A critical analysis of osmotic and ionic effects of salinity in two barley cultivars

Abstract

Salinity is an important constraint to crop productivity in many agricultural areas, especially in arid and semi-arid regions. Despite intensive research on plant physiological responses to salinity, the relative importance of ion excess and water deficit to yield reduction under field condition remains unclear. This may be further complicated in soil-grown plants where the effect of soil physical properties may interact with the soil solution to determine the soil water potential and water uptake. A factorial experiment comprising different concentrations of NaCl, CaCl2 and concentrated nutrient solution was conducted using two varieties of barley (Hordeum vulgare) in a completely randomised design with six replicates. Addition of NaCl or CaCl2 strongly inhibited plant growth by up to 60%, but there was no significant difference between the effects of NaCl and CaCl2.The concentrated nutrient solution also reduced the growth of the plants. The Na+ concentration of plant tissues increased with soil EC, but Clipper accumulated less Na+ than Sahara. Dry matter production of both cultivars declined as tissue Na+ increased with Clipper being less tolerant to high Na+ than Sahara. Photosynthesis rate declined as soil EC increased, but there was no significant difference in the responses to NaCl, CaCl2 or to concentrated nutrient solution. In conclusion, growth of the barley was reduced by salinity primarily due to an osmotic stress following by excess ionic toxicities over the time. Sahara was more tolerant to induced salinity at all levels than Clipper. Na+ exclusion did not always reflect salt tolerance. Osmotic stress is the predominant limiting factor in terms of plant growth.