Science 7 Unit 2 Topic 2 - Leaves
Let's explore Leaves, Photosynthesis, and Respiration
Author tomwhyte1
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Leaves just like roots and stems are very important in keeping a plant alive.
http://maryt.files.wordpress.com/2008/08/autumn-leaves.jpg
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A pigment called chlorophyll makes the leaves green. The energy of the sun is trapped in the leaves and changed into a kind of chemical energy.
http://www.usoe.k12.ut.us/curr/Science/sciber00/8th/energy/images/chloro.jpg
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Carbon dioxide and water are used by the leaves in the process called PHOTOSYNTHESIS to make sugar and give off oxygen.
http://www.harcourtschool.com/activity/science_up_close/311/deploy/interface.html
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Watch and listen to this song on Photosynthesis...
http://www.teachertube.com/view_video.php?viewkey=ae32e2ab61810ae2133e
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The above image shows the movement of gases and liquids in the process of photosynthesis.
http://www.life.uiuc.edu/plantbio/102/lectures/LEAFSEC.JPG
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During respiration the process of photosynthesis is reversed. Oxygen is absorbed and Carbon Dioxide, Water and Energy is released, giving the plant the needed energy for its life processes. The cells that controls the gases and liquids in and out of a plant are called Guard Cells and they control the opening (stomata).
http://www.dynamicscience.com.au/tester/solutions/stick%20insects/respiration.jpg
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Guard Cells open the stomata (shown above) during the day (to allow Carbon Dioxide in) for photosynthesis, and then closes at night. The Guard Cells and Stomata open and closes dependent on water within the plant. When the Plant has a lot of water, the stomata is open, and when the plant has little water the stomata will close. Water enters and leaves the cells in the leaves through the guard cells. When they absorb water they swell, opening the stoma (which lets in carbon dioxide and lets out water vapor). The loss of water through evaporation is called transpiration.
http://ksjtracker.mit.edu/wp-content/uploads/2007/08/stomata.jpg
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Now how does the roots, stem and leaves work together? One way is the process of transpiration which moves the water from the roots, through the stem and out the leaves. This process (pushing and pulling action) of osmosis (pushing water up from the roots) and transpiration (pulling the water up the xylem tissue from the roots) moves water up to the very top of the plant, forcing dissolved minerals and nutrients through out the plant.
http://extension.oregonstate.edu/mg/botany/images/tree1.html