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Inland and coastal populations of the salt-tolerant plant Distichlis spicata were grown under three salinity levels (0, 1000 and 2000 mg Na+ added kg-1 soil as NaCl) with and without inoculum of vesicular-arbuscular mycorrhizae. Mycorrhizal infection averaged 28% for the inland plants and 9% for the coastal plants, and was unaffected by soil salinity. Dry mass of non-mycorrhizal plants was significantly higher at the low salinity for inland plants and the intermediate salinity for coastal plants. Mycorrhizal roots had higher Na concentrations than did non-mycorrhizal roots, but also had higher K and P concentrations, and thus maintained a high K/Na ratio. Leaf concentrations of Na were similar in mycorrhizal and non-mycorrhizal plants. Excretion by salt glands may serve to maintain constant leaf Na concentrations. Stomatal conductances were the same for mycorrhizal and non-mycorrhizal plants at all salinities. While mycorrhizae had little effect on D. spicata in this short-term greenhouse experiment, a full evaluation might require long-term field observations.
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