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CO2 Root Absorption

    

In spite of the fact water is not an efficient medium for delivery of CO2 to soil it can be used to show how roots absorb carbon dioxide in water. We will also see how green plants respond to a new source of carbon

     In a simple experiment with two Dieffenbachia maculata plants we observed substantially greater growth rate and mass gain in the plant watered with beverage type soda water compared to distilled water.  We used distilled water as it is more like rain than tap or well water.  Tap water has minerals and additions like chlorine that are bad for plants.

The plant receiving distilled water, while always viable, lost weight during the trial where the soda watered plant gained weight consistently.  And, the CO2 watered plant showed an increasing ability to accept and use CO2 soda water which it indicated with declining transpiration rates as well as increasing weight.  We were quite surprised to see the plant adapting so quickly.



 In this 120 day demonstration Plant A is the black graph above.  It received distilled water.  Plant B is the pink graph.  It received beverage type soda water.  We determined when to water by a finger touch test for dryness so the watering periods varied as we did not want to encourage bacteria with excessively moist soil.  Periods ranged from four to six days extending, for example during an 11 day deep overcast, days 26 through 37.  At the end of the 120 days Plant A had gained only three grams, but Plant B had gained 86 grams! 

At the start of the trial pot A had a mass of 190 grams and pot B 130 grams.  At each data spike pot A had received 60 grams of distilled water and pot B got 60 grams of beverage type soda water. There was significant runoff.  The net gain after a one hour runoff was about 40 grams of water in each pot.

The greatest reductions in Plant B transpiration rates were seen immediately after each watering indicating a quick response to CO2 again confirming the inverse relation between the aqueous CO2 concentration and transpiration.  The changes were determined with daily weighings.  They included an average weight gain for plant B of about 0.72 grams/day.  This could only be fully accounted for after the trial.  The actual transpiration and evaporation daily loss was greater by that amount, but we had a track of the trend.  Soda water loses CO2 in time so its’ effect declines every day between waterings.  In the actual application of this technology the level of CO2 available will be high and constant.

Outcomes

  Water demand varies inversely with CO2 concentration in soil. The more CO2 in the soil, the less water will be used.  And, green plants not only respond to carbon dioxide taken in through their root systems, but were increasingly accepting of it.  Plants can be greatly optimized for this system by selection in each generation and with genetic engineering for fewer and smaller stomata.  

When the watering mass loss was charted as it was clear the carbonated watered plant lost less water progressively.  This is thought due to stomata behavior change in response to carbonated water where both pots were in the same circumstance.  The only difference was the CO2 in the water for pot B.  Both pots had exposed soil which contributed to water and CO2 loss.   Transpiration difference was greater than that seen in this trial as the potting soil was very loose and open to the air thereby increasing water and CO2  loss from both pots.  In the field with delivery at one foot or injection at three feet the gas will be well trapped by dry soil. 

       In the work we saw an astounding 2866% greater weight gain in the CO2 watered plant over the distilled water plant and reduced transpiration up to 50% on some days, but the mean difference was only 12% we believe due to evaporation from the soil.  Selection and genetic engineering can reduce transpiration adapting our agricultural plants to much drier environments than they can now tolerate. 

In hydroponic greenhouses water consumption is not tracked.  CO2 enhancement is in the air of the greenhouse.  Water is in open contact with the roots in open containers subject to evaporation making water tracking irrelevant.  We conclude that our plant’s water use reduction was due to CO2 root absorption causing the stomata to close when the plant received enough CO2 through the roots.  This is consistent with the literature and our hypothesis that the primary function of the stomata is to exchange water vapor for carbon dioxide and not to cool the plant as has been thought and taught.  


Phase II

The original study ran from 11/12/06 to 03/12/07, 120 days which covers the terms of plants grown for food, fuel or fiber.  We observed our test plants were getting "root bound" in small pots.  We put the pots aside deciding to get some decorative containers and make house plants of them.  We stopped the daily weighing, but continued to water the pots as we had with distilled water only to pot A and soda water to pot B, but much less often as a stress test.

        During this test the water only plant leaves grew larger while the CO2 watered plant dropped its' large leaves and made small replacements.  The new leaves were half size.  We did not know what to make of this as it seemed plant "B" had clearly made a decision!  Intelligence?  We continued watering the plants as during the study:  Plant "A" got distilled water and Plant "B" received soda water which we had on hand to drink.  

        On 6/16/07, 98 days after we stopped daily weighings we weighed the plants.  Pot "A," water only, had only 115 grams having lost 78g while pot "B," soda water, weighed 165 grams for a loss of 51grams.  The CO2 watered plant took the dry stress much better than the pure watered plant.

       Through both phases, there was a net gain of 35 grams for the CO2 enriched plant as opposed to a net loss of 75 grams for the water only plant showing that plants are more robust in any circumstance receiving CO2 via their roots. The overall difference between the two plants is 110 grams (A’s loss + B's gain) over the 200 days of this test which is stunning.

         The results are remarkable in several respects:  (1) Plants adapt immediately and positively to a root source of carbon dioxide.  (2) The response to reduced transpiration is virtually intelligent as large leaves are dropped and replaced with small leaves.  This occurred in plants that were initially grown on plain water. It suggests that plants starting with CO2 from the ground will have small leaves and low transpiration.  In plants we are dealing with very different organisms that what we have thought.  We expect subsequent generations will make modified genetic codes for smaller leaf size reducing transpiration.  Selecting seeds from these plants will give us new generations of low-transpiring stock.   (3) Where the CO2 watered plant gained so much more weight we can conclude that larger leaves are not required for greater for better use of sunlight. 

 

          Seen from above on 7/04/07, plant "A" on the left and plant "B" onr the right, we see how the CO2 root fed plant adapted by growing smaller leaves while it gained substantially more mass and transpired much less water. 

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