Halophytes: Structure and Adaptation

Abstract

Halophytes are an ancient ecological type the origin of which is connected with the zone littoralis.A Saline environment of their habitat has a positive effect on them, as it reduces competition, prevents diseases and vermin and creates humidity at the expense of accumulation of moisture by salt. The negative qualities of this habitat are the high osmotic pressure of the soil solution and the toxic effect of salt. The morphogenesis and structure of vegetative and generative organs of hyperhalophytes (Halocnemum strobilaceum, Salicornia europaea) and euhalophytes from Suaeda (S. arcuata, S. microsperma, S. prostrata) and from ephemers (Hymenolobus procumbens, Spergularia microspermoides) were studied in the Kyzylkum desert with chloride-sulphate salting of soil, showing the characteristics of plant development caused by the specific habitat. The fruits of halophytes are not sclerified. The pericarp is parenchymatous. The testa have two layers of cells. Their adaptations to extreme desert conditions, including salinization, are implemented at the expense of the submerged position of fruits in fleshy cortex, the presence of tannins and melanins in the testa and fat in the embryo, which makes it difficult for salt to penetrate. The assimilating organs of hyperhalophytes are the shoots with reduced leaves and chlorenchymatic non-Kranz cortex of stems. Euhalophytes have small cylindrical leaves with Kranz (Suaeda arcuata, S. microsperma) and non-Kranz structure (S. prostrata, Hymenolobus, Spergularia ). However, the main line of adaptation of halophytes in both group is the succulent strategy whereby moisture is preserved at the expense of abundant water-bearing cells with thin walls. The structure of stems and roots of the species studied is anomalous, polycambialous and sclerenchymatous, which guarantees protection of lateral meristems and their substitution when they are damaged.