David E. Ross wrote:
On 8/8/13 8:19 PM, David Hare-Scott wrote:
Higgs Boson wrote:
Have often wondered how plants with dark foliage, like the dark red
canna, handle chlorophyll.

Wikipedia has a long article; this is the first graph:

Chlorophyll (also chlorophyl) is a green pigment found in
cyanobacteria and the chloroplasts of algae and plants.[1] Its name
is derived from the Greek words χλωρός, chloros ("green") and
φύλλον, phyllon ("leaf").[2] Chlorophyll is an extremely important
biomolecule, critical in photosynthesis, which allows plants to
absorb energy from light. Chlorophyll absorbs light most strongly in
the blue portion of the electromagnetic spectrum, followed by the
red portion. However, it is a poor absorber of green and near-green
portions of the spectrum, hence the green color of
chlorophyll-containing tissues.[3] Chlorophyll was first isolated by
Joseph Bienaimé Caventou and Pierre Joseph Pelletier in 1817.[4]

Read the whole thing if interested, and make any
comments...appreciated.

HB

The third section on why chlorophyll is green not black is quite
interesting to me. The explanation given, which I think is widely
accepted in the botanical community, is that some (apparently
superior) structures and functions of living organisms have not been
reached by evolution because there was no evolutionary pathway from
where they came from to get there. This accounts for the less than
optimal structure of many aspects of life, eg the human eye and the
giraffe's neck. In fact it is characteristic of a process that
proceeds by many small connected steps to have such inferior
outcomes. A process of design (such as human engineering) can
abandon a bad design and take a completely different approach.
Evolution cannot do that. Evolution is undirected and has no 'final'
target nor does it look to the future as an engineer does, it can
only work incrementally on choosing which variation of structure or
function is better suited to the environment the organism is in at
that time.

In case anybody thinks that evolution is too academic or even off
topic, I think it is fair to say that having an understanding of
evolution of plants and organisms that relate to plants (eg
predators and symbiots) will make you a better gardener.

David


In the August 2013 issue of Scientific American, the article "The
Surprising Origins of Life's Complexity" suggests that evolution
strongly depends, not so much on mutations that are advantageous, but
more on mutations that are neutral. As such mutations accumulate in
the gene pool, their combination eventually leads to changes in an
organism. See
http://www.scientificamerican.com/article.cfm?id=the-surprising-origins-of-evolutionary-complexity.

This application of complexity theory is not universally accepted. No
matter the point that I was trying to make, that the outcomes of evolution
are limited by the availablity of pathways from the previous situation to a
new one remains. Whether this postulated mechanism opens up more pathways
that permit greater leaps from one state to another remains to be seen, as
does how often it might occur.

D

D