ABSTRACT
The stem is the major organ through which water and nutrients are transported around the plant. Figure 8.2 shows that it contains both unspecialized tissue, such as parenchyma packing/support cells, and specialized tissue, such as vascular bundles. Within the vascular bundles of dicotyledonous plants, three types of specialized tissue are found (xylem, phloem, cambium). The xylem vessel is strengthened by a compound called lignin to enable it to withstand the tremendous pressures that build up in transporting the weight of water upwards. The phloem is strengthened with cellulose and transports the sugars made during photosynthesis around the plant to where it is needed. The cambium, which is absent in monocotyledonous plants, contains specialized growth cells (meristems) and is responsible for the manufacture of new xylem and phloem cells. In addition new roots grow from the cambium after cuttings have been taken.
