Comparative effect of sodium carbonate, sodium sulphate, and sodium chloride on the growth and related metabolic activities of pea plants

Osmotic and specific ion effects are the most frequently mentioned mechanisms by which saline substrates reduce plant growth. However, the relative importance of osmotic and specific ion effect on plant growth seems to vary depending on the salt tolerance of the plant under study. Pea plants grew in Na2SO4 and NaCl treatments up to the -1800 kPa level, but only in the Na2CO3 treatments up to the -1200 kPa level. The higher toxicity of Na2CO3 compared to that of Na2SO4 and NaCl treatments was observed. This point was made clear by their effects on fresh dry matter and water content of the pea plants. The value of osmotic pressure was markedly increased with increasing NaCl concentration in the soil and under the moderate levels of the Na2SO4 treatments, while it was significantly decreased with increasing Na2CO3 concentration. This was also related to the accumulation of soluble saccharides, proteins, amino acids, and prolines in plants treated with NaCl and in plants grown under Na2SO4, with the accumulation of soluble saccharides and proteins observed The chloride (Cl) and sulphate (SO4) contents accumulated to a greater degree for plants treated with NaCl and Na2SO4, respectively. Thus, these anion accumulations may contribute to the osmotic adjustment for the Cl- and SO4-treated plants. Therefore, the degree of salt tolerance during pea plant growth in Na2CO3, Na2SO4, or NaCl may not be always the same.