Responses to Water Deficit and Salt Stress in Silver Fir (Abies alba Mill.) Seedlings

Irina Maria Todea (Morar),Oscar Vicente,Monica Boscaiu,Sara González-Orenga,Jaime Prohens,Adriana F Sestras,Radu E Sestras,Mariola Plazas

doi:10.3390/f11040395

Irina Maria Todea (Morar), Oscar Vicente + Show 6 more

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https://doi.org/10.3390/f11040395

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Abstract

Forest ecosystems are frequently exposed to abiotic stress, which adversely affects their growth, resistance and survival. For silver fir (Abies alba), the physiological and biochemical responses to water and salt stress have not been extensively studied. Responses of one-year-old seedlings to a 30-day water stress (withholding irrigation) or salt stress (100, 200 and 300 mM NaCl) treatments were analysed by determining stress-induced changes in growth parameters and different biochemical markers: accumulation of ions, different osmolytes and malondialdehyde (MDA, an oxidative stress biomarker), in the seedlings, and activation of enzymatic and non-enzymatic antioxidant systems. Both salt and water stress caused growth inhibition. The results obtained indicated that the most relevant responses to drought are based on the accumulation of soluble carbohydrates as osmolytes/osmoprotectants. Responses to high salinity, on the other hand, include the active transport of Na+, Cl− and Ca2+ to the needles, the maintenance of relatively high K+/Na+ ratios and the accumulation of proline and soluble sugars for osmotic balance. Interestingly, relatively high Na+ concentrations were measured in the needles of A. alba seedlings at low external salinity, suggesting that Na+ can contribute to osmotic adjustment as a ‘cheap’ osmoticum, and its accumulation may represent a constitutive mechanism of defence against stress. These responses appear to be efficient enough to avoid the generation of high levels of oxidative stress, in agreement with the small increase in MDA contents and the relatively weak activation of the tested antioxidant systems.

Highlights

Drought and soil salinity are considered the most adverse and critical environmental factors for plants, causing massive losses in agricultural production worldwide and, at the same time, substantially affecting the distribution of wild species in nature [1,2]
300 mM NaCl than in the control pots, confirming the high correlation between EC and the concentration of the saline solutions used in the salt treatments
The experiments performed in the present study showed a significant increase in total soluble sugars (TSS) levels under water deficit and salt stress conditions, suggesting the participation of these osmolytes in the responses of silver fir seedlings to both drought and salinity

Summary

Introduction

Drought and soil salinity are considered the most adverse and critical environmental factors for plants, causing massive losses in agricultural production worldwide and, at the same time, substantially affecting the distribution of wild species in nature [1,2]. Plants can perceive abiotic stresses, such as water deficit and salt stress, and activate appropriate physiological, biochemical and molecular responses, with altered metabolism, growth. Forests 2020, 11, 395 and development [7] The study of these responses and the mechanisms of tolerance to drought and salinity is currently one of the major topics of research in plant biology. Silver fir (A. alba Mill.) is an economically and ecologically important forest tree species, especially in lower-mountain forests. This species covers the main mountain areas in central and southern

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