Silicon mitigates aluminum toxicity in lettuce by improving photosynthetic pigments and antioxidant defense system.

Abstract

Lettuce is economically an important leaf vegetable. Its production under acidic soils is low due to excessive aluminum (Al). Silicon (Si) supplementation is an effective approach to enhance stress tolerance in vegetables under acidic soil conditions. The present work aimed to explore the significance of Si application on lettuce plants under Al toxicity by modulation of morpho-physiological and biochemical indices. The current work comprises four treatments Al, Si, and a combination of Al + Si along with control. Al toxicity reduced lettuce growth and yield characteristics i.e., plant height, number of leaves, plant fresh biomass, plant dry biomass, rosette diameter, root fresh weight, root dry weight, SPAD index in comparison to normal plants (control). However, Si enhanced plant height, number of leaves, plant fresh biomass, plant dry biomass, rosette diameter, root fresh weight, root dry weight, SPAD index. The combination of Si + Al partially improved all the studied growth and yield traits. Al toxicity declines chlorophyll a, chlorophyll b, and carotenoids, while enhancing hydrogen peroxide (H₂O₂), malonaldehyde (MDA), superoxide dismutase (SOD), and catalase (CAT). Si improved chlorophyll a, chlorophyll b, carotenoids, SOD, and CAT, while Si declined H₂O₂ and MDA. The combination of Si + Al restored photosynthetic pigments and boosted the antioxidant defense system by decreasing oxidative stress markers. Al lessened photosynthesis, transpiration rate, and stomatal conductance, while Si enhanced these traits. Leaf gas exchange traits maintained under Si + Al. Hence, Si is considered a promising approach for the mitigation of Al toxicity in lettuce by modulation of morpho-physiological and biochemical insights, focusing on sustainable production.