Mass flow in phloem occurs because

  1. hydrostatic pressure is higher at the source than at the sink
  2. transpiration pulls sap upwards
  3. sucrose diffuses through sieve plates
  4. pressure is higher at the sink
Answer

A) hydrostatic pressure is higher at the source than at the sink

Sap flows down the pressure gradient. AS & A Level Biology · Topic 7 Transport in Plants · 7.2 Transport mechanisms

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