Plant Responses Flashcards
how do plants respond to a light stimulus?
they will grow towards the light
what is tropism?
the growth of a plant towards a directional stimulus
what are phototropisms?
growth responses to light from one direction
what is positive phototropism?
growth towards the light
what is auxin and where is it found within a plant?
it is a hormone that controls the growth towards a stimulus and is found in the tip of the stem
what is the process of tropisms?
- the tip of the shoot produces the auxin, which diffuses down the shoot to cause elongation (lengthening) of cells
- when light intensity is higher on one side of the stem, auxins build up on the shaded side
- this causes the cells on the shaded side to elongate more; as a result the shoot bends towards the light
in an experiment growing plants, how are plants modified to experiment phototropism?
plant A - tips are cut off, therefore no growth because no auxins
plant B - tips are covered, therefore the stem grows directly upwards as no light reaches the tip
plant C - stem grows towards the light, this is called positive phototropism
what is geotropism?
the growth towards or away from gravity - roots are positively geotropic
