On Dec 29, 3:15*pm, Michael Bell wrote:
In message
* * * * * Stewart Robert Hinsley wrote:



In message , Michael
Bell writes
I am germiminating Alnus seeds and growing them up under lights and I
want to grow them as big as possible as quick as possible to graft
them onto "adult" trees this spring to produce catkins and fruits next
year.

I am growing them on compost, under "Eco-Light Grow" lights (as
supplied by one of those indoor growing shops which not-quite supplies
the indoor cannabis industry). Indoors, this keeps them at 23°C, just
right. But, it's text-book stuff: Growing plants need CO2, carbon
dioxide. Would it increase their growth to provide more CO2? How might
this be done?

The most obvious thing to do is to use a CO2 cylinder, feeding the CO2
through a regulating valve. Is suitable equipment available at
reasonable cost?

The next most obvious thing to do is to go back to school chemistry
and use Kipp's apparatus, that involves limestone, not a problem, and
acid, which might be a problem.

The next easiest source of supply is a flame. Not a wax flame from
those little tea-lights, they produce soot, the last thing I want! but
a meths flame, which burns cleanly, which is why a meths flame is
dangerous. And flames in general are dangerous in a house.

And how to make sure any CO2 stays in the enclosure, over the leaves,
where it will be used?

There are ventilation holes in the top of the cowl and in the
upside-down U- trough which holds the lighting tubes, and there must
be upwards air-flow, so the seedlings will be in fresh air. So, would
it be good to put a transparent sheet (Of what? Glass, perspex, one of
many kind of plastic?) just above the seedlings and supply the CO2
under that sheet?

Michael Bell

1) Adding CO2 only helps if CO2 is the limiting factor.
2) Adding CO2 has been experimentally found to result in plants more
susceptible to pests.
3) Indoor CO2 levels are usually already elevated.
4) At sufficient concentrations CO2 is toxic. While I doubt that you
would achieve those concentrations, you don't have any easy means of
monitoring concentrations.

One possibility is to fill the space with my outbreath - about 4% CO2

Have you inoculated the compost with Frankia alni?

I have mixed in soil which had Alnus in last year, just a very little
bit. But growing compost contains enough nitrates for the first few
weeks.

Michael Bell

Indoor CO2 levels are already well above outdoor, especially in modern
fairly well sealed houses. Lighting is far more likely to be a
limiting factor. I don't know what type of lighting you're using, that
might be more productive to discuss.

If adding more CO2 helped growth, use of gas & paraffin heaters would
presumably be more widespread in greenhouses.

NT