XYLEM, TRANSPIRATION AND PHOTOSYNTHESIS

Review of what we’ve done so far:  We have observed what happens to a seed when it is placed in the right environment; it comes out of its dormancy and germinates.  During germination we observed the root grew first from the embryo in order to bring the seed the most essential component for its growth – WATER.  Then the stem grew from the embryo upwards toward the light to begin its function of photosynthesis.  The water travels from the roots, up the stem, to the leaves which is called XYLEM.  Up to 90% of the water can evaporate through the stomata which is called TRANSPIRATION.  Water that does not evaporate is use in PHOTOSYNTHESIS.  Photosynthesis occurs when carbon dioxide enters the leaf through the stomata and makes contact with chlorophyll in the chloroplasts.  The chlorophyll uses light energy to combine the carbon dioxide with hydrogen atoms that came from the water to make SUGAR (food, carbohydrates, starch).  The chemical formula for this is:

6 CO2 + 6 H2O + LIGHT =  C6H12011 + 6 O2