| If it is positive it goes where | towards the stimulus |
| if its negative it goes where | goes away from the stimulus |
| What is a taxis | a taxis is a directional response to a stimulus |
| what is a kinesis | a non directional response to a stimulus |
| Tropism ( plants) | growth movement of part of a plain to a directional stimulus |
| What is positive phototropism | shoots grow towards light |
| Negative phototropism | roots grow towards from light |
| Positive gravitropism | roots grow downwards towards gravity |
| Negative gravitropism | shoots grow upwards easy gravity |
| What does IAA affect | causes cell elongation
inhibits growth in the roots |
| IAA causes phototropism response in shoot tips | 1.Cells of the shoot tip make and release IAA, which diffuses down the shoot through cells.
2. Light causes IAA to move (active transport) from the lit side to the shaded side of the shoot, so a greater concentration of IAA builds up in the cells on the shaded side.
3. IAA causes shoot cells to elongate so the cells on the shaded side lengthen more than cells on the lit side
4. Due to this, the shaded side of the shoot grows faster, causing
the shoot to bend TOWARDS the light source |
| If IAA is in the root tips | 1.IAA gathers in the LOWER cells of the root tissue;
2.inhibits cell elongation;
3.so the lower cells lengthen at a slower rate than the upper cells;
4.this causes the root to grow downwards. |
