Biol 351 Notes PDF

# CAM Plants - second strategy to minimize photorespiration - have Crassulacean acid metabolism (~C4) - temps are lower at night and humidity is higher - at night, CO₂ is fixed into organic acids in mesophyll cells - during the day, light rays supply ATP + NADPH to Calvin cycle and H₂O from organic...

# CAM Plants - second strategy to minimize photorespiration - have Crassulacean acid metabolism (~C4) - temps are lower at night and humidity is higher - at night, CO₂ is fixed into organic acids in mesophyll cells - during the day, light rays supply ATP + NADPH to Calvin cycle and H₂O from organic acids to be used - But you need to - be able to activate PEP-carboxylate in the dark - in C3 plants, PEP is activated only in the light. These plants have light-inactivated PEP - carbonic anhydrase is pH activated ## Dark - the carbonic anhydrase is activated by H⁺. - pyruvate from starch - PEP carboxylase - oxaloacetate - NAD⁺ malic dehydrogenase - malate - starch (storage) - CO₂ ## Light - CO₂ - *malate* - malic acid - pyruvate - **starch** - mesophyll cell CO₂ malic acid is sequestered to keep the cytosol from getting too acidic, which would make all the HCO₃ go back to CO₂. CO₂ starch is converted and pyruvate, in the chloroplast, is used as a substrate to move malic acid. Plants have to make starch during the day. ## C3 Intermediates - Triose Phosphates - Triose Phosphates - Triose Phosphates - Triose Phosphates - Triose Phosphates - RuBP - Erythrose-4-Phosphate - Ribose-5-Phosphate - 5-C Intermediates ## Pathways - Starch synthesis - Sucrose synthesis - Cellulose synthesis - Glycolysis, Krebs Cycle - Pentose Phosphate - Shikimic acid pathway ## Products - Starch - Sucrose - Cellulose - CO₂, Organic & Amino Acids (supports NADH synthesis) - CO₂ (supports NADPH synthesis) - Lignin, Aromatic Amino acids - RNA, ATP - Hemicelluloses ## Physiological Acclimation - improves ability of plants to exploit environmental resources & survive hazards - plants naturally acclimate to conditions (like adapting to higher CO₂ levels) - can make plants adapt by slowly “hardening” them to tough conditions. - we want to know how we can fine-tune plants to survive better in the future, to support future humanity. ## Summary Table | C3 Intermediates | Pathways | Products | |------------------|-----------|-----------| | Triose Phosphates | Starch synthesis | Starch | | Triose Phosphates | Sucrose synthesis | Sucrose | | Triose Phosphates | Cellulose synthesis | Cellulose | | Triose Phosphates | Glycolysis, Krebs Cycle | CO₂, Organic & Amino Acids | | Triose Phosphates | Pentose Phosphate | CO₂ | | RuBP | Shikimic Acid Pathway | Lignin, Aromatic Amino Acids | | Erythrose-4-Phosphate | | RNA, ATP | | Ribose-5-Phosphate | | Hemicelluloses | | 5-C Intermediates | | | Essentially, CO₂ is taken in at night, and water loss occurs at night. So: Time separated, not spatially separated like C4 bundle sheath cells. # Translocation of photoassimilate (vasculature) PHLOEM - transports both things made by the *plant* and transported by roots. - interfascicular cambium - bundle sheath - xylem - phloem ## Phloem - transports things made by plant - water and nutrients (from outside plant) - phloem and xylem are bundled together, and spread throughout the stem - interfascicular layer of cells that give rise to cambium, the mother cells, which make new tissues. - Here, the plant decides what cell type is going to be produced and when ## Primary phloem/xylem = height ## Secondary = girth - vascular cambium is responsible for secondary growth (lower down on the stem) - long distance transport trick - If the phloem is girdled, it can no longer transport sugars to the roots of the plant. **4 cell types:** 1. **sieve elements:** - thick, permeable walls, *alive*, lack *nuclei* and *cytosol* is filled with P-protein - have sieve plates (pores on sides or ends) which are lined with callose (sugar) - form sieve tubes - callose is a beta 1,3-linked polymer. All glucan (sugar) carbons face the same way, so it does not crystallize, and it is easy to break down. - all glucose - a very globular sugar - can plug up the pores and stop the flow of sugars through the phloem 2. **companion cells:** - have nuclei, *dense cytoplasm* - same as sieve elements - connected by plasmodesmata (cells with pores) to other cells - **Types**: - **Ordinary:** Few plasmodesmata or cell wall ingrowths - **Transfer** - many cell wall ingrowths - **Intermediate:** Many plasmodesmata, many small vacuoles. 3. **Phloem parenchyma:** - thin walled for storage or lateral transport (alive) 4. **Phloem fibers:** - dead - xylem turns into mother cells - vascular cambium stays as cambium - mother cells that divide become phloem - mother cells that stay as cambium - xylem expands and then turns into mother cells Essentially, the vascular cambium decides what cells are needed. - The vascular cambium can also divide side to side, allowing for growth of the cambial layer without breakage. In general, 70% of divisions give rise to xylem, 30% to phloem. ## Source -Predetermined Pathways - connections in plants, orthostichy – predetermined - sugars from old leaves (source) go to certain new leaves. The pathway has been set, so not all source leaves give sugar to all sink leaves. - So if you wound a leaf, the ones next to it, and the ones which it feeds (the sinks) are the most affected by the damage. ## Sink - sugars from the old leaf go down and in/out - sugars go from source to sink. To develop (fruit/new leaves) - Sink- anything continuing **How to collect phloem?** - Aphids! They find a phloem cell, perfectly every time. - The phloem drops out their backside when they are anaesthetised. If you remove leaves, anastomosis (the ability to make new connections) happens. **If a leaf is removed, another leaf will fill the spot to feed the sink leaves that the old leaf was responsible for.** - As a leaf grows, it becomes less sink and more source. ## Phloem vs. Xylem - **Phloem**: Slightly basic, *tons of sucrose*, some amino acids, and other essential nutrients. - **Xylem**: Actually transports nutrients + H₂O from soil. **NO SUGAR MOVED** # Material that gets moved: - sucrose (or raffinose, stachyose, verbascose) or sugar alcohols (sorbitol, mannitol) - proteins, amino acids - mineral nutrients (but not N₂) - hormones (like cytokinins) - organic compounds - mRNA (viruses too!) - Dwarf mistletoe - find phloem and synthesize hormones to tell the plant to keep producing sugars for the mistletoe. - Papaya - Get ringspot virus. - Moved in phloem vasculature - Made transgenics to survive ringspot (phloem of roots touch each other and can wipe out an entire field) # Mechanism of Transport: ## Diffusion too slow. ## Pressure flow model: - The flow itself is passive. Loading & unloading. - It is not bulk flow driven by transpiration. - The model works until the source is gone. **Aquaporins** - don't transport water, *let* water into cells. Flow must be pushed. * **Symplastic** - from companion cell to sieve (90%) * **Apoplastic** - from mesophyll to companion cell (uses symporter) to sieve * **Based on**: - Number of plasmodesmata (ports). If ↑, then raffinose - Sucrose loaded apoplastically **ATP loading** - phloem loading is active. - **Symplastic**: Flows through intermediary cells of the plant. - **Apoplastic**: Forces bulk flow loaded symplasmically. If not, symplasmically goes through intermediary cells of the plant. **How do sugars not backflow?** **Polymer Trapping Model!** - Create sugar bigger than the holes to enter. (Raffinore) - Means you can make high sugar concentration without backflow. ## Starch Metabolism: - What do I do with the sugar when it is unloaded? - Major storage carbohydrate - Transitory (day/night), heterotrophic storage (Long term, summer/winter) - Plants vary in extent of sucrose accumulation and starch - Do I make sucrose or starch? Some are constant all day long, others produce starch when sucrose cannot be stored or there is enough. - Can and method under environmental stressors or seasons. **Transitory:** In chloroplasts of leaves. **Storage:** Stored in amyloplasts (in tubers, cereals, roots and bulbs) - **Glucose (which becomes starch)** - Triose phosphate becomes ADP-glucose - The rest becomes UDP-glucose - Starch is made by the chloroplast - **Sucrose** becomes UDP-glucose - Storage for things other than starch - **So, ADP-glucose enzymes control starch pud. (AGP-ase)** ## Day (Leaf): - Add ADP-glucose to primer. - Sucrose is made in the cytosol and starch in chloro - Can make long chains of starch by just adding more glucose to existing chains. - Leftover from the day before. ## Night (Leaf) - Transpiration - H⁺/sucrose higher ups, so water flows back to xylem - Sucrose flows into phloem, so source cell pressure (leaf) and sugars flow down. - **Active** Loading: - Sink cell pressure is active - Starch is broken down into maltose and glucose (in chloroplast) - Goes into sucrose (in cytosol) - Then sucrose goes to vascular. ## Starch Elongation: - Need a primer to start, then add ADP-glucose - **SAME Pathway in all starch** - Starch starts to branch from linear polymer (by branching enzyme) - Starch is broken into (some is cleaved off): maltose and glucose (in chloroplast) - Then into sucrose (in cytosol) - Then sucrose goes to storage *Need to break 1-4 bonds to get glucose, (from transitory) *Break alpha 1-4 bonds, then branching *To degrade branched starch, have to break alpha 1-6, then break alpha 1-4 to get glucose. # Control of Transitory/ Storage Starch: - **Tetramer,** held together by disulfide bridges - AGP-ase is regulated by: - **Protein phosphorylation** Unsure of the mechanism - **Redox modulation** (like nitrate reductase) - **Allosteric regulation** (Light/ Dark) - **Transcriptional regulation** (Nitrate reductase) - **Ferrodoxin** - cleaving S-S bond - Sugars increase and Nitrate decreases (because ferrodoxin is used in nitrogen metabolism) - Expression of genes for 4 subunits - Spatially Regulated. - Small subunits turned on everywhere - Large subunits are regulated # Hemicellulose: - Side chains prevent from forming long chains - Made exactly like cellulose, but with some extra sugars on the side. - Hydrogen bond to cellulose. - Regulates cell enlargement # Pectins: - Multi - Different types - Can be very simple or highly branched - Hold water, become globby (lots of O-H groups) - Love water ## Membrane Associated Proteins: - Signaling # Plant cell walls - synthesis: - Mechanical properties contribute to the complexities of plant cell shape. ## Callose - Beta 1,3 linked glucose. - Recently found in cell walls. - Cell plate + primary walls contain callose. - Do not know whether it stays when the wall is formed. ## Components - Mannose makes mannan - ALL SUGARS FROM TRIOSE PHOSPHATES - Cellulose (i.e., *Microfibrils*) 50% - Pectins - Sugars - Made of homogalacturonan - Lignin, structural proteins 25-30% ## Primary vs. 2º wall - **Primary** can expand, 2º cannot - 2 º forms after expansion is completed - Callose - 1º - 2º - 2º is deposited inside thin primary walls ## *Need Boron* - To make 2º walls - 2º can have elaborate ingrowths. ## *What Makes a Plant a Plant?:* - *Lignin* - *Highly Ignighted* - *Only have in 2º Walls* ## *What Makes a Plant a Plant?:* - *Same things can have 1º walls. Others have both but no lignin.* ## Cellulose: - Cellulose and callose are synthesized at the plasma membrane from glucose ## Matrix polysaccharides - Hemicellulose + pectin - made in Golgi, delivered to PM by vesicles ## Enzymes, structural proteins - Made by rough ER - Must glycoproteins are glycosylated in the Golgi complex. ## Hemicellulose: - Like cellulose - Xylan - Glucomannan 20-25% - Lignin, structural proteins 25-30% ## Primary vs. 2º wall: - Woody, structural proteins - Primary can expand, 2º cannot - 2º forms after expansion is completed - Callose - 1º - 2º - 2º are deposited inside thin primary walls ## *Need Boron* - To make 2º walls - 2º can have elaborate ingrowths ## Cellulose: - Cellulose, callose are synthesized in plasma membrane from glucose. ## Matrix Polysaccharides: - Hemicellulose + pectin are made in the Golgi, delivered to PM by vesicles ## Enzymes, structural proteins: - Made by rough ER - Must glycoproteins are glycosylated in the Golgi complex. # Cellulose: - *Cellulose, callose synthesized @plasma membrane from glucose* - *Most abundant polymer synthesized @ PM by enzyme complexes* ## Cell Wall - UDP glucose is starting. - Glucan chain - Cellulose microfibrils - Pectin & hemicellulose (made in golgi) ## Plasma membrane: - *Get built as they move through the golgi, then veride breaks bits off. Can be premade sugars* ## Pectin Properties: - *Or proteins to help make other components (like ces-A)* ## Primary wall: - *Has very little cellulose orientation* ## Sucrose: - *Glucose - fructose* ## Cellulose Microfibrils: - *Glucan chains!* - *Rosettes* - made up of multiple Ces A's. - *Ces A's: specific to primary or secondary walls* ## *Rosettes move within membrane and leave a trail of cellulose.* - *Direction of movement is governed by microtubules, which are used to depolymerize and orient cellulose.* - **Orientation of cellulose determines cell shape/direction.** - *That happens in wood based on seasonality, a size of cell and thickness.* ## *Some things only have 1º walls. Others have both, but no lignin.* ## *Not radicalized until they get through membrane.* - *p-coumaroyl alcohol* - *Coniferyl alcohol* - *Sinapyl alcohol* - *All polymers are made* # Apical meristem: - The *stem cells of plants* - At roots and shoots # Water ## Evaporation - Transpiration - Evapotranspiration - 69% of water taken up is transpired. - If plant = 500g, 500g of water has gone through plant to make - Precipitation is uneven and aridity is extensive. - More water = more productivity until it plateaus. ## Physiological Importance of Water - Turgor pressure - Transports - Reactions - Component of cytosol - Heat regulation (evaporation cooling) - Hydrolysis ## Giant cacti - How do they store enough water? - Giant, wide roots - Swell up with water and pleats help to increase surface area and allow for expansion. (Latent heat) - Heat of fusion - super high altitude plants - As the day changes to night, condensation forms and drips down (red) - Water crystallizes and gives off heat, keeping the apical meristem warm and undamaged. - Process is also used in orchards and vineyards. (Spray a fine mist over fruit when temps dip below freezing, like wine.) - 4 seasons give plants time to adjust. - Grapes change sugar concentration in grapes to protect from freezing (breaking of membranes) - Harvest at first frost to get extra sweet components. ## Components of Ψ (always -) - **Solute Potential** Ψs - Measure of effect a solute has on chemical potential of solvent (water) - Always negative - More negative as fraction of water decreases (more solute, more negative) - **Van't Hoff formula**: - Ψs = - CRT(solute concentration) - C = 0.00831 L3 MPa mol⁻¹ K⁻¹ (gas constant) - R = absolute temperature (K) = 273 + °C - Solute concentration in molality (mol/kg) - Ionization constant (dependent on type of solute) - IE. 1 molal of glucose at 0 °C = Ψs = -0.00831 x 273 x 1 = -2.269 (don't need to memorize constants) - **Ionization constant** - for glucose, it is 1 - You have to calculate separately for each type of sugar then add together. - What about sucrose (dimer)? - It does not depend on charge. - Like salt, it goes into Na⁺ and Cl⁻. So the ionization constant will be 2 - **Sugars do not dissociate** ## Freezing point depression: - Each molal of carbohydrate and freezing point by 1.86°C - First, find Ψs (solute potential) - IE 1 molal of glucose Ψs = -2.269 - -2.269 / 1.22 = ΔT (°C) - 1.86°C lower then normal freezing temperature. ## Plant: **Ψw = Ψe – Ψp + Ψm** - Soil: Ψw = Ψs – Ψp + Ψm - Ψm and gravity are not involved because they are so small, so we usually ignore them - Ψm in plants is small, but in soil, it is important, so include it. ## Water moves from: 1. Higher **Ψw** 2. Lower [Solute] 3. Higher **Ψp** - As you increase temperature, pressure increases. - Water under + or pressure = tension (Ψp) - seen in xylem and transpiration - Can reach 2 MPa ## Matric Potential (always (-) or 0) - Caused by hydrogen bonds (mainly in the *matrix*) - Cell walls, proteins, soil particles - They are charged - Extends only a few molecules from surface - Important in seeds, dry soil. Not as important in hydrated tissues. ## What about Volume, Ψω? - Volume as water moves, and solute concentration changes, so Ψs changes and also Ψp. - **Ψw = Ψs – Ψp + Ψm** - If 10% of total volume, Ψp has a huge effect. - Beyond that, solute has a bigger impact. ## Plants are super dynamic. ## Plasmolysis: - Cell shrinks way down when placed in sucrose solution (more negative than the cell sap) ## Kelp - Grows at 0 m below sea level at 20 °C and a molality of 0.62 - Kelp is turgid - Ψp kelp =1.0, What is Ψs kelp? - Ψs kelp = -CRT = -0.62 x 0.00831 x 293 = -1.5 MPa - Ψw ocean = -3.02 MPa - It is because of salt ## Can assume: - Ψw ocean = Ψw kelp - So Yw ocean = -3.02 +0.1 = -2.92 - Ψw kelp = -2.92 - -2.92 = - Ψs /1 - **So Ψskelp = -3.92** ## IE: - Ψw = 0.5 MPa and Ψe = 1 MPa (what is Ψs if pond is freshwater?). ## Pond: - Freshwater, so I'm is 0, and Ψw has to be close to 0. Therefore the Ψs of the pond would be -1.5 MPa # Water Movement: - J = (AΔΨ/) conductance - Water enters roots by diffusion, moves up by bulk flow. - Soil Plant Atmosphere Continuum (SPAC) - Soil must be more negative than the root, and so on up the plant. - In the end, Ψw air < Ψw plant - Soil outward to xylem, root (matrix and Casparian strip) ## *Plant* - Plant has to manufacture a lower Ψw than the soil to get water to move into the plant. ## *How does the plant get Ψw < Ψw air?* - **Know:** - Relative humidity - Ψair = 0.4619 * T * ln(1% RH/100%) - 100% Relative Humidity = Ψair = 0 (because no more water can be added) - Ψair drops as RH drops. - If 95% Relative Humidity, Ψair = -7 MPa. ## *This negative Ψair causes water on the ground to be sucked up into the plant*. # Soil Characteristics: - Ψw soil is governed by Ψw mix - Ψs soil is determined by particle morphology & size - 1g to 100g, 100x of these small particles is way more negative in changes than one big particle. - Plants must overcome negative charges in soil to draw up water. ## Field Capacity: - Wet but freely drained soil - When saturated, Ψw = 0 - When water is removed, Ψs and Ψm are more important - Ψw soil < Ψw root for water to move ## Types of Loading: 1. **Symplastic:** Cytoplasm - cytoplasm 2. **Apoplastic:** Along/through cell walls. 3. **Casparian strip:** - It's waterproof - Gates are built into the endodermis to let water in.