Biology 5 | Plant Hormones

Meristem

The region in a plant where cells undergo mitotic cell division.

Apical Meristem

Causes primary growth (i.e lengthening of the plant)

* Occurs at tips of shoots and roots
* Produces new leaves and flowers

Lateral Meristem

Causes secondary growth (i.e widening of the plant)

* Occurs at the cambium
* Produces bark on trees

Growth Promoters

* Auxins
* Gibberellins
* Cytokinins

Growth Inhibitors

* Ethylene gas
* Abscisic acid

Tropism

The turning of all or part of an organism in a particular direction in response to an external stimulus.

Phototropism

Tropism in response to light

Gravitropism

Tropism in response to gravity

Thigmotropism

Tropism in response to touch

Auxin

* Plant Growth (tropisms)
* Flowering
* Fruit development

Stimulates genes associated with plant growth that promote cell elongation, and increasing rate of cell division.