Lecture 6 -- Plants Flashcards
2 main things phloem transport does
takes up energy and transports sugar water.
where and how does phloem transport occur
in the sieve tube elements – pressure-flow hypothesis
Phloem flow directions and from what to what
occurs in all directions. from source to sink
source area
where fluid starts
sink area
where fluid ends up
steps of phloem transport
- source leaf cell will undergo photosynthesis making the sugar ; sucrose.
-sucrose is then transferred from the source into the sieve tube element (phloem).
-this transferred sugar lowers the water potential, therefore water will also flow into the sieve tube from source cell and neighbouring xylem spontaneously. - this flow of water builds up pressure potential at the top, therefore water will flow from source cell end (the top) to the sink cell (the bottom)
- sucrose is ACTIVELY (taking up energy) transported into the storage root cell at the bottom.
- the water potential of neighbouring xylem vessel element has lower water potential therefore the water will flow back into the xylem.
source and sink can be what at different times of year
same tissue
phloem vvs xylem pressure
phloem = positive pressure
xylem = negative pressure
xylem vs phloem energy
xylem = passive (no energy used)
phloem = active (energy used)
what are the two main tissues for transport, think about sap and sugar water
xylem: sap: tracheids and sometimes vessel elements
phloem: sugar water: sieve tube elements
summary of the two vascular tissues (transport cell types, what is transported, direction, and mechanism)
transport cell types:
xylem – tracheids and vessels
phloem – sieve tube
what is transported:
xylem – sap (water+minerals)
phloem – sugar water
direction:
xylem – upward
phloem – any
mechanism:
xylem – transpiration-cohesion-tension
phloem – pressure flow hypothesis
photosynthesis, source of
oxygen in atmosphere – 50% terrestrial and 50% marine
– first step in moving energy into living world, source of all energy in ecosystems.
stomata
where photosynthesis occurs – always on bottom of leaf – openings
mesophyll cell location
sits inside of leaf
reactants and products of photosynthesis
R: water and carbon dioxide
P: glucose, oxygen, and water.
where does oxygen come from from photosynthesis
water
what kind of reaction is photosynthesis
redox – involves transfer of electrons
reduced
molecule accepting electrons
oxidized
molecule donating electrons
CO2 is made into sugar; is it reduced or oxidized
reduced
H2O is made into O2; is it reduced or oxidized
oxidized
what are the two stages of photosynthesis
light reactions and Calvin cycle (dark reactions)
where do light reactions occur
in the thylakoid of chloroplast
where does Calvin cycle occur
in stroma of chloroplast
light reaction steps
- light hits chlorophyll molecule
- electrons bounce off of chlorophyll to higher energy levels.
- chlorophyll doesn’t like that so it steals electrons from hydrogen, making hydrogen oxidized.
- this causes the water molecule to fall apart (photolysis) which leads to production of oxygen.
- electrons and protons from the water molecule then get transferred to NADP+, which accepts these electrons and protons and becomes reduced to NADPH.
- ADP and inorganic phosphate yields ATP through photophosphorylation – making chemical energy.
what is NADPH in terms of the photosynthesis cycle, and reducer H2O
it has greater reducing power than H2O
summer of steps of photosynthesis ; products (energy, oxygen)
light energy is converted into chemical energy, and H2O makes oxygen.
Light reaction equation
H2O+light+NADP+ + ADP + P —> O2 + NADPH + ATP
O2 = oxygen
NADPH = reducing power
ATP = chemical energy
what are chemical bonds made from
electrons
NADP+ and NAD+ what are they
they are oxidizing agents – they remove electrons from other molecules.
NADPH and NADH what are they
they are reducing agents, places electrons on other molecules
what is NADPH used in and what is NADH used in
NADPH = photosynthesis
NADH = respiration
what’s a major feature of light reaction
chlorophyll being hit by light – this is what causes electrons to bounce to higher energyy levels
chlorophyl absorption spectra
why plants are green
chlorophyll a absorbs mostly violet-blue and red light, and it REFLECTs GREEN light – why plants are green
accessory pigments
chlorophyll b and carotenoids
Dark reactions (Calvin c cycle) who proposed this
Melvin Calvin
what does Calvin cycle do
makes sugar – precursor that is then turned into glucose
occurs in stroma (where chloroplast’s DNA is housed)
uses NADPH and ATP from light reactions
supplies NADP+ and ADP to light reactions
draw the Calvin cycle steps. PHASES 1, 2, and 3
you start with 3 molecules of CO2. where 3 molecules of RuBP is added by rubisco. this will create 18 carbon atoms. this is short lived and then it fixates carbon (phase 1) – turns into C3 (3-phosphoglycerate) this is also known as C3 photosynthesis, still 18 carbons, 3 long chain, 6 molecules. —- phase 2 is reduction, this will turn into G3P (glyceraldenyde-3-phosphate) this will lose one molecule, leaving 5 molecules (5x3 = 15 carbon atoms) this output of G3P will be turned into glucose. —- phase 3 – recreate RuBP – then cycle starts back up.
rubisco
very special protein – takes CO2 and adds it to organic RuBP molecule
what is rubisco’s problem
it is dual nature
dual nature – rubisco meaning – actual name of rubisco
“carboxylase” means take carbon from CO2 and onto organic molecule (plants like this)
“oxygenase” means that it can also put oxygen onto organic molecule (plants DONT like this)
this is the problem
what is the addition of oxygen called
photorespiration – uses energy
photorespiration
consumes O2,
releases CO2,
makes NO ATP,
wastes energy,
decreases photosynthetic output
solution that plants in dry areas use
New enzyme – called PEP carboxlyase (PEPC)
C4 photosynthesis
occurs in around 3% of species.
– uses bundle sheath cells and mesophyll cells. (this is called the kranz anatomy)
Spatial sparation
PEPC’s role in C4 photosynthesis
PEPC takes CO2 and makes oxaloacetate (C4) – first stable carbon – then makes malate which turns into acid – this is shunted to the bundle sheet cells LOWER (protected from atmosphere) and then CO2 then enters Calvin cycle.
mesophyll and bundle sheath cell rubisco vs no rubisco
mesophyll cells : O2 exits, CO2 enters, NO rubisco
bundle sheet cells : Rubisco ONLY in bundle sheath cells, kept away from low concentration of CO2
CAM photosynthesis
temporal separation (time) – opens stomates at night, uses PEPC to turn CO2 into acid
basic rundown of CAM photosynthesis
at night, organic acids are produced – day time these acids are then turned into CO2 and the Calvin cycle proceeds.
plants respond to herbivores
physical defences: thorns, trichomes (hairs)
chemical defences: distasteful compounds, toxic compounds
some plants even recruit predatory animals that help defend against specific herbivores.
example of recruitment in plants
in MAIZE LEAF
– caterpillar eats leaf – causes release of chemicals, – signals will be send – wasps detect signal and then lay their eggs within caterpillar.
what are the wasps in the recruitment example referred to
parasitoids
what are parasitoids `
not insects and not predators – somewhere in between
hormone definition
organic substance made in one place and transported to another place – affects in growth and other processes
hormone action – three steps
– reception, transduction, response
hormone action simple steps
– hormone binds to specific protein receptor
– protein receptor then alters its shape
– this stimulates production of “relay molecules” in cytoplasm
– relay molecules trigger responses to OG signal.
abscisic acid “ABA”
regulates stomate opening and closing – misnamed – ABA causes K+ to leave guard cells
ethylene – a gas
produced by most plant parts,
major functions:
- leaf abscission (shedding) – apple/leaf falling
– triple response in seedlings
– most importantly fruit ripening
– root hair production
abscission + ethylene
caused by an increase in ration of ethylene:auxin
triple response
what a plants does when it is germinating/growing and comes across something it cannot grow past
what does ethylene do relative to triple response
allows the seed to go around it, by slowing stem elongation, thickening the stem, nd allowing horizontal growth.
three things ethylene does
- promotes fruit ripening and produced during fruit ripening
- autocatalytic : promotes its own production
- increases respiration
