For the uninitiated, indoor gardening can seem a bit strange.
I mean think about it: plants have evolved over 450 million years to
exploit solar radiation-- a very special energy emitted by the sun.
Ahhhh! Then one day, a young man named Everest had a pipe dream about growing
plants in his basement. A place that, thanks to be encased in bricks, stone
and cement, receives pretty much no solar radiation whatsoever.
Who'da thought that was a good idea, huh? Well, grow lamp manufacturers.
Yes. Grow lights, by virtue of their name, can grow plants without the sun, but how
well do they actually perform?
Suffice to say, the more accurately our grow lights are able to replicate the
characteristics of the sunlight hitting the surface of our planet,
the better chance my basement dwelling plants will have a growing, blooming and
delivering all the good stuff.
So, today folks, we're going to discuss the characteristics of sunlight, how this
energy affects plants, and look at some technologies and strategies available to
indoor growers who want to try and replicate it indoors.
Everybody knows that plants absorb sunlight — well yes, kind of, but not how
tissue paper absorbs a spillage.
That's just a physical absorption: one substance (ewwww!) being mopped up by another.
Nice!
The crucial difference here is that sunlight is energy, and it's this energy
which powers important chemical reactions inside the plant.
Think about it: plants uptake water via their roots and absorb carbon dioxide
through their leaves, but it's the light which provides the energy needed to
break these molecules apart and join them together again as something else.
In this case: carbohydrates. Without light
this reaction couldn't happen. So what's going on here? Well, plants contain
special light-harvesting molecules called pigments, and one family of these
pigments is called chlorophyll.
It's what makes plants green. Now, a photon of light hits the chlorophyll, an
electron in the chlorophyll becomes excited.
(oooh!) In this higher energy state the excited electron can be passed along to
another adjacent molecule.
Think of it like a chain: the electron moving from one chlorophyll molecule to
another until finally it gets passed to a molecule of carbon dioxide and BAM!
Together with good old H2O, this energy helps bust these apart to create
carbohydrate and oxygen. One photon is only capable of exciting one electron;
however, complex pigment molecules such as chlorophyll contain many different
electrons which only get excited by photons traveling at certain
wavelengths. Now, sunlight is a full-spectrum continuous light source.
It appears white but it actually contains all of the visible colors, all
of the time. Because sunlight contains photons of all of these different
wavelengths, the chlorophyll gets excited. Really, really excited! Okay ....
I've already discussed PAR, or photosynthetically active radiation, in
an earlier video.
This refers to the band of radiation, between 400 and 700 nanometers, which
plants use for photosynthesis. PAR is a measure of light intensity for plants,
but it tells us nothing about the spectral quality of the light source. A
high PAR value could be generated from very narrow bands of greens, yellow, or red
light that would be far from ideal from growing plants. So, with full spectrum
sunlight as our gold standard,
what's the closest we can get to it indoors with grow lights? Light emitting
plasm,a my friends, or L.E.P. or 'lep' if you're super lazy, is the nearest to full
spectrum light.
The problem is it's still expensive, so I guess we should keep our fingers crossed
that it becomes more affordable soon.
HPS and double-ended HPS tend to be heavy on yellow, orange, and red,
not much going on in the blue; however, EYE Hortilux offers a super HPS which
has 25% more light energy in the violet, blue, and green
bands.
This makes an awesome flowering light which doesn't just bombard the plant
with orange-yellow photons, helping to increase overall crop quality. Commercial
indoor growers following a compound multiple lighting plan often supplement
the spectrum of their HPS lamps with light emitting ceramic, light-emitting
plasma or enhanced metal halide such as Hortilux Blue. If, like me you, grow on a
smaller scale,
you could opt for a dual-arc tube lamp. It's basically a 1000-watt rated lamp
that combines a 400 watt metal halide and a 600 watt HPS in one. A more recent
development is nanometer-specific T5 lamps.
There are physical limitations on the spectral output you can achieve from a
single triphosphate lamp, so the idea here is that you mix and match different
lamps in the same fixture. Say if you have an eight lamp fixture for vegetative
growth you could choose 4 power veg full-spectrum + UV lamps and add 2 x 420
nanometers lamps and add 2 x 460, or divide these numbers in two for a four lamp fixture.
For flowering, switch out the 420 and 460s for 633 and 660 nanometer lamps. Plants grown
in full spectrum, or at least broader spectrum, tend to be more structurally
sound,
more disease resistant, and have better tastes and aromas.
Remember folks, it's not just all about PAR and photon count, it's about
spectral quality too. Okay, that'll do it for now. Let me know your questions
and comments below. As always, this is Everest, in a full spectrum of white
light ... OUT!