AIIMS2011BotanyTransport in Plants
Assertion : Movement of materials inside phloem is bidirectional i.e. it can be both upwards or downwards. Reason : Movement of molecules inside xylem is unidirectional i.e. always upwards.
Options
- AIf both assertion and reason are true and reason is the correct explanation of assertion
- BIf both assertion and reason are true but reason is not the correct explanation of assertion
- CIf assertion is true but reason is false
- DIf both assertion and reason are false.
Correct answer
B. If both assertion and reason are true but reason is not the correct explanation of assertion
Step-by-step solution
Long distance bulk movement of substances that occurs through conducting or vascular tissues of plants is called translocation. There are two vascular tissues, xylem and phloem. Xylem translocation is mainly from roots to aerial parts. It passes water with mineral salts, some organic nitrogen and hormones i.e. unidirectional. Phloem translocates organic substances and inorganic solutes first from leaves to all other parts of the plant and storage organs. Storage organs re-export organic nutrients to those parts whi