364 FACTORS AFFECTING PHOTOSYNTHESIS 



10. Why should a deficiency of water have a smaller retarding effect on photo- 



sjnthesis than on transpiration? 



11. Absorption spectra of the chlorophylls (Fig. 81) indicate much less absorp- 



tion of light in the green portion of the spectrum than in the blue and 

 red, yet photosynthesis is not greatly less in the green than in the red and 

 blue (Fig. 90). How can these facts be reconciled? 



12. Assuming "standard day" conditions would you expect a greater rate of photo- 



synthesis in a plant in perfectly quiet air or in a similar plant subjected 

 to a moderate breeze? 



13. Assuming otherwise "standard day" conditions would you expect the photosyn- 



thesis of an entire apple tree to be greater on a perfectly clear day or one 

 with scattered cumulus clouds in the sky? Explain. 



14. If increasing the intensity of light to which a leaf is exposed results in an 



increase in the rate of photosynthesis does this indicate conclusively that 

 light was initially a limiting factor? 



15. Elodea plants immersed in dilute solutions of sodium bicarbonate show an 



immediate increase in rate of photosynthesis if the temperature is raised 

 from 30° to 35° C. The rate of photosynthesis in leaves of many land 

 plants exposed to full sunlight increases only slightly or not at all with the 

 same rise in temperature. Explain. 



Suggested for Collateral Reading 



Duggar, B. M., Editor. Biological effects of radiation. McGraw-Hill Book 



Co. New York. 1936. 

 Lundegardh, H. Environment and plant development. Translated and 



edited by E. Ashby. Edward Arnold and Co. London. 1931. 

 Miller, E. C. Plant physiology. 2nd Ed. McGraw-Hill Co. New York. 



1938. 

 Spoehr, H. A. Photosynthesis. Chemical Catalog Co. New York. 1926. 

 Stiles, W. Photosynthesis. Longmans, Green and Co. London. 1925. 

 Willstatter, R., and A. Stoll. Untersuchungen iiber die Assimilation der 



Kohlensdure. Julius Springer. Berlin. 19 1 8. 



Selected Bibliography 



Bates, C. G., and J. Roeser, Jr. Light intensities required for growth of 

 coniferous seedlings. Amer. Jour. Bot. 15: 185-194. 1928. 



Blackman, F. F. Optima and limiting factors. Ann. Bot. 19: 281-295. 1905. 



Blackman, F. F., and G. L. Matthaei. Experimental studies on vegetable 

 assimilation and respiration. IV. A quantitative study of carbon dioxide 

 assimilation and leaf temperature in natural illumination.. Proc. Roy. 

 Soc. (London) B. 76: 402-460. 1905. 



Briggs, G. E. Experimental researches on vegetable assimilation and respira- 

 tion. XVL The characteristics of subnormal photosynthetic activity re- 

 sulting from deficiency of nutrient salts. Proc. Roy. Soc. (London) B. 

 94: 20-35. 1922. 



Brown, H. T., and F. Escombe. Static diffusion of gases and liquids in rela- 

 tion to the assimilation of carbon and translocation in plants. Phil. Trans. 

 Roy. Soc. (London) B. 193: 223-291. 1900, 



