Partial root-zone drying irrigation improves growth and physiology of tobacco amended with biochar by modulating phytohormonal profile and antioxidant system

Background and aimsBiochar is a porous-pyrogenic carbon that can improve crop productivity in suboptimal conditions, yet the combined effects of biochar and soil water deficit under partial root-zone drying irrigation (PRD) on plant growth and physiology remain largely elusive. This study therefore investigated the ecophysiological responses of tobacco amended with biochar to different irrigation regimes including PRD.MethodsTobacco plants were grown in split-root pots to implement PRD under Ferralsol and Anthrosol amended with wheat-straw (WSBC) and soft-wood (MWBC) biochar, and subjected to three irrigation regimes. Key parameters of plant growth and physiology were determined.ResultsCompared to plants grown under full irrigation (FI), deficit irrigation (DI) and PRD decreased leaf area (LA), leaf dry matter (LDM) and leaf relative water content (RWC) but increased leaf N content ([N]leaf); also decreased leaf photosynthetic rate, maximum rate of carboxylation by rubisco and stomatal conductance, while significantly enhanced the intrinsic water-use efficiency (20% and 45%). Compared to non-biochar, WSBC increased LA and LDM but lowered RWC and [N]leaf. DI and PRD significantly increased leaf abscisic acid ([ABA]) and zeatin riboside ([ZR]) while reduced gibberellic acid ([GA3]) and indole-3-acetic acid ([IAA]) concentrations; PRD possessed greater [ABA] and [ABA]/[GA3] but lower [GA3] and [GA3]/[ZR] than DI, which was further magnified by WSBC. Additionally, superoxide dismutase and peroxidases activities were up-regulated by WSBC especially under PRD.ConclusionCollectively, incorporating WSBC and PRD might be an effective strategy to improve water productivity by optimizing phytohormonal profile and antioxidant system thereby growth and physiology of tobacco.Highlights Partial root-zone drying irrigation (PRD) and biochar addition altered tobacco phytohormonal profile and antioxidant system. Wheat-straw biochar amplified the PRD-induced increased leaf abscisic acid and lowered gibberellic acid concentrations. Wheat-straw biochar up-regulated superoxide dismutase and peroxidases activities. Combined PRD/wheat-straw biochar application improved tobacco growth and Water-use efficiency.