subjected to different levels of water availability (60%, 40%, and 20% of pot capacity). The experiment was conducted using a completely randomized design using a 3 × 2 factorial scheme, comparing the accession BGF 11-001 and the cultivar BRS-Bela (cv. Bela). Physiological traits, biochemical variables, and antioxidant enzyme activity were analyzed. The accession BGF 11-001 showed resilience under water deficit, maintaining high chlorophyll content even under severe stress. This response was associated with increased accumulation of amino acids such as proline, as well as enhanced antioxidant activity, indicating a tolerance mechanism based on osmotic adjustment and cellular protection. In contrast, cv. Bela exhibited higher sensitivity to water stress, with a pronounced reduction in photosynthetic pigments and greater accumulation of compatible solutes, including total soluble proteins, reducing sugars, amino acids, and proline, without significant activation of antioxidant enzymes. Overall, the results demonstrate that the genotypes adopt distinct strategies to cope with water stress, with BGF 11-001 being more efficient in activating defense mechanisms. Therefore, BGF 11-001 has agronomic potential for cultivation in drought-prone regions and is a promising genetic resource for forage breeding programs aimed at improving drought tolerance.