Biology - Hormonal Control of Plant Responses
Hormonal Control of Plant Responses
The plant coils around the supporting structures in response to the
stimulus of touch
Regulation of plant growth and development results from:
* the interaction between external environmental factors and hormones
* the effect of hormones
Growth responses to the presence of hormones are called tropism .
Growth towards the stimulus is a positive tropism, while growth away from
the stimulus is a negative tropism. Plants show other kinds of response to
stimuli; for example, the closure of leaves of some mimosas when touched,
the following of the sun by heads of some flowers, and the opening and
closing of petals. Some photosynthetic unicellular organisms, such as
Euglena, move towards a light source - ataxis.
View the video of a Venus fly trap: the plant has a specialised response
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