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09 Photosynthesis & plant structures
 

09 Photosynthesis & plant structures

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    09 Photosynthesis & plant structures 09 Photosynthesis & plant structures Presentation Transcript

    • All you ever wanted to know about photosynthesis but were afraid to ask!
    • Leaf Structure
      • Most photosynthesis occurs in the palisade layer.
      • Gas exchange of CO 2 and O 2 occurs at openings called stomata surrounded by guard cells on the lower leaf surface.
      Palisade Spongy
    • Chloroplast Structure
      • Inner membrane called the thylakoid membrane.
      • Thickened regions called thylakoids . A stack of thylakoids is called a granum . (Plural – grana)
      • Stroma is a liquid surrounding the thylakoids.
    • Overview of photosynthesis and respiration PHOTOSYNTHESIS CELL ACTIVITIES RESPIRATION SUN RADIANT ENERGY GLUCOSE ATP(ENERGY)
    • EQUATION FOR PHOTOSYNTHESIS 6CO 2 + 6H 2 O + ENERGY C 6 H 12 O 6 + 6O 2 CARBON DIOXIDE WATER GLUCOSE OXYGEN
    • EQUATION FOR RESPIRATION C 6 H 12 O 6 + GLUCOSE 6O 2 OXYGEN 6CO 2 + CARBON DIOXIDE 6H 2 O + ENERGY WATER ATP
    • Photosynthesis in Overview
      • Process by which plants and other autotrophs store the energy of sunlight into sugars.
      • Requires sunlight, water, and carbon dioxide.
      • Overall equation:
      • 6 CO 2 + 6 H 2 0  C 6 H 12 O 6 + 6 O 2
      • Occurs in the leaves of plants in organelles called chloroplasts.
    • Photosynthesis: The Chemical Process
      • Occurs in two main phases.
        • Light reactions
        • Dark reactions
      • Light reactions are the “photo” part of photosynthesis. Light is absorbed by pigments.
      • Dark reactions are the “synthesis” part of photosynthesis. Trapped energy from the sun is converted to the chemical energy of sugars.
    • Light Reactions
      • Light-dependent reactions occur on the thylakoid membranes.
        • Light and water are required for this process.
        • Energy storage molecules are formed. (ATP and NADPH)
        • Oxygen gas is made as a waste product.
    • Dark Reactions
      • Dark reactions (light-independent) occur in the stroma.
        • Carbon dioxide is “fixed” into the sugar glucose.
        • ATP and NADPH molecules created during the light reactions power the production of this glucose.
    • The photosynthetic reaction
        • Water + ADP – sunlight -> oxygen + hydrogen ions + ATP
        • Carbon dioxide + hydrogen ions + ATP -> glucose + ADP
      H 2 O + ADP + CO 2 + H + + ATP --sunlight-> O 2 + H + + ATP + C 6 H 12 O 6 + ADP 6H 2 O + 6CO 2 --sunlight-> 6O 2 + C 6 H 12 O 6
    • Plant Structures
    • General leaf adaptations
      • Flat shape .
      • Many stomatal pores
      • Very thin with internal air chambers
      • Extensive network of vascular tissue
        • Xylem
        • Phloem
      • Large photosynthetic surface
      • Gaseous exchange
      • Easy diffusion of CO 2 to photosynthetic cells
      • Delivery of essential nutrients
        • Water & minerals
        • Sucrose & hormones
    • General stem adaptations
      • Xylem vessels running entire length
      • Rigid structure of xylem
      • Phloem vessels running entire length
      • Branching of stem . .
      • Transport water and minerals from roots
      • Helps plant to remain upright
      • Transports sucrose from leaves
      • Provides broader, multileveled photosynthetic area
    • General adaptations of roots
      • Broad and deep spread of roots .
      • Root hairs
      • Taps a large area of soil for water and nutrients
      • Provide larger surface area for absorption of water and minerals
    •  
    •  
    • Plant Transport Systems
    •  
    •  
    • Xylem
      • Water and mineral are transported from the roots to the photosynthetic areas of the plant.
      • Composed of dead, hollow cells
      • Provides extra internal support for plant
      • Water moves up the plant through the process of a transpiration vacuum.
    •  
    •  
    • Transpiration moves water and minerals up the stem of the plant
    • Movement of water through the xylem
      • Water transpires from stomatal pores
      • … which is replaced by water from the air spaces in the mesophyll
      • … which is replaced by H 2 O in leaf cells
      • … which is replaced by H 2 O in leaf xylem
      • … which is replaced by H 2 O in stem xylem
      • … which is replaced by H 2 O in root xylem
      • … which is replaced by drawing H 2 O from soil
      Movement of water through the xylem
    • Phloem
      • Glucose is produced through the process of photosynthesis in the leaves and is then packaged in to sucrose
      • Transported through living sieve cells of the phloem, along with hormones to the non-photosynthetic parts of the plant known as ‘sinks’.
      • This movement is known as ‘translocation’
      • Sugars are either stored as starch or broken down in to monosaccarides and metabolised for growth
    •  
    •  
      • Transport of sugars is performed via active transport & osmosis.
      • ATP is provided by the companion cells
      • High sugar content in sap in leaf phloem causes intake of water via osmosis
      • As sugar is transported out of phloem at sinks, water returns to xylem via osmosis.
      • Therefore there is a region of high pressure at the source and low pressure at the sinks, facilitating movement of sap
      Movement of sugars through the phloem
    •  
    • Ringbarking
    • I would never do that! Gaseous echange in plants
    • For what purposes is gaseous exchange required?
      • Photosynthesis
        • Intake of carbon dioxide
        • Disposal of excess oxygen
      • Respiration
        • Intake of oxygen
        • Disposal of excess carbon dioxide
    • Mechanisms for gaseous exchange
      • # 1 Stomata
      • Stomata comprise of an opening, the stoma and two guard cells either side.
      • When the guard cells are turgid (full of water) the stomata is open
      • When the guard cells are flaccid (empty) the stomata is closed
    •  
    • Structure of a guard cell Cellulose fibrils Thick cell wall Thin cell wall When the guard cell swells with water, it bows in to the shape of a jelly bean.
    • Effect of Chloroplasts on Stomata function K + K + K + ATP H 2 O
    • Opening of stomata
      • Sun shines on plant
      • Chloroplasts carry out photosynthesis 1 (light dependant)
      • ATP from photosynth powers NA/K pump
      • K + ions pumped in to guard cells, thus creating a concentration gradient
      • Water enters cell via osmosis
      • Guard cells swell, stomata opens
    • Mechanisms for gaseous exchange
      • # 2 Lenticels
      • The woody part of plants is still growing, and therefore performing cellular respiration. (O 2 in, CO 2 out)
      • Lenticels are a protrusion of living cells in to the dead cambium layer
    • Lenticels Lenticel (dead) cork cambium (living) parenchyma cells
    • Altered photosynthetic cycle in desert plants
      • Desert plants would lose too much water if they opened their stomata during the day.
      • Instead they only perform photosynthesis 1 during the day.
      • Then at night they release the stored waste O 2 and take in CO 2 to complete the photosynthetic process.