Salinity and Australian Food Crops in a Changed Climate

Over-irrigation and poor drainage of the soil is a main contributor to salinity. Salt stress effects about 20% of the world’s total land-mass. It has been reported that salt stress affects 50% of the global cropland (Tavili & Biniaz, 2009). The Australian soils are subject to high levels of salinity. This is a result of historic land clearing associated with pasture and cropping land use purposes.

Taiz et al. (2015) assert that when plants are exposed to salinity, their cytosolic concentrations of Na+ and Cl ions can reach more than 100mM. This leads to cytotoxism and protein denaturation as well as the destabilization of membranes. Additionally, when accumulations of Na+ in the leaves reaches toxic levels the ability of the plant to perform photosynthesis and other biosynthetic processes can become inhibited.

The main staple food crop in all of Asia is wheat (Triticum sp.). Wheat makes up the primary staple food for 30% of the global population (MuRahman et al., 2008). Another major food crop is barley which is of the Hordeum sp.

Studies like those that were mentioned in the work of Flowers and Hajibagheri (2001) show that the concentrations of potassium ions decrease linearly as the concentrations of NaCl in a plant’s environment increase. The differences in the accumulation of different ions in the cytoplasm of plant cells greatly affect that plant’s capacity to survive and to grow. The capacity of the wheat and barley that were exposed to the higher concentrations of NaCl was clearly affected to the point where some of the seedlings were unable to emerge at all (Fig. X). The concentrations of K+ ions vary between 100-220 mol m-3 in most plants that are classed as being glycophytic and under non-saline conditions the cytosol of higher plant cells contain less than 10mM Na+ ions, favoring higher concentrations of K+ ions instead (Taiz et al., 2015).

The problems with water uptake could be compounded as NaCl causes hardening of cell walls as well as inhibiting the water conductance of the plasma membrane. Tavili and Biniaz (2009) suggested that the effects that NaCl exposure has on the cell wall membrane impact upon the water potential of the cell and thus, the cell’s osmotic potential.

Areas of further study in regards to the improved production of staple food crops, such as wheat and barley, in saline environments could focus on various relationships of salt tolerant rhizobacterium with the crop species of interest. In research by Upadhyay and Singh (2013), several strains of soil microbes were used to inoculate wheat specimens that were kept in both the greenhouse environment and in the field. It was found that the salt-tolerant plant growth-promoting rhizobacterium (ST-PGPR) improved the growth and yield of wheat exposed to saline environments. Another interesting finding that is relevant to this report was that when the Bacillus subtilis bacterium was used to inoculate the wheat, Na content in the leaves was reduced by about 23% and that specimen seemed to outgrow the control.

References

Flowers, TJ, Hajibagheri, MA (2001) Salinity tolerance in Hordeum vulgare: ion concentrations in root cells of cultivars differing in salt tolerance. Plant and Soil 231, 1-9.

 

Mujeeb-ur-Rahman, Soomro, UA, Zahoor-ul-Haq, M, Gul, S (2008) Effects of NaCl Salinity on Wheat (Triticum aestivum L.) Cultivars. World Journal of Agricultural Sciences 4, 398-403.

 

Taiz, L, Zeiger, E, Møller, IM, Murphy, AS (2015) ‘Plant physiology and development.’ (Sunderland, Massachusetts U.S.A. : Sinauer Associates, Inc:

 

Tavili, A, Biniaz, M (2009) Different Salts Effected on the Germination of Hordeum vulgare and Hordeum bulbosa. Pakistan Journal of Nutrition 8, 63-68.

 

Upadhyay, SK, Singh, DP (2014) Effect of salt-tolerant plant growth-promoting rhizobacteria on wheat plants and soil health in a saline environment. Plant Biology 17, 288-293.

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