Chemical Factors in General 



365 



deposited in these structures, whereas if nitrogen were abundant it 

 would be used in protein synthesis. Shields and Mangum (19.54) studied 

 the content of total and of amino nitrogen in the leaves of '40 species of 

 plants and found it highest in thin, mesophytic herbaceous leaves, next 

 in small xeromorphic dicotyledons, and least in monocotyledons with 

 much mechanical tissue. 



L3X 38-11 



/ 38-1 1 



0.032 0.16 08 4.0 



MILLIMOLES OF N PER LITER 



Fig. 17-1. Nitrogen and hybrid vigor. Two inbred lines of maize and their hybrid 

 grown in sand culture with various amounts of nitrogen. The increase in size with 

 added nitrogen is much greater in the hybrid than in either parent. (From'Burk- 

 holder and McVeigh. ) 



Nitrogen supply may be related to the differentiation between male 

 and female sex organs, for Kocher (1941), studying the dioecious species 

 Melandriurh album, found markedly more nitrogen (as percentage of 

 dry weight) in leaves of female plants than of male. This difference 

 was slight in seedlings, rose until flowering took place, and then disap- 

 peared. 



There may be interaction between nitrogen and other factors. In onion, 



