Which of the following is the consumption end of the plant?

Analogy type questions:
$(1)$ In Xylem : Vessel :: In Phloem : ..........
$(2)$ Synthesis of food : Source :: Regions of need : ...........

When a plant stem is cut using a suitable method,a few drops of fluid are obtained. Which of the following tests,when performed on this fluid,confirms that it is phloem sap?

The carbohydrates synthesized in the leaves are transported through sieve tubes most commonly in the form of

Phloem loading and unloading processes are respectively:

Explain why xylem transport is unidirectional and phloem transport bi-directional.