174 INFLUENCE OF TEMPERATURE OX BIOLOGICAL SYSTEMS 



I. The growth in length of young pea plants is independent of temperature 

 over the range of 13°-23°G. The internal 24-hour rhythm of development 

 of most plants is almost temperature indejiendent. 



At a Qio of 2-3 it can be assumed that a chemical process controls plant 

 growth. Below 17°C it can be reasonably certain that reactions involving 

 auxin and other growth substances limit growth: only below 17° can to- 

 mato growth be accelerated by auxin or vitamins. Above this temperature 

 physical processes involving all molecules, and not just the activated ones, 

 become limiting for plant development. 



REFERENCES 



1. Bonner, J. Effects of application of thiamine to Cosmos. Bot. Gaz. 104: 475-479, 

 1943. 



2. BiJNNiNG, E. Untersuchungen iiber die autonomen tagesperiodischen Bewegungen 

 der Primarbliitter von Phaseolus multiflorus. Jahrb. wiss. Bot. 75: 439-480, 1931. 



3. BfNNiNG, E. Uber den Tagesrhythmus der Mitosehaufigkeit in Pflanzen. Zeit. /. 

 Bot. 40: 193-199, 1952. 



4. Candolle, a. de Geographie botanique raisonnee I. Paris: Masson, 1855, 606 pi). 



5. HiGHKiN, H. Plant Physiology. Supp., Aug. 26, 1956, vol. 31, p. iii. 



6. HiLLE Ris L.\MBER.s. M. TempcwtuHr en protoplasma-strooming. Thesis, Utrecht, 



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9. Osborne, D. J. and F. W. Went. Climatic factors influencing parthenocarpy and 

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10. Went, F. W. Plant growth under controlled conditions. II. Thermoperiodicity m 

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II. Went, F. W. Plant growth under controlled conditions. III. Correlation between 

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 597-618, 1944a. 



12. Went, F. W. The experimental control of plant growth. Chronica Botanica 17: 



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