Characterization of the effect of high salinity on roots of Chloris gayana Kunth: carbohydrate and lipid accumulation and growth

Branched nodal roots comprise the largest portion of the root system mass in Chloris gayana Kunth and the effects of high salinity on nodal root appearance and elongation rates were analysed in cv. Boma in greenhouse experiments. Roots from salt-treated plants (0·2 mol l^–1 NaCl) were smaller than controls, and accumulated higher concentrations of soluble sugars and reserve lipids. The number of nodal roots was reduced by the saline treatment. Leaf, tiller and nodal root appearance were delayed by salinity but the correlation among these processes was maintained, indicating that the developmental pattern was not altered by this level of salinity, only its rate. Initial nodal root growth rates varied as a function of plant size and were decreased by salinity only after 2 weeks of treatment. When shoots of non-salinized plants were cut, a drastic reduction in nodal root appearance was observed, suggesting emerging leaves were stronger sinks than roots for available reserves. However, when the shoots of salt-treated plants were cut, the already depressed root appearance rate was not further reduced. This suggests that, under salinity, alterations in root ability to metabolize reserves could have been more significant than reserve availability for controlling elongation.