1 / 94

Resource Acquisition & Transport in Vascular Plants

Resource Acquisition & Transport in Vascular Plants. Campbell and Reece Chapter 36. genus of plants ( Lithrops , known as stone plants) found in Kalahari Desert of southern Africa has mostly subterreanean existence tips of 2 succulent leaves above ground

ramya
Download Presentation

Resource Acquisition & Transport in Vascular Plants

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. Resource Acquisition & Transport in Vascular Plants Campbell and Reece Chapter 36

  2. genus of plants (Lithrops, known as stone plants) found in Kalahari Desert of southern Africa has mostly subterreanean existence • tips of 2 succulent leaves above ground • clear, lens-like cells allow light  cells underground • conserve moisture (~20 cm rain/yr), hide from grazing tortoises, avoid high temperatures (up to 45ºC, 113 ºF,) & high light intensity • overall reduces water loss but inhibits photosynthesis,  grow very slowly Underground Plants

  3. nonvascular • earliest land plants • grew photosynthetic, leafless shoots above the shallow water in which they lived • most had waxy cuticles & few stomata Early Land Plants

  4. anchoring & absorbing functions done by base of stem or threadlike rhizoids Early Land Plants

  5. typical land plant inhabits 2 worlds: • under ground • above ground Adaptations of Vascular Plants

  6. as competition for light, water, & nutrients grew: • plants with broader leaves had advantage for light but then lost more water by evaporation as surface area increased • larger shoots required more of an anchor which favored production of multicellular, branching roots • as shoots grew higher, needed long-distance transport of water, minerals, products of photosynthesis Evolution of Plants

  7. evolution of vascular tissue meant; • Xylem: tubular dead cells that conduct most of the water & minerals upward from roots  rest of plant • Phloem: vascular plant tissue consisting of living cells arranged into elongated tubes that transport sugar & other organic material thru out plant Xylem & Phloem

  8. transpiration creates a force thru leaves that pulls xylem sap upward • water & minerals up as xylem sap • phloem sap flows up & down delivering sugars • water & minerals in soil absorbed by roots

  9. Xylem & Phloem

  10. function: • gather light • take in CO2 LEAVES

  11. arrangement of leaves on a stem called: phyllotaxy LEAVES

  12. most angiosperms (flowering plants) have alternate phyllotaxy • each successive leaf emerges 137.5º from site of previous leaf • this angle minimizes shading of lower leaves by upper leaves • plants in intense sun: opposite phylloxy which increase shading & so water loss LEAVES

  13. affects amt light capture • leaf area index: ratio of total upper leaf surface of a single plant or entire crop ÷ surface area of land on which it grows • valuesup to 7 possible for mature crops • not much agricultural benefit to having higher values • more leaves increases shading of lower leaves to pt. where respiring > photosynthesizing LEAF NUMBERS or SIZE

  14. affects amt light captured LEAF ORIENTATION

  15. function: • supporting structures for leaves • conduit for long-distance transport of water & nutrients STEMS

  16. generally. Enables plants to more effectively capture sunlight • only finite amt of nrg to give to shoot growth • more nrg to shoot growth the less there is for height which may compromise their chances for capturing sunlight • if lots nrg goes into being tall, plant not optimizing resources above ground • species have variety of branching patterns BRANCHING PATTERNS

  17. BRANCHING PATTERNS

  18. function: • mine the soil for water & minerals • anchor whole plant • evolution of branching roots enabled plants to be more efficient & more anchored ROOTS

  19. tallest plants typically have longest taproot & most branches • fibrous roots don’t anchor as well so those plants generally not as tall • fewer branches as root grows thru soil with fewer nutrient; more branching in nitrogen-rich areas ROOTS

  20. ROOT GROWTH

  21. mutualistic associations formed between roots & some soil fungi that aid in absorption of minerals & water MYCORRHIZAE

  22. important ass’c in evolution of land plants • ~80% land plants • fungi provides increased surface area to root system  more water & mineral absorption • especially phosphates Mycorrhizae

  23. both active & passive transport controls movement of substances in/out of cells • plant tissues have 2 major compartments: • Apoplast: everything external to plasma membrane of living cells • cell walls, interior of dead cells, tracheids (long tapered water-conducting cell in xylem in most vascular plants • extracellular spaces • Symplast: all cytosol of all living cells in plant Transport in Plants

  24. Apoplastic Route • water & solutes  cell walls & extracellular spaces • Symplastic Route • water & solutes  cytosol  plasma membrane  plasmodesmata  next cell • Transmembrane Route • out of 1 cell  cell wall  neighboring cell 3 Routes for Transport in Plants

  25. plant plasma membranes have same types of transmembrane proteins as other cells • some differences: • H+ pumps • (not Na+) play primary role in basic transport processes • maintains membrane potential • H+ often ½ cotransporter (Na+ in animals) • part of absorption of neutral solutes, ions, & sucrose Short-Distance Transport Across Plasma Membranes

  26. Solute Transport across Plant Cell Membranes

  27. free water (not bound with other particle) moves down its concentration gradient across semipermeable membranes = osmosis • Water Potential: physical property that predicts direction in which water will flow based on water pressure & solute concentration Osmosis & Water Potential

  28. free water moves from areas of higher water potential  areas of lower water potential if no barrier to its flow • as water moves it can perform work • “potential” refers to its PE • Ψ (psi) represents water potential • measured in a unit of pressure: megapascalMPa Water Potential

  29. the Ψ of pure water in open container under standard conditions (sea level, room temperature) = 0MPa • 1 Mpa ~ 10x atmospheric pressure @ sea level • internal pressure of living plant cell due to osmotic uptake of water is ~ 0.5 MPa Water Potential

  30. Water Potential equation: How Solutes & Pressure Affect Water Potential

  31. directly proportional to its molarity • aka osmotic potential • solutes affect direction water moves in osmosis • plant solutes • mineral ions • sugars Solute Water Potential

  32. in pure water the Ψs = 0 • as add solute they bind with water so there is less free water molecules which decreases water’s capacity to move & do work • reason Ψs always a (-) # • as concentration of solute increases Ψs becomes more (-) How Solutes & Pressure Affect Water Potential

  33. Ψp = physical pressure on a solution • can be (+) or (-) relative to atmospheric pressure Pressure Potential

  34. force directed against a plant cell wall after the influx of water & swelling of the cell due to osmosis Turgor Pressure

  35. critical for plant function: helps maintain stiffness of plant tissues & is driving force for cell elongation Turgor Pressure

  36. Wilting in Nonwoody Plant

  37. difference in water potential determines direction water will flow • How does water get in/out of plant cells? • some molecules diffuse thru lipid bilayer • does not affect the rate water moves • transport proteins called aquaporins affect the rate water molecules move across the membrane Aquaporins

  38. Aquaporins

  39. on cellular level diffusion effective but too slow for long-distance transport w/in plant • Long-distance transport occurs thru • bulk flow • movement of liquid in response to a pressure gradient (always high  low) Long-Distance Transport

  40. occurs in tracheids & vessel elements of xylem & w/in sieve-tube elements of the phloem • tracheid: long, tapered water-conducting cell found in xylem of nearly all vascular plants; functioning tracheids are no longer living Bulk Flow

  41. diffusion, active transport, & bulk flow act together transporting resources thru out whole plant

More Related