Superabsorbent Polymer Reduces β-ODAP Content in Grass Pea by Improving Soil Water Status and Plant Drought Tolerance

Purpose Grass pea ( Lathyrus sativus L.) has significant nutritional value and broad-spectrum resistance properties. However, the neurotoxin β-N-oxalyl-L-α, β-diaminopropionic acid (β-ODAP) in its seeds increases exponentially during drought stress, and overconsumption can lead to neurogenic hypoparalysis. Superabsorbent polymer (SAP) has the potential to improve soil physicochemical properties and alleviate plant drought stress, but the effects of different SAP concentrations on soil water availability, physiological traits, and β-ODAP content of grass pea under drought conditions are unclear. The objective of this study was to elucidate the impact of SAP on the physiological and biochemical characteristics, as well as the β-ODAP content, of grass pea under drought conditions. Methods We conducted potting experiments of natural drought with L. sativus cv. Wugong Yongshou (WGYS), L. sativus cv. Jingbian (JB), L. sativus cv. Aksu (AKS), and cultivated grass pea (ZP) materials with different SAP ratios (0.00%, 0.25%, 0.50%, 0.75%, 1.00%). Results The research confirmed that the addition of 0.50% SAP had a positive effect on soil physicochemical properties and growth parameters of grass pea, including plant height, leaf area, leaf water potential, seed yield, and straw yield per plant; Following an eight-day cessation of irrigation, the transpiration rate (E), stomatal conductance (GH 2 O), intercellular CO 2 concentration (Ci), and net photosynthetic rate (A) of the four grass pea leaves exhibited a notable optimization in comparison to the control without SAP; The levels of superoxide dismutase (SOD), catalase (CAT), peroxidase (POD), malondialdehyde (MDA), and β-ODAP (leaves, seeds, and straw) of four grass pea plants treated with 0.50% SAP were significantly decreased. Conclusion SAP can improve soil water-holding capacity, leaf photosynthesis to alleviate oxidative damage caused by drought stress in grass pea, reduce β-ODAP content, and promote low-toxicity and high-yield planting.