128 
Journal of Agricultural Research voi. xxm, no. 
From Table VII and the previous table of temperature coefficients 
(Table III) it is evident that the values of Q 10 for the respiration of seeds 
for any given temperature interval may depend upon a number of dif¬ 
ferent factors, which have not as yet been worked out, but among which the 
physiological condition of the seed and its previous treatment are important. 
It is impossible to draw reliable conclusions as to the nature of the 
complex of processes which constitute respiration from any one set of 
temperature coefficients. Nevertheless, it seems entirely safe to say that 
different steps in the complex are differently affected by temperature 
changes—in other words, have differential temperature coefficients—and 
that these differences are reflected in the physiological condition of the 
living embryo can scarcely be doubted. 
IMPORTANCE OF STUDYING OXYGEN CONSUMPTION AND C 0 2 PRODUC¬ 
TION IN THEIR RELATION TO EACH OTHER 
A great many, though by no means all, investigators of respiration have 
confined their attention to either oxygen consumption or C 0 3 production 
to the exclusion of the other, and frequently the apparatus used has ren¬ 
dered the study of the other impossible. Different investigators have been 
led to consider of paramount importance one or the other of these two 
evidences of respiratory activity. Mayer (18), for instance, studied only 
oxygen consumption because this was supposed to correspond much more 
nearly to the amount of heat produced by respiration than does C 0 2 pro¬ 
duction. Much of the oxygen consumed does not reappear as C 0 2 but is 
built into the plant tissues. In this case C 0 2 is not the end product of the 
oxidation. On the other hand, he points out that C 0 3 is given off by the 
reduction of oxygen-rich mineral acids, quite independent of true respira¬ 
tion. Tashiro (22) and, following him, Gurjar (10) emphasized C 0 2 pro¬ 
duction as “ an accurate index of respiratory activity.” 
It would seem from the data in this paper that neither oxygen consump¬ 
tion nor C0 2 production can be considered as “an accurate index of res- 
priatory activity.” Both depend upon external as well as internal con¬ 
ditions, which affect the two differently, so that neither alone gives a 
complete picture, much less a satisfactory understanding of respiratory 
exchanges. It seems certain, furthermore, that following oxygen intake 
and C 0 2 output, in their relation to each other and to external factors, 
will be useful in pointing the way to fruitful investigations in other fields 
of plant physiology. 
SUMMARY 
(1) The respiratory intensity of dormant apple seeds is low. The 
respiratory intensity of seeds capable of germination is higher and 
becomes very high with advancing germination but soon falls some¬ 
what if the germinated seeds are kept at too high a temperature (30°). 
(2) Removal of the outer seed coats or of both seed coats increases 
respiratory intensity and accelerates germination. 
(3) The respiratory quotient of dormant apple seeds at ordinary tem¬ 
peratures (19 0 C.) corresponds to complete oxidation of fats (0.70) or 
to only slight increase in sugars. 
(4) The respiratory quotient increases with increase in temperature, 
causing impoverishment in easily oxidizable substances and possibly 
indicating oxygen deficiency in the respiring tissues. 
(5) The respiratory quotient decreases with decrease in temperature, 
indicating a storage of oxygen which becomes very considerable at io° 
and o° C. and probably leads to increase in acids and sugars. 
