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Plant gas e/t
Gas exchange + transport in plants
| Question | Answer |
|---|---|
| What structures facilitate gas exchange in vascular plants? | stomata in the leaves + stems, and the root hairs of roots |
| Fibrous vs taproots (root systems) | Fibrous: in monocots; well adapted to shallow soil + dry regions, where water is near the surface Taproot: in eudicots; well adapted to deep soils where water is far from the surface |
| how have mycorrhizae assisted in the colonization of land by vascular plants? | fungi + plants work together in a symbiotic relationship; the fungi extend the plants root systems, allowing them to obtain more nutrients and water from the soil to survive |
| Function of the cuticle | protective barrier, waterproofs the leaf + prevents waterloss |
| Stomata location + function | stomata/stoma are openings on the surfaces of leaves formed by 2 guard cells; they regulate the gas exchnage for synthesis + respiration. (CO2 in, O2 and water out) |
| describe xylem in location, structure and function | dead, very thick with a secondary lignin wall; found in vascular bundles; provide rigid support to vascular bundles & carry water and minerals from the root upwards |
| describe phloem in location, structure and function | living cells with interconnected cell walls that form sieve plates; found in the vascular bundles and carry substances (mostly sugar) produced by the plant to other areas of the plant |
| what are the 2 vascular tissues in leaves + arrangement differnce between eudicot + monocots? | xylem + phloem - eudicots have their vascular bundles arranged in a ring + monocots have theirs scattered |
| describe the 3 structural adaptations of guard cells that enable stomata function | uneven cell walls allow them to open/close when they get more turgid/flaccid - chloroplasts for photosynthesis/energy for ion pumping (for stoma opening) - cellulose microfibrils arranged in a ring pattern helping cells curve open when they take in water |
| describe the mechanism of the stomata opening + closing | light triggers ion/solute transport, solute conc. increases, water is drawn in by osmosis + turgid cells = stoma open lack of light shuts down proton pumps, solute conc. decreases, water leaves the stoma, turgor pressure lost =flaccid cell =stoma close |
| 3 cues that trigger the stoma opening | light, low CO2 concentration in the leaf, + circadian rhythms |
| list adaptations of arid enviroment plants to reduce water loss (7) | rain dependant leaf growth, thick cuticle, multilayerd epidermis, recessed stomata + trichomes, reduced leaves (spines) water storing stems, light reflecting bristles |
| describe direction of flow of xylem + phloem sap | xylem sap flows upwards only phloem sap flows either up or down, but always from a source to a sink |
| how does the vascular system enable leaves + roots to function together? | xylem moves minerals + water upwards from roots to leaves. phloem moves sugars from leaves to roots or other parts of the plant where its needed |
| what is the apoplastic route? (water + mineral transport) | (outside of the cell membrane) passive pathway that water + minerals can move through non living cell walls (driven by conc./pressure gradients) non-selective + fast bc its passive. |
| what is the symplastic route? (water + mineral transport) | (inside of the cell membrane) cell to cell movement between the cytoplasms of plant cells through plasmodesmas (microscopic channels) slower, selective + requires energy |
| composition, location + function of the endodermis | tightly packed single layer of living parenchyma cells located in the roots of vascular plants. it is a selective barrier thats between the vascular cylinder (where xylem/phloem are) and the cortex |
| composition, location + function of the casparian strip | part of the endodermis; made of lignin + suberin; creates a waterproof barrier (blocking the apoplast) allowing the plant to control what comes through its semi-permeable membranes into the vascular system/tissues |
| root pressure + it's importance | pos. pressure that forces water/minerals up the xylem/plant. plant will create a conc. gradient of solutes to drive water towards them + into/up their tissues (water goes from low to high solute areas) imp. in maintaining water colum integrity |
| transpiration definition | process of leaves realeasing water through their stomata. cools + draws water/minerals up the plant |
| how does evaportation of water through the stomata create a pulling force? | it creates a transpirational pull as the constant evaporation of water through the stomata creates a negative pressure in the xylem, like a suction force |
| how does cohesion + adhesion facilatate upward movement of water through the xylem? | the water molecules are very cohesive, sticking to eachother and forming a continuous colum in the xylem. Adhesion then helps the water adhere to the xylem walls, keeping the water colum from breaking as its drawn up through the plant |
| sugar sink vs sources (+ examples) | sources: organs that produce more sugar then they consume (mature leaves + stems) sinks: organs that consume or store sugars (roots, fruits/flowers, developing seeds/leaves) |
| describe the mechanism of pressure flow of phloem sap through sieve tubes | (requires energy) phloem sap moves from source between sieve elements of phloem following a turgor pressure gradient (generated by water uptake) sugar is transported to sink, xylem recycles water |
| how is sucrose loaded into sieve tube elements at the sugar source? | by the symplastic pathway (cell to cell transport) or apoplastic pathway (through concentration gradient) |
| why does the movement of phloem sap by pressure flow requre living cells? | the movement of phloem sap requires energy (is not passive) so living cells are needed for active transport. The active loading creates a high sugar concentration, drawing in water, creating high turgor pressure that drives the sap movement |
| how would tempurature, humidity, and drought effect stomata opening? | tempurature: open at optimal temps, closed at too high/low to conserve water humidity: low/dry stoma closed, high reduces tranpiration stoma open drought: closed to conserve water |
| how does mesophyll tissue (in leaves) facilitate photosynthesis and gas exchange | it has 2 layers, palisade + spongy mesophyll. palisade has chloroplasts for photosynthesis; mesophyll has loosely packed cells/air spaces so gases can easily diffuse through the leaf |
Created by:
every_august
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