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IGCSE Biology (O610) Workbook

© A. Nixon 2016

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Chapter 8 Transport in Plants

The stuff you need to know in this chapter: 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 • Identify root hair cells, as seen under the light microscope, and state their functions 8.2 WATER UPTAKE Core: • State the pathway taken by water through root, stem and leaf as root hair cell, root cortex cells, xylem and mesophyll

cells • Investigate using a suitable stain, the pathway of water through the above ground parts of a plant Extended: • Explain that the large surface area of root hairs increase 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 Extended: • 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


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8.4 TRANSLOCATION (Extended candidates only) Extended: • 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


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8.1 TRANSPORT IN PLANTS State the function of the following components of the vascular bundle: Xylem: ______________________________________________________________________________________________________________________________________ Phloem: ______________________________________________________________________________________________________________________________________ Look at the following images. In each one label the xylem and phloem. Zea stem (dicotyledonous): Erica leaf (dicotyledonous):


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Look at the sketch below and label the xylem and phloem in each. Also label each of the diagrams as “leaf”, “stem” or “root”.


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8.2 WATER UPTAKE Look at the images below of root hair cells. Draw a single root hair cell on the box (remember to follow the rules of biological drawings:

Root hair cells vary in length between 80µm and 1,500µm. Assuming the cell picture above is 100 µm in length, calculate the magnification of your drawing . SHOW YOUR WORKING (Help: µm = “micrometer”. There are 1000µm in one mm) ANSWER: _________________________________ Name the process by which root hair cells take in water.


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Name the process by which root hair cells take in ions (by the way, the concentration of ions inside the root hair cells is usually higher that their surroundings). State how the structure of root hair cells makes them suitable for their function. 8.3 TRANSPIRATION Define “Transpiration” There are many air spaces in the leaf. Explain how this aids water loss with transpiration. When stomata open, they allow water to escape from the leaf. In terms of changes in term of water potential and evaporation, describe how this encourages more water to move towards the leaves.


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Explain the effect following things effect the rate of transpiration from a leaf Temperature

Humidity Wind Speed

Light Intensity

Water Supply

Explain why plants “wilt” (go soft/limp)


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8.4 TRANSLOCATION Define the word “translocation” Use the word “source” and “sink” in sentences NOT related to biology: Source sen tence : S ink sen tence :


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Complete the table to state the sources and sinks of carbohydrates in plants (These carbohydrates might include glucose, sucrose, starch and others).

Sources Sinks

Glucose is produced mostly in the _____________ of the plant. This can be converted into ________________ and transported away.

All parts of the plant, including: • _______________, where it may

be converted into _______________ and stored.

• The _________________, which use sucrose to make _______________, which attracts insects.

• _______________, which are often very sweet and attract animals to eat them.

In some plants (e.g. potatoes) _______________ is stored in the tubers (the potatoes), which stay _______________ when the temperature is low over winter. These tubers act as a source of starch during _______________ time.

The growing _______________ and _______________ of the potato plant receive _______________ from the tubers.


© A. Nixon 2016


You should realize from the table that different parts of a plant can be both a source AND a sink at different times. Draw a diagram to summarise how the different parts of potato plant act as both sources and sinks at different times of year. (Remember scientific drawing rules and labels).

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