176 PLANT PHYSIOLOGY 



N=CNH 2 



CH C— NH 



\ 

 CH 



N--C— N 



which are then built up into proteins. There is little in support 

 of this theory and it is questionable whether free HCN is ever 

 found in plants. The formation of the glucosides in light is prob- 

 ably due to the formation of the glucose under those conditions, 

 and the combination with the HCN may be a way of removing 

 poisonous waste products which result from some other activity 

 within the plant. Rosenthaler (1927) found an increase in HCN 

 in Sambucus when amino acids were supplied to the plant, and 

 suggested that the HCN production occurs when plants produce 

 or contain an excess of amino acids. The HCN is considered not 

 exactly a " waste product" but rather an auxiliary form of nitrogen 

 metabolism resorted to under these conditions. It thus seerrs to 

 be of only minor importance in the large problem of protein 

 synthesis. 



QUESTIONS 



1. Why are legumes generally richer in proteins than other plants? 



2. Why do growing organisms need more protein than mature ones? 



3. What is the chief function of protein within the plant? 



4. Discuss the life and work of Emil Fischer. 



5. Are the color reactions infallible tests for proteins? Why? 



REFERENCES 



Green, F. — The precipitin reaction in relation to grafting. Genetics, 11:73, 



1926. 

 Maximov, N. A. — Internal factors of frost and drought resistance in plants. 



Protoplasma, 7:259, 1929. 

 Muenscher, W. — Protein synthesis in Chlorella. Bot. Gaz., 75:249, 1923. 

 Nightingale, G. T., and Schermerhorn, L. G. — Nitrate assimilation by 



asparagus in the absence of light. N. J. Exp. Sta. Bui. No. ^76, 1928. 

 Priestley, J. — Recent work on proteins. Sri. Prog., 16:201, 1921. 

 Robinson, M. E. — The protein metabolism of the green plant. New Phytol., 



28:117, 1929. 

 Cyanogenesis in plants. Biol. Rev., 5:126, 1930. 



