Accumulation and excretion of sodium, potassium and chloride from leaves of two accessions of Diplachne fusca (L.) Beauv.

summary When two accessions of brown beetle grass [ Diplachne fusca (L.) Beauv. syn. Leptochloa fusca (L.) Kunth], differing in tolerance to salinity, were exposed to NaCl over 15 d, Na concentrations were constant in the shoot. However, there were differences in shoot Na concentration between the two accessions which were manifest after 5 d exposure to 100 mol m −3 NaCl. Na and Cl concentrations in the shoot were found to be controlled within a narrow range and did not increase any further after 5 d exposure to NaCl. Leaves of differing maturity and growth rate of both accessions did not differ in their Na concentrations. Na concentrations remained stable in leaves of differing ages after the first 6 d of exposure to NaCl whereas K declined with time, possibly due to remobilization to younger leaves. Avoidance of high concentrations of Na in younger leaves by its sequestration in older tissue does not appear to be a salt‐tolerance mechanism in D. fusca. The primary mechanism of exclusion of Na and Cl from the plant is in the root, with secondary control of leaf Na and Cl concentration by excretion of excess Na and Cl through leaf salt‐glands. Total Na uptake for the relatively salt‐tolerant accession of D. fusca. M1, was similar to that for the relatively intolerant accession F3, although M1 had a lower Na concentration in its leaves than F3 after 5d exposure to NaCl. This suggests a possible mechanism for the higher tolerance of M1 to NaCl. Leaf Na concentration was significantly higher in F3 than M1, but M1 had significantly higher Na excretion rates than F3. The leaf salt‐glands of both accessions of D. fusca were found to be capable of excreting approximately 50–80 % of the Na entering the leaf.