NOVEMBEB 6, 1908] 



SCIENCE 



633 



principle of ehemieal mechanics it is quite 

 impossible to see how vital chemistry can 

 fail to exhibit it also. 



ACCELERATION OF VITAL PROCESSES BY 

 TEMPERATURE 



At present we have but a small number 

 of available data among plants to consider 

 critically from this point of view. But all 

 the serious data with which I am ac- 

 quainted, which deal with vital processes 

 that are to be considered as part of the 

 protoplasmic catalytic congeries, do ex- 

 hibit this acceleration of reaction-velocity 

 by temperature as a primary effect." 



Let us briefly consider these data. On 

 the katabolic side of metabolism we have 

 the respiratory production of CO2, and op- 

 posed to it on the anabolic side the intake 

 of carbon in assimilation. 



As a measure of the rate of the meta- 

 bolic processes constituting growth we have 

 data upon the division of flagellates; and 

 finally there is the obscure process of cir- 

 culation of protoplasm. 



The intensity of CO2 production is often 

 held to be a measure of the general in- 

 tensity of metabolism, but any relation be- 

 tween growth-rate and respiration has yet 

 to be clearly established. Our science is 

 not yet in the stage when quantitative 

 work in relation to conditions is at all 

 abundant; we are but just emerging from 

 the stage that chemistry was in before the 

 dawn of physical chemistry. 



Taken by itself the COg-production of 

 an ordinary green plant shows a very 

 close relation with temperature. In the 

 ease of the cherry-laurel worked out by 

 Miss Matthffii and myself the respira- 

 tion of cut leaves rises by a factor 

 of 2.1 for every 10° C. This has been 



" A collection of twenty cases, mostly from ani- 

 mal physiology, by Kanitz [Zeits. fiir Elektro- 

 chemie, 1907, p. 707), exhibits coefficients ranging 

 from 1.7 to 3.3. 



investigated over the range of tempera- 

 tures from 16° C. to 45° C. At this 

 higher temperature the leaves can only 

 survive ten hours in the dark, and their 

 respiration is affected in quite a short 

 time, but in the initial phases the COj 

 output has the value of .0210 gr. per hour 

 and unit weight of leaf, while at 16°. 2 C. 

 the amount is only .0025 gr. CO2. Thus 

 the respiration increases over a range of 

 tenfold with perfect regularity solely by 

 increase of temperature. No reaction in a 

 test-tube could show less autonomy. At 

 temperatures above 45° C. the temperature 

 still sooner proves fatal unless the leaf is 

 illuminated so as to carry out a certain 

 amount of photosynthesis and compensate 

 for the loss of carbon in respiration. 

 Thus, with rising temperature, there is at 

 no time any sign of an optimum or of a 

 decrease of the intensity of the initial 

 stage of respiration. 



Here, then, on the katabolic side of 

 metabolism we have no grounds for assu- 

 ming that "temperature-stimuli" are at 

 work regulating the intensity of proto- 

 plasmic respiration, but we find what I 

 can only regard as a purely physical- 

 chemical effect. The numbers obtained by 

 Clausen^ for the respiration of seedlings 

 and buds at different temperatures indi- 

 cate a temperature coefficient of about 2.5 

 for a rise of 10° C. 



To this final process of katabolism there 

 could be no greater contrast than the first 

 step of anabolism, the assimilation of 

 carbon by the protoplasm as a result of 

 photosynthesis. "We must, therefore, next 

 inquire what is the relation of this process 

 to temperature. 



This question is not so simple, as leaves 

 can not satisfactorily maintain the high 

 rate of assimilation that high temperatures 

 allow. The facts of the case were clearly 



'' LandwirtschaftUche Jahrbiicher, Bd. XIX., 

 1890. 



