Polyamines are new plant growth regulators and intracellular messengers that regulate plant growth, development, and responses to abiotic environmental stresses. However, little is known about the impact of different polyamines on physiological and biochemical processes of field-grown plants exposed to water deficit stress. A two-year field experiment was conducted as a split-plot based on a randomized complete block design with four replications. Water treatments (Irrigation after 70 and 170 mm evaporation from class A evaporation pan) were assigned to main plots, and foliar application of polyamines including Putrescine, Spermidine and Spermine (at 0 and 0.1 mM) was apportioned to subplots. Average of two years results showed that compared with control, water stress significantly (P < 0.05) reduced adenosine three phosphate (ATP), chlorophyll content index (CCI) and chlorophyll stability index (CSI), rubisco activity, efficiency of photosystem II (Fv/Fm), endogenous polyamine contents, membrane stability index (MSI), nitrogen (N2), potassium (K+), calcium (Ca2+), magnesium (Mg2+), and grain yield, while polyamine oxidase activity, antioxidant enzymes activity, reactive oxygen species (ROS) and lipid peroxidation (MDA) increased significantly (P < 0.05) upon exposure to water deficit stress. However, exogenous application of polyamines improved ATP content, CCI, CSI, rubisco activity, Fv/Fm, endogenous polyamine content, MSI, antioxidant enzymes activity, N2, K+, Ca2+, Mg2+, and grain yield, while decreased ROS level and MDA content. Compared with the other polyamines, Putrescine showed better effects on physiological, biochemical and agronomical performance in mung bean plants under both irrigation treatments.
