Hacker News Reader

Comment by MrBuddyCasino | Hacker News Reader

„By maximizing green content and minimizing red content versus standard lighting LEDs, this LED color enables significant enhancements to luminaire cost and performance.“

I thought plants look green because thats what they reflect? Meaning that the other wavelengths are absorbed for photosynthesis.

View on HN

The red content is intended to be supplied by a separate red LED. A red LED produces red much more efficiently than the phosphor on a white LED, so it saves power to leave red out entirely if you know it will be paired with red.

This web page claims that the different frequencies of photosynthetically active light can cause different reactions in plants: https://www.voltlighting.com/grow/best-light-spectrum-plant-...

That, too. But it's also much easier to sell plants that look the right color to people perusing them. Ever see a commercial or resale garden center using fuchsia-tinted grow lights? No? That's because they're out of business.

The plants look terrible when the light is on, for sure.

But I know of plenty of commercial greenhouses that use them prior to shipping to retail.

That's assuming a wholesaler business that ships to retail. There are plenty of us out there who actually let people - even commercial customers - into our greenhouses in person. Until this development by Cree, all of our viable options for LED lighting were huge pains in the posterior (hence I'm still on fluorescent). This is much much simpler, and will definitely accelerate my own switch to LED.

In a way, you might say that until now, LED grow lighting was only feasible on a very very large scale, or a very small scale, and the medium-sized local nurseries and greenhouses were just out of luck. Cree seems to have changed that.

Yeah that seems odd to me. Chlorophyll largely doesn't do anything with 500-600nm wavelengths, and that's where this LED outputs a lot of energy. If this was a bulb that could switch between red and green that might be useful for dealing with day/night cycles for plants, but this LED seems like it just outputs more green light than normal?

A graphic on the page notes that these are designed to be used with red 660nm bulbs. A lot of current grow lights are white, blue, and red bulbs. It seems these are aiming to create the blend of blue and white so manufacturers can blend them with red without worrying about the white/blue mix.

Sensitivity of Seven Diverse Species to Blue and Green Light: Interactions with Photon Flux https://journals.plos.org/plosone/article?id=10.1371/journal...

>In contrast to the significant effects of blue light, increasing green light in increments from 0 to 30% had a relatively small effect on growth, leaf area and net assimilation at either low or high PPF. Surprisingly, growth of three of the seven species was not reduced by a treatment with 93% green light compared to the broad spectrum treatments.

Seems like green light is not useful for all cases, but I would indeed like to know exactly why that's the case.

There's too much green light in sunlight, so to reduce free radical formation, most plants reflect most green light (something you may have noticed.) Converting light into chemical changes (splitting water, then sugar) without causing a lot of damage from free radicals is not trivial.

>most plants reflect most green light (something you may have noticed.)

Subtle !

A joke on myself, too. I swear our associative minds, knowing that peeps who wear green clothes and buy green cars, like and want more green; decide plants aren't rejecting green light (the obvious physics) but that they must want, love and use green light. An error I made myself until fairly recently.

It's possible that some green light improves aesthetics.

Reply on news.ycombinator.com