PJB-2018-1045
OSMOTIC ADJUSTMENT IN ROOTS AND LEAVES OF TWO COTTON CULTIVARS WITH DIFFEREING TOLERANCE TO SOIL SALINITY
TINGTING CHEN
Abstract
We aimed to assess the accumulation of organic and inorganic solutes and their relative contribution to osmotic adjustment (OA) in the roots and leaves of cotton (Gosspium hirsutum L.) subjected to heterogeneous salinity conditions. We grew two cotton cultivars, salt-sensitive ‘Simian 3’ and salt-tolerant ‘CCRI-79’, in low-, medium-, and high-salinity conditions. All conditions were subjected to three replications. We measured dry weight of leaves and roots, as well as fluctuations in organic and inorganic solute content across all treatments. Soil salinity reduced the biomass in cotton leaves and roots, especially in ‘Simian 3’. Increasing soil salinity increased Na+ and Cl- in leaves and roots of both cultivars. Soil salinity reduced K+, Ca2+, and Mg2+ contents in the leaves in both cultivars, but root Ca2+ and Mg2+ contents in ‘CCRI-79’ remained stable, while root K+, Ca2+, and Mg2+ contents decreased in ‘Simian 3’. Moreover, the osmotic potentials (ψs) of leaves and roots were lower in ‘Simian 3’ than in ‘CCRI-79’, mostly due to the higher accumulation of Na+ and Cl- in the former cultivar. Under low salinity, K+ contributed the most among inorganic solutes to ψs, but its contribution decreased as soil salinity increased, especially in ‘Simian 3’. Amino acids were the largest contributors among organic solutes to root and leaf ψs, but no differences in amino acid contribution were observed between two cultivars. The major contributors to OA in cotton leaves and roots were Na+ and Cl-, which enable ‘CCRI-79’ to maintain a more suitable OA under heterogeneous salinity than ‘Simian 3’. This study suggests that OA could be a mechanism developed by cotton to overcome fluctuating salinity conditions, and this strategy could be exploited in breeding programs for improved salt tolerance.
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