TRANSPORT SYSTEM IN PLANTS

BY H.W CHINANGWE

CONTENTS

The role of the STOMATA

XYLEM

PHLOEM

ROOT HAIRS

…and the effect of TRANSPIRATION on the above mentioned

EXTERNAL RESOURCES

BIBLIOGRAPHY

Diagrammatic Summary

The Transport System

Vascular plants transport systems consist of two main systems which are the xylem and phloem.

Just like animals plants need food, sunlight, oxygen, nitrogen, and other essential nutrients to survive.

These are obtain via the transport system in plants by means of root pressure, cohesion-adhesion-tension and transpiration.

XYLEM

• Xylem transports the water and minerals from the root hairs to the shoot system.

• It is made of many hollow dead cells joined end to end of which the end cell wall has disappeared to form a long tube.

• Xylem vessels contain no cytoplasm or nuclei

• Xylem tissue is made of cellulose and lignin which in result assists to keep the plant upright.

The Phloem

In vascular plants, phloem is the living tissue that carries organic nutrients (known as photosynthate), in particular, sucrose, a sugar, to all parts of the plant where needed. In trees, the phloem is the innermost layer of the bark.

The phloem is concerned mainly with the transport of soluble organic material made during photosynthesis. This is called translocation.

The Phloem

Vascular bundles

Xylem and phloem tubes are normally found close together, the arrangement of these tubes is called a vascular bundle

In the root system vascular tissue is found at the centre

In the shoot system they are found near the outside edge to help support the plant

Transport of water

Plants take in water from the soil through the root hairs and it is carried in the xylem throughout the plant

Water is absorb by root hairs by means of osmosis. The cytoplasm and cell sap inside it are quite

concentrated solutions and the water in the soil is normally slightly diluted

Water therefore diffuses down its concentration gradient through a partially permeable membrane

Transport of Water…

Water is a polar molecule.  When water molecules approach they form a Hydrogen Bond.  The negatively charged oxygen atom of one water molecule forms a hydrogen bond with the positively charged hydrogen atom in another water molecule.

Water enters the xylem in the roots by Osmosis.  Once in the xylem the water molecules hydrogen bond forming a continuous string of water molecules up to the leaf.

Water is constantly lost by Transpiration in the leaf.  When one water molecule is lost another is pulled along.  Transpiration pull is the main cause of water movement.

Transport of Water…

The Transpiration Stream

Transpiration Pull

What is Transpiration

The evaporation of water from the plant Most of which takes place from the leaves

through the stomata Guard cells around the stomata control the

rate of transpiration by opening and closing

What is Transpiration…

Transpiration

When water is lost through transpiration water from the xylem vessel in the leaf will travel to the cells to replace it

Water is constantly being taken from the top of the xylem vessel to supply the cells in the leaves

This reduces the pressure at the top of the xylem so water flows up

This process is known as the transpiration stream, or transpiration ‘pull’

Evaporation of water at the surfaces of the mesophyll cells followed by loss of water vapour from plant leaves, through the stomata

Effects That Affect Transpiration

Temperature Humidity Wind speed Light intensity Water supply

Transport of Food

TRANSLOCATION is the movement of sucrose and amino acids in phloem, from regions of production to regions of storage, or to regions of utilization in respiration or growth.

Transport of Food…

The part of the plant from which sucrose and amino acids are being translocated is called a SOURCE.

The part of the plant to which they being translocated is called a SINK.

Leaves are generally the major sources of translocated material.

Sinks include the roots, flowers and fruits.

Transport of Food… Sugar is made in the leaves by photosynthesis. Sugar moves into the phloem tubes. 3a. The phloem tubes carry sugar to growing buds, which need

it for energy. 3b. The phloem tubes carry sugar to the roots, where it may be

used for energy or changed into starch and stored. Transport the ‘food’ (sucrose and amino acids) They are also made of many cells joined end to end, however

their end wall is not completely broken down; instead they form sieve plates. The cells are called Sieve tube elements.

The cells contain cytoplasm but no nucleus and they do not have lignin in their cell walls.

Each sieve cell has a companion cell next to it which does contain a nucleus and many other organelles and supply sieve tube elements with some of their requirements.

External Resources

External Resources…

ACTIVITY

BIBLIOGRAPHY Slide share

http://www.slideshare.net/PreetiGhosh1/transport-in-plants-31618755 date visited: 2014/03/05

Google images

https://www.google.co.za/search?q=diagrammatic+summary+of+transport+in+plants&safe=off&rlz=1C1CHNQ_enZA571&espv=210&es_sm=93&source=lnms&tbm=isch&sa=X&ei=OAIXU53kKomAhAfUo4DACw&ved=0CAcQ_AUoAQ&biw=1280&bih=923

https://www.google.co.za/search?q=TRANSPORT+IN+PLANTS&safe=off&rlz=1C1CHNQ_enZA571&espv=210&es_sm=93&source=lnms&tbm=isch&sa=X&ei=NfAWU574K46DhQfA74HABw&ved=0CAkQ_AUoAQ&biw=1280&bih=923#q=TRANSPORT+IN+PLANTS+HD&safe=off&tbm=isch&facrc=_&imgdii=_&imgrc=NXvDsuELagB8wM%253A%3BQpc0WVCWGfc-rM%3Bhttp%253A%252F%252Fesciencenews.com%252Ffiles%252Fimages%252F201105034793340.jpg%3Bhttp%253A%252F%252Fesciencenews.com%252Farticles%252F2011%252F05%252F03%252Ffirst.rainforests.arose.when.plants.solved.plumbing.problem%3B400%3B300

Date visited: 2014/03/05

Mindset Learn Channel

https://www.mindset.co.za/learn/s22/t17358/t64388

http://www.mindset.co.za/creativecommons

Date visited: 2014/03/05

BIBLIOGRAPHY…

Campbell and Reece. (2010) Biology. 8th addition. Pearson International Edition.

Taylor, D.J., Green, N.P.O. and G.W. Stout, 1998. Biological science 3rd Edition. Cambridge University Press: London

Williamson J. .2010. life Science for Teachers FET Study Guide. University of Johannesburg: Auckland park.