The Response of Cowpea (Vigna unguiculata) Plants to Three Abiotic Stresses Applied with Increasing Intensity: Hypoxia, Salinity, and Water Deficit.

Jayamini Jayawardhane,Abir U. Igamberdiev,Somaieh Zafari,Juran C. Goyali

doi:10.3390/metabo12010038

Jayamini Jayawardhane, Abir U. Igamberdiev + Show 2 more

Open Access

https://doi.org/10.3390/metabo12010038

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Abstract

Exposing plants to gradually increasing stress and to abiotic shock represents two different phenomena. The knowledge on plants’ responses following gradually increasing stress is limited, as many of the studies are focused on abiotic shock responses. We aimed to investigate how cowpea (Vigna unguiculata (L.) Walp.) plants respond to three common agricultural abiotic stresses: hypoxia (applied with the increasing time of exposure to nitrogen gas), salinity (gradually increasing NaCl concentration), and water deficit (gradual decrease in water supply). We hypothesized that the cowpea plants would increase in tolerance to these three abiotic stresses when their intensities rose in a stepwise manner. Following two weeks of treatments, leaf and whole-plant fresh weights declined, soluble sugar levels in leaves decreased, and lipid peroxidation of leaves and roots and the levels of leaf electrolyte leakage increased. Polyphenol oxidase activity in both roots and leaves exhibited a marked increase as compared to catalase and peroxidase. Leaf flavonoid content decreased considerably after hypoxia, while it increased under water deficit treatment. NO emission rates after 3 h in the hypoxically treated plants were similar to the controls, while the other two treatments resulted in lower values of NO production, and these levels further decreased with time. The degree of these changes was dependent on the type of treatment, and the observed effects were more substantial in leaves than in roots. In summary, the responses of cowpea plants to abiotic stress depend on the type and the degree of stress applied and the plant organs.

Highlights

Cowpea (Vigna unguiculata (L.) Walp.) is an important legume and a key crop in the context of global climate change and food security [1]
Our study reveals how legume plants respond to a stepwise or gradual increase in three abiotic stresses—including post-hypoxia, salinity, and water deficit, which are common in agriculture—and how these stresses affect the morphology, physiology, and biochemistry of plants
When the salt stress was applied with the increased intensity, sugar production in leaves and Nitric Oxide (NO) emission rates decreased, while protein levels remained unchanged

Summary

Introduction

Cowpea (Vigna unguiculata (L.) Walp.) is an important legume and a key crop in the context of global climate change and food security [1]. Most of the studies of cowpea are focused on active breeding to combat poverty in developing countries [3] This species is used in sustainable farming for being relatively tolerant to drought, water deficit, high temperature, and high salinity, as well as having the ability to fix atmospheric nitrogen and to reduce soil erosion [1,2,4,5,6]. It represents an environmental friendly, stress-tolerant, and inexpensive source of protein in many countries, and is especially indispensable for vegetarian populations. The study of biochemical and physiological mechanisms of cowpea following abiotic shock, applied on different individuals using the same experimental setup, has been pursued by several authors, a comprehensive investigation of the morphological, physiological, and biochemical parameters of this species following the gradual or stepwise increased stress is lacking

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