Sample Question: Form 5 Chapter 1: Transport (Biology)

Sample Question: Form 5 Chapter 1: Transport (Biology)Sample Question:

In the Stem:Water moves up the xylem vessels by capillary action, root pressure and/or transpirational pull.Xylem vessels are narrow and capillary force pushes water upwards.The cells of the root endodermis actively secrete salts into the xylem vessel, making the xylem sap in the root very concentrated.This draws water onto the xylem vessel, creating a pressure which pushes the sap upwards.Evaporation of water from the leaves by transpiration creates a tension in the xylem vessels which is transmitted back to the roots.Water molecules stick to each other in the xylem vessels, thus the water column is continuously pulled upwards towards the leaves.