Describe an experiment to show that ascent of sap takes place through xylem.

Explanation

Experiment showing sap ascent through xylem : Take a twig of a plant and remove a ring of bark (i.e. all the tissue outer to the cambium) of about an inch. Take another twig in which the xylem elements are removed without destroying phloem. Immerse both the twigs in beaker containing water separately for a few hours as shown in fig.

In condition 1, it was found that plant remains unchanged and leaves were fresh and turgid. It is because of continued transport of water even after the removal of phloem and cortex. This shows that water must have been transported through xylem and phloem. Phloem and cortex does not have any role in the upward movement of water. In condition 2, the leaves wilt because the water did not reach the leaves due to removal of xylem. It shows that upward movement of water or ascent of sap does not take place even though the phloem and cortex are present and that the upward movement of water takes place only through xylem.