Zusammenfassung der Ressource
Plant Growth
Hormones
- Plants respond to stimuli
- Light
- Phototropism
- 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