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

Branched nodal roots comprise the largest portion of the root system mass i n Chloris gayana Kunth and the effects of high salinity on nodal root appea rance and elongation rates were analysed in cv. Boma in greenhouse experime nts. Roots from salt-treated plants (0.2 mol l(-1) NaCl) were smaller than controls, and accumulated higher concentrations of soluble sugars and reser ve lipids. The number of nodal roots was reduced by the saline treatment. L eaf, tiller and nodal root appearance were delayed by salinity but the corr elation among these processes was maintained, indicating that the developme ntal pattern was not altered by this level of salinity, only its rate. Init ial nodal root growth rates varied as a function of plant size and were dec reased by salinity only after 2 weeks of treatment. When shoots of non-sali nized plants were cut, a drastic reduction in nodal root appearance was obs erved. suggesting emerging leaves were stronger sinks than roots for availa ble reserves. However, when the shoots of salt-treated plants were cut. the already depressed root appearance rate was not further reduced. This sugge sts that, under salinity, alterations in root ability to metabolize reserve s could have been more significant than reserve availability for controllin g elongation.