Concept in Definition ABC

At the behest of the Botany, is called Liberian phloem, tube or glasses, to the conductive tissue of a plant that deals with the transport from nutrients organic, mainly, the sugars produced by the photosynthetic aerial part and autotrophic towards the subterranean basal parts, not photosynthetic; that is, it is that part of the cylinder Central of dicotyledonous angiosperm plants, which is made up especially of bundles or bundles of sieve vessels that carry the descending sap.

There are two types of phloem: primary and secondary. The first constitutes the vascular bundles and matures in the parts of the plant that are still growing in extension, their sieving elements becoming inactive very soon. It should be noted that in those plants that do not have secondary growth, it constitutes the functional phloem of the adult organs. And the secondary phloem, has its origin in the cambium (tissue vegetable specific to woody plants), located towards the periphery of the stem or root. It has an axial system and a radial system.

Meanwhile, the elements that make up the phloem are: sieving elements (They are the most specialized, of variable thickness and side walls with pearly thickenings. Its function is to facilitate radial apoplast transport. They can be observed through the microscope optical); companion cells (highly specialized cells associated with the sieve tubes. They assume the nuclear functions of the sieving elements and die once the latter cease to be functional. They take care of the loading and unloading of the screening elements); Y parenchymal cells (They are presented in a variable quantity, they are less specialized than the previous ones and they present different appearances in the primary and secondary phloem. They take care of the loading and unloading of the sieving elements, taking the sugar to the accompanying cells; They are storehouses of starch, tannins, fats and crystals).