Effects of Vascular Tissue Containing a Meristem on Adjacent Pith: Hormone-Like Factors
The growth potential of meristems and young organized tissues is shown in their production of special growth stimulating metabolites. The capacity to produce these metabolites is low in senescent tissues and may be insufficient in tissue cultures which grow and/or develop poorly in spite of being supplied with different combinations of nutrients and growth regulators. These metabolites may involve, in addition to well known compounds such as cytokinins and auxins, some unknown regulatory factors. The existence of these factors can be proved using primary expiants cultured on appropriate media and consisting of either a massive complex of senescent (old) tissue only or of senescent tissue with adjacent young and/or metabolically active tissue (e.g. cambial meristem and pith rays). The less active tissue in the complex expiant can serve as a detector of regulatory impulses coming from the tissue(s) with high metabolic activity, while the expiant consisting of a single tissue serves as a control. Explants of this type can be derived from different organs, especially stems and thick roots.
KeywordsVascular Tissue Starch Accumulation Stem Explants Complex Explants Exogenous Sucrose
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