Showing posts with label Plants. Show all posts
Showing posts with label Plants. Show all posts
Monday, 23 July 2012
What is Photosynthesis?
Photosynthesis is the process by which plants, some bacteria, and some protistans use the energy from sunlight to produce sugar, whichcellular respiration converts into ATP, the "fuel" used by all living things. The conversion of unusable sunlight energy into usable chemical energy, is associated with the actions of the green pigment chlorophyll. Most of the time, the photosynthetic process uses water and releases the oxygen that we absolutely must have to stay alive. Oh yes, we need the food as well!
We can write the overall reaction of this process as:
Most of us don't speak chemicalese, so the above chemical equation translates as:
six molecules of water plus six molecules of carbon dioxide produce one molecule of sugar plus six molecules of oxygen
Diagram of a typical plant, showing the inputs and outputs of the photosynthetic process. Image from Purves et al., Life: The Science of Biology, 4th Edition, by Sinauer Associates (www.sinauer.com) and WH Freeman (www.whfreeman.com), used with permission.
Life Cycle of Plants
A plant's life cycle describes how long a plant lives or how long it takes to grow, flower, and set seed. Plants can be either an annual,perennial, or biennial.
Annual
A plant that completes its life cycle in one growing season. It will grow, flower, set seed, and die.
Examples: Marigolds, tomatoes, and petunias.
Perennial
A plant that lives for 3 or more years. It can grow, flower, and set seed for many years. Underground parts may regrow new stems as in the case ofherbaceous plants, or the stems may live for many years like woody plants (trees).
Examples: Daisies, chrysanthemums, and roses.
Biennial
A plant that needs two growing seasons to complete its life cycle. It grows vegetatively (produces leaves) one season. Then it goes dormant or rests over the winter. In the spring, it will begin to grow again and grow flowers, set seed, and die. The seed that is left behind on the ground germinates and the cycle begins again.
Examples: Parsley, carrots, and foxglove.
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