Transport in plants

Learning objectives

State the functions of xylem (transport of water and mineral ions, and support) and phloem (transport of sucrose and amino acids), and identify their positions in sections of roots, stems and leaves

Relate the structure of xylem vessels to their function: thick lignified walls, no cell contents, and cells joined end to end with no cross walls to form a continuous tube (Extended)

Explain how root hair cells are adapted for the uptake of water and mineral ions, describe the pathway of water through root hair cells, root cortex cells, xylem and mesophyll cells, and investigate the pathway using a stain

Define transpiration as the loss of water vapour from leaves, describe how water evaporates from the surfaces of mesophyll cells into the air spaces and diffuses out through the stomata, and investigate and describe the effects of temperature and wind speed on its rate

Explain how water vapour loss depends on the internal surface area of the air spaces and the size and number of stomata, explain the effects of temperature, wind speed and humidity, and explain the transpiration pull that draws up a column of water molecules held together by forces of attraction, and how and why wilting occurs (Extended)

Define translocation as the movement of sucrose and amino acids in the phloem from sources to sinks, and explain that a part of a plant can act as a source at one time and a sink at another (Extended)