A water-absorbent hydrogel prepared with arabinoxylans from flaxseed (Linum usitatissimum) and galactomannans from subabul (Leucaena leucocephala) impacts the growth and composition of cherry tomatoes in potted experiments

Abstract

A water-absorbent hybrid hydrogel was prepared using arabinoxylans from flaxseed (Linum usitatissimum) (FX) and galactomannans from subabul (Leucaena leucocephala) (SG) in the presence of kappa-carrageenan (κC) with variable concentration of potassium chloride as crosslinker (0.01, 0.05, 0.1, 0.25 and 0.3 M), and evaluated on the basis of their swelling rate (%). The optimized hydrogel (GAXH) from a blend of SG, κC, FX and KCl at 5.5% w/v, 1.32% w/v, 1% w/v and 0.3M, respectively, showed 300% swelling in water at room temperature and pH 7.4 with 100% retention of water for 30 days at 10 °C. Blending 50% w/w GAXH in the soil could retain 140% water for 30 days, acting as a water reservoir in the soil system at 35 °C and pH 7.4 which reached 100% evaporation after 60 days. Incorporation of 50% w/w GAXH in sandy, loamy soil was used for the potted cultivation of cherry tomatoes (Solanum lycopersicum var. cerasiforme) and observed for growth and composition of the tomatoes. GAXH enhanced the physiological growth of both the plant as well as cherry tomatoes by controlling the release of KCl into the soil and maintaining soil moisture when 3 day intermittent watering schedule was used. An additional advantage was an improved water use efficiency and reduction in water footprint from 3.23 cm3/g to 9.32 cm3/g and 19.87 mL/fruit to 8.56 mL/fruit, respectively. The fully ripened tomatoes grown on GAXH-incorporated soil showed higher contents of lycopene, total carotenoids, and total polyphenols from 166 to 257 μg/g fresh weight, 99–107 mg β-carotene equivalent/100g fresh weight, 223–241 mg gallic acid equivalent/100 g fresh weight, respectively, than control cherry tomatoes grown in soil with no added GAXH. This was also reflected in enhanced antioxidant activity of cherry tomatoes grown in GAXH-incorporated soil.