Osmoregulation in halophytic higher plants: a comparative study of soluble carbohydrates, polyols, betaines and free proline.

Abstract

Abstract. The levels of soluble carbohydrates, polyols, betaines and free proline have been determined in different organs of sixteen plants collected on coastal salt marshes. Among the carbohydrates, sucrose, fructose and glucose accumulated at quite high levels. Sucrose is particularly abundant in the monocots Juncus maritima, Phragmites communis and Scirpus maritimus. Maltose is quite abundant in Atriplex hastata and rhamnose in Plantago maritima roots. High levels of polyols were detected in Aster tripolium, Juncus maritimus, Plantago maritima and Phragmites communis. According to their capacity to accumulate carbohydrates and (or) nitrogenous solutes, halophytic higher plants can be divided into three main groups: (1) species producing high levels of soluble carbohydrates only, (2) species accumulating both carbohydrates and nitrogenous compounds, (3) species producing more nitrogenous solutes than soluble carbohydrates. The possible functions of these various organic solutes, including a role in equalizing the relative water potentials of cytoplasm and vacuole and to lower the internal potential, are discussed.