Abstract
A greenhouse hydroponic experiment was performed using salt-tolerant (cv. Suntop) and -sensitive (Sunmate) wheat cultivars and a salt-tolerant barley cv. CM72 to evaluate how cultivar and species differ in response to salinity stress. Results showed that wheat cv. Suntop performed high tolerance to salinity, being similar tolerance to salinity with CM72, compared with cv. Sunmate. Similar to CM72, Suntop recorded less salinity induced increase in malondialdehyde (MDA) accumulation and less reduction in plant height, net photosynthetic rate (Pn), chlorophyll content, and biomass than in sensitive wheat cv. Sunmate. Significant time-course and cultivar-dependent changes were observed in the activities of antioxidant enzymes such as superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), ascorbate peroxidase (APX), and glutathione reductase (GR) in roots and leaves after salinity treatment. Higher activities were found in CM72 and Suntop compared to Sunmate. Furthermore, a clear modification was observed in leaf and root ultrastructure after NaCl treatment with more obvious changes in the sensitive wheat cv. Sunmate, rather than in CM72 and Suntop. Although differences were observed between CM72 and Suntop in the growth and biochemical traits assessed and modified by salt stress, the differences were negligible in comparison with the general response to the salt stress of sensitive wheat cv. Sunmate. In addition, salinity stress induced an increase in the Na+ and Na+/K+ ratio but a reduction in K+ concentrations, most prominently in Sunmate and followed by Suntop and CM72.
Highlights
Salt inhibited the growth of the barley and wheat plants, with the treated plants showing wilting, necrosis and chlorosis (Figure 1A)
In comparison to the other two cultivars, the effects of salt stress on plant growth was much more noticeable in Sunmate; it had the least effect on shoot height and the biggest effect on shoot weight
The fresh shoot weight was reduced by 68%, 55%, and 59%, while shoot dry weight was reduced 68%, 53%, and 49% in Sunmate, Suntop and CM72 in salinity stress plants respectively
Summary
Saline soils are a major problem in many countries with the Environment Program of UnitedNations estimating that of the 9–34% of the world’s irrigated land is adversely affected by salinity [1].Salinity can kill plants and other soil organisms and is referred to as a “silent killer” in some regions or as “white death” in others as it invokes images of a lifeless, shining land studded with dead trees.Approximately 32 million ha of dry lands [2] and 60 million ha of irrigated land [3] are affected by human-induced soil salinization, and it is well documented that salinity is one of the most severeAgronomy 2020, 10, 127; doi:10.3390/agronomy10010127 www.mdpi.com/journal/agronomyAgronomy 2020, 10, 127 environmental stresses hampering crop production [4,5]. Saline soils are a major problem in many countries with the Environment Program of United. Nations estimating that of the 9–34% of the world’s irrigated land is adversely affected by salinity [1]. Salinity can kill plants and other soil organisms and is referred to as a “silent killer” in some regions or as “white death” in others as it invokes images of a lifeless, shining land studded with dead trees. Saline soils limit plant growth due to osmotic stress, ionic toxicity, and a reduced ability to take up essential minerals [9,10]. Water deficits affect a cascade of physical, signaling, gene expression, biochemical, and physiological pathways and processes, resulting in decreased cell elongation, wilting, and, plant death; these harmful effects of salinity can be considered as water-deficit effects [3,11,12]. NaCl comprises 50–80% of the total soluble salts [13]
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