Sodium concentration in xylem sap in relation to ion exclusion, accumulation and secretion in halophytes
Acta botanica neerlandica , Volume 30 - Issue 4 p. 309- 311
Salt secretion, salt accumulation and transpiration were simultaneously measured in salt-secreting and non-salt-secreting halophytes and glycophytes. The sodium content of the xylem sap was calculated. It is concluded that salt-secreting halophytes differ considerably in their sodium secretion rates, but less in their sodium exclusion capacity. Salt-sensitivity of the non-secreting species was related to a comparatively high sodium xylem content (15.1 mM Na). Transpiration rates are remarkably similar for all species. It is argued that the distinction between salt accumulators and salt excluders is not only based on differences in ion exclusion but is also related to the capacity to accumulate compatible osmotic solutes. In experiments aiming at an ecophysiological comparison of the mineral and water economy in relation to halophyte zonation, secretion, accumulation of sodium and transpiration were simultaneously measured in four salt-secreting and four non-salt-secreting halophytes and glycophytes. Plants were grown in a greenhouse (20°C, 65% RH; 6-18 hr light 7000Lux)in 0.25 strength Hoagland's solution with 0.2 M NaCl added. Salt secretion was measured by rinsing the leaves with distilled water over a 6 day period. Relative humidity of the air was kept at 65% in order to avoid the loss of secreted salt through run-off from the leaves, which occurs under more humid conditions (Rozema & Riphagen 1977). Transpiration rates were determined by weight measurement for a 48 hr period. The total weight of the plants which were precultured for four weeks on NaClfree 0.25 strength Hoagland increased only slightly during the 6 day period. After harvesting and drying, the sodium content of the whole plant was determined by flame emission spectrophotometry. The sodium content of the xylem sap was calculated from the equation; . secretion + accumulation ion concentration xylem sap = transpiration
|Acta botanica neerlandica|
|CC BY 3.0 NL ("Naamsvermelding")|
|Organisation||Koninklijke Nederlandse Botanische Vereniging|
J. Rozema, H. Gude, F. Bijl, & H. Wesselman. (1981). Sodium concentration in xylem sap in relation to ion exclusion, accumulation and secretion in halophytes. Acta botanica neerlandica, 30(4), 309–311.
|541310.jpg Cover Image , 12kb|