[AGA Member] Re: AGA Member - Digest V1 #63

[Steven Olson <stevenkentolson@yahoo.com>]

I do believe we're dealing with many factors here. 
Many garden plants only get red with lots of sun.  The
red reduces the amount of light, heat reaching the
chloroplasts so that they can continue to function and
not burn up.  Not less green here, I think, just more
red.  Cactus, simply vastly reduce the amount of
chloroplasts to body tissue ratio in light and heat
because they need to conserve water and because
they'll burn up.  They have to use an entirely
different metabolic pathway as they light and heat
prevents them from actually photosynthesizing during
the day.  They hold the light energy chemically and
use it at night.  If you've ever started tomato seeds
for the garden, you know they get leggy because they
get too little light and are "reaching" for more
light.  They don't try to grow fast because they are
above the canopy.  Lobelia grows well in a wet garden
situation and is not a pure aquatic.  I don't know
enough about this to explain why some plants would get
red in lower light.  Clearly, we're dealing with very
complex situations which are in part species specific
and would likely vary with the habitat the plant
evolved to deal with.  Very interesting discussion
though.  I do know some garden plants can bleach (grow
most Hosta in the sun and see what happens).  Under
water would almost always be low light situation I
think as would the jungle.  That's why most
houseplants, very low light, come from the tropical
understory.  Most jungles have fewer daylight hours
than temperate summers typically have.  The intensity
of light is high because of the more perpendicular
angle of the light.  On the other hand there is more
atmosphere filtering out certain rays at lower
elevations.  Once a plant breaks the surface of water,
but only if it does, that's a very high light
situation typically. 

Enough of my rambling.

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