Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
32 Cards in this Set
- Front
- Back
|
How do auxins move around the plant |
diffusion & active transport > short distances Via phloem > long distances |
|
|
Phytochromes |
• A type of photoreceptor (detects & absorbs light) • consists of protein bonded to a (non-protein) light absorbing pigment/ photo pigment • non protein component exists in 2 forms: Pr & Pfr (which are different isomers) |
|
|
Germination |
• red light > ^ Pfr > promotes growth > germination occurs as • far red light > less Pfr > inhibits growth > germination x occur |
|
|
Photoreceptors |
Receptor cells that detect & absorb light |
|
|
How does tropism ^ the chance of plant survival? (2 marks) |
^ chances of survival • sense direction of light > grow towards this > maximises light absorption for photosynthesis • Sense gravity > roots & shoots grow in the right direction > maximises mineral absorption |
|
|
Tropism |
Response of a plant to a directional stimulus causing directional growth (Directional growth of plant in response to directional stimuli) |
|
|
Positive tropism |
Grows towards stimulus |
|
|
Negative tropism |
Grows away from stimulus |
|
|
Phototropism |
Growth of a plant in response to light |
|
|
Phototropism in roots |
1) uneven light 2) IAA transported to underside 3) ^ conc. of IAA inhibits cell elongation (cells on unshaded part continue to elongate) 4) root bends away from light > -vely phototropic |
|
|
Phototropism (in shoots) |
1) uneven light 2) IAA transported to shaded area 3) ^ conc. of IAA causes cells to elongate (cell walls become stretchy & loose causing cells to get longer) 4) shoot bends towards the light > +vely phototropic |
|
|
Geotropism (define) |
Growth of a plant in response to gravity |
|
|
Geotropism in roots |
1) uneven gravitational pull 2) IAA is transported to underside (closer to pull of gravity) 3) ^ conc. of IAA on underside INHIBITS cell elongation (cells continue to elongate on non-shaded region) 4) root bends towards gravitational pull > +vely geotropism |
|
|
Geotropism in shoots |
1) uneven gravitational pull 2) IAA is transported to underside (closer to pull of gravity) 3) ^ conc. of IAA causes cells to elongate (cell wall becomes stretchy & loose causing cells to become long) 4) root bends away from gravitational pull > -vely geotropic |
|
|
How do plants respond to directional stimuli |
Regulate their growth using growth factors |
|
|
What are growth factors |
Chemicals that speed up/ slow down plant growth |
|
|
Auxins |
A growth factor that stimulates growth by cell elongation |
|
|
What does high auxin concentration do in roots |
Inhibits growth |
|
|
What is IndoleAcetic Acid (IAA) |
An important auxin |
|
|
Where is IAA produced |
Shoot tips, roots, stems |
|
|
Why is IAA moved around the plant |
To control tropisms |
|
|
How does IAA result in directional growth/ tropism? |
Uneven distribution of IAA > ^ conc in shaded region > uneven growth of the plant |
|
|
What does IAA do (process) |
1) enters the nucleus of a cell 2) regulate transcription of genes related to cell elongation & growth |
|
|
What responses are controlled by phytochrome |
1) flowering time 2) germination 3) greening |
|
|
Pr |
• phytochrome red (inactive) • absorbs red light which converts Pr to Pfr (fast) • absorbs light of wavelength 660nm • more red light present during the day |
|
|
Pfr |
• phytochrome far red (active) • absorbs far red light, converts Pfr to Pr (fast) • absorbs light of 730nm • less far red light during the day • darkness converts Pfr to Pr (slow) at night |
|
|
Controlling flowering time |
• ^ Pfr indicates day is longer (as ^ Pr > Pfr) • ^ Pr indicates day is shorter (as ^ Pr > Pfr) • in short day plants presence of Pfr will inhibit flowering • in long day plants presence of Pfr will promote flowering |
|
|
Purpose of phytochromes |
dif amounts of Pr & Pfr > regulate (control) transcription of genes involved in response to light |
|
|
Phytochromes in daytime |
• absorption of red light - Pr > Pfr (fast) • absorption of far red light - Pfr > Pr (fast) • ^ red light in day than far red |
|
|
Phytochromes at night |
slow conversion - Pfr > Pr (no light) |
|
|
What type of hormone is IAA? |
Peptide |
|
|
Effect of IAA on transcription (Process) |
1) binds to receptors on cell membrane > activates second messenger molecules 2) activate enzymes called protein kinases > cascade of reactions 3) activates transcription factors 4) control the transcription of auxin regulated genes 5) responses include cell expansion (elongation), division (^ growth) |
