In the 3.4 billion year history of photosynthesis, you’d think that nature would have found the most optimal formula for powering our plants. But in reality, our green plants capture and store only 1% to 2% of the sun’s energy. And in turn, some scientists are testing the possibility of turning plants black.
If you’ve forgotten the grade school science lesson, remember that the light that shines down on us contains all the colors of the rainbow (called wavelengths). We see color in something only when it reflects that wavelength back at us. So a red car is, somewhat ironically, actually painted in a shield from red, while in fact, that car is absorbing the wavelengths of every other color but red.
White reflects all wavelengths. Black absorbs all wavelengths. And as logic would ask, if black is the best way to absorb all of this energy, well then why are plants green? Why didn’t nature, over billions of years of evolution, design a better system?
Edible Geography published a fascinating exploration of the topic. And what they found is that, in fact, black may be too efficient at absorbing energy, to the point that plants get so hot that they damage their own cells. From the article:
Not to be defeated, a recent study looking at light usage in leaves proposed that, if re-engineered to produce a kind of internal antioxidant (a protective carotenoid called siphonaxanthin), plants “could close the so-called ‘green window’ and increase their absorptance”–and thus, one hopes, their yield.
Another toughening-up approach focuses on tweaking a plant’s in-house repairman, the D1 protein, so that it can rebuild light-damaged photosynthetic machinery more quickly and efficiently. For example, last year, an international team of scientists sent algae samples for a two-week holiday in space in order to see whether bombardment with cosmic radiation might produce a D1 with super-healing powers. Apparently, two mutant strains showed particular promise both in space and on earth, and now form the focus of future research.
Of course, there’s a catch: In the only known study that compared the photosynthetic efficiency of black and green plants, black plants performed no better than their green counterparts. So did the study miss something, or are we humans not as clever as we’d thought?