24-epibrassinolide enhances drought adaptation in physiological level but lowers β-ODAP levels in grass pea (Lathyrus sativus L.) seedlings

摘要

During 1960s, a toxin β-N-oxalyl-L-αt, β-diamino propionic acid (β-ODAP), a non-protein amino acid, was reported in the seeds and other organs of grass pea (Lathyrus sativus L.).This amino acid has been reported to be a critical physiological indicator associated with drought tolerance in grass pea.Low-or zero-toxin grass pea cultivars have been developed, but whether this has affected their drought tolerance is unknown.We conducted an experiment using the exogenous application of 24-epibrassinolide (EBL), a phytohormone known to reduce β-ODAP to determine whether β-ODAP acts as an indicator of drought tolerance in grass pea.Twelve combinations of treatments were imposed, including four watering regimes: 1) sufficient water supply (CK, 80％ field capacity, FC), 2) mild drought stress (MS, 50％ FC), 3) moderate drought stress (MOS, 40％ FC), and 4) severe drought stress (SS, 30％ FC), and three exogenous hormone application methods: (i) seed priming (sp), (ii) foliar application (fa), and (iii) foliar application + seed priming (sf).The results showed that sf with EBL significantly increased the leaf proline content by up to 60％ and enhanced the activity of some key antioxidant enzymes: the activity of SOD increased by 68％ and CAT by 239％, but markedly lowered the concentration of β-ODAP in the leaves of grass pea under SS.Furthermore, EBL treatment promoted the growth on plant height and leaf area of grass pea seedlings under MS, MOS and SS, and increased the grass pea seedling survival days by 2 days and decreased the soil water content at which permament wilting occurred by 2％.Our results suggest that sf with EBL could improve the drought tolerance in physiology level but lower the β-ODAP content in grass pea seedling.β-ODAP is not directly linked to improved drought tolerance and probably a defense metabolite in grass pea.