keith.ray

Comment Threads

• J Thomas commented on Implications
  OK, on closer look that paper doesn't say what I hoped it did. They used arabidopsis leaves. Their green diodes were centered at 522 so about half of their output would be in the range the carotenoids would absorb. But the minimum absorption was only down to around 50%. On their graphs they measure the absorbed light, ignoring the light that isn't absorbed, so their green lines never extend as far because their equipment doesn't produce enough green light to get as much of it absorbed. I wanted it to mean that the frequencies of light that are not used...
• J Thomas commented on Implications
  "IIRC, the plants try to shift as much of the light gathering and protection-from-surplus-light activities onto the carotenoids as possible, because they're physiologically cheaper[...]" Thank you! Very clear as usual....
• Jay commented on Implications
  They found the same amount of photosynthesis from all three, proportional to absorption. That paper shows that an absorbed green or blue photon enables photosynthesis better than a red photon, which isn't really surprising. The surprising things about photosynthesis on Earth are (1) green photons, despite being more numerous than red photons, are more likely to be rejected (reflected) by leaves, which is why leaves look green, and (2) green and blue photons have more energy apiece than red photons, and the fact that each absorbed green or blue photon counts only as much as a red photon is actually...
• J Thomas commented on Implications
  It sounds like the photoelectric effect. If there's enough light energy in the quanta to catalyze the reaction, then the reaction happens. If there's extra energy the reaction still happens and does not happen more often or harder, it just happens....
• Jay commented on Implications
  It's similar to the photoelectric effect, in that the absorption bands of the chlorophyll limit the useful energy of an incoming photon. To get more energy out of a photon, the plant would need a different absorber with a shorter cutoff wavelength. I used to make photovoltaic cells (more or less, it's complicated) and the more efficient ones would have several layers. The top layer strips out high - energy photons (for a simplified example, let's say 500 nm and below in wavelength); the next layer strips out the medium energy photons (say 600 nm and below) and the last...