Some deviation in the type of photosynthesis and Kranz structure are found in cotyledons and leaves of the same plant among the C-4 Salsola species. The current study attempted to reveal the pattern of Kranz and cell-type-specific C-4 enzyme accumulation in cotyledons and leaves of Salsola collina and S. komarovii. Structural aspects of the bundle sheath and mesophyll cell differentiation, as well as immunolocalization of the bundle sheath cell-specific enzyme, RuBPCase, and the mesophyll cell-specific enzyme, PEPCase, were used particularly in S. komarovii to follow the development of the C-4 pattern. The study revealed the Salsoloid Kranz type having either continuous or discontinuous concentric chlorenchyma in all leaves and cotyledons. The Kranz pattern and ultrastructure of the bundle sheath and mesophyll cell in the cotyledons were almost identical to those of mature leaves in S. komarovii, where cellular differentiation into the bundle sheath cell and mesophyll cell occurred simultaneously with development of the secondary plasmodesmata. Accumulation of RuBPCase appeared early in the bundle sheath precursor cell stage. Strong RuBPCase reaction was shown at the time of bundle sheath tissue-delimitation and further on in developing stages. PEPCase was restricted to the mesophyll cells and detected only in later stages at low levels. The leaf/cotyledon structure in these species was C4-S/C4-S, according to Pyankov et al. (2001), with a characteristic bundle sheath- and mesophyll cell-specific C-4 enzyme accumulation pattern.

Key words: C-4 photosynthesis, cotyledons, immunolocalization, Kranz pattern, leaves, Salsola species