Water enters the sieve tube at the source because

  1. sucrose lowers the water potential of the sap
  2. sucrose raises water potential
  3. transpiration pulls it in
  4. active transport pumps water
Answer

A) sucrose lowers the water potential of the sap

Water follows by osmosis. AS & A Level Biology · Topic 7 Transport in Plants · 7.2 Transport mechanisms

Biology MCQ · More A Level Biology: Transport in plants MCQs · Practise