PLANT HORMONES

Chemical messenger that stimulates or suppresses the activity of cells Produced in one location of an organism and causes a response in another Hormones

Dramatic increase in size End seed dormancy, start germination. And promote rapid growth of seedlings. Big fruit, long stems Gibberellins

Causes ripening Naturally produced by the plant Ethylene

Stimulate cytokinesis ( last stage of cell division) Produced in growing roots, seed, and fruits Lateral growth- side branches Cytokinins

Lengthening of plant- apical meristem Stimulate growth of the primary stem-preventing growth of new branches. Controls some forms of tropism Auxins

PLANT RESPONSES

Tropisms Tropisms are a plant’s response to conditions in the environment. The responses can be affected by gravity, light, touch, and seasonal changes.

TROPISMS –Gravitropism –Phototropism –Thigmotropism

Gravitropism -Up and down growth of a plant -Plant responding to gravity -Down ( +) – with gravity -Up (-)- against gravity

Phototropism A phototropic response is when a plant grows toward a source of light. Stems may bend toward a window or nearest source of light. This growth allows their leaves to capture the most sunlight for the process of photosynthesis.

Thigmotropism When plants respond to touch Climbing plants/vines

Thigmotropism Examples: –A plant that is touched regularly may be stunted in its growth- sometimes quite dramatically –Vines and climbing plants-tips wrap around objects Thigmotropism

Rapid Responses Some responses do not involve growth; they are not tropisms Examples: –Mimosa pudica: the “sensitive plant” –The Venus flytrap