- their state to be sensitive to or irritated by light.
- sensitiveness to, or discomfort due to light
- A motile symptom in plants caused by exposure to light.
- An irritable condition of protoplasm, causing action, because of a specific intensity of light.
- In botany, a phrase suggested by Sachs the particular symptom in which the protoplasm can perform exhibiting frustration induced in a few plant-organs by contact with light of a certain strength.