Salt Tolerance in the HalophyteSuaeda maritimaL. Dum. Growth, Ion and Water Relations and Gas Exchange in Response to Altered Salinity

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Abstract
Clipson, N. J. W. 1987. Salt tolerance in the halophyte Suaeda maritima L. Dum. Growth, ion and water relations and gas exchange in response to altered salinity.—J. exp. Bot. 38: 1996–2004. Shoot and root fresh and dry weights and shoot sodium, chloride and potassium contents were measured and shoot relative growth rates calculated in seedlings of Suaeda maritima over a period of 11 d following a raising of culture solution salinity from 0 to 200 mol m3– NaCl. Growth, growth rates and sodium and chloride contents, as compared to plants growing in the absence of salt were increased whilst potassium contents declined. Shoot sodium accumulation rate and the rate of transport of sodium from root to shoot, osmotic potential, and rates of photosynthesis and transpiration were also measured for up to 72 h after transfer of plants originally growing at 0 and 200 mol3– NaCl to 200 and 400 mol m3– NaCl respectively. Ion uptake and transport rates were maximal 6‐12 h after transfer and then declined to new steady-state levels within 48 h; osmotic potentials were lowered over a 72 h period on average by approximately 1·0 MPa; and after 9 h photosynthetic and transpiration rates were reduced by about 20percnt; and 30% respectively. Results are discussed in terms of the ability of halophytes to adjust to fluctuating salinity and to salt tolerance mechanisms in general.