A comparative study of growth, differentiation, maturation, and senescence of three plant species representing three photosynthetic pathways was made at three altitudes. Irrespective of the photosynthetic pathways the species displayed significant decrease in the extension growth rate, leaf differentiation and higher senescence with increasing altitudes. In relation to the altitudinal gradient the phenological expressions fluctuated minimally in CAM species, Bryopylhtm tubiflorum, and maximally in C4 species, Amaranthus, peniculatus. The dry matter accumulation per unit time was the maximum in C4 species, less in C3, and least in CAM species at all altitudes studied. The allocation of photosynthate to the leaves decreased with time at a faster rate in C3 and C4 species but remained at a very high level in CAM species. This pattern in photosynthate allocation was observed irrespective of the altitude at which these species were grown.
While there are differences in the magnitude of expression of morpological characters in C3, C4 and CAM species at different altitudes, the physiological functions studied here do not show any well defined pattern of differences which may be attributed to differences in altitude in these three types.
