B3.2.6 Plant Hormones Flashcards
What is tropism
Response to a stimulus by growth in a particular direction
Positive tropism
Growth response toward a stimulus
Negative tropism
Growth response away from stimulus
Phototropism
Growth response to light
Gravitopism
Growth response to gravity
How do plants respond to their environment
The response to a stimulus occurs because of an uneven distribution of auxin
This causes an unequal growth rate which results in shoot or root bending
How do plants respond to light
When light hits one side of a shoot tip, the auxin moves to the other side of the shoot
This causes the concentration of auxin to build up in the shaded side
The cells respond by elongating
This increases the length of the side of the shoot, so the shoot bends towards the light
When light falls evenly on the shoot…
The level of auxin is evenly distributed throughout the tip
All the cells in the tip grow at the same rate so the shoot grows straight
The root grows more..
On the side with the least auxin
Making it bend and grow down towards the force of gravity
When it has grown down, auxin is evenly spread again
