THE EFFECT OF ACCUMULATED CARBON DIOXIDE ON PLANT RESPIRATION

Abstract

The respiration of apple twigs at 0[degree] C, of potato tubers at about 22[degree] C, and of wheat grain at 40[degree] C. was studied from the standpoint of the effect of allowing the CO2 to accumulate in the respiration chamber. Under such conditions the rate of CO2 production continuously decreased with time. After the first 30-40 hrs., the relation is CO2/(log t - 0.566) = k, and the rate is affected by a phenomenon which can be described as follows: When aspiration of the atmosphere surrounding the tissue is commenced, after a period of accumulation of CO2, the rate of respiration immediately assumes a far higher value than it had during the accumulation period, the magnitude of this value being possibly proportional to the amount of CO2 previously accumulated. It is a matter of several hrs. before the rate becomes constant. This phenomenon may be due to an equilibrium between the CO2 in the atmosphere surrounding the tissues and that dissolved in the tissues, the excess CO2 in the latter being removed but slowly when aspiration is commenced; or it may be due to decrease of the pH of the tissues as CO2 accumulates, bringing the proteins of the protoplasm nearer to their isoelectric point and hence increasing the permeability of the protoplasm and causing an actual increase in rate of CO2 production. The evidence in the literature on the pH of cell sap and on the isoelectric points of plant proteins bears out this latter view to a certain extent. Direct evidence in its favor was secured by passing HCl gas into a respiration chamber containing wheat grain. A duplicate of the CO2 effect was obtained.