Plant Growth Hormones

Tropisms

Plant growth responses

Positive tropism

Growth towards a stimulus

Negative tropism

Growth away from a stimulus

Phototropism

A growth towards light

Gravitropism

A growth downwards (positive) or upwards (negative) in response to gravity

Auxins

Plant growth hormones which control growth at the tips of shoots and roots

Gibberellins

Plant growth hormones which stimulate seed germination, stem growth and flowering

Uses of gibberellins

Weedkillers, rooting powder for currings, controlled ripening of fruits while in transportation or in shops, applying them to unpollinated flowers so the fruit grows but not the seeds