Plants, anyone?

[FishEggs]

i just trimmed some brazilian pennywort if you are interested in it i can send you some.

 

[ingg]

Ok, back to the light question. I'm confused about something. Plants use photosynthetic pigments to harvest electrons from light. These pigments absorb electrons at different wavelengths. All plants contain chlorophyll a, which absorbs light most effectively at around 440 nm. Chlorophyll a is also effective at 680 nm, but it actually reduces the wavelength to 440 before absorbing it. Carotenoids are in most aquatic plants and absorb light between 550-620 nm. Here's the absorption spectra for these:
http://www.life.illinois.edu/govindjee/paper/fig5.gif
So, looking at the spectrum from the 50/50 bulbs below, they should be great for the plants. Why aren't they better?

And you hit the crux of it.

What people who are always saying "actinics are bad" fail to realize (or just don't want to explain the detail of) is that many Actinics DO provide useful light for plants, but others can indeed be useless.

There are many actinics that completely miss that 440 nm peak. The actinics that miss it are indeed useless for plants. Many 50/50 bulbs are built in ranges that happen to hit it, however - at least those I've looked up in the past.

The Actinics that do hit it are actually quite useful for plant growth, as plants need BOTH the high and the low side, the 440 and the 680.

One of the reasons planted folks in general push 6500k and 10k bulbs is that they happen to hit both of those ranges in at least small peaks of output from almost all manufacturers. They also, however, have a ton of greens and yellows, which gives them a pleasing to the eye look as well.

Very pure plant bulbs are pink/purple hues - purely the 680 and 440 - ugly for our eyes, but grow plants well.

50/50's are a crap shoot in terms of hitting the correct blue or not, but when they do, they are almost in line with those purple/pink bulbs - in that they hit the hues for growth right, just maybe not the hues for viewing as well as a 10k or 6500k may to our eyes.

 

[HennaHonu]

Thanks ingg!
My crypts and anubias nana's have been growing exceptionally well, so they must be hitting it right =]