<Li> Ray initials (smaller and round to angular in shape) </Li> <P> The vascular cambium is maintained by a network of interacting signal feedback loops . Currently, both hormones and short peptides have been identified as information carriers in these systems . While similar regulation occurs in other meristems of plants, the cambial meristem receives signals from both the xylem and phloem sides for the meristem . Signals received from outside the meristem act to down regulate internal factors, which promotes cell proliferation, and promotes differentiation . </P> <P> The phytohormones that are involved in the vascular cambial activity are auxins, ethylene, gibberellins, cytokinins, abscisic acid and more to be discovered . Each one of these plant hormones are vital for the regulation of the cambial activity and are dependent on their concentration . </P> <P> Auxin hormones are proven to stimulate mitoses, cell production and regulate interfascicular and fascicular cambium . Applying auxin to the surface of a tree stump allowed decapitated shoots to continue secondary growth . The absence of auxin hormones will have a detrimental effect on a plant . It has been shown that mutants without auxin will exhibit increased spacing between the interfascicular cambiums and reduced growth of the vascular bundles . The mutant plant will therefore experience a decreased in water, nutrients, and photosynthates being transported throughout the plant, eventually leading to death . Auxin also regulates the two types of cell in the vascular cambium, ray and fusiform initials . Regulation of these initials ensures the connection and communication between xylem and phloem is maintained for the translocation of nourishment and sugars are safely being stored as an energy resource . Ethylene levels are high in plants with an active cambial zone and are still currently being studied . Gibberellin stimulates the cambial cell division and also regulates differentiation of the xylem tissues, with no effect on the rate of phloem differentiation . Differentiation is an essential process that changes these tissues into a more specialized type, leading to an important role in maintaining the life form of a plant . In poplar trees, high concentrations of gibberellin is positively correlated to an increase of cambial cell division and an increase of auxin in the cambial stem cells . Gibberellin is also responsible for the expansion of xylem through a signal traveling from the shoot to the root . Cytokinin hormone is known to regulate the rate of the cell division instead of the direction of cell differentiation . A study demonstrated that the mutants are found to have a reduction in stem and root growth but the secondary vascular pattern of the vascular bundles were not affected with a treatment of cytokinin . </P>

The vascular cambium cells differentiate into meristematic cells phloem parenchyma xylem