plant nutrition Flashcards
YAY NO MORE HUMANS
State one function unique to upper epidermis (not cuticle)
protects photosynthetic tissue against mechanical damage
State the functions of waxy cuticle
- reduces water loss due to evaporation of water from epidermal cells
- transparent to allow light to pass through to palisade layer
State the function of palisade mesophyll cells
high concentrations of chloroplasts to allow maximum light absorption for photosynthesis
State the function of spongy mesophyll
large intercellular spaces to allow rapid diffusion of oxygen and carbon dioxide into and out of mesophyll cells
State the functions of vascular bundle
- veins provide support for the leaf
- xylem transports water and dissolved mineral salts from the roots to the mesophyll cells
- phloem transports synthesised sucrose and amino acids away from leaf to rest of plant
State 2 differences between palisade mesophyll cell and spongy mesophyll cell
- PMC is cylindrical in shape while SMC is irregularly shaped
- PMC has more chloroplasts than SMC
State 4 differences between guard cells and epidermal cells
- in surface-view, guard cells are bean-shaped while epidermal cells are irregularly shaped
- guard cells contain chloroplasts while epidermal cells do not contain chloroplasts
- guard cells control the rate of diffusion of gases into and out of leaf by controlling size of stomata while epidermal cells merely protect inner regions of the leaf
- guard cells’ cell wall near stoma is thicker than rest of cell wall while epidermal cells’ cell wall is of uniform thickness
State the function of guard cells
control the opening and closing of stomata to regulate the diffusion of gases like carbon dioxide and oxygen into and out of the leaf, as well as the amount of water vapour escaping from leaf
Explain what happens to guard cells in presence of light
- chloroplasts in guard cells photosynthesise, using energy in light to synthesise glucose
- increase in glucose concentration decreases water potential of cell sap of guard cell
- glucose is metabolised to release chemical energy via respiration to pump K+ ions from neighbouring epidermal cells into guard cells
- water molecules from neighbouring epidermal cells enter guard cells by osmosis across the partially permeable cell surface membrane, so they become more turgid
- guard cells have thicker cellulose cell wall on side of cell around stomatal pore and curves around the stoma, hence opening the stoma
Explain what happens to guard cells in the dark
- K+ ions accumulated in guard cells during the day diffuse out of guard cells
- this increases water potential in cell sap of guard cells and water molecules leave them by osmosis
- guard cells become flaccid and stoma closes
Explain what happens to guard cells on hot days
there is excessive evaporation of water causing guard cells to become flaccid. thus the stoma closes to prevent excessive loss of water from leaf.
Contrast photosynthesis and anaerobic respiration (7 points)
- photosynthesis is an anabolic process resulting in synthesis of carbohydrate molecules from simple inorganic molecules while anaerobic respiration is a catabolic process resulting in breakdown of carbohydrate molecules into simple inorganic molecules
- energy from photosynthesis is stored in glucose while energy from anaerobic respiration is incorporated into ATP for energy-requiring processes
- O2 is released in photosynthesis while O2 is used up in anaerobic respiration
- CO2 and H2O are used up in phyotosynthesis while CO2 and H2O is released in anaerobic respiration
- photosynthesis leads to increase in dry mass , while anaerobic respiration leads to decrease in dry mass
- photosynthesis occurs in chloroplast while anaerobic respiration occurs in mitochondria
- photosynthesis only occurs in cells possessing chlorophyll and in the presence of light while anaerobic respiration occurs continuously in nearly all cells in living organisms
State 3 similarities between photosynthesis and anaerobic respiration
- metabolic processes
- require mechanisms for exchange of CO2 and O2 with environment
- require organelles
List the 6 fates of glucose from photosynthesis
- used immediately by plant cells for tissue respiration to release energy for cellular activities
- excess glucose is converted to starch for storage within chloroplasts
- used to form cellulose cell walls
- excess gluclose is converted to sucrose, and transported by phloem to storage organs where it is then converted to starch
- fats formed from glucose in leaves used in cellular respiration or to form new protoplasm
- glucose in leaf react with nitrates to form animo acids which combine to form proteins ,
Describe how light intensity affects rate of photosynthesis
as light intensity increases, rate of photosynthesis increases from 0 to X (light intensity is limiting)
beyond X, light intensity is no longer limiting, rate of photosynthesis remains constant
Describe how concentration of carbon dioxide affects rate of photosynthesis
as carbon dioxide concentration increases, rate of photosynthesis increases (limiting)
State the wavelengths of light most and least effectively, absorbed by chlorophyll
- most : blue and red. indicates higher rate of photosynthesis
- least : green. produces lowest rate of photosynthesis
Based on enzymes, describe and explain how temperature affects rate of photosynthesis
Photosynthesis is an enzyme-controlled reaction where rate of photosynthesis doubles for every 10°C / increases with temperature.
As temperature increases, kinetic energy of substrates and enzymes increases, resulting in higher frequency of effective collisions.
More enzyme-substrate molecules formed per unit time
How to explain why something is limiting (e.g. why is light limiting forom the graph)
an increase in light intensity, at the same temperature, leads to increased rate of photosynthesis
How to explain the net carbon dioxide used/produced?
Rate of photosynthesis is higher/lower than rate of respiration, net carbon dioxide used up / produced
OR
no photosynthesis.. only respiration / no respiration.. only photosynthesis
