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Wednesday, April 20, 2016

WHY ARE PLANTS GREEN INSTEAD OF BLACK?

Today I will address what has been on my mind for some time, but never had a chance to really think about why.  That is, if Nature had optimized the use of solar energy, all plants would be colored black.  However, first, I had a Hawaii's Best Kitchens chicken bento at the Diamond Head parking lookout:


The half chicken is so large that a portion sticks out of the container.  Looking up from this location you can see the Diamond Head Lookout, a decent hike up to the top from the inside of the crater.


The view looking down to the ocean is spectacular:


On my way to the Ala Wai Golf Course, I noticed in the rarely visited (almost never see tourists there) Queen Kapiolani Garden, a black elephant ear plant:


I've long wondered why all plants were not black, for the color black absorbs more light than any other hue, and, you would think, should determine the course of evolution.   When you see the color green, it is because the chloroplasts absorb deep blue and red light for the plant to use, reflecting the green portion of the spectrum, the range with the highest sunlight intensity.  Thus the plant only converts 0.1% to 6% of impacted light.  Even well-designed solar photovoltaic cells (and notice that they're always black) can convert around 15% of the sunlight into electricity.  The latest record is 46% using a tiny exotic multi-junction semiconductor system (left) and concentrated light.

It is true that:

  • Plants generally have too much sunlight, and green is reflected, thus protecting the plant,
  • Light below 4000 angstroms can cause mutations, while those over 7000 angstroms can denature proteins.

Thus, perhaps excessive sun is worse than not enough, and green is the resultant color.  Another theory is that early forms of plant life, algae, lived in a watery environment that captured most of the sunlight, only allowing deep blue and red to be used by plants.  

Today, we consider green to be a healthy and natural color because plants are good.  If plants evolved to be black, no doubt that would be considered to be the color of nature.  Someday, I'll explain why we are shaded from white through brown to black, and why we don't have purple people.

Not sure if you noticed, but the U.S. stock market is at a high for the year, and approaching the all-time record of 18,312 set in May last year:


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In the Indian Ocean, Tropical Cyclone Fantala is still at 120 MPH, but will soon, again, reverse paths, that is, back to Africa, and weaken:



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