BIOLOGY TOPIC 9 PLANT BIOLOGY (HL)
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BIOLOGY TOPIC 9 PLANT BIOLOGY (HL) - Marcador
BIOLOGY TOPIC 9 PLANT BIOLOGY (HL) - Detalles
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| What are the 2 types of active transport in root uptake? | Direct: protein pumps move ions against a gradient indirect: proton pumps expel H+ ions into the soil displaces the cations which diffuse back into the root |
| What are vascular bundles? what are they used for? (3) | Xylem and phloem is used for transporting materials |
| NA | NA |
| How are halophytes adapted to conserve water? (4) cut the root salt | Cellular sequestration = separating ions and salts in vacuoles tissue partitioning= concentrating salts into specific tissues root level exclusion = root structured to exclude salt salt excretion = glands to eliminate salt |
| What are autotrophs? | Plants bec they can make their own food from inorganic sources |
| How do plants make organic molecules? | Through photosynthesis |
| What are the organic molecules that plants make? | Glucose and starch |
| How are halophytes adapted to conserve water? (4) | Cellular sequestration = separating ions and salts in vacuoles tissue partitioning= concentrating salts into specific tissues root level exclusion = root structured to exclude salt salt excretion = glands to eliminate salt |
| How are halophytes adapted to conserve water? (4) | Cellular sequestration = separating ions and salts in vacuoles tissue partitioning= concentrating salts into specific tissues root level exclusion = root structured to exclude salt salt excretion = glands to eliminate salt |
| How are halophytes adapted to conserve water? (4) | Cellular sequestration = separating ions and salts in vacuoles tissue partitioning= concentrating salts into specific tissues root level exclusion = root structured to exclude salt salt excretion = glands to eliminate salt |
| How does capillary tubing model transpiration? (4) | Water can flow in narrow spaces against gravity = capillary action bec of cohesive forces and adhesion to the walls thinner tube . less dense fluid = higher the liquid will rise |
| What do plants use cell respiration for? | To make ATP from the stored organic molecules |
| What is the function of leaves? | It contains chloroplasts (photosynthesis) and pores for gas exchange |
| How are mineral ions up taken in the roots? | Actively transported = causes absorption of water by osmosis |
| How are roots specialized for water and mineral uptake? (2) | Branched to optimize ACTIVE uptake of water and minerals from soil Extensive branching to maximize the surface area |
| What is the function of stems? | Vascular bundles to transfer materials bw the leaf and root |
| What are the 3 main parts of a plant? | Leaves stem roots |
| What are the layers in the leaf called? and what are the functions of each layer? (3) | Upper palisade mesophyll = tightly packed w many chloroplasts (light absorption) lower spongy mesophyll = loosely packed with air spaces near stomata = increase gas flow vascular bundles between layers (xylem and phloem) |
| What are the 2 types of root systems? | Fibrous roots = thin and very spread out (increases SA for absorption) tap roots = penetrating w lateral branches (deeper reservoirs of water) |
| How are roots specialised for optimal water absorption? | Root hairs = increase surface area |
| How is water uptake controlled by the casparian strip in roots? (4) | Absorbed by ROOT EPIDERMIS diffuses across CORTEX towards CENTRAL STELE pumped across CASPARIAN STRIP that is impermeable = controls uptake rate |
| What are vascular bundles? what are they used for? | Xylem and phloem is used for transporting materials |
| What does xylem transport? | Water = transpiration |
| What does phloem transport? | Nutrients (source to sink) = active translocation |
| What is transpiration? | Loss of water vapor from stems and leaves due to gas exchange |
| What are the steps of transpiration? (5) | Light energy converts water in the leaves into vapor water vapor is lost through evaporation new water is absorbed from the soil through the roots = P difference in leaves and roots water flows up stem (xylem) in mass flow along the pressure gradient |
| How does evaporation cause transpiration? (3) | Some light that is absorbed becomes heat = water becomes vapor in spongy mesophyll vapor diffuses out of stomata and is evaporated = tension forces negative hydrostatic P = draws new water out of xylem |
| What is the transpiration stream? | The way water flows in the xylem from the roots to the leaves and involves mass flow |
| How is water taken up into the root? | It is taken up through osmosis when mineral ions are actively transported into the roots |
| What is mass flow? | Movement of fluid down a pressure gradient (roots - leaves) leaves = lower pressure bec of evaporation roots = higher pressure bec of osmotic uptake |
| What is capillary action? | Water rising through tubes against gravity due to cohesive and adhesive forces |
| What is cohesion? (4) | Water molecules stick together (hydrogen bonding) bw 2 particles of the same substance water is polar and can form H bonds through intermolecular bonding = water molecules can be pulled up the xylem in a continuous stream |
| What is adhesion? (6) | When water molecules stick to the xylem wall (polar associations) bw 2 particles of different substances xylem wall + water are both polar = as water moves up by capillary action, pulls inward on the xylem to create more tension |
| What are the features of the xylem? (7) | Inner lining of dead cells fused into a continuous tube vessel element / tracheid hollow to enable water movement cell walls have thickened cellulose reinforced w/lignin = provides structural stability outer layer is perforated (pores) to facilitate water movement indents and pits |
| Why is the movement of water a passive process? | Bec the cells are dead and happen in one direction only |
| What are the 2 patterns of lignification? | Spiral = coil annular = circular rings |
| What is lignin? | A complex organic polymer in the cell walls of plants to make them rigid and woody = structural stability |
| Which part of the plant regulates the transpiration rate? | Stomatal pores on the leaf's underside |
| How do stomata close? | When the guard cells beside it loses turgor and becomes flaccid = by cellular signals in response to external triggers |
| How can transpiration be modelled? (3) | Capillary tubing filter paper porous pots |
| How does capillary tubing model transpiration? (4) | Water can flow in narrow spaces against gravity = capillary action bec of cohesive forces and adhesion to the walls thinner tube . less dense fluid = higher the liquid will rise |
| How does filter paper model transpiration? (3) | Absorbs water bec of cohesive and adhesive properties = similar to how water moves up the xylem paper and xylem wall are both made of cellulose |
| How does porous pots model transpiration? (3) | Semi permeable containers water loss is similar to evaporation of water in the leaves if an airtight seal is used = negative P = More liquid |
| What are potometers used for? | Used to measure the transpiration rate by measuring the distance travelled by an air bubble every minute |
| Why is not all the water lost to transpiration? | A small amount is used in photosynthesis and to maintain the turgidity of the plant |
| What factors increase transpiration rate? (3) | Light = opens stomata for photosynthesis = more water vapor lost temp = increases evaporation = more water loss in leaves wind = more air flow removes water vapor = more diffusion |
| How can all the factors affecting transpiration rate be tested with a potometer? (4) | Light = diff distances from a lamp temp = heaters / heated water baths wind = fans to circulate air around the plant humidity = plastic bags with diff levels of vapor |
| What factors decrease transpiration rate? | Humidity = more water vapor in the air = less diffusion |
| What are xerophytes? | Desert plants they have higher rates of water loss bec of high temps increasing evaporation rate |
| How are xerophytes adapted to conserve water? (4) | Thick waxy cuticles = prevents water loss from leaf surface low growth and small leaves = small SA rolled leaves with stomata in pits = traps WV CAM physiology = stomata closed during the day |
| What is the difference between proto-xylem and meta-xylem? | Proto-xylem is smaller in diameter than meta-xylem |
| What are halophytes? | Saltmarsh plants that have low levels of water uptake bec of high salinity in the soil reducing osmosis rates |
| How are halophytes adapted to conserve water? (4) | Cellular sequestration = separating ions and salts in vacuoles tissue partitioning= concentrating salts into specific tissues root level exclusion = root structured to exclude salt salt excretion = glands to eliminate salt |
| How does rate of photosynthesis affect rate of transpiration? (3) | Stomas are used for gas exchange for photosynthesis = so when they are open transpiration occurs as well bec WV is lost at the same time |
| When is the hormone ABA released in plants? (6) | When a plant begins to wilt from water stress the dehydrated mesophyll cells release ABA = causes K to flow out from guard cells = reduces water P = loses turgor = stomata closes bec the guard cells become flaccid = blocks opening |
| Which type of plant has vessel elements? | Angiosperms |
| All vascular plants have what? | Tracheids |
| What are tracheids? | Tapered cells that exchange water through pits = slower water transfer rate |
| What are vessel elements? | End walls are fused to form a continuous tube = faster water transfer |
| How are minerals taken up in plants? | 1) fertile soil has negatively charged clay particles for cations to attach to 2) passively diffuses into the roots 3) indirect active transport = H+ ions are released by proton pumps in the roots 4) these ions displace the positive ions from the clay = diffuse into the root along a gradient 5) anions can bind to the H+ ions and be reabsorbed with the proton |
| How is water taken up from the roots? | Follows the mineral ions with mass flow through osmosis to a region of higher solute concentration |
| How is the rate of water uptake regulated? | With specialized water channels = aquaporins on the root membrane |
| What is the symplastic and apoplastic pathways? | The way water moves towards the xylem symplastic = cytoplasm apoplastic = through cell wal |
| At what point can the water not cross in the apoplastic pathway? | When it reaches the casparian strip = transferred to the cytoplasm |
| What features need to be included when drawing xylem? | Vessel elements = continuous tube tracheids = interlinking tapered cells gaps lignin either spiraled or in rings |
| How do plants transport organic compounds? | Source to sink |
| What are aphids? | Insects that feed on the sap in phloem |
| What are the properties of the phloem? (6) | Transport water and food 2 directional made of sieve element cells which forms a tube sieve cells are connected with a holey sieve plate supported by companion cells for loading/un movement is controlled w hydrostatic P from X |
| What is active transport used for in phloem? | To load organic compounds into pl=hloem sieve tubes at source |
| How does the phloem cause water uptake? | High solute concentrations in source cause water to be take up through osmosis |
| What does the hydrostatic pressure gradient in the phloem do? | Causes the material in the phloem to flow towards sinks |
| What is translocation? | Movement of organic compounds from source to sink |
| What materials are transported? | Sugars, amino acids |
| What is the source ? | Where organic compounds are made = leaves |
| What is the sink? (2) | Where the compounds are sent to / stored roots, fruits, seeds |
| In what form is sugar transported? (2) | Sucrose (disaccharide) soluble and metabolically inert (still) |
| What makes up the phloem tube? (2) | Sieve element cells companion cells |
| What are sieve element cells used for? | Connect to form sieve tube |
| How are sieve tubes specialized? (5) | Long and narrow connected by sieve plates porous for flow no nuclei to maximize space for translocation thick rigid cell wall for hydrostatic pressures |
| What are companion cells used for? | Metabolic support to help with loading and unloading materials at source and sink |
| How are companion cells specialized? (3) | Infolding plasma membrane = + SA: Vol ratio for more material exchange many mitochondria = active transport of materials from source to sink transport proteins in membrane: move materials in / out of sieve tube |
| How can phloem and xylem cells be distinguished? | Xylems have a larger diameter |
| What kinds of cells do phloems have for support? (3) | Schlerenchymal parenchymal fills additional spaces + provides support |
| Why do sieve element cells need companion cells? (3) | Bec sieve cells have no nuclei and few organelles plamodesmata is a lot bw sieve elements and companion cells = connects the cytoplasm of the 2 cells |
| How does the arrangement of x + p differ in roots for monos and dis? (5,3) | Monocotyledons large stele (middle part) vessels form a radiating circle around it xylems are placed more internally phloem places more externally O = outside Dicotyledons small stele xylem internally placed = forms an X phloem surrounding it = surrounding gaps |
| How does the arrangement of x + p differ in stems for monos and dis? (2,3) | Monocotyledons vascular bundles are scattered through the stem phloem is placed externally o= out Dicotyledons vascular bundles arranged in a circle around the stem's centre (pith) x+p is separated w/ cambium xylem inside, phloem outside |
| How is organic compounds pass through the cells to be loaded into the sieve tube? (2) | Passes through interconnecting plasmodesmata (Symplastic) or through the cell wall by membrane proteins (Apoplastic) |
| How is ATP used for apoplastic loading of sucrose? (4) | 1) H+ ions are AT out of P cells by proton pumps (hydrolysis of ATP) 2) conc of H+ ions + out of cell = proton gradient 3) H+ ions passively diffuse back into phloem w/ co-transport protein = sucrose movement 4) loads sucrose into sieve tube |
| What does the active transport of solutes cause the sap solution to be.. | Hypertonic (more solutes than water) |
| Why does the sap solution being hypertonic cause water to be drawn up? what does this cause?(4) | Water is drawn up by the xylem bec the water moves to the higher solute concentrations bec water is incompressible = hydrostatic p in phloem increases forces phloem sap to move to areas with lower pressure (mass flow) = solutes are transported away from source to the sink |
| What happens once the solutes are unloaded in sinks? (3) | Sap solution = hypotonic water is drawn out of phloem = xylem by osmosis = hydrostatic p at sink is always lower than hydrostatic p at source |
| What happens to the solutes when they are transported to the sink? (2) | Metabolised stores within the tonoplast of vacuoles |
| What are aphids? | Insects that feed on the sap in phloem |
| How are aphids specialized to drink phloem? (3) | Stylet which pierces plant sieve tube = sap extraction aided w/ digestive enzymes to soften tissue layers if stylet is severed = saps continue to flow bec of hydrostatic P |
| How can aphids be used to measure translocation rate? (6) | 1) used to collect sap at various sites of the plant's length 2) plant grown w' leaves in radioactively labelled CO2 3) CO2 becomes radioactively labelled sugars 4) once stylet is severed the sap continues to flow 5) sap is analysed for radioactively labelled sugars translocation rate is calculated based on time taken for the radioisotope to be detected in diff positions of the plant's length |
| How is the rate of phloem transport determined? | By the conc of dissolved sugars in the phloem |
| What are the factors affecting translocation rate? (4) | Photosynthesis rate (light intensity, CO2 conc, temperature) respiration rate (affected by factors that stress the plant) transpiration rate (determines how much water enters phloem) sieve tube's diameter (affects hydrostatic P + differs bw plant species) |
| What are undifferentiated cells in the meristem used for? | Indeterminate growth |
| What do mitosis and cell division do? | Proved cells with extension of stem and leave development in the shoot apex |