Separating multiple, short-term, deleterious effects of saline solutions on the growth of cowpea seedlings
2011
Kopittke, Peter M. | Blamey, F. Pax C. | Kinraide, Thomas B. | Wang, Peng | Reichman, Suzie M. | Menzies, Neal W.
• Reductions in plant growth as a result of salinity are of global importance in natural and agricultural landscapes. • Short-term (48-h) solution culture experiments studied 404 treatments with seedlings of cowpea (Vigna unguiculata cv Caloona) to examine the multiple deleterious effects of calcium (Ca), magnesium (Mg), sodium (Na) or potassium (K). • Growth was poorly related to the ion activities in the bulk solution, but was closely related to the calculated activities at the outer surface of the plasma membrane, {Iz}₀ o. The addition of Mg, Na or K may induce Ca deficiency in roots by driving {Ca²⁺}₀ o to < 1.6 mM. Shoots were more sensitive than roots to osmolarity. Specific ion toxicities reduced root elongation in the order Ca²⁺ > Mg²⁺ > Na⁺ > K⁺. The addition of K and, to a lesser extent, Ca alleviated the toxic effects of Na. Thus, Ca is essential but may also be intoxicating or ameliorative. • The data demonstrate that the short-term growth of cowpea seedlings in saline solutions may be limited by Ca deficiency, osmotic effects and specific ion toxicities, and K and Ca alleviate Na toxicity. A multiple regression model related root growth to osmolarity and {Iz}₀ o (R² = 0.924), allowing the quantification of their effects.
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