Re: : D. diandra either red or green depending of light source

[Paul Krombholz <krombhol at teclink_net>]

     * From: "Philippe Lemaire" <ph.lemaire at CompaqNet_be>
>
>Hello again,
>
>here are the pictures :
>
>http://users.compaqnet.be/PLemaire/red.jpg
>http://users.compaqnet.be/PLemaire/green.jpg
>http://users.compaqnet.be/PLemaire/both.jpg
>
>The plants are in the same tank : same NO3, PO4, Fe
>The red is between a blue/red and a yellow lamp
>The green is between the yellow and white lamp
>
>The effect is not only a SHOWN colour effect but the leaves ARE different
>in colour when seen with the same lamp.
>


If one is going to show that the color of the light influences 
whether or not plants produce red leaves and stems, one must rule out 
an alternative hypothesis which is that plants can be more or less 
red because they get more or less light.  The important word, here, 
is "get".  You can't just measure the intensity of light with a 
photometer because photometers don't absorb light the way plants do. 
Plants absorb light and use it to power photosynthesis mostly in the 
red or blue regions of the spectrum, and pass through or reflect most 
of the green.  That is why they are green. They are not absorbing 
green.  According to the alternative hypothesis, the photosynthesis 
rate determines how much of the red pigment is manufactured.  In 
order to show that the color of light affects whether or not the 
plant is red or green, you have to grow the plant in different colors 
where you adjust the intensities so that photosynthesis rate is the 
same in all the different colors.  You would find that you would have 
to use extremely high intensities of light in the green region to get 
the same amount of photosynthesis as caused by a modest intensity in 
the red or blue regions.
-- 
  Paul Krombholz in dried-out central Mississippi.