To answer your last question first, photosynthesis is the way in which a plant feeds itself by producing energy from sunlight. If photosynthesis could be artificially reproduced, a lot of our current problems with energy and food shortage would be at least partially resolved.
Not all plants can do this; some plants live as parasites on a "host" plant, filching off its energy reserve. However, most plants (the green ones) can synthesize energy from sunlight "captured" by their leaves. There sugar is produced when the leaves take in carbon dioxide (yes, all those car fumes are their delight!) whereas a plant gets most of its water supply from its roots. In the process, a plant gives off oxygen, a fair exchange between the needs of the plant and animal kingdom.
The chemical process of photosynthesis could be written as the following:
6H2O + 6CO2 ----------> C6H12O6+ 6O2
which could be "translated" as
'six molecules of water plus six molecules of carbon dioxide produce one molecule of sugar plus six molecules of oxygen.'
There are two complementary steps of photosynthesis (light dependent and light independent), as under normal conditions a plant has a day and night cycle. The light reactions occur in the grana; the dark reactions, in the stoma of the chloroplasts (leaf cells). (Note that one dark process enzyme is triggered into action by light, so that its name 'dark process' is not entirely correct.) The first process is where the carbon from carbon dioxide is "fixed" into the plant; the second (much more complicated) is when the sugar is made.
Two video clips can be viewed at the following site:
http://video.google.ch/videosearch?client=firefox-a&rls=org.mozilla:fr:official&channel=s&hl=fr&q=photosynthesis&um=1&ie=UTF-8&ei=J1Z1StPoNZPd-Qax0JXMBw&sa=X&oi=video_result_group&ct=title&resnum=8#
Check out the following references for more information about these complementary functions.
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