Plant Hormones Flashcards
Auxins ?
●Group of plant Hormones produced in the apical meistem of the stem
●high concentration of auxins are produced in the growing tip of the stem and small amount produced in tip of the roots
●Indole acetic acid most natural auxin in plants
Functionof auxins
●Stimulate Elongation
●IAA stimulates elasticity in cell wall facilitating the elongation of the cells
● stimulated cell division bit only in presence of other plant auxins
●Stimulates development of fruits
- controlling abscession of leaves and plants
●inhabits the growth of lateral branches (apical dominance)
Abscission
●Is the cutting off of fruit and leaves
●The abscission layer forms when the cell wall gets thinner
●This causes the fruit or leaf to fall off
●High concentration of auxin inhabits abscission and the decrease of auxin causes the obsession layer to form and fruits/ leaf falls off
In stem
High concentration of auxins promote growth
In roots
High concentration of auxin inhibit growth
Inhabit growth in lateral branches (apical dominance)?
●apical buds grow more thn side brunches
●due to high concentration of auxin at the tip of the stem it inhibits the development of lateral buds
● if you remove the top of the stem by cutting it off the concentration of auxins decrease and the lateral buds grow into later branches
● if tip is damaged the auxin concentration will decrease and the lateral buds closer to the tip will no longer he inhibited and will develop into lateral branches
●pruning artificially remove the tips of the stem and the plant grows bustier
Tropism?
The growth movement of a plant in response to stimulus
Growth towards the stimulus?
Is positive
Growth away from stimulus
Is negatively
D8fference between Phototropism and geotropism
Has to do with light =p
Has to do with gravity =g
Phototropism
Growth movement of plant in response to unilateral light source
●stem and leaves grow towards the light therefore it is positively photitropic
How does phototropism work
●Auxins are sensitive to light so they move to opposite direction tion of light
●thy accumulat on the shaded side of the stem
●high concentration of auxins in sterm stimulates elongation
●shaded side grows faster
●sterm curves in direction of light and it will ne positively phototropusm
Geotropism
Growth movement of plant in the direction of unilateral gravitational stimulus
How Geotropism works
● small amount of auxins gather at the bottom of the root due to gravity
●high concentration of auxins on the lower side inhabits cell elongation on low side of roots
●upper side grows faster since there is no auxins
●root curves downwards
In sterm (geo)
●Auxins accumulat on the lower side of the root
●high concentration of auxins Stimulate the elongation of roots
●there will be more growth on the side with the the auxins
●therefore tge root grows upward
●it will be negatively grotropic
Gibberellins
Production in terminal buds of sterm and roots in young leaves and embryo
Function of Gobberellins
Stimulates root group
Sterm elongation
Promotes flowers
Abscisic Acid
Growth inhibitor works against auxins helps plants under stressful conditions
Function of abscisic acid
Promotes abscission of leaves
Closing of stoma
Weed control in plants using hormones
Weed killers contain auxins Stimulate growth in divots and monocots
Weed grows too fast the plant can’t keep up with water absorption and food production
Defence mechanism divided into
Chemical
Mechanical
Machemical defence
The amount of layers protecting the inside of plants
Thorn spine
Chemical
Hh
Chemical
Toxic digestibility of plants
