Salinity response of a freshwater charophyte, <i>Chara vulgaris</i>

Abstract

Abstract. Chara vulgaris L. growing in an oligohaline lake was adapted to laboratory conditions and subjected to long‐term salinity treatments ranging from 0 to 350 mol m 3 NaCl added to the lake water (40–680 mosmol kg 1 ). Osmotic potential and concentration of the main osmotically active solutes (K + , Na + , Mg 2+ , Cl and sucrose) in the vacuolar sap of the central internodal cells were estimated. C. vulgaris did regulate turgor but incompletely. Turgor decreased from 335 mosmol kg 1 under control conditions to 52–111 mosmol kg 1 at 350 mol m 3 NaCl. The enhancement of π i was achieved by increase in both ions and sucrose. Sterile and fertile plants differed in their response to osmotic stress. In sterile plants, the ions accounted for about 87% of the vacuolar osmotic potential. The increase of π i under osmotic stress was exclusively due to an accumulation of Na + and Cl ‐ . In fertile plants, sucrose accounted for about 35% of π i and ions for about 51% Under osmotic stress, sucrose content increased together with the ionic content of Na + and Cl ‐ .