The Philippine Journal of Science, C. Botany. 

 Vol. XIII, No. 6, November, 1918. 



THE THEORY OF LIMITING FACTORS 



By William H. Brown 



(From the College of Liberal Arts, University of the Philippines, and the 

 Bureau of Science, Manila, P. I.) 



one text figure 



Since the appearance in 1905 of Blackman's 1 paper on limit- 

 ing factors, this subject has received considerable attention. In 

 his paper Blackman postulates as an axiom: When the process 

 is conditioned as to its rapidity by a number of separate factors, 

 the rate of the process is limited by the pace of the 'slowest' 

 factor. 



While such a theory might work in some cases, it may be said 

 that it is a theory only, and that it has not been proven to be 

 generally applicable to physiological processes. Blackman's best 

 evidence appears to have been deduced from Matthei's work on 

 photosynthesis. 2 However, Brown and Heise 3 have shown that 

 the conclusions reached by Matthei were due to misinterpreta- 

 tion. An examination of their paper would seem to show that 

 this work cannot be used in proof of Blackman's theory. In re- 

 viewing Brown and Heise's paper Crocker 4 made a mistake in 

 saying that they misquoted Kanitz's formula, an error which 

 he himself has since corrected. 



The idea of limiting factors as developed by Blackman has 

 not been clearly understood by all writers on the subject, so it 

 may be well to examine its meaning. According to Blackman's 

 development of this theory, there would appear to be a limiting 

 factor for a physiological process under all conditions. An 

 increase in the intensity of any other factor (unless, perhaps, 

 the increase were so great as to be harmful) would be without 

 effect, as the rate of the process is limited by the limiting factor. 



Blackman, F. F., Optima and limiting factors, Ann. Bot. 19 (1905) 

 281-295. 



- Matthei, G. L. C, Experimental researches of temperature on carbon 

 dioxide assimilation, Phil Trans. Roy. Soc. London B97 (1905) 47-105. 



' Brown, W. H., and Heise, G. W., The application of photochemical 

 temperature coefficients to carbon dioxide assimilation, Philip. Journ. Sci. 

 12 (1917) Bot. 1-25. 

 7 Crocker, Wm., Photosynthesis, Bot. Gaz. 65 (1918) 568-569. 

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