Differential responses of dwarf cashew clones to salinity are associated to osmotic adjustment mechanisms and enzymatic antioxidative defense.

Nara Lídia M Alencar,Enéas Gomes-Filho,José T Prisco,Elton C Marques,Juan C Alvarez-Pizarro,Alexandre B De Oliveira

doi:10.1590/0001-3765202120180534

Abstract

This study evaluate growth, gas exchange, solute accumulation and activity of antioxidant enzymes in dwarf cashew clones subjected to salinity. Shoot dry mass reduced 26.8% (CCP06) and 41.2% (BRS189) at 16 dS m-1, concerning control. For net photosynthesis, CCP06 and BRS189 presented 69.8% and 34.7% of reduction, respectively. Na+ and Cl- contents increased in leaves and roots, in both clones, although CCP06 leaves presented Na+ concentrations lower than those of BRS189, the first one was the clone that the most accumulated such toxic ion, whereas K+ content remained almost unchanged for both clones. Soluble N-amino was the organic solute that more varied with salinity in cashew seedlings. Salt stress increased the activity of superoxide dismutase in both clones, mainly 16 dS m-1 treatment. Additionally, salinity promoted increases in ascorbate and guaiacol peroxidase activities, and the last enzyme was the main involved in H2O2 removal. Despite the reductions in growth and gas exchange, dwarf cashew seedlings of both clones presented an osmotic adjustment mechanism, and an efficient enzymatic antioxidant system that were able to attenuate the salt and oxidative stress, respectively. Our research suggested that BRS189 clone is more tolerant to salt stress than CCP06.

Highlights

In natural and agricultural conditions, plants are exposed to many stressors originated from biotic and abiotic factors (Taiz et al 2015)
We hypothesized that salinity could affect negatively growth, gas exchange, water status, osmoregulation and antioxidative enzymes of two cashew genotypes, and we investigate if these genotypes show different tolerance responses to these parameters mentioned above
Salt stress effects on shoot dry mass (SDM) and leaf area (LA) were similar in both clones, presenting evidenced damages only under higher salinity conditions (16 dS m-1). Seedlings growing in such conditions had their SDM average and LA values reduced by 26.8% and 41.2%, for CCP 06 and BRS 189, respectively, when compared to the control treatment (0 dS m-1) (Figure 1)

Summary

Introduction

In natural and agricultural conditions, plants are exposed to many stressors originated from biotic and abiotic factors (Taiz et al 2015). Among these factors, salinity is one of a major abiotic stress affecting plant growth and crop productivity, occurring specially in arid and semi-arid regions, where soil salt content is naturally high, and rainfall can be insufficient for leaching salt excess (Taiz et al 2015). In addition to water deficit, ion toxic absorption, such as Na+ and Cl-, promoting ionic toxicity, following by nutritional and metabolic imbalance (Zhu 2003, Praxedes et al 2010). The control of the absorption of toxic ions by the roots and their

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Conclusion