plant mt Flashcards
what responses does the CO gene trigger?
long day plants: stimulates flowering
short day plants: inhibits flowering
what are the steps for a C4 pathway?
- CO2 + H2O = HCO3 (bicarbonate)
- bicarbonate + 3-C forms malate (4-C) catalyzed by PEPCase
- malate diffuses into vascular bundles
- NADP-malate dehydrogenase removes a CO2 from malate, end result is a pyruvate, CO2 is sent to rubisco directly
- pyruvate diffuses out and enzyme regenerates 3-C
briefly describe the phosphorylation cascade
after ligand binds to receptors, chain of enzymes phosphorylating each other (adds P from ATP)
briefly describe C3 plants
- calvin cycle (RuBP + CO2 = 3 PGA)
- found in seasonal environments
- stomata open in daytime
- high photorespiration
briefly describe C4 plants
- C4 pathway (3-carbon + CO2 = malate)
- hot/tropical/dry conditions
- stomata open shorter periods (less water loss)
- low photorespiration
- Kranz leaf structure
what were the four experiments done by Darwin? what conclusion did they lead to?
1) control: coleoptiles intact, shoot bends
2) experiment 1: coleoptile removed, shoot stays straight
3) experiment 2: coleoptiles covered, shoot stays straight
4) experiment 3: “jackets” put below coleoptiles, shoot bends
conclusion: substance found in coleoptiles causes bending
what are some auxin receptors and where are they found?
- ABP 1 found in membrane
- T1R1 found inside cell
what is phototrophism?
directed movement in response to light
what do brassinosteroids do?
- promotes growth and regulation of body size
- alters gene expression
- helps with other hormonal responses
- BRI1 and BRL receptors
briefly describe secondary messaging
after ligand binds to receptors, messengers activate other molecules that initiate response
how are gibberellins and ABA related?
gibberellins - stimulates seed germination by releasing alpha-amylase, digesting nutrients in endosperm
ABA - inhibits seed germination when conditions require dormancy, stores nutrients in endosperm, receptors cause K + Cl to move out, water follows to exit and stomata to close
(calvin cycle) what happens during regeneration?
- 5 G3P + 3 ATP forms the initial 3 RuBP from fixation
what responses does de-etiolation cause?
- opening of apical hooks
- lateral growth
- production of chloroplasts (photosynthesis can occur)
how is auxin involved in gravitrophism?
- auxin unevenly distributed in favour of gravity, collects on bottom side of root cap
- cell elongates in direction of auxin and pulls plant downward
what two conditions are needed to elongate a cell?
1) expansins need to loosen cell wall
2) proton pumps need to create electrochemical gradient of ions by pumping out protons, allowing water to diffuse in and create turgor pressure
what responses do ligands trigger?
gene expression, activation of transport proteins, changing electropotential/pH
what experiment did Went do? what conclusion did it lead to?
- agar tips infused with auxin placed offf center. shoots bend away from auxin
what role does auxin have in plant maturation?
- promotes fruiting (seeds)
- lack of auxin causes abscission (leaves/fruit)
- differentiation of xylem and phloem (roots/shoots)
- stimulates root growth
briefly describe CAM plants
- extremely arid conditions
- stomata only open at night
- low photorespiration
- very few but thick/waxy stomata
- can be obligates or switch between C3 and CAM depending on water avail.
- aquatic CAM plants adapted to limited CO2 availability vs limited water
(calvin cycle) what happens during reduction?
- 6 3-PGA + 6 ATP + 6 NADPH makes 6 G3P (1 as an output, 5 to regenerate)
- enzymes = 3-PGA kinase (adds P from ATP), NADP-glyceraldehyde-3-phosphate dehydrogenase (adds H from NADPH)
what is the kranz structure of C4 plants?
- bundle sheath cells surround vascular tissue, mesophyll cells surround bundle sheaths
- mesophyll make C4
- bundle sheaths undergo calvin cycle
- creates a barrier for diffusion
- provides separation of CO2 and O2 so less competition
what is rubisco?
- most abundant enzyme on earth
- has 8 different binding sites
- CO2 and O2 compete for binding sites (leads to different results)
- active when light is available, inactive when CO2 is low
what is the statolith hypothesis?
mechanoreceptors detect amyloplasts (starch storage) and causes them to be pulled in direction of gravity to bottom of root caps
what are the 7 steps of a plant’s action potential?
phase 0: rest
phase 1: depolarization from Ca+ channels opening
phase 2: activation of K+ and Cl- channels and movement out
phase 3: peak K+ outward movement
phase 4: repolarization as channels close
phase 5: hyperpolarization
phase 6: inward K+ and Cl- movement reverses hyperpolarization
what is the acid-growth hypothesis?
- auxin binds to receptors, signalling an increase of proton pump production
- more H+ ions out, lowering pH
- cell elongates
what are the different fates of a G3P molecule?
- can make amino acids/nucleotides
- can be broken down in cellular respiration to make ATP
- converted into starch for storage
- converted into sucrose for sugar delivery through phloem
how can multiple hormones be active at once?
different receptors
what responses does etiolation cause?
- hypocotyl growth
- yellow colour (no chloroplast/photosynthesis)
- thin upward growth
what do cytokinins do and where are they produced?
- produced in root apical meristems
- causes budding
- regulates growth by binding to receptors in target cell ER
- maintains cell cycle (CycD3)/cell division (Cdc25)
how does overgrazing/gardening practices affect a plant’s growth?
clipping of apical buds from wildlife or gardeners stops upward growth (no auxin) and allows lateral growth instead, resulting in shorter bush like appearance
where is auxin located and what physiological response does it trigger?
- found in stems and leaves
- causes elongation of cells
how does the venus fly trap respond to touch?
- sensory hairs inside trap send signals after contact
- signals travels through plasmodesmata as APs
- AP causes swelling in outer trap cells, shutting trap
how does ABA cause stomata to close?
- inhibits ATPase in guard cells
- Cl- ions move outward, electrochemical potential changes
- K+ ions move out, water follows and guard cells become flaccid
what are the major end products of photosynthesis?
ATP and NADPH
what is thigmotrophism and what are the two types?
- movement in response to physical touch
- positive thigmotrophism: plant grows towards contact (i.e tendrils grappling)
- negative thigmotrophism: plant grows away from contact (i.e roots and obstacles)
what is heliotrophism?
movement tracking the sun
how do plants sense gravity?
starch granules in root caps sense direction of gravity
what are phototropins? what responses do they trigger?
- receptors for blue light
- causes chloroplasts to move towards light and triggers opening of stomata
how is flowering triggered?
Ft gene activated by florigen enzyme and travels from leaves –> shoot apical meristems to become flowers
what is the difference between red and far red light?
red light (Pfr) = germination of seeds, de-etiolation
far red light (Pr) = dormancy of seeds, etiolation
(calvin cycle) what happens during fixation?
- 3 RuBP binds to 3 CO2 (+ 3 H2O) to make 2 3-PGA (carbon molecules)
- enzyme = rubisco
what is the CAM pathway?
nighttime:
1. stomata opens, CO2 + H2O = HCO3 (bicarbonate) (C4)
2. bicarbonate + 3-C forms malate (4-C) catalyzed by PEPCase (C4)
3. malate sent to vacuoles
daytime:
4. stomata closes, no new CO2 enters, malate is released from vacuoles
5. malate converted to pyruvate and CO2, CO2 enters calvin cycle
what happens to rubisco during photorespiration? what happens during photosynthesis?
photorespiration: RuBP + O2 -> 1 3-phosphoglycerate + 1 2-phosphoglycolate
photosynthesis: RuBP + CO2 -> 2 3-phosphoglycerate
what conditions triggers the release of gibberellins?
- break in seed coat to expose seed
- exposure to red light
what happens when ethylene triggers fruit ripening?
- starch turned into sugar
- cell walls break down
- chloroplasts break down
- changes colour to signal for consumers
what happens during leaf senescence?
- auxin levels drop
- enzymes in leaf stem activate and causes stem to weaken at the tip
- protective cap forms on tip and leaf drops
