Mineral Ion composition and occurrence of CAM-like diurnal malate fluctuations in plants of coastal and desert habitats of israel and the Sinai.

1. The mineral ion composition and the occurrence of CAM-like diurnal malate fluctuations in species from 6 field locations in Israel and the Sinai were studied during the spring of 1974. The sites were a) a salt swamp near Acre on the Mediterranean Sea shore in the northern part of Israel, b) the high coast near Tel Aviv, c) the southern Dead Sea area near Sedom, d) the Negev highlands surrounding the ancient town of Avdat, e) the Wadi Paran in the southern Negev desert, and f) the Red Sea shore near the southeastern tip of the Sinai peninsula close to the Bedouin village of Nabek. The carbon assimilatory organs of the plants were analysed for Na+, K+, Cl- and SO42- as well as for malate at dawn and dusk. 2. Most species analysed are characterized by high levels of mineral ions (mainly Na+/and Cl-) often exceeding 300-400 μeq per g fresh weight, and by high Na+/K+ ratios in their tissues mainly ranging from 10 to 20. These typical halophytic attributes are particularly found in species of the Acre salt swamp, of the Dead Sea area and the Red Sea shore and in many species of the Negev highlands. 3. In plants occupying the Tel Aviv high coast habitats Na+ and Cl- are lower averaging 100 to 200 μeq per g fresh weight. The Na+/K+ ratio is about 5. 4. Numerous species mainly inhabiting the less saline loessial plains and wadis of the Negev desert contain only up to 100 μeq Na+ and Cl- per g fresh weight and are characterized by Na+/K+ ratios of about 1 and below. 5. The salt-accumulating species of the coastal habitats contain Na+ and Cl- in more or less equivalent amounts, i.e. halophytes of the "chloride type" in the terminology of Walter dominate these sites. In contrast, many inland halophytes chiefly belonging to the Chenopodiaceae accumulate much more Na+ than Cl- and/or SO42-. 6. The special feature of Na+ contents which far exceed the sum of Cl- and SO42- distinguishes the inland Chenopodiaceae as a "physiotype" from members of other taxa. The Zygophyllaceae included in this study form a further "physiotype" which is characterized by higher Cl- than Na+ concentrations. 7. Five species of the Aizoaceae family investigated showed no special pattern of mineral ion content. 8. Certain species, especially some belonging to the Brassicaceae, showed a slight malate accumulation during the day. 9. CAM-like diurnal malate fluctuations were only observed in four species: the halophytic Aizoaceae Mesembryanthemum crystallinum, M. forsskalii and M. nodiflorum and the non-halophytic Asclepiadaceae Caralluma It is suggested that, among halophytes, the capability to perform CAM is generally restricted to members of the Aizoaceae.