Submitted by: Troy Mackay

Answer:
Yes, it is hard to find information on this topic; we could find none on the net either.  However, we quote below an extensive passage from the book Carbon Dioxide and Global Change: Earth in Transition, written and published by our father in 1989:

"Although several investigators have claimed that plants should receive little direct benefit from dissolved CO2 (Stolwijk et al., 1957; Skok et al., 1962; Splittstoesser, 1966), a number of experiments have produced significant increases in root growth (Erickson, 1946; Leonard and Pinckard, 1946; Geisler, 1963; Yorgalevitch and Janes, 1988), as well as yield itself (Kursanov et al., 1951; Grinfeld, 1954; Nakayama and Bucks, 1980; Baron and Gorski, 1986), with CO2-enriched irrigation water.  Early on, Misra (1951) suggested that this beneficent effect may be related to CO2-induced changes in soil nutrient availability; and this hypothesis may well be correct.  Arteca et al. (1979), for example, have observed K, Ca and Mg to be better absorbed by potato roots when the concentration of CO2 in the soil solution is increased; while Mauney and Hendrix (1988) found Zn and Mn to be better absorbed by cotton under such conditions, and Yurgalevitch and Janes (1988) found an enhancement of the absorption of Rb by tomato roots.  In all cases, large increases in either total plant growth or ultimate yield accompanied the enhanced uptake of nutrients.  Consequently, as it has been suggested that CO2 concentration plays a major role in determining the porosity, plasticity and charge of cell membranes (Jackson and Coleman, 1959; Mitz, 1979), which could thereby alter ion uptake and organic acid production (Yorgalevitch and Janes, 1988), it is possible that some such suite of mechanisms may well be responsible for the plant productivity increases often observed to result from enhanced concentrations of CO2 in the soil solution."

References
Arteca, R.N., Pooviah, B.W. and Smith, O.E.  1979.  Changes in carbon fixation, tuberization, and growth induced by CO2 applications to the root zones of potato plants.  Science 205: 1279-1280.

Baron, J.J. and Gorski, S.F.  1986.  Response of eggplant to a root environment enriched with CO2.  HortScience 21: 495-498.

Erickson, L.C.  1946.  Growth of tomato roots as influenced by oxygen in the nutrient solution.  American Journal of Botany 33: 551-556.

Geisler, G.  1963.  Morphogenetic influence of (CO2 + HCO3^-) on roots.  Plant Physiology 38: 77-80.

Grinfeld, E.G.  1954.  On the nutrition of plants with carbon dioxide through the roots.  Dokl. Akad. Nauk SSSR 94: 919-922.

Idso, S.B.  1989.  Carbon Dioxide and Global Change: Earth in Transition.  IBR Press, Tempe, AZ.

Jackson, W.A. and Coleman, N.T.  1959.  Fixation of carbon dioxide by plant roots through phosphoenolpyruvate carboxylase.  Plant and Soil 11: 1-16.

Kursanov, A.L., Kuzin, A.M. and Mamul, Y.V.  1951.  On the possibility for assimilation by plants of carbonates taken in with the soil solution.  Dokl. Akad. Nauk SSSR 79: 685-687.

Leonard, O.A. and Pinckard, J.A.  1946.  Effect of various oxygen and carbon dioxide concentrations on cotton root development.  Plant Physiology 21: 18-36.

Mauney, J.R. and Hendrix, D.L.  1988.  Responses of glasshouse grown cotton to irrigation with carbon dioxide-saturated water.  Crop Science 28: 835-838.

Misra, R.K.  1951.  Further studies on the carbon dioxide factor in the air and soil layers near the ground.  Indian Journal of Meteorology and Geophysics 2: 284-292.

Mitz, M.A.  1979.  CO2 biodynamics: A new concept of cellular control.  Journal of Theoretical Biology 80: 537-551.

Nakayama, F.S. and Bucks, D.A.  1980.  Using subsurface trickle system for carbon dioxide enrichment.  In Jensen, M.H. and Oebker, N.F. (eds) Proceedings of the 15th Agricultural Plastics Congress, National Agricultural Plastics Association, Manchester, MO, pp. 13-18.

Skok, J., Chorney, W. and Broecker, W.S.  1962.  Uptake of CO2 by roots of Xanthium plants.  Botanical Gazette 124: 118-120.

Yorgalevitch, C.M. and Janes, W.H.  1988.  Carbon dioxide enrichment of the root zone of tomato seedlings.  Journal of Horticultural Science 63: 265-270.

Splittstoesser, W.E.  1966.  Dark CO2 fixation and its role in the growth of plant tissue.  Plant Physiology 41: 755-759.

Stolwijk, J.A.J. and Thimann, K.V.  1957.  On the uptake of carbon dioxide and bicarbonate by roots and its influence on growth.  Plant Physiology 32: 513-520.