IGCSE Biology Paper-2: Specimen Questions with Answers 195 - 195 of 203

Question 195




Which description of translocation is correct?


Choice (4)
a.Movement of sucrose and amino acids from a sink to a source
b.Movement of glucose and amino acids from a sink to a source
c.Movement of sucrose and amino acids from a source to a sink
d.Movement of glucose and amino acids from a source to a sink




  • The synthesis of carbohydrate food materials, mainly through the process of photosynthesis, occurs in green cells of plant. The non-green cells are therefore, dependent on photosynthetic cells for their carbohydrate supply. The organic food mainly from the leaves is transported to the non-green parts where it is needed for respiration and biosynthesis. “This movement of organic food or solute in soluble form, from one organ to another organ is called translocation of organic solutes. “
  • It has been now well established that carbohydrates are translocated from leaves to roots and storage organs (tubers, bulbs, fruits, etc. ) along the phloem in the form of sucrose. They are transported through living sieve elements of phloem (chiefly sieve tube members in seed plants). The process of translocation requires expenditure of metabolic energy and the solute moves at the rate of 100cm/hr.

Directions of translocation

  • Downward translocation: It is of most important type, i. e. , from leaves to stem and roots.
  • Upward translocation: From leaves to developing flowers, buds, fruits and during germination of seeds and tubers, etc.
  • Radial translocation: From pith to cortex and epidermis.

Thus, we find that the translocation of food takes place from organs where food is in high concentrations (e. g. , leaf, tuber, and rhizome) to organs where it is in low concentration (e. g. , roots). The first are called supply ends and the later as consumption ends.

Description of translocation

Description of Translocation

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