Combined foliar application of nutrients and 5-aminolevulinic acid (ALA) improved drought tolerance in Leymus chinensis by modulating its morpho-physiological characteristics

Water deficit is an environmental constraint restricting plant growth and productivity, and is further worsened by reduced soil fertility. Plant growth-regulating substances ameliorate damaging effects of abiotic stresses, and their efficacy is improved by application of adequate nutrients. An experiment was undertaken to investigate the influence of foliar-applied nutrients (nitrogen, phosphorus, potassium: NPK) and 5-aminolevulinic acid (ALA) alone and in combination on morpho-physiological indices of the perennial grass Leymus chinensis (Trin.) Tzvel under drought and well-watered conditions. Drought stress caused a reduction in growth and photosynthetic pigments while increasing the accumulation of malondialdehyde (MDA) and osmolytes compared with well-watered conditions. However, application of NPK and ALA improved plant height, fresh and dry weights, and chlorophyll content. Production of soluble proteins and sugars, proline content, and antioxidant enzyme activities (superoxide dismutase, peroxidase, catalase, ascorbate peroxidase and glutathione reductase) were increased and MDA accumulation was lowered by application of NPK and ALA relative to the control (no application). Combined application of NPK and ALA proved more advantageous than NPK or ALA alone in exerting ameliorative effect on L. chinensis under drought-stressed conditions. The results suggest that combined application of NPK and ALA improves the growth and development of L. chinensis by modulating physiological processes and aids in sustaining drought.