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Name: Fabrice
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Question:
How does a plant stays in a upright position?


Replies:
Basically by the xylem in woody plants, and by turgid plant cells in non-woody plants. The following should be helpful.

http://www.biology-online.org/biology-forum/about9633.html

http://www.blurtit.com/q746024.html

http://www.microscopy-uk.org.uk/mag/indexmag.html?http://www.microscopy-uk.org.uk/mag/artoct99/plantupright.html

Sincerely,

Anthony R. Brach
Missouri Botanical Garden
c/o Harvard University Herbaria


Different plants use slightly different strategies to remain upright. The majority of plants we see are vascular plants - they have veins and tubes throughout their structure to transport nutrients in liquid solution. Examine almost any leaf and you will see veins arranged in branching formations from the center of the leaf. The liquid being transported is used to 'pump up' certain cells, and it is these which support the leaf, and the soft parts of the plant. They stay rigid because of the pressure of fluid inside the support cells, just as the sides of an inflatable boat are rigid while they are full of air. When liquid is lost, such as when you forget to water mum's African Violets, they lose support, and we see the plant wilt. Larger plants use a second strategy. As they grow, the walls of some of the support cells develop a layer of rigid support by depositing a substance called lignin on the cell walls. When lignin builds up substantially, we call it wood. Wood remains rigid even when there is a loss of water, so the plant remains upright. The soft parts of the plant can still wilt, but the lignin not only supports, but protects vital portions of the plant from further water loss.

Nigel
Tennant Creek Australia



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