and Carbon Dioxide
People laughed when it was claimed that playing music to plants
made them grow better. It really did because the sound vibrations
actually strengthen the stem fibres, shorten the internode length,
and cause stress growth reactions from the plants.
Then people laughed when it was claimed that singing to plants
made them grow better. However, it is true. The CO2 from human
breath actually makes plants grow faster. If you and a few gardeners
stay in the indoor garden area during the light period, the plants
would do very well.
It is thought that the massive plants that developed millions
of years ago had
lived an environment with much more carbon dioxide in it. In their
evolution, the plants still maintained the capacity to use much
more carbon dioxide than the world has now.
Luckily in the smoggy cities, the CO2 level can be as high as
500 PPM, and by just having a good circulating fan, the plants
should have enough CO2 for a medium-light indoor garden.
A high-light indoor garden with the carbon dioxide amount increased
from an ambient level of 300 PPM to a high level of 2,000 PPM
can nearly double plant growth.
Why All Plants Need CO2
The dry matter in a plant is 90% carbon, hydrogen, and oxygen.
carbon has to come from the carbon dioxide (C02) in the air.
CO2 molecules are only necessary during the light times. Plants
do not need CO2 in the dark period, and in fact plants breathe
out CO2 all the time, just as humans do. The slight difference
is that in the light period, leaves use up their own CO2 to make
sugars and so appear to breathe out only oxygen in the daytime.
The more light available to a plant, the more CO2 it needs for
photosynthesis. Experiments have shown that during photosynthesis,
it takes about 1 a photons to make enough electrons to create
sufficient energy to split one CO2 molecule into carbon (c) and
oxygen (02) atoms and form a sugar. There are trillions of photons
striking the plant leaves, so a grower must provide enough CO2
or else the photons will just bounce off the leaves without doing
A plant in full Sunlight (about 5,000 lumens per square foot)
could process about 2,000 PPM of CO2 if it was made available
in a greenhouse. Outdoor CO2 is nowhere near that. Indoor gardens
with the light level at 3,000 lumens per square foot need about
1,500 PPM of CO2 for the limited light. With the level at 1,000
lumens per square foot, only about 300 PPM of CO2 is required
- which is less than ambient air (city air normally has 400 PPM
of CO2), The lower the CO2 level, the more the air has to be kept
moving past the leaves.
Remember that it is the PAR value (not lumens) that indicates
the plants' use of CO2 because the light that the leaves cannot
sense is totally wasted and does not go down the photon funnel
to be used for splitting CO2 into sugar.
How Much Carbon Dioxide Can Your Indoor Garden
Experiments have shown that plants can handle up to 10,000 PPM
of CO2 with no ill effects. At very high light densities, indoor
plants have a maximum CO2 uptake of just over 2,000 PPM.
Light intensity increases with closer distance, so the CO2 level
around plants needs to be increased respectively:
Lights Distances CO2 Needed for
from Plants Sugar Production
HID Lamps 4ft (120 cm) * Ambient
3 ft (90 cm) 400 PPM
2ft (60 cm) 1,000 PPM
1 ft (30 cm) 2,000 PPM
This is with maintaining all plant resources at MAXIMUM and at
a temperature NOT EXCEEDING 30°C (86°F).
* Ambient CO2 in the cities is between 400-500 PPM.
* Ambient CO2 in the country is about 300 PPM.
Note: Any time your indoor garden temperature goes above 30°C
(86°F), start shutting down the CO2