Effects of Water Deficit and Different some Substances Foliar Sprays on Growth, Antioxidants and Biochemical Components in Loquat (Eriobotrya japonica) Seedlings

Water scarcity poses a major environmental challenge affecting plant growth and productivity, especially in arid and semi-arid regions like Egypt. This study evaluates the response of loquat (Eriobotrya japonica) seedlings to water deficit stress under three irrigation regimes [100%, 66% and 33% of full irrigation requirements (FIR)] and six foliar treatments, including tap water ( control ), ascorbic acid, salicylic acid, glutathione, potassium silicate and kaolin aiming to enhance the plant’s stress tolerance. Growth parameters (i.e., plant height and leaf area), photosynthetic pigments (chlorophyll a and b) and leaf nutrient content (N, P, K) were measured 60 days after treatment initiation. Also, biochemical analyses were conducted to assess antioxidant activity, including enzymatic antioxidants [Superoxide Dismutase, (SOD), catalase (CAT) and Ascorbate Peroxidase (APX)], non-enzymatic antioxidants (total phenol) and malondialdehyde (MDA) levels as a marker of lipid peroxidation and cellular damage. Antioxidant enzyme activities and malondialdehyde (MDA) levels were re-evaluated after two months to monitor adaptive responses to prolonged stress conditions. Preliminary results indicate that reducing irrigation levels to 66% and 33% of FIR notably decreased vegetative growth, while specific foliar treatments mitigated oxidative stress damage by enhancing antioxidant activity, with glutathione being the most effective followed by potassium silicate, ascorbic acid, salicylic acid and letely kaolin. Overall, the findings demonstrate the potential of targeted foliar treatments to improve drought tolerance in loquat seedlings, offering valuable insights for sustainable crop management in water-limited environment conditions.