Alleviation of Osmotic Stress Effects by Exogenous Application of Salicylic or Abscisic Acid on Wheat Seedlings

Izabela Marcińska,Kinga Dziurka,Michał Dziurka,Katarzyna Cyganek,Katarzyna Juzoń,Maria Filek,Edyta Skrzypek,Piotr Waligórski,Maciej Grzesiak,Ilona Czyczyło-Mysza,Franciszek Janowiak,Stanisław Grzesiak

doi:10.3390/ijms140713171

Abstract

The aim of the study was to assess the role of salicylic acid (SA) and abscisic acid (ABA) in osmotic stress tolerance of wheat seedlings. This was accomplished by determining the impact of the acids applied exogenously on seedlings grown under osmotic stress in hydroponics. The investigation was unique in its comprehensiveness, examining changes under osmotic stress and other conditions, and testing a number of parameters simultaneously. In both drought susceptible (SQ1) and drought resistant (CS) wheat cultivars, significant physiological and biochemical changes were observed upon the addition of SA (0.05 mM) or ABA (0.1 μM) to solutions containing half-strength Hoagland medium and PEG 6000 (−0.75 MPa). The most noticeable result of supplementing SA or ABA to the medium (PEG + SA and PEG + ABA) was a decrease in the length of leaves and roots in both cultivars. While PEG treatment reduced gas exchange parameters, chlorophyll content in CS, and osmotic potential, and conversely, increased lipid peroxidation, soluble carbohydrates in SQ1, proline content in both cultivars and total antioxidants activity in SQ1, PEG + SA or PEG + ABA did not change the values of these parameters. Furthermore, PEG caused a two-fold increase of endogenous ABA content in SQ1 and a four-fold increase in CS. PEG + ABA increased endogenous ABA only in SQ1, whereas PEG + SA caused a greater increase of ABA content in both cultivars compared to PEG. In PEG-treated plants growing until the harvest, a greater decrease of yield components was observed in SQ1 than in CS. PEG + SA, and particularly PEG + ABA, caused a greater increase of these yield parameters in CS compared to SQ1. In conclusion, SA and ABA ameliorate, particularly in the tolerant wheat cultivar, the harmful effects and after effects of osmotic stress induced by PEG in hydroponics through better osmotic adjustment achieved by an increase in proline and carbohydrate content as well as by an increase in antioxidant activity.

Highlights

Wheat is one of the crops that are exposed to many environmental stresses, limiting their yield.These stresses may be of a biotic or abiotic nature
The concentration of 0.05 mM salicylic acid (SA) or 0.1 μM abscisic acid (ABA) in solution containing half-strength Hoagland medium and PEG 6000 caused a number of physiological changes in the examined wheat cultivars, among others: in water relations, gas exchange, chlorophyll content, morphological traits and
Exposure of seedlings of two wheat cultivars to osmotic stress induced by PEG in hydroponic culture resulted in a greater decrease of gas exchange parameters for resistant CS than for susceptible

Summary

Introduction

Wheat is one of the crops that are exposed to many environmental stresses, limiting their yield.These stresses may be of a biotic or abiotic nature. After being subjected to environmental stresses, plants activate a range of defensive mechanisms which cause, for example, changes in gas exchange [1,2,3,4] or accumulation of low molecular osmoprotectants, like carbohydrates, proline or polyamines [5,6,7]. These mechanisms may be induced or enhanced by the application of chemicals to the plants. SA pretreatment initially caused formation of reactive oxygen species (ROS) and decreased net photosynthetic rate and stomatal conductance, but prevented

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Conclusion