Distribution and differentiation of the laticifer system in Chamaesyce thymifolia (L.) Millsp. (Euphorbiaceae)

Leaves and stems of Chamaesyce thymifolia (L.) Millsp. (Euphorbiaceae) were analysed using light and electron microscopy with special emphasis on the distribution and differentiation of non-articulated laticifers. Stem laticifers were found among parenchyma cells of the cortex. Laticifers formed a discontinuous ring in the boundaries of primary phloem and branching into the cortex. In leaves, they formed a network in the mesophyll. In the vascular system, they appeared close to the phloem. Laticifer tubes were branched, forming a network in both organs. The development of C. thymifolia laticifers showed two distinct stages: undifferentiated and differentiated ones. The undifferentiated laticifers were characterized by electron-dense cytoplasm, a nucleus, abundant mitochondria, rough endoplasm reticulum and a considerable number of small vacuoles. During the laticifer tube development, a gradual degeneration of organelles was observed while a central vacuole with latex particles was formed. The differentiated laticifers presented intact cell membranes, cellular debris and an accumulation of latex particles inside the tubes. Plasmodesmata and primary pit fields could not be observed between the laticifer and the adjacent parenchyma cells. Developed laticifers presented peculiar cell walls that were thicker than the adjacent cell walls. Various morphological types of starch grains were observed in the C. thymifolia latex.