4.5 Plant Hormones
2026-05-12 19:15
Status: #new
Plant Hormones
Types of Plant Hormones
Auxins
- Auxins are signals calling for cells to elongate
- When released by the apical meristem, it causes plants to grow taller
- When cutting off the apical meristem of some plants, it encourages to grow side branches
- Too much exposure to auxins kills a plant, making it a weedkiller component
Cytokinins
- Cytokinins encourage cell division and differentiation
- These chemicals also delay plant aging
Gibberellins
- These hormones promote growth, and strengthen plants, and encourage earlier flower growth.
- This can result in longer growing season and larger fruits.
Ethylene
- When fruits age, ethylene gas is released when they ripen
- When exposes to ethylene, plant cells start to decompose
Abscisic Acid (ABA)
- This is a inhibitor. It is produced in mature areas of plants to stop growth.
- When a environment is unfavourable for a plant to grow ABA, is made.
Hormone Responses to the environment
- Plant Responses
- Most plant responses (tropisms) results in plants moving in the direction of the stimulus
- Phototropism
- Response of a plant to light
- Gravitropism
- Response of a plant to gravity
- Plants feel up and downwards directions
- Thigmotropism
- Plants have vines or vine-like structures to wrap around an object
- Phototropism
- Non directional plant reactions are called nastic responses
- Most plant responses (tropisms) results in plants moving in the direction of the stimulus
- Plant Stress responses
- In some plants, exposure to extreme light or temperatures makes them emit high pitched sounds.
- Humans cannot detect these frequencies, due to air bubbles forming and bursting in the xylem.