Page 2 - Lesson Notes

Plants also respond to stimuli

 Plants grow towards the source of light. The light is the stimulus and the
growth towards the light is called response. This property in plants is called
PHOTOTROPISM.
 The roots of a plant grow in the direction of the Earth and the stem in the
direction opposite to the Earth. This property is called GEOTROPISM.

 R
oot
s
ex
hib
it
po
siti
ve
ge
otr
opi
sm
an
d stem shows negative geotropism.
 TheEarth’s gravity is the stimulus and the respective growth of the stem and
rootsare the responses.
 Stems are positively phototropic but negatively geotropic while roots are
positively geotropic and negatively phototropic.

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