Hormones in plants.

Kinesis, taxism and tropism.
Movements in response to a stimulus can be categorised into 3 specific processes...
Kinesis- Random, undirected movement in response to a stimulus.
Taxism- Directed movement in response to a stimulus.
Tropism- Directed bending or twisting movement in response to a stimulus.

The last two directed movements can be either positive (towards the stimulus) or negative (away from the stimulus).
The types of stimuli are varied. In this section we will deal with the three main types: photo (light); geo (gravity); and thigmo (touch).

Thus by combining these prefixes with the movement categories we can get -- phototropism, phototaxism, etc. Cockroaches in a dark environment are startled into running randomly once a light is turned on- so this would be photokinesis.

So how do these movements occur in plants? They have no obvious sense organs and not even a simple brain to allow them to respond to a stimulus. So how can they perform phototropism?
The following videos are an excellent introduction plant hormones and their functions (THE FIRST VIDEO CONNECTS AUTOMATICALLY TO PĂ„RTS 2 AND 3--- YOU WILL NEED TO VIEW ALL THREE)



Below you may find a video on auxin and plant growth:




Another plant hormone Giberellin is reviewed here:_



The table below will highlight the main plant hormones and their functions:
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