Feb 9, 2011

Glossary

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Phytohormones

Plant hormones

Plant hormones are messengers within the plant that regulate its growth and development. Each hormone affects different processes, depending on where in the plant and at what point in the plant’s development it is active. Phytohormones work in tandem with one another and are carefully balanced. A plant presents a characteristic plant hormone spectrum at each stage of its development.

Known groups of plant hormones are auxins, gibberellins and cytokinins, which tend to promote plant growth, and abscisic acid and ethylene, which tend to inhibit growth.

For instance, auxin influences cell division and differentiation and a plant’s directional response to light stimuli (phototropism), whereas the gaseous ethylene mainly promotes fruit ripening. For instance, unripe bananas are exposed to the gas after transportation so that they ripen within a few days. Conversely, it is necessary to prevent the formation of ethylene if fruit is to be stored. To do this, fruit is stored at low pressure to remove any ethylene that is released.