Kerboodle 9 Flashcards
a a plant adapted to live in standing water (1 mark)
hydrophyte ü
b a part of a plant to which sucrose is transported (1 mark)
sink ü
c the pathway where water moves through a plant through cell walls (1 mark)
apoplast ü
d a plant that possesses transport tissues (1 mark)
vascular ü
e an apparatus to measure water uptake in a plant (1 mark)
potometer ü
2 Describe the difference between:
a transpiration and translocation (4 marks)
transpiration: two from: loss of water from a plant’s leaves ü causes upward pull of water (and mineral salts) ü in xylem ü translocation: two from: transport of sucrose (and amino acids) ü in phloem ü from source to sink ü
2 Describe the difference between the distribution of xylem in a herbaceous dicotyledonous root and a stem as shown by a light microscope on low power. (4 marks)
in root: two from: xylem forms central column ü may be star shaped ü with phloem to the outside ü in stem: two from: xylem in discrete bundles ü in cortex/near outer edge of stem cylinder ü to the inside of cambium ü
3 a Explain the significance of hydrogen bonding in water for the transport of water in the xylem of a plant. (3 marks)
three from: weak (electrostatic) attractions form ü between δ+ hydrogen atom and δ− oxygen atom ü of different water molecules ü causing cohesion / column of water sticks together ü causing adhesion to walls of xylem ü
i Explain why the palisade mesophyll and spongy mesophyll are referred to as ‘tissues’. (2 marks)
two from: consist of many cells ü of one / a few types ü specialised for a particular function ü
iii List two functions of vascular bundle. (2 marks)
two from: supports leaf / maintains large surface area to receive light ü transports water to leaf cells ü transports sucrose / assimilates away from leaf ü cambium generates new vascular tissue ü
c Water is required for photosynthesis by the cells of the palisade mesophyll tissue. Describe the different pathways by which water may travel from vascular bundle to the palisade cells. (4 marks)
four from: apoplast pathway is through cell walls and intercellular spaces ü by simple diffusion ü (apoplast) is a non-living pathway ü ORA (apoplast) carries greater volume / has higher rate of flow/has less resistance ü ORA symplast is through cytoplasm ü (and) symplast is also through vacuoles ü by osmosis ü across, tonoplast membrane / cell surface membrane ü (and) through plasmodesmata ü
b Explain how the features relate to the functions of the phloem sieve tube cell and the companion cell.
companion cell: two from: mitochondria for aerobic respiration/make ATP ü RER / many ribosomes to make proteins ü nucleus and genes coding for proteins / ribosomes ü sieve tube element: two from: cytoplasm, peripheral / pushed against walls ü no nucleus / RER / vacuole / Golgi to reduce resistance to flow ü few organelles / reduced ER / few to reduce resistance to flow ü sieve plates stop bulging / allow mass flow ü plasmodesmata for diffusion of sucrose from companion cell / to sieve tube cell ü
5 Suggest explanations for the following pieces of practical advice: a Seedlings (small plants a few days old), when being transplanted to new soil in a bigger pot, should be moved in the evening. (3 marks)
three from: evening is cool(er) (time of day) ü low(er) light intensity makes stomata close ü reduce transpiration from leaves ü as loss of water / wilting could kill seedling ü disturbed roots not yet taking up water to compensate ü
b When transplanting seedlings, handle them by the leaves and not by the stem. (3 marks)
(6 marks)
three from: seedling easily damaged/delicate ü new leaves grown to replace one damaged one ü but if xylem / phloem crushed plant dies ü as no water transport to stem apex ü as no sucrose transport to roots ü
