MadSci Network: Cell Biology
Query:

Re: are all cells in plants green?

Date: Thu Dec 14 21:30:15 2000
Posted By: Cynthia Galloway, Faculty Biology
Area of science: Cell Biology
ID: 969498495.Cb
Message:

Lucy,  Plants appear green because many of their cells contain chloroplasts 
 which contain the green pigments, chlorophyll a and chlorophyll b.  
Surprisingly, the outer layer of cells covering the plant, the epidermis, 
is devoid of chloroplasts and is colorless or transparent.  The only 
epidermal cells containing chloroplasts are the guard cells of the stomatal 
apparatus.  The cells that give a plant its green appearance are 
chloroplast containing parenchyma cells.  Leaves have two types of 
parenchyma cells called palisade and spongy parenchyma cells.   Below 
ground organs of plants, such as roots and underground stems, are normally 
not green because their plastids contain starch which is not green.  
Chlorophyll develops in response to light.  A good experiment to show this 
is to plant some pea, bean or corn seeds in a pot and then place the pot in 
the dark for a week or more.  Plant another pot of seeds and leave it in 
the light.  Compare the plants in the two pots and see if there is a color 
difference.


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