Managing the pools of cellular redox buffers and the control of oxidative stress during the ontogeny of drought-exposed mungbean (Vigna radiata L.)â€”role of sulfur nutrition

Naser A Anjum,Muhammad Iqbal,Ibrahim M Aref,Shahid Umar

doi:10.3389/fenvs.2014.00066

Naser A Anjum, Muhammad Iqbal + Show 2 more

Open Access

https://doi.org/10.3389/fenvs.2014.00066

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Abstract

Impacts of increasing environmental stresses (such as drought) on crop productivity can be sustainably minimized by optimizing mineral nutrients (such as sulfur, S). This study, based on a pot-culture experiment conducted in greenhouse condition, investigates S-mediated influence of drought stress (imposed at pre-flowering, flowering and pod-filling stages) on growth, photosynthesis and tolerance of mungbean (Vigna radiata L.) plants. Drought stress alone hampered photosynthesis functions, enhanced oxidative stress [measured in terms of H2O2; lipid peroxidation (LPO); electrolyte leakage (EL)] and decreased the pools of cellular redox buffers (namely ascorbate (AsA); glutathione (GSH)], and the overall plant growth (measured as leaf area and plant dry mass), maximally at flowering stage, followed by pre-flowering and pod-filling stages. Contrarily, S-supplementation to drought-affected plants (particularly at flowering stage) improved the growth- and photosynthesis-related parameters considerably. This may be ascribed to S-induced enhancements in the pools of reduced AsA and GSH, which jointly manage the balance between the production and scavenging of H2O2 and stabilize cell membrane by decreasing LPO and EL. It is inferred that alleviation of drought-caused oxidative stress depends largely on the status of AsA and GSH via S-application to drought-stressed V. radiata at an appropriate stage of plant growth, when this nutrient is maximally or efficiently utilized.

Highlights

Recognized as one of the major environmental stress factors, and as a main constraint for crop production worldwide, drought affects virtually every aspect of plant growth, physiology and metabolism (Harb et al, 2010)
Drought stress imposed during pre-flowering stage caused significant decrease in photosynthetic functions, as compared with the control
During the pod-filling stage, leaf area and plant dry mass decreased significantly due to imposition of drought stress and S application deepened the decline in leaf area and plant dry mass

Summary

Introduction

Recognized as one of the major environmental stress factors, and as a main constraint for crop production worldwide, drought affects virtually every aspect of plant growth, physiology and metabolism (Harb et al, 2010). At the wholeplant level, drought stress affects mainly the plant photosynthetic functions, causing imbalance in “CO2 fixation and electron transport.” This facilitates transfer of electrons to reactive oxygen species (ROS), including H2O2, as a result of over-reduction of the electron-transport-chain components (Anjum et al, 2008a; Lawlor and Tezara, 2009). The ascorbate-glutathione (AsA-GSH) pathway constitutes the major part of antioxidant defense system in plants where a number of ROS are effectively metabolized and/or detoxified by a network of reactions involving enzymes and metabolites with redox properties. Both AsA and GSH (tripeptide GSH; γ-glutamate-cysteine-glycine) are cellular redox buffers closely linked in major physiological functions. Exogenous application of AsA or GSH was reported to help plants to withstand consequences caused by a range of abiotic stresses including Cd (Cai et al, 2011; Son et al, 2014), salinity (Wang et al, 2014) and high temperature (Nahar et al, 2015)

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