Phosphate uptake and its pH-dependence in halophytic and glycophytic algae and higher plants

Phosphate uptake in various organs of higher plants, i.e. Hordeum roots Avena coleoptiles, leaves of Elodea, and seedlings of the halophytes Cakile maritima, Cochlearia anglica, and Plantago maritima is optimal in the acidic pH range and is not stimulated by Na⁺ when tested in comparison to K⁺.In certain algae, i.e. the thermophilic blue-green alga Anacystis nidulans, the freshwater red alga Porphyridium aerugineum and the marine red alga Porphyridium cruentum, phosphate uptake is optimal in the alkaline pH range. In the red algae phosphate uptake is enhanced by Na⁺; in the marine species the increase is up to 100 times the rate in the presence of K⁺. It is suggested that the Na⁺-stimulated phosphate uptake has some phylogenetic and ecological significance.