PLANT RESPONSE TO THE ENVIRONMENT
Functions of hormones:
AUXINS GIBBERELLINS ABSCISIC ACID
Brings about Elongation of Stimulates
tropism (bending internodes of stems dormancy in winter
action such as (of seeds by slowing
Geotropism and germination and
phototropism) dormancy of apical
buds)
Promote cell division Stimulates root Contributes to seed
growth dormancy
Cell enlargement Promote flower Closing of stomata
development during water
shortage
Apical dominance Promote sprouting Promotes abscission
(in the apical bud of buds that were of fruit and leaves
promote vertical dormant
growth, inhibits
growth of lateral
branches. If the
apical bud is
removed, growth of
lateral branches is
promoted).
Root development Aids in seed
germination
Fruit development Increase fruit size
Controls abscission
, Control of weeds using plant hormones:
Auxin-based selective herbicides (made by chemical synthesis and main factor in controlling
weed growth), which are pesticides that kill only one specific unwanted plant as long as they
are used in the appropriate dosage.
Advantage: non-toxic and don’t need to handpick weeds
Disadvantage: plants similar to weeds (in terms of broad-leaves) can be damaged.
Symptoms: distorted or twisted leaf stalks, swollen stems, wart and galls.
If used in high quantities, it can cause reduced plant growth and death.
HORMONES IN AGRICULTURE
1 Auxinsfruit development -Pollination produces seeds that release
auxins that promote fruit growth
-auxins sprayed, ensure fruit development
although no pollination has taken place
-fruit are seedless
Low con. Sprayed to delay abscission
2 Auxinsherbicide Synthetic auxins =weed killers
2,4D kills broad leaved weeds not grasses
Maize safe
3 Auxinsapical dominance Auxins produced by apical bud(tip)
Slows down growth of lateral buds
Plants grow rapidly upwards, side branches
grow slow
Cone shape structure =apical dominance
Pruning process
4 Gibberellinsfruit development Fruit without seeds (parthenocarpy)
On grapes larger and greater internodes
on vines which limits fungal infections
5 Ethylene gas injected into airtight storage
roomsripen bananas and other fruit
Functions of hormones:
AUXINS GIBBERELLINS ABSCISIC ACID
Brings about Elongation of Stimulates
tropism (bending internodes of stems dormancy in winter
action such as (of seeds by slowing
Geotropism and germination and
phototropism) dormancy of apical
buds)
Promote cell division Stimulates root Contributes to seed
growth dormancy
Cell enlargement Promote flower Closing of stomata
development during water
shortage
Apical dominance Promote sprouting Promotes abscission
(in the apical bud of buds that were of fruit and leaves
promote vertical dormant
growth, inhibits
growth of lateral
branches. If the
apical bud is
removed, growth of
lateral branches is
promoted).
Root development Aids in seed
germination
Fruit development Increase fruit size
Controls abscission
, Control of weeds using plant hormones:
Auxin-based selective herbicides (made by chemical synthesis and main factor in controlling
weed growth), which are pesticides that kill only one specific unwanted plant as long as they
are used in the appropriate dosage.
Advantage: non-toxic and don’t need to handpick weeds
Disadvantage: plants similar to weeds (in terms of broad-leaves) can be damaged.
Symptoms: distorted or twisted leaf stalks, swollen stems, wart and galls.
If used in high quantities, it can cause reduced plant growth and death.
HORMONES IN AGRICULTURE
1 Auxinsfruit development -Pollination produces seeds that release
auxins that promote fruit growth
-auxins sprayed, ensure fruit development
although no pollination has taken place
-fruit are seedless
Low con. Sprayed to delay abscission
2 Auxinsherbicide Synthetic auxins =weed killers
2,4D kills broad leaved weeds not grasses
Maize safe
3 Auxinsapical dominance Auxins produced by apical bud(tip)
Slows down growth of lateral buds
Plants grow rapidly upwards, side branches
grow slow
Cone shape structure =apical dominance
Pruning process
4 Gibberellinsfruit development Fruit without seeds (parthenocarpy)
On grapes larger and greater internodes
on vines which limits fungal infections
5 Ethylene gas injected into airtight storage
roomsripen bananas and other fruit
