9.1 Transport in the xylem of plants

Essential idea: Structure and function are correlated in the xylem of plants.

One of the key structural features of xylem is the rings of lignin (seen above in the lower power scanning EM image). The lignified walls of xylem help them to withstand the the low pressure inside the xylem which drives the transpiration pull.

To find out more about how the transpiration pull works watch the Verisatium video (right).

Understandings, applications and skills

9.1.U1	Transpiration is the inevitable consequence of gas exchange in the leaf.
9.1.U2	Plants transport water from the roots to the leaves to replace losses from transpiration.
9.1.U3	The cohesive property of water and the structure of the xylem vessels allow transport under tension.
9.1.U4	The adhesive property of water and evaporation generate tension forces in leaf cell walls.
9.1.U5	Active uptake of mineral ions in the roots causes absorption of water by osmosis.
9.1.A1	Adaptations of plants in deserts and in saline soils for water conservation.
9.1.A2	Models of water transport in xylem using simple apparatus including blotting or filter paper, porous pots and capillary tubing.
9.1.S1	Drawing the structure of primary xylem vessels in sections of stems based on microscope images.
9.1.S2	Measurement of transpiration rates using potometers. (Practical 7)
9.1.S3	Design of an experiment to test hypotheses about the effect of temperature or humidity on transpiration rates.

[Text in square brackets indicates guidance notes]

Presentation and Notes

The presentation is designed to help your understanding. The notes outline is intended to be used as a framework for the development of student notes to aid revision.

Vocabulary

Correct use of terminology is a key skill in Biology. It is essential to use key terms correctly when communicating your understanding, particularly in assessments. Use the quizlet flashcards or other tools such as learn, scatter, space race, speller and test to help you master the vocabulary.

Use the Cornell style template to collate your own notes for Topic 9 - Plant biology

Quick quiz

Use the BioK Quick Quiz on 9.1 - 9.2 Transport in the xylem and phloem of plants (as directed) to check your understanding of the topic.

Weblinks

Transport in vascular tissue
Animation - Transport of water and sugar in plants by SAPS
Pressure flow model by W H Freeman
Plant transport by UIC
Transport of materials in a flowering plant by LeavingBio

Virtual transpiration labs
Measuring transpiration by the University of Reading

Nature of science

Use models as representations of the real world—mechanisms involved in water transport in the xylem can be investigated using apparatus and materials that show similarities in structure to plant tissues. (1.10)