8. transport in plants

8.1 Transport in plants

Core

• State the functions of xylem and phloem

• Identify the position of xylem and phloem as seen in sections of roots, stems and leaves, limited to non-woody dicotyledonous plants

8.2 Water uptake

Core

• Identify root hair cells, as seen under the light microscope, and state their functions

• State the pathway taken by water through root, stem and leaf as root hair cells, root cortex cells, xylem and mesophyll cells

• Investigate, using a suitable stain, the pathway of water through the above-ground parts of a plant

Supplement

• Explain that the large surface area of root hairs increases the rate of the absorption of water by osmosis and ions by active transport

8.3 Transpiration

Core

• State that water is transported from the roots to leaves through the xylem vessels

• Define transpiration as loss of water vapour from plant leaves by evaporation of water at the surfaces of the mesophyll cells followed by diffusion of water vapour through the stomata

• Investigate and describe the effects of variation of temperature and humidity on transpiration rate

Supplement

• Explain how water vapour loss is related to the large surface area of cell surfaces, interconnecting air spaces and stomata

• Explain the mechanism by which water moves upwards in the xylem in terms of a transpiration pull that draws up a column of water molecules, held together by cohesion

• Explain how and why wilting occurs

• Explain the effects of variation of temperature and humidity on transpiration rate

8.4 Translocation

Supplement

• Define translocation in terms of the movement of sucrose and amino acids in phloem:

– from regions of production (source)

– to regions of storage OR to regions where they are used in respiration or growth (sink)

• Explain that some parts of a plant may act as a source and a sink at different times during the life of a plant