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