Comportement écophysiologique de deux chénopodiacées des genres Atriplex et Spinacia soumises au stress salin.

Abstract

In arid and semi-arid areas, particularly around the Mediterranean Basin, soil salinisation is one of the major abiotic factors which reduce the yield of several cultures. The introduction of tolerant plants to salinity is one of the techniques most used to improve the quality of soil in these areas. Chenopodiaceae constitute a very important family of halophyts, of which are genus Atriplex and Spinacia. To highlight the potentialities of adaptation to the salinity of Atriplex halimus L, Atriplex canescens L and two varieties of spinach: Spinacia oleracea L., a saline stress was induced by the application of various NaCl doses (0g/l, 6g/l, 12g/l, 18g/l and 24g/l), in semi-controlled conditions. The tolerance of these genotypes was studied by the capacity of growth and output. Indeed, the average height of the stems, the length of roots and the dry weight at the end of the experiment vary according to the level of saline stress. The two species of Atriplex showed a great resistance to the salinity expressed by their development of important shoots and roots. The two varieties of spinach present a growth adapted to the saline stress, but the introduced variety (Linda) is shown to be more sensitive than the local variety (GSN).The study of the growth of the plants was supplemented by DNA dosage and chlorophylls (A), (b) and (a+b); these two parameters reflect the mitotic and photosynthetic activities respectively. The accumulation of osmoregulators varies from one species another, namely the free proline and soluble sugars. Atriplex and spinach accumulate proline in shoots and roots. As for soluble sugars, they are accumulated according to salinity only at the two species of Atriplex. The comparison of the SDS-PAGE profiles of the protein leaves reveals 7 proteins which appear in stress, of a molecular weight of 190, 185, 158, 136, 127.5, 27 and 12 KDa, whose presence and degree of accumulation vary from one genotype to another.