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
