the growth of a plant in response to light. Shoots are
positively phototropic
Gravity
Geotropism
The Growth of a plant in
response to gravity, roots are
positively geotropic
moisture
a plants
growth
response
it called a
tropism
Growth Hormones
Auxin
controls growth at the tips of shoots
and roots
Auxin is produced in
the tips and diffuses
backwards to stimulate
the cells just behind
the tips to elongate
When a shoot tip is exposed to
light more auxin accumulates on
the side that's in the shade this
makes the cells elongate faster
so the shoot bends towards the
light.
Roots are positively Geotropic
when a root is growing sideways,
gravity produces an unequal
distribution of auxin in the tip with
more auxin on the lower side.
Gibberellin
stimulates seed
germination, stem growth
and flowering
it stimulates plants to
grow by stem elongation.
If a dwarf variety of a
plant is treated it will
become tall.
commercial uses
As a selective weedkiller
been developed from plant
growth hormones which only
effects broad-leaved plants
disrupts normal growth
pattern which kills them but
the grass and crops are
fine
cuttings with rooting powder
adding rooting powder will produce roots rapidly
this enables growers to
produce lots of clones of
really good plant
controlling the ripening of fruit
allows the fruit to be picked while
it's still unripe
ripening hormone is
added so it will ripen
on the way to the
shops and be perfect
seedless fruit
growth hormones are applied to unpollinated
flowers so that the fruit grows but the seeds dont
hormones are also
used to make seedless
grapes but they are
fertilised first