

ROOT HAIRS AND GROWTH 



3 6 9 



the role of the chlorine is thus probably 

 secondary. The effect of the anion upon 

 root hair elongation can thus better be 

 ascertained by a comparison of the one 

 anion with another, such as chloride with 

 nitrate. This will be done below. 



The results for the growth of collards in 

 calcium nitrate are given in the accom- 

 panying figures (8 and 9). It is apparent 

 that at low concentrations the pH graph 



however, some differences. The maxi- 

 mum rate is slightly less in nitrate than 

 in chloride. The range does not extend 

 quite so far on the acid side in nitrate; 

 but it is apparent that the antagonism of 

 calcium for hydrogen ions is greater in the 

 nitrate than in the chloride. That is, 

 the addition of less nitrate to an acid 

 solution is necessary in order to permit it 

 to produce root hairs, than of chloride. 



5 6 7 8 9 10 11 



Fig. 8. Average Rate of Root Hair Elongation in Calcium Nitrate 



12 pH 



for nitrate is trimodal, for medium con- 

 centrations it is bimodal, and for high 

 concentrations it is monomodal. The 

 relationship becomes, however, perfectly 

 clear when we consider the data in terms 

 of the three dimensions. 



The results for nitrate approach very 

 closely to those for chloride (fig. 10) and 

 indicate that the cations have doubtless 

 much greater effect upon root hair elonga- 

 tion than do the anions. There are, 



By the construction of similar maps to 

 these for each of the nutrient and non- 

 nutrient anions it is hoped that a clear 

 picture may be presented of the effect of 

 each constituent of the nutrient and then 

 of the soil solution. 



It is important to notice the very wide 

 range of hydrogen ion concentration in 

 which the root will produce root hairs. 

 This is not to be taken as an indication of 

 the ability of root hairs to adjust them- 



