Histological study of nodule morphogenesis from Cichorium intybus L. leaves cultivated in vitro.

摘要

Chicory root, stem, and leaf tissues have the propensity to regenerate organogenetic nodules following a wounding treatment. Using histological methods, this phenomenon was examined on leaves of Cichorium intybus cv. Witloof cultured in vitro. Nodule morphogenesis and bud regeneration from nodules were characterized with the assistance of light and transmission microscopy techniques. Semithin and ultrathin sections of leaves and nodules were prepared from nodule induction to bud regeneration phases. Starch and inulin in differentiating tissues were histochemically detected in semithin and handmade sections. This study demonstrates that nodules are formed in direct contact with vascular bundles of the leaves. The nodules consist of organized structures: a vascular centre is surrounded by large parenchyma tissue, which is delimited by a periderm of multiple cork cell layers. Inside the vascular centre near phloem tissues, a secretory network of articulated pseudolaticifers develops. From parenchymatous cells, in the vicinity of vascular centres, endogenous buds can be induced. In this region, several cords of vessel initials formed the vascular connection between neoformed buds and vascular centres. Simultaneously, transfer cell specialization occurs near the neoformed vascular strands. Vascular centres play a major role in this kind of organogenesis. Sugar metabolism appears to be closely related to nodule morphogenetic events.