Regulation on Antioxidant Defense System in Rice Seedlings (Oryza sativa L. ssp. indica cv. ‘Pathumthani 1’) Under Salt Stress by Paclobutrazol Foliar Application

Bundit Khunpon,Kobkiat Saengnil,Jamnong Uthaibutra,Bualuang Faiyue,Suriyan Cha-Um

doi:10.15835/nbha47111282

Abstract

The present study investigated the effect of paclobutrazol (PBZ) foliar application on oxidative metabolism in salt-stressed rice (Oryza sativa L. cv. ‘Pathumthani 1’; PTT1) seedlings. Fourteen-days-old rice seedlings, grown in the pots were pretreated with 15 mg L-1 paclobutrazol supplied as foliar spray. One week after pretreatment, the rice seedlings were exposed to salt stress (150 mM NaCl) for 12 days. It was observed that salinity enhanced the production of reactive oxygen species (ROS), including superoxide radical (O2•−), hydrogen peroxide (H2O2) and hydroxyl radical (OH·). It also increased reactive oxygen species-associated oxidative damage, measured in terms of lipoxygenase activity, conjugated dienes, malondialdehyde content and relative electrolyte leakage. Increase in these parameters was associated with the decrease in the activity of enzymatic antioxidants [superoxide dismutase (SOD), ascorbate peroxidase (APX) and catalase (CAT)] and the levels of non-enzymatic antioxidants [ascorbic acid (AsA), total glutathione and α-tocopherol contents). Pretreatment of seedlings with paclobutrazol significantly lowered reactive oxygen species accumulation and membrane damage (p < 0.05), which can be correlated with the increased antioxidant activity (both enzymatic and non-enzymatic traits) under salt stress. The study concluded that paclobutrazol-treatment up-regulates the antioxidant defense system and recuperates the salt-induced oxidative damage in ‘Pathumthani 1’ rice seedlings under salt stress.

Highlights

Salinity is the major problem in agriculture that limits the plant development and crop productivity
Lipid peroxidation alters membrane properties, thereby causing cell defects such as ion leakage, cellular decompartmentalization and dysfunction (Sharma et al, 2012).To alleviate the oxidative damage induced by reactive oxygen species (ROS), plants have evolved antioxidant defense system, including enzymatic antioxidants such as superoxide dismutase (SOD), ascorbate peroxidase (APX), catalase (CAT), glutathione peroxidase (GPX), peroxidase (POX), monodehydroascorbate reductase (MDHAR), glutathione reductase (GR) and dehydroascorbate reductase
Reactive oxygen species content The ROS levels in leaves and roots of salt-stressed rice seedlings continuously increased during the experimental period as compared to the control plants (Fig. 1)

Summary

Introduction

Salinity is the major problem in agriculture that limits the plant development and crop productivity. It induces the production of free radicals especially reactive oxygen species (ROS) (Puyang et al, 2015; Chakraborty et al, 2016). ROS such as superoxide radical (O2−), hydrogen peroxide (H2O2), hydroxyl radical (OH) and singlet oxygen (1O2) are the most prevalent free radicals in plants under salt stress (Puyang et al, 2015; Chakraborty et al, 2016). Received in revised form: 07 Oct 2018.

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Results

Conclusion