As plants grow their genotype is expressed in the phenotype which is modified by the environmental conditions that they experience. Somehow the rates of growth and differentiation of cells in different parts of the plant are coordinated in response to these inputs.
There has to be communication between these levels: how does the plant receive and respond to environmental inputs or "signals"? What communication is there inside the plant to adjust growth and development to the environment?
When growing plants commercially we can ask similar questions:
what environmental input will produce the kind of growth that we want?
or can we modify the growth by applying a chemical regulator?
can change the genotype to achieve the kind of growth we want (by traditional breeding or by genetic manipulation)?
The answers to each of these questions depends on an understanding of how plant growth is regulated. Hormones in animals coordinate body functions by being produced in one place and acting in another. Plants do not have a circulatory system and "action at a distance" may not be a feature of plant hormones. They are molecules that are not directly involved in metabolic or developmental processes but they act at low concentrations to modify those processes.
There are five generally recognized classes of plant hormone, some of the classes are represented by only one compound, others by several different compounds. They are all organic compounds, they may resemble molecules which turn up elsewhere in plant structure or function, but they are not directly involved as nutrients or metabolites.
There has to be communication between these levels: how does the plant receive and respond to environmental inputs or "signals"? What communication is there inside the plant to adjust growth and development to the environment?
When growing plants commercially we can ask similar questions:
what environmental input will produce the kind of growth that we want?
or can we modify the growth by applying a chemical regulator?
can change the genotype to achieve the kind of growth we want (by traditional breeding or by genetic manipulation)?
The answers to each of these questions depends on an understanding of how plant growth is regulated. Hormones in animals coordinate body functions by being produced in one place and acting in another. Plants do not have a circulatory system and "action at a distance" may not be a feature of plant hormones. They are molecules that are not directly involved in metabolic or developmental processes but they act at low concentrations to modify those processes.
There are five generally recognized classes of plant hormone, some of the classes are represented by only one compound, others by several different compounds. They are all organic compounds, they may resemble molecules which turn up elsewhere in plant structure or function, but they are not directly involved as nutrients or metabolites.
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