Abstract
Comparative analyses of the responses to abiotic stress in related taxa with different degrees of tolerance can provide useful information to elucidate the mechanisms of stress tolerance in plants. This kind of study has been carried out in four Silene species, which were subjected to salt and water deficit treatments under controlled greenhouse conditions. Growth parameters and leaf levels of photosynthetic pigments, ions, osmolytes, malondialdehyde (MDA, an oxidative stress biomarker), total phenolic compounds and flavonoids, were determined in control and stressed plants. The degree of stress-induced growth inhibition allowed establishing the relative tolerance of the studied species, identifying S. vulgaris as the most tolerant to salinity and S. sclerocarpa to water deficit; these data correlated well with the characteristics of their natural habitats. All four species showed a high resistance to stress-induced leaf dehydration, and a good negative correlation was found between tolerance and the degradation of photosynthetic pigments. Salinity tolerance is mostly based on the inhibition of Na+ transport to the leaves and the maintenance of relatively high leaf K+ levels in the salt-treated plants. Proline is a reliable stress biomarker but does not appear to be involved in tolerance mechanisms in this genus, as it accumulates at higher levels in the more sensitive species. MDA contents did not increase significantly in response to the stress treatments – except in water-stressed S. latifolia, the species most affected by water deficit – suggesting that the plants were not affected by secondary oxidative stress under the experimental conditions used. Accordingly, the measured variations in the levels of total phenolic compounds and flavonoids were not statistically significant or did not correlate with the relative stress resistance of the studied species. Therefore, stress responses based on the activation of antioxidant systems do not seem to be relevant for abiotic stress tolerance in Silene.
Highlights
Soil salinity and drought are the most adverse environmental stress factors for agriculture, considering the damage they inflict on crop yields worldwide; they are important because of their impact on the distribution of wild plant species in nature
In all four investigated Silene species, salt stress had a negative effect on vegetative growth, as indicated by the concentration-dependent reduction in the fresh weight of the aerial part of salt-treated plants – in relation to the corresponding controls
NaCl; under the same conditions, biomass accumulation was reduced by 50%, approximately, in S. latifolia and S. vulgaris; the latter appears to be the most salt-tolerant taxon, with FW
Summary
Soil salinity and drought are the most adverse environmental stress factors for agriculture, considering the damage they inflict on crop yields worldwide; they are important because of their impact on the distribution of wild plant species in nature. It is well established that all plants, regardless of their tolerance to stress, activate the same series of basic, conserved reactions in response to abiotic stresses such as salinity or water deficit; these responses are based, for example, in the control of ion transport and ion homeostasis, the synthesis of specific compatible solutes for osmotic adjustment or the activation of antioxidant systems (Zhu, 2001; Flowers et al, 2010; Ariga et al, 2013) This fact justifies the use of salt and drought-sensitive species, such as Arabidopsis thaliana, as models to explore the mechanisms of response to such abiotic stresses (Sanders, 2000; Zhu, 2001; Ariga et al, 2013; Rejeb et al, 2015). No single model can provide a general view of the mechanisms of abiotic stress tolerance in plants, the elucidation of which should be based on studies performed in different species
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