Proline-Induced Modifications in Morpho-Physiological, Biochemical and Yield Attributes of Pea (Pisum sativum L.) Cultivars under Salt Stress

Climate change is aggravating soil salinity, causing huge crop losses around the globe. Multiple physiological and biochemical pathways determine the ability of plants to tolerate salt stress. A pot experiment was performed to understand the impact of proline levels, i.e., 0, 10, 20 mM on growth, biochemical and yield attributes of two pea (Pisum sativum L.) cultivars (cv. L-888 and cv. Round) under salt stress (150 mM) along with control (0 mM; no stress). The pots were filled with river-washed sand; all the plants were irrigated with full-strength Hoagland's nutrient solution and grown for two weeks before application of salt stress. Foliar spray of proline was applied to 46-day-old pea plants, once a week till harvest. Data for various growth and physio-biochemical attributes were collected from 70-day-old pea plants. Imposition of salt stress significantly checked growth, gas exchange characteristics [net CO2 assimilation rate (A), transpiration rate (E), stomatal conductance (g(s))], total soluble proteins, concentration of superoxide dismutase (SOD), shoot and root K+ and Ca2+ contents, while sub-stomatal CO2 concentration (Ci), coefficient of non-photochemical quenching ((qN)), non-photochemical quenching (NPQ), concentration of catalase (CAT) and peroxidase (POD), free proline, and shoot and root Na+ contents increased substantially. Foliar application of proline significantly improved growth, yield, A, g(s), activity of POD, and shoot and root K+ and Ca2+ contents, while decreased NPQ values in both pea cultivars under stress and non-stress conditions. Moreover, both pea cultivars showed significant differences as cv. Round exhibited a higher rate of growth, yield, gas exchange, soluble proteins, CAT activity, free proline, shoot and root K+ and Ca2+ contents compared to L-888. Hence, the outcomes of this study pave the way toward the usage of proline at 20 mM, and cv. Round may be recommended for saline soil cultivation.