Phytohormones Promote the Growth, Pigment Biosynthesis and Productivity of Green Gram [Vigna radiata (L.) R. Wilczek]

Abstract

Globally, optimized doses of exogenously applied growth regulators hold the potential to sustainably boost the growth and productivity of leguminous crops, including green gram. A field investigation was undertaken at the Agronomy Farm of the University of Agriculture Faisalabad, Pakistan in 2021–2022 to determine the highest-performing doses of foliar-applied salicylic acid (S1 = 0 and S2 = 75 ppm) and gibberellic acid (G1 = 0, G2 = 30, G3 = 60, G4 = 90 and G5 = 120 ppm) for green gram (cv. NIAB-MUNG 2011) sown under irrigated conditions in a semiarid climate. The response variables included physiological growth traits (CGR and net assimilation rate (NAR)), yield attributes (plant height (PH), PBs and the number of pods per plant−1 (NP), pod length (PL) and SW, grain (GY) and biological yields (BY), the biosynthesis of pigments (chlorophyll a, chlorophyll b and total chlorophyll along with carotenoids) and protein (P) contents. The results revealed that S2G5 remained unmatched in that it exhibited the highest crop growth rate, while it remained on par with S2G4 and S2G3 in terms of its net assimilation rate. Additionally, S2G5 maximized plant height, the number of pod-bearing branches and pods per plant, pod length, seed number per pod−1 and 1000-seed weight, which led to the highest grain yield and biological yield (104% and 69% greater than those of the control, respectively). Moreover, the same treatment combination also surpassed the rest of the treatments because it recorded the largest amounts of chlorophyll and carotenoid contents, and the P content was increased to 24% greater than that observed for the control treatment. Thus, the exogenous application of salicylic acid (75 ppm) and gibberellic acid (120 ppm) might be recommended to green gram growers to sustainably increase the plant’s yield and nutritional value, and these findings may serve as a baseline for conducting more studies to test higher doses of these growth regulators.