Researches on plant respiration. II.―Variations in the respiratory quotient during germination of seeds with different food reserves

Abstract

Determinations of respiratory activity in plants have nearly always been made by measuring the rate of carbon dioxide evolution by the tissues. Much less frequently the rate of oxygen adsorption has been used as a measure of the process. In comparatively few researches have determinations been made of both carbon dioxide evolution and oxygen adsorption. Yet it is clear that a true measure of respiratory activity can only be given by one or other of these quantities alone, it they bear a fixed numerical relation to one another; where this is not so, it is obvious that at least one of these quantities cannot be taken as a measure of respiration, and it may not always easy in such cases to decide which of them is to be regarded as giving the truer value of this process. Indeed, a determination of both carbon dioxide output and oxygen adsorption by respiring tissues seems eminently desirable as providing data allied should assist in the elucidation of the mechanism of the respiratory process. In the work described in this paper, which deals with the course of respiratory activity of plants of a number of species during germination of the seeds and the early development of the seedling, we have accordingly determined not only the rate of carbon dioxide evolution, but the rate of oxygen adsorption. Such determinations appear to be the more desirable as the existing information on the respiratory quotient of germinating seeds is scanty, and such data as have been recorded are highly contradictory.