31 - Signals

Any response that causes the movement of plant organs toward or away from stimuli

Hydrotropism - water Geotropisim - gravity Phototropism - light Thighmotropism - touch Chemotropism - chemical signals

Tip of the plant response to light Tip sends chemical signals to the stem Auxin, the chemical responsible for moving the stem

Sends signals down the stem, and it elongates cells away from the light, causing the plant to bend towards the light.

Determine root or shoot growth More Cytokinin Shoot More Auxin than Cytokinin Root

Induce elongation and cell division in stem seed break dormancy

Stomata closure Seed dormancy

Ripening of fruit

Light - external stimulus hits the receptor (photoreceptor blue light and photo chrome redlight) Transduction - turns on gene expression Response -The small molecule is produced Chlorophyll

Pr - in the inactive state and promotes germination - start PFR - in the active state inhibits germination - stop (storage)

If critical fark time is less than dark time will not germinate.

Chemical - secrete itself in toxins Physical - spikes, prods, thorns Behavior / Signals - release hormones attracting preditors