modified atmospheres.doc
Some comments on how I understand this:
At 05:42 AM 6/25/2008, you wrote:
Keith Kridler Mt. Pleasant, Texas
I posted the other day about plant matter needing CO2 and insects needing
Oxygen to live and the gentleman posted that plant roots also need Oxygen to
grow which they do.
Plants need both oxygen to breathe, and CO2 as a substrate for photosynthesis.
We all agree that higher nitrogen levels in the hot, moist summer soils when
the daffodil bulbs are dormant are BAD for the bulbs as this leads to
increased basal rot.
One problem with nitrogen is that it allows the bulbs to grow quickly and soft, and thus be more vulnerable to attack. I imagine that it also allows the fungus to grow more quickly. It is a nutrient source for either, providing the nitrogen needed for protein synthesis.
Same goes for storing daffodil bulbs in plastic bags or
sealed up plastic tubs where the bulbs cannot breathe or get air exchanges
to remove moisture as the bulbs continue to respiration!
Here I think the problem is the humidity rather than the lack of oxygen. I think we use the word "breathe" in two different senses: to get oxygen, and also to receive dehumidifying ventilation. The basal rot fungus needs a humid environment to flourish, and in a humid environment the bulb is more likely to be in a stage where roots can emerge than to have a dessicated hard surface. Places of root emergence from the basal plate are like small wounds and allow entry points for fungus.
OK you ADD nitrogen fertilizer to compost piles to INCREASE the numbers of
living organisms in the compost and they consume the nitrogen, use up the
oxygen in the compost piles, break down the carbon in the pile and produce
Carbon Dioxide and heat in such quantities that you need to "turn or fluff
up" the compost pile every week or so to get MORE oxygen into the middle of
the pile or it will contain so much Carbon Dioxide that it will turn
anaerobic and smother the oxygen loving organisms. Thus allowing species
that breathe and live off of CO2 to multiple in the compost pile as these
types then give off Methane gas.
I’m not sure that it is CO2 that is the problem in compost piles, but I agree that it gets "stuffy" in there and needs more oxygen, however I agree that the breakdown of the plant matter will give off CO2. Think of fermentation, and the fizz in beer.
It would seem that the nitrogen fertilizers added to daffodil beds might not
be the actual problem but possibly this triggers a change in the numbers of
soil organisms and THEY change the soil levels of CO2 and Oxygen and this
triggers increased basal rot by improving this organisms habitat. We CANNOT
go out and fluff up the daffodil beds every week during the summer!
I would guess, again, that it is the nutritional boost that the Nitrate gives to the microorganisms, rather than a detrimental change in the soil gas content, that allows the basal rot to get the upper hand with the bulbs.
OK Normal CO2 levels outside your house today are about 387 parts per
million. Inside a normal office building or shopping mall they are about 750
parts per million. Some humans start to notice when CO2 levels exceed 1,500
parts per million as our bodies use up the oxygen and give off more CO2 in
confined office areas.Organic pesticide use of CO2 in greenhouses to kill pest insects on the
leaves of plants utilize filling and maintaining the greenhouse with 10,000
parts per million CO2 for just a couple of hours. Or for every 100 gallon
sized container (or 100 liter sized container) you would add just ONE gallon
of pure CO2 gas to raise the levels of CO2 to 10,000 parts per million. (In
a greenhouse this would be cubic feet or cubic meters and you monitor the
levels with a CO2 meter.)You HAVE to exchange the air in a greenhouse that has 10,000 parts per
million of CO2 BEFORE humans or pets return to work in the Greenhouse!!!In Canada and countries where they grow a LOT of Marijuana or tomato plants
inside houses/greenhouses they use CO2 generators (open flame natural gas
heaters) to maintain the CO2 at about 2,400 PPM as this is IDEAL for maximum
plant growth in full sun or under halogen lighting and humans can work in
these levels for 3>4 hours at a time safely.Now to my whole point! It would SEEM that we MIGHT be able to use cheap
welding gas CO2 to fumigate daffodil bulbs to kill off pupating bulb flies
or in some of your bulbs possibly mites or aphids.
This is a fascinating idea.
Has there been any scientific research into this that you all know of?? We
nearly all have root knot nematodes in tomato and vegetable plants so it
would be simple to test these nematodes in say a 20 gallon fish aquarium
filled with CO2 at X number PPM how long it takes to kill them in a plastic
sealed aquarium. Could you even kill the daffodil pests like bulb flies
sealed up in the daffodil bulbs?? Again how many hours at what PPM?The REALLY BIG question is do daffodil bulbs use up Oxygen while in storage
or do they use up CO2 while in storage? Again it would be easy to use the
welding gas Oxygen and add it to sealed bags or containers if higher levels
of this gas were to be beneficial for test purposes.
It seems unlikely to me that daffodil bulbs use any CO2 while in storage. After all, there is no part of them that is green. The photosynthesis in plants requires chloroplasts: they’re filled with chlorophyl and very green. During storage, the daffodil is satisfying its meager energy needs by catabolism of stored carbohydrate.
Would you kill daffodil bulbs if they were stored in either type of gas for
a few days? Does ANYONE REALLY care:-))) KK
You notice that the CO2 level in the greenhouses, even for insecticidal treatment, is still one part in a hundred. It is not pure CO2. I would guess that the daffodil, like any aerobic organism, would die if it were held in pure CO2 for any length of time.
If you search with Google on "CO2 Insecticidal Use" there is a lot that appears (See attached file).
For example in Avocado:
Fruit exposed to MA[modified atmosphere] for more than 1 d and then ripened in air had exocarp and mesocarp injury. Fruit in MA for more than one day had decreased concentrations of three glycolytic metabolites: glucose 6-phosphate, fructose 6-phosphate and 2-phosphoglycerate. Other metabolites were not affected. Insecticidal MA can only be used as a potential insect control treatment in avocado fruit for periods of 1 d or less
A nice explanation on the mechanism:
Arthropods cope with reduced oxygen and elevated carbon dioxide atmospheres with a reduction in metabolic rate, also called metabolic arrest. The reduction in metabolism lessens the pressure on the organism to initiate anaerobic metabolism, but also leads to a reduction in ATP production. The natural permeability of cellular membranes appears to be important for the survival of the arthropod under low oxygen or high carbon dioxide atmospheres. Despite the similarities in response, arthropod mortality is generally greater in response to high carbon dioxide as apposed to low oxygen atmospheres. There appears to be a greater decrease in ATP and energy charge in arthropods exposed to high carbon dioxide as compared with low oxygen atmospheres, and this may be due to greater membrane permeability under carbon dioxide leading to an inefficient production of ATP. Reduced oxygen and elevated carbon dioxide atmospheres can have an additive effect in some cases, depending on the concentrations used. The effect of these atmospheres on arthropods depends also on temperature, species and life stage. Additional work is needed to fully understand the mode of action of controlled atmospheres on arthropod pests.
And from Google Books:
Application of insecticidal atmospheres at high temperatures can accelerate the mortality of insects. Manila and Oro mangos treated with a combination of dry-forced heat at 44C and insecticidal CA (0.7% O2 and 67%CO2) for 160 minutes resulted in 100% mortality of eggs and third instar larvae of Anastrepha ludens and A. oblique without causing fruit injuries (Yahia et al. 1997).
There is no current commercial use of insecticidal atmospheres for horticultural crops. However, treatments with MA/CA [modified atmospheres/controlled atmospheres] alone or in combination with other treatments such as cold or heat are now being evaluated as a means of commercial insect control for tropical fruits (Kader and Ke 1994)
Have fun with Google yourselves!
Melissa