58 



MISC. PUBLICATION 3 69, U. S. DEPT. OF AGRICULTURE 



there was a fairly consistent relationship between the variety of sugar 

 beets and their potassium and sodium contents. A variety consist- 

 ently high in potassium was usually found to be low in sodium. 



Smirnova and Lavrova (529), working with the soybean plant in 

 Russia, concluded that variations of the ash content of different varie- 

 ties grown on one soil are not significant. Conditions of growth were 

 associated with greater differences in mineral content than was varietal 

 difference. 



Definite conclusions as to the effect of the variety of the plant on the 

 chemical composition cannot be made at this time. It is entirely 

 possible that in some species one variety is a better feeder on certain 

 nutrients than are other varieties of the same species. Such a supposi- 

 tion would seem to be at least a reasonable one. There are few data to 

 support this assumption, however, because experiments of this nature 

 have not included careful investigations that would assure uniform 

 soil conditions. 



MINERAL CONTENT OF DIFFERENT PARTS OF THE PLANT 



Many examples of variations in the mineral content of the different 

 parts of the plant have been cited in the compilation of analyses given 

 in the appendix. Thus, the average value for calcium in the stem of the 

 alfalfa plant is nearly 40 percent less than that in the leaf, and the 

 data for the corn plant show that the leaf contains about 14 times as 

 much calcium and less than one-third the phosphorus as does the 

 grain. Similar differences are always found among the seed, stalk, or 

 leaves of plants. As an example of the care that must be taken in 

 sampling a crop, the data in table 19 are presented, showing the enor- 

 mous differences in the calcium content of the leaves of the same head of 

 cabbage. 



Table 19. — Calcium content of leaves of cabbage 



[Cowell (125)] 



Sample No. 



Description of leaf 



Ca per 100 



gm. moist 



leaf 





(Outer dark-green leaf.. _____________ 



Mg. 



476 



1 





35 





("Outer dark-green leaf ._ _ _ ... 



910 



2 . 



(Inner yellowish-heart leaf _ _ . 











("Outer dark-green leaf .... _ . ... __ __ ... . 



998 



3 



(Inner pale-green leaf . .... 













708 



4 .. 



< Third leaf from outside, pale-?reen . . 



96 







26 







1,058 





1 Third leaf from outside, dark-green. _ ___________ 



216 

















32 









Sarata {502), on the contrary, reported in 1937 only slight differences 

 in the copper content of different leaves of the Pe-tsai cabbage. The 

 structure of this plant is, however, quite different from the compact 

 head of common cabbage. Darkis and coworkers (136) have recently 

 determined the difference in composition of the leaves from different 

 parts of the tobacco plant, and they report that both calcium and potass- 

 ium vary considerably according to the position of the leaf on the 

 stalk. This factor is also of importance in the studies of Thomas and 

 of Lagatu and M aume already cited. 



