- Plant Growth Factors -
Plants respond to many different things, a number of factors they do respond to would include:
- Light
- Gravity
- Water
Control of tropism by IAA.
IAA = Indoleacetic acid // an important auxin produced in the tips of the shoots.
IAA is moved around the plant to control of tropism - moving by:
short distance = diffusion or active transport
long distance = via the phloem
Different parts of the plants would have different concentrations of IAA.
Uneven distribution of IAA means there is uneven growth of the plant.
Light is detected by photorecpetors, which set off a chain of reactions leading to the redistribution of the auxin IAA. More IAA moves to the shaded side of the stem.
IAA causes the cells to elongate by loosening the structure of the cell wall. The mechanism, for this process is unknown, but is thought to involve hydrogen ions (H+).
Because the cells on the shaded slide have a higher concentration of IAA they stretch more than the cells in the light. This causes the shoot to bend towards the light. // = Positive phototropism.
IAA is moved around the plant to control of tropism - moving by:
short distance = diffusion or active transport
long distance = via the phloem
Different parts of the plants would have different concentrations of IAA.
Uneven distribution of IAA means there is uneven growth of the plant.
- How is Indoleacetic acid (IAA) involved in phototropism? -
Light is detected by photorecpetors, which set off a chain of reactions leading to the redistribution of the auxin IAA. More IAA moves to the shaded side of the stem.
IAA causes the cells to elongate by loosening the structure of the cell wall. The mechanism, for this process is unknown, but is thought to involve hydrogen ions (H+).
Because the cells on the shaded slide have a higher concentration of IAA they stretch more than the cells in the light. This causes the shoot to bend towards the light. // = Positive phototropism.
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