PLSC400 Fejio Exam 1

List 3 ground tissue cell types and how they differ in wall structure and fxn

1. parenchyma

   1. thin, flexible primary walls, living, multifunctional

2. collenchyma

   1. unevenly thickend, living, flexible mechanical support

3. sclerenchyma

   1. thick, lignified secondary walls, dead, rigid structural support

list 3 tissue systems in plants & purpsoe

1. dermal

   1. epidermis, periderm (controls gas exchange and water loss)

1. ground

   1. paranechyma, collenchyma, sclerenchyma (site of photosynthesis and storage)

2. vascular

   1. xylem and phloem (network from roots to leaves)

Describe major cell types in xylem and phloem

Xylem: tracheids (long, tapered, pits, dead), vessel elements (short, dead, wide, perforation plates)

Phloem: sieve tube elements (living sieve plates) and companion cells (metabollaically active, connected to SE via plasmadesmata)

∆ primary and secondary growth

primary: elongation from apical meristems to make primary body

secondary: lateral meristems to increase girth (vascular cambium → secondary vascular bundle; cork cambium → periderm)

describe structure of chloroplast

bounded by outer and inner envelop membranes

stroma (interior): calvin cycle happens, has ribosomes, DNA, enzymes

thylakoids: internal flattened memebrane sacs with photosyntehsis macheriny (PSII, cyt v6f, PSI, ATP synthase, antenna complexes)

grana: stacks of thylakoids with proton gradient across membrane for additional ATP syntehsis

list the flower plant life stages

1. seed germination (metabolism activaited by water)

2. development of plant body (organs expand & biomass inc as it grows)

3. development of reproductive organs (most genes expressed to make reprod tissue and structures than photosynthesis)

4. seed formation (embryogeneiss to complete life cyle)

How do plants develop organs & cells types?

Permanent Organogenesis (apical meristems and indefinite growth)

• cell division

• enlargement or elongation

• differentiation of cell types

What is the pericycle?

in roots, it is the genetic program area in root to prime cells to active gene expression to create secondary roots or lateral roots

what does the central vacuole play in plant cells?

• turgor: accumulates ions → lower osmotic potential → drives water via diffusion → turgor pressure of vac

• storage: stores water, ions, sugars, proteins, secondary metabolites

• degradation: lytic vac contain hydrolyses

• defense: stores toxic compounds

what are plastids and the main types

• plastids: double membrane organelle

  • chloroplast

  • amyloplasts

  • chromoplasts

describe molecular structure and assembly of cellulose microfibrils

Celluolose: unbranched polymer of glucose units

• chains H-bond in paralell to form microfibrils

Synthesis:

• cellulose synthase CesA complexes (resettes) in plasma membrane

• move along microtubule tracks

What is xyloglucan and how does it function in the primary cell wall

Xyloglucan: abundant hemicellulose in primary walls

coats and cross links cellulose microfibrils, controlling wall extensibility

what is pectin and list main types

Pectin: acidic polysaccharides ; controls wall porosity and pH

1. HG: Ca2+ cross links between HG chains to stiffen wall

2. RG-I: flexible backbone with galactan side chains

3. RG-II: complex, reserved cross linked by borate

what is lignin, how is it made and why important?

lignin: hydrophobic polymer

made in cytoplasm → exported to wall → oxidative polymerization

deposited in secondary walls of xylem vessles, fibers, casparian strip, etc

FXN: structure reigidty, waterproofing of xylem

what is middle lamella and how are cells glued together

pectin layer bt walls made in gogi vesicles make cell to cell adhesion

What is polyploidy, allopolyploidy, and autopolyploidy

polyploidy: 2+ complete chromo sets

allopolyploidy: duplication of same genome

autopolyploidy: hybridzation between species and chromosome doubling

Write full water potential equaiton and define every term

Ψ = Ψs+ Ψp+ Ψg + Ψm

Ψs = solute potential (-iCRT)

Ψp = pressure potential (+=turgor, -=tension)

g for gravity, only big trees

m for matric potential, for soil and root

Define osmosis

net movement of water across membrane from lower to higher solute concentration (high to low potential)

Describe aquaporin structure

channel proteins

what is pressure bomb and what does it measure

chamber with a lot of postiive pressure on cut leaf to balance negative pressure in xylem to access water status of plant

what is plasmolysis and what does it tell us about cell osmotic potential

protoplast shrinks away from cell wall when solute potential is lower than the cell → water leaves the cell and shrinks within teh cell wall

what is symplastic vs apoplastic

apoplastic: water moves through cell walls and intercellular spaces (non selective, fast, endodermis and casparian strip blocks)

symplastic: water moves through cytoplasm and plasmadesmatas (slower, selective, transcellular, required at endodermis)

what is the casparian strip

band of suberin and ligin walls of root endodermal walls (makes a the impermeable stele)

blocks apoplastic water movement and soltutes → transport via transporters only for fine control of ion selectivity into xylem

How do plants repair xylem embolism

prevention:

• small tracheid diameter, pit membrane anatomy with valves to shut the cell via drying and shrinking like contact lenses

describe stomatal opening in response to light

phototrophins in GC PM starts autophosorylation → H ATPase pumps H out of GC → K+ channels allow K+ enter & malate forms → Cl acculumate in vac (dec solute potential) → water enters and guard cell swell & open stomate

explain pathway of the soil-plant-atmosphere continuum

soil water → root → xylem → leaf mesophyll → stomata → atmosphere

water potential gradient is the moving force

soil: -0.1

root to leaf: -1

atmophere: -100

Crietera to essential elements/nutrition

• needs it to complete life cycle

• cannot be substituted with toehr element

• element has a direct effect to metabolism of plant

Describe nitrogen cycle to plant nutrition

N2 from air from bacteria → NH3+ to plant

NH3 or NH4+ direct taken up by nitrogen fixing bacteria

describe rhizobium & legume symbiosis

legume w/ flavonoids → rhizo node gene expresion → NOd factors to get root hair to curl → express nitrogenase and fix N2 to NH4+ to plant for malate and sucrose for rhizo

define waht the nernst equation is

an equation to predict passive equilibrium potential for an ion

if measured ion potential is negative: cation must be actively accumulated

Nernst: Uncharged molecule movement

(diffusion)

- passive transport is DOWN concentration gradient

- active is AGAINST concentration gradient

Nernst: Charged molecule movement

- passive is DOWN electrochemical gradient

- active is AGAINST an electrochemical gradient

Difference bt primary and secondary active transport

primary: uses ATP to move ions AGAINST electrochem gradient (H+ ATPase in PM and vacuole, Ca2+ into vacuole)

secondary: uses gradient created by primary pumps (symporters and antiporters)

What is the fxn of chlorophyll a vs b

A: absrobes blue adn red with reaction centers P680 and P700

B: absorbs shifted light and is only in antenna complexes to broaden aborption spectrum

Describe 3 phases of Calvin Cycle

1. carboxulation: RuBisCo catalyzes CO2 + RuPB (5C) → 2 3-PGA

2. Reduction: 3-PGA + ATP → G3P

3. Regeneration: 5/6 G3P dedicated to make more RuBP, but one G3P gain

3CO2 fixed, 9ATP + NADPH consumed

Photosynthesis path and stages

endgoal: make ATP and NADPH and convert to sugars

1. light dependent reactions on thylakoid membranes to split water and get electron

2. light independent reaction in stroma: calvin cycle

What is the antenna complex

the light harvesting comples that has pigment molecules to absorb light, pass energy, and funnel electron to reaction center

what is the z-scheme

diagram to show the path electrons take to travel through light reactions

note that the y axis is in reverse order (more negative as you go up meaning more potential for energy)

what odes PSI do diff than PSII

PSI picks up electron from the chain from PSII to give second energy boot with P700 to move electron to convert NADP+ to NADPH

What is NPQ

non photochemical quenching: excess energy from sun dumped bc lumen acidicty lowers a lot to make Zeaxanthin to make heat instead of damage

safe a reversible

what is photoinhibition

when npq isnt enough = damage to tissue (D1 protein)

sunburn damage and D1 protein hurting is the reason why photosynthesis delays are seen days after high temps

calvin cycle description and end goal

end goal: use CO2 to build sugar with ATP and NADPH

• stroma of thylakoid

CO2 → ATP and NADPH to reduce CO2 → rengeneration of G3P to make more RuBP and G3P for glucose

phases of calvin cycle

1. carbon fixation (Rubisco to RuBP)

2. Reduction (use energy from light, 3-PGA → G3P)

3. Regeneration (G3P for 5 RuBP, 1 G3P for sugar)

What is ribisco and what is it imperfect

grabs CO2 and attaches to sugar backbone

Rubisco can’t tell CO2 from O2 => photorespiration that costs plant carbon and energy

What is Calvin Cycle turned on and off depending on whether day or night

Thioredoxin system protein switch prevent running cycle when light is off

How C4 plants work

mesophyll cells with PEP Carboxylase grabs CO2 (C4)

Bundle sheath cells bring C4 and release CO2 around Rubisco

rubisco works with high CO2 environments and has less chance for photorespiration

What is the first electron acceptor in photosynthesis

Pheophytin

What are the 4 steps to C4 photosynthesis

1. carboxyloation (CO2 → HCO3- and PEPcase → Malate)

2. Decarboxylation (Malate with NAD-malic enzyme to make CO2 for calvin cycle & Pyruvate)

3. C3 reduction (Pyruvate moved to chloroplast)

4. Regeneration of PEP (Pyruvate turned into PEPcase)

5 main functions of plant cell wall

1. cell shape and support

2. protection

3. cell ot cell adhesion

4. conductance (water and ions penetration)

5. gas diffusion

What links cellulose microfibrils together

xyloglucans and the wall matrix

What is the movement of photosynthesis in the thylakoid

stroma: sugar and proton gradient to get H-ATPase working

membrane: light and electron movement

lumen: water splitting and highly acidic

How do electrons go from excited to fundamental state (neutral)

releasing heat or by fluorescing

List teh protein complexes for thylakoid membrane

PSII → PQ → Cytochrome → PC → PSI

H-ATPase

how does a biosynthesis of glucose made in plants?

reducing power of NADPH to oxidize precursors and ATP to combine and form ATP

Name main driving forces of water movement and where located in plant

Pressure gradient (root/soil) (-0.5)

Water potential (across the root) (-1)

Pressure potential (up the xylem and out the leaf) (-100)

In the roots, what are the main ions used that drag water into root

Cl- and K+

hydration shell and membrane potential to be driven into cells (concentration gradient water movement)

What can go through the phosphlipid bilayer of the membrane?

apolar things and gasses (aquaporins bring water tho)

polar ions are transported through the membrane, not through difussion through phospholipid bilayer

Describe the mode of action for channels, pumps, and transporters

Channels: passive (simple diffusion)

Pump: primary active and burns ATP

Transporters: facilitated transport (driven by gradients and whether or not they are going with or against it)

Describe how the H+ ATPase pump works step by step

1. ATP binds and phosphorylates binding center of protein → conformational change

2. Proton is grabbed from cytosol and moved outside (AGAINST GRADIENT MOVEMENT)

3. Phosphate group releated → return to normal conformation

creates negative charge inside, low pH outside cell

What are symporters and anitporters

Symporters: 2 binding sites for protons and ion

H flows DOWN gradient → conformation change to pull ion AGAINST gradient

Antiporter: H moves in DOWN gradient → ion pushed OUT against gradient

How does secondary active transport work and what is the energy source

uses proton gradient as energy source (HATPase)

What are the two cell types in phloem and how do they work together

Sieve cells and companion cells (joined via plasmadesmatas, which CC only have with the sieve cell)

together is called the sieve tube elements

CC is like casparian strip → symplastic movement from parychyma to CC then funnel to SCWhat

What is source-sink concept

Source: organ that produces sugar into pholem

Sink: organ that consumes sugar

Source has negative Ws bc of sugars → water enters by osmosis → high turgor pressure

Sink unloads sugar and makes Ws more postive → lowers turgor pressure

once solute pressure drops, water moves into sieve and sucrose moves throughout the plant

Write out steps of how stomata opens

1. phototropin senses blue light and activates H ATPase

2. H ATPase burns ATP to pump H+ outside (H+ AGAINST)

3. Channel allows K+ in (ion WITH)

4. Symport Cl- & H+ in (ion AGAINST)

5. CO2 and PEP make Mal2-

6. H ATP burns atp to pump H+ into vac (H+ against)

7. Channel lets Cl- into vacuole (ion WITH)

8. Antiporter to let Mal2- into vac (H+ and ion WITH)

9. Antiporter to let K+ into vac (ion AGAINST)

Write out steps on how stomata closes

1. Ca2+ channel into cell (ion AGAINST) to stop ATPase

2. Cl- channel out cell (ion AGAINST)

3. K+ channel out cell (ion AGAINST)

4. H2O out the cell bc Ws inc

5. drives K+ and H20 channels out of vac (ion against)

6. Cl- leaves vac (ion WITH)

much faster process bc the cell is returning to og state from Ws differences

How does the parychyma deposit sugars into the phloem

sucrose symplastically move towards phloem bc veins and gradients

Phloem loading is when acidic apoplastic move it into companion cell

PP use SWEET protein to push sugar into apoplast and H+ ATPase pushes protons out to make symporter drive WITH proton gradient

Connect proton pump to different processse

1. stomatal opening: acidify apoplast to make Cl- symporter work better to make osmotic potential drop

2. Phloem loading: acidivy apoplast to get SUC symporter to use acid gradient to pull in sucrose into companion cell

3. Secondary active ion transport : creates proton gradient for secondary active transporters to use

How does pH affect nutrient availability

protons precipiates positivly charged ions that are attached to soil (silica is negatively charged naturally)

nutrient availability is tied with concentration of protons

List some micro nutrients and their roles in plant phys

Fe: electron carriers and chlorophyll synthesis

B: cell wall with pectin and membrane function

Cl: PSII oxygen evolution, stomatal guard cells

List some macro nutrients and their roles in plant phys

N: amino acids, proteins, chlorophyll

P: ATP and phospholipids

K: stomata regulation

Ca; Cell wall and pectins

Why do plants have to assimilate nutrients and not use raw minerals directly?

plants have to convert inorganic molecules into organic via processing

N: convert NO3- → NH4- → glutamine → amino acids

S: SO4-3 → S-2 → cysteine

P: H2PO4+ used directly in ATP, DNA< phospholipids

How convert nitrogen in soil into amino acid in plant

1. Uptake in roots: NO3- in soil to root via NRT transporters

2. Reduction: cytoplasm convert NO3- to NO2- via nitrate reductase Reduction in chloroplast: NO2- → NH4+ via nitrite reductase

3. Incorporation: NH4+ and glutamate = glutamine via glutamine synthase and ATP

What is biological nitrogen fixation

making N2 into NH3+ from nitrogen fixing bacteria

Nitrogenase reaction: N2 + 8H+ + 8 e- + 16 ATP

what is ABA and why is it the stress hormone

Abscisic acid made in vascilar tissue when leaf starts to lose water.

1. stomata closes if ABA builds up and reaches stomates (PYR recognize on GC and turns on downstream effect to open gates to make Cl- and malate flow out of cell)

2. genes turn on: protect molecules

3. seed dormancy: wait for conditions to be favorable

wants to shift plant in conservation mode

How many proteins are in Cellulose synthase complexes?

3 proteins per unit (previously thought the rosette had 6)

Name organs and a key function of each

Leaf: site of photosynthesis & evaporation

Stem: leaf and root transport & mechanical support

Root: water uptake & anchoring

Name tissue systems found in plants

Dermal

Ground

Vascular

Meristem (root apical and shoot apical)

what is the difference btween a B-1,4 and B1,3 glycosidic linkage? Name the polysaccharide made by each

1,4 → side groups alternate on glucose (linear molecule = cellulose)

1.3 → side groups attached on same side (curved & flexible molecule = callose)

What role does Calcium play in wall rigidity? What component do they interact with?

Ca works with PECTIN in middle lamella and primary wall

Ionic bridges with pectin chains to make stiff lattice structure

Name two main components of the secondary wall

Cellulose and ligin

List layer of root cross section from outer to innermost

Epidermis → Cortex (parenchyma) → endodermis (casparian strip) → Pericycle → Vascular bundle

name 3 types of ATPase

V: vacuole (acidify vacuole)

P: plasma (electrochemical gradient)

F: thylakoid membrane (acidify lumen)

Explain how proton gradient in thylakod is connected to ATP synthesis.

lumen is filled with H+ from water splitting and H+ pumping from process of electron chain. Since [H+ lumen] > [H+ stroma], the H+ wants to diffuse through the only exit, ATPase. movement of H+ provides mechanical energy with ATP ring spinning, which phosphorylates ADP to ATP

How/what forms are P and N taken up in plants?

P: PO4-

N: NH3 and NO4-

What are the mutual benefits of symbiosis

Plant gets WATER and PO4-

Fungi gets carbon via SUGARS and other amino acids

What process fixed the most nitrogen in the history of world/

Haber Bosch process to capture N2 to usable forms like NH3 and NO4-

nitrogen cycle and its form in the environ to plant

through decaying OM → ammonification (NH4+ → Nitrite NO2- → Nitrate NO3- → N2 gas for symbiotic bactera fix for plant)

How do plants regulate how much mineral and ions takes up?

mainly through root epidermal proton pumps for cation exchange with surrounding soil

How do plants get rid of excess nutrients?

storing them in vacuoles, shedding old leaves

Plants can sense nutrient level and respond to it. E.g. lateral roots induced under low Pi. How?

auxin sensitivity via enhanced TIR1 expression and auxin/IAA degradation, alongside root-derived signals

local sensing, ROS signaling, and phosphorus starvation-induced genes (PSRs)

How do plants perceive these messages (regarding nutrient) and respond to it?

root-microbiome interactions (rhizomicrobiome)

Explain the pressure flow aka Munch hypothesis of phloem transport. what creates the pressure gradient from source to sink

source: sucrose laded in sieve tubes → Ws drops → water flows in from xylem via osmosis → POSITIVE TURGOR PRESSURE

sink: sucrose unloaded for consumption → Ws climbs → water exits → low turgor pressure

pressure diff of high source, low sink makes BULK FLOW of pholem sap