Calcium effects on root cell wall composition and ion contents in two soybean cultivars under salinity stress

Abstract

An, P., Li, X., Zheng, Y., Eneji, A. E. and Inanaga, S. 2014. Calcium effects on root cell wall composition and ion contents in two soybean cultivars under salinity stress. Can. J. Plant Sci. 94: 733–740. It has been widely suggested that calcium (Ca) application ameliorates salt stress, but characteristic changes in root cell wall due to Ca application under saline conditions are poorly documented. Our objectives were: (1) to determine the effect of Ca on root cell wall composition, using two soybean cultivars differing in sensitivity to salt stress and (2) to understand the relationship between the internal effects of sodium–calcium interaction on the root cell wall. Uniform seedlings were transplanted into mixed solutions of NaCl (0, 40 mM,) and CaCl2 (0, 0.5, 2 mM). Root lengths were measured after an exposure of 14, 24 and 40 h to the treatments and cell wall analysis performed for total sugars, uronic acid and ion contents. Without salinity stress, Ca application caused no significant changes in root growth and cell wall constituents in both cultivars. However, it did ameliorate the decrease in the amount of cell wall under stress, especially the pectin fraction. Both cell wall and cellular Ca2+ and K+ contents were significantly increased by additional Ca2+ under saline condition. Therefore, by applying Ca2+, the maintenance of pectin level and increase in cell wall Ca2+ may contribute to the restoration of root growth under salinity. Calcium application significantly increased the pectin level under salinity and soybean root growth also showed notable restoration. One way Ca ameliorates salt toxicity may be by maintaining the composition of the cell wall. This ameliorative effect was more conspicuous in the salt-tolerant cultivar, Dare, than the salt-sensitive cultivar, Touzan 69.