Plant Hormones Flashcards
How does the distribution of auxins
1)Light causes the auxin to m laterally across the shoot producing a great concentration on the unlit side
2) the shoot tip act as a photoreceptors
3)more of the hormone diffuses down to the region of cell elongation on the darker side —> more cell elongation on the darker side —> more growth
4)so the shoot bends towards the light
5)once the shoot is growing directly towards the light there is no longer a brighter side or darker side
6) the auxins again become evenly distributed and growth towards the light
The role of auxins
1) IAA is made in the tip of the shoot and diffuse back towards the zone of elongation
2) IAA bind to specific receptor site on the cell surface membrane
3) active transport of H+ into the cell wall space
4) pH of around 5 for enzyme that break bonds between cellulose microfibrils
5) the plant cell absorb the water by osmosis and cell wall stretching —> cell elongation
6) then, IAA is destroyed by the enzyme—> pH rises and enzyme that break bonds between the cellulose microfibrils are inhibited
7) cell wall becomes more rigid
Info of auxin
Produced in young shoots and move down from the shoot to the roots
Promote shoot growth by suppressing the growth of lateral shoot
If remove the tip of the stem —> no auxin production —> root growth slow and stop
Movement of auxin
Light causes auxin to move laterally across the shoot to the darker side —> more auxins diffuse to the zone of elongation on the darker side —> more growth on the darker side
Plant grow towards the light
What is gibberellins
It is a plant growth regulator
- controlling seed
-germination
-stem elongation
Etc
Where does gibberellins affect
Internode of stems
What does gibberellins stimulate and promote
Stimulate the elongation of growing cells
Promote growth of fruit
Process of gibberellins
1) seed absorb water and swells —> embryo activated
2) embryo secretes gibberellins that diffuse to aleurone layer
3) gibberellins stimulate aleurone layer to produce amylase that diffuse into the endosperm and break down food stores to provide embryo with Material for respiration and growth
4) enzyme produced in response to gibberellins digest the endosperm
Products released from endosperm are used by embryo to make new cells and germinate
Synergy
The growth regulator or hormones interact and work together for greater response
Antagonism
The growth regulators or hormones have opposite effect
Short dayplant
Summer/spring —> not flowering
In autumn/winter—> flower
Short day plant
Pfr inhibits flowering
(Long darkness = almost all Pfr is converted back to Pr)
What does long day plant stimulate
Pfr stimulate flowering
(Short darkness = relatively little Pfr is converted back to Pr
After the shoot break through the soil
1) elongation of stem slow down
2) stem straightens
3)cotyedoms and or first leaves open
4)chlorophyll forms and the seedling begins to photosynthesis
5)Pr —> Pfr which inhibits the lengthening of the internode, stimulate leaf development and product of chlorophyll
Phy to chrome as a transcription factor
1) when Pr is converted into Pfr in the presence of light it moves into the nucleus through the pores of the nuclear membrane
2)in the nucleus it binds to PIF3
3) PIF3 - transcription factor
4) PIF3 only binds to Pfr. It doesn’t bind to Pr
5)PIF3 only activates gene transcription and the formation of mRNA if it is bound to Pfr
