Relationship of Salinity Tolerance to Na+ Exclusion, Proline Accumulation, and Antioxidant Enzyme Activity in Rice Seedlings

Maha Abdelaziz,Tran Xuan,Tran Khanh,Ahmad Mekawy,Hongliang Wang

doi:10.3390/agriculture8110166

Maha Abdelaziz, Tran Xuan + Show 3 more

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https://doi.org/10.3390/agriculture8110166

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Abstract

Rice is a staple crop for over 50% of the world’s population, but its sensitivity to salinity poses a threat to meeting the worldwide demand. This study investigated the correlation of salinity tolerance to Na+ exclusion, proline accumulation, and the activity of antioxidant enzymes in some rice cultivars originating from Egypt. Giza 182 was shown to be the most tolerant of the five cultivars, as judged by visual symptoms of salt injury, growth parameters, and patterns of Na+ accumulation, while Sakha 105 appeared to be highly susceptible. In detail, Giza 182 accumulated the lowest Na+ concentration and maintained a much lower Na+/K+ ratio in all plant organs in comparison to Sakha 105. The salinity-tolerant varieties had higher accumulation of proline than the salinity-susceptible cultivars. The salinity-tolerant Giza 182 accumulated a higher concentration of proline, but the lipid peroxidation (MDA) level was significantly reduced compared to in the salinity-susceptible Sakha 105. In addition, Giza 182 had stronger activity of both catalase (CAT) and ascorbate peroxidase (APX) compared to Sakha 105. The findings of this study reveal that the salinity tolerance in rice is primarily attributable to Na+ exclusion, the accumulation of proline in rice organs, a low Na+/K+ ratio, and a low level of lipid peroxidation. The levels of the antioxidant enzymes CAT and APX and the accumulation of proline may play important roles in salinity tolerance in rice. However, the comparative involvement of individual antioxidant enzymes in salinity stress in rice should be further investigated. Giza 182 has the potential to be cultivated in salinity-affected areas, although the effects of salinity stress on its grain yield and quality should be evaluated during the full crop cycle.

Highlights

Climate change causes alterations to the surrounding environment and markedly imposes soil salinization
Giza 182 has the potential to be cultivated in salinity-affected areas, the effects of salinity stress on its grain yield and quality should be evaluated during the full crop cycle
Out of the five screened rice varieties, Giza 182 and Sakha 105 were selected as the salinityOut of the five screened rice varieties, Giza 182 and Sakha 105 were selected as the salinity-tolerant tolerant and salinity-susceptible cultivars, respectively, based on the standard evaluation system and salinity-susceptible cultivars, respectively, based on the standard evaluation system (SES)

Summary

Introduction

Climate change causes alterations to the surrounding environment and markedly imposes soil salinization. The osmotic stress due to the higher Na+ concentration causes dehydration that impairs crop growth. The ionic stress from the accumulation of a high Na+ concentration in plant cells, which may cause K+ deficiency, disrupts cellular ion homeostasis [3]. Plants synthesize proline, which acts as an osmolyte to preserve the cell osmoticum, protecting cells from dehydration [3,4]. Proline is an active solute which regulates the osmotic adjustment of cells and protects enzymes, proteins, membranes, and cellular structures in water deficient conditions, conferring stress tolerance [5]. To adapt to ionic stress, Na+ is excluded from cells, and excess cytosolic Na+ is transferred into the vacuoles or recirculated and partitioned to different plant organs through the activity of Na+ transporters and/or channels. The maintenance of the appropriate K+ /Na+ ratio for a certain species is imperative for plant adaptation and growth under conditions of salinity stress [3,7]

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