Folic acid as a protective agent in snap bean plants under water deficit conditions

Abstract

The role of folic acid (FA) or its derivatives (folates) in plant responsiveness to drought stress is still unclear. Here we investigated the effect of foliar application of FA (50, 100 and, 150 µM/l) on snap beans (Phaseolus vulgaris L.) grown under two levels of surface drip irrigation (100% and 70% of water requirements) in two successive seasons of 2018 and 2019. The results showed that deficit irrigation led to a significant decrease in plant growth, leaf relative water content (RWC) and cell membrane stability index (CMSI). These responses negatively affected green pod yield and quality indicators in terms of total soluble solids (TSS) and protein. Conversely, malondialdehyde (MDA), proline, free amino acids (FAA), total soluble sugars, antioxidant enzymes (SOD, CAT and POX) and the fibres of green pods were significantly increased. The regression analysis revealed that all investigated osmolytes and antioxidant enzymes were negatively and significantly correlated with RWC in both seasons. Under deficit irrigation, plants treated with 150 µM FA had higher water use efficiency (WUE) by 29.2% and 16.6% over the FA-untreated plants in both seasons, respectively. The foliar application of 150 µM FA significantly improved most studied traits and could be recommended as a protective agent against deficit irrigation.