| Feature | Phototropism | Gravitropism |
|---|---|---|
| Stimulus | Light direction | Gravitational pull |
| Positive Response | Shoots growing toward light | Roots growing downward |
| Negative Response | Roots growing away from light | Shoots growing upward |
| Auxin Effect in Tissue | Promotes elongation in shoots | Inhibits elongation in roots |
Always specify whether the organ is a shoot or a root, as auxin has opposite effects in each. Many exam errors occur when students assume auxin always promotes growth.
Include the term ‘cell elongation’ when explaining how tropisms occur; exams reward precision in describing growth mechanisms.
Relate response direction to auxin distribution, since exam questions often involve diagrams requiring interpretation of hormone movement.
Confusing auxin roles is common, as students may forget that auxin stimulates shoot growth but inhibits root growth. This leads to incorrect predictions about bending direction.
Assuming cells divide to cause bending is incorrect, as bending relies primarily on differential elongation of existing cells rather than formation of new ones.
Neglecting stimulus direction often leads to errors; students may describe general growth patterns without connecting them to the stimulus
Tropisms relate to plant hormones, forming part of broader chemical coordination systems. Auxins interact with other hormones such as cytokinins for developmental control.
Agricultural applications include using artificial light orientation or hormone treatments to shape plant structure for higher yield. Understanding tropisms helps optimize growing environments.
Ecological significance lies in how plants adapt to shaded conditions or unstable soil. Tropisms allow plants to adjust growth in competitive or stressful environments.
