MORPHOLOGICAL TYPES AND PHOTOSYNTHESIS OF C-4 PLANT-LEAVES UNDER LONG-TERM SOIL-SALINITY

Plants of ten species, seven of C-4 type, with different tolerance to salinity, were grown in a greenhouse under natural daylight. The effec ts of long-term (2.5 months) treatments with various concentrations of sulfates and chlorides added to the soil, were studied. The anatomica l structure of leaves, their potential capacity for photosynthesis, an d the content of chlorophylls a and b were characterized in the plants of various morphological types. The salt tolerance of potential photo synthesis was correlated with the degree of plant succulence. We subdi vided all studied plant species into several groups differing in their succulence. The special performance of C-4 plants (C-4 syndrome) was found not to be a decisive factor in the tolerance of potential photos ynthesis to salt stress. It is concluded that succulence is mainly res ponsible for the successful adaptation of C-4 plants to the long-term soil salinity.