The genus Rebutia (Cactaceae): change of the anatomical and morphological characteristics during the pregenerative period

Anatomical and morphological features of 3-, 6- and 12-month Rebutia flavistyla and R. minuscula plants were analized. Increasing of the epidermal cells number per unit area and the thickening of their external walls are typical for the growth and development processes from 3- to 12-month ages. At this time hypodermis has emerged, sizes of the cortex and pith parenchyma cells have increased, the pith diameter-cortex thickness ratio have increased, the mucilage cells have emerged and their number increased, besides number of the vascular bundles and xylem elements in each bundle have growth. The slowing of the epidermal and parenchyma cells division and the intensification of their growth and stretching in 6-month age were noted. The differences in the anatomical structure of different species, that may have taxonomic significance, were observed.