Chemical Factors in General 



369 



tions without calcium the chromosomes in root-tip cells were markedly 

 smaller than when grown in complete nutrient. When phosphorus was 

 in excess, however, the chromosomes were about twice normal size. 

 These differences were also reflected in the size of the nucleus. 



e/8 



12 



16 



20 



24 



28 



32 



TIME IN DAYS 

 Fig. 17-2. Effect of zinc on tomato plants grown in nutrient solution. Curve I, plants 

 to which zinc was applied from the start; Curves II and III, plants in which zinc was 

 added to the medium at the times indicated by arrows. Dash lines show growth 

 without further addition of zinc. ( From Skoog. ) 



There is a good deal of evidence that phosphate fertilizers increase the 

 growth of roots as compared with tops, particularly in root crops. 



Calcium is closely connected with the formation of the cell wall. When 

 it is deficient in amount the cytoplasm tends to break down, the walls 

 to fall apart, and meristems to degenerate. Calcium itself does not enter 



