Relations of Manganese and Other Cations 



181 



to this particular soil, the development of the part of the plants above the 

 surface is 1.5 centimeter, but the root growth is considerable as is shown 

 in the table below. The injury to the roots of the plants is insignificant in 

 the cultures that contain N/50 MnClo. Slight stimulation results from the 

 addition of a solution of N/500 MnCl2 to this soil. 



TABLE 3. 



Experiment in Soil Cultures, Continued for Thirty Days. 

 Ten Plants 



Data for 



Culture 



Composition oi 

 solution 



Average 

 length 

 of tops 

 (centi- 

 meters) 



Average 

 length 



of roots 

 (centi- 

 meters) 



Weight 

 of roots 

 (grams) 



Color 

 of tops 



1 



2 

 3 

 4 

 5 

 6 



N/5MnCl2.. 

 N/10 MnClo. 

 N/25 MnCl2. 

 N/50MnCl2. 

 N/500 MnCl2 

 Control 







1.5 

 10.0 

 12.5 

 16.0 

 15.0 



Very slight 



6.0 



8,7 



12.5 



13.0 



12.5 



Not taken 

 3.75 

 5.00 

 8.20 

 10.40 

 9.10 



Yellow 

 Yellow 

 Pale green 

 Green 

 Green 



Chlorosis of the leaves of the plants is noticeable in all the soil cultures 

 except cultures 5 and 6. Chlorophyll apparently does not develop in 

 the leaves of the plants grown in soils dosed as heavily as are cultures 

 2 and 3. In pot 4 the yellow, or loss of green color of the leaves, is not 

 observable until the plants are ten to fifteen days old. The loss of the 

 green color is doubtless the result of an accumulation of manganese in 

 the leaves; hence, in the soil cultures that contain less concentrated solu- 

 tions of this element, chlorosis does not appear for several days. The 

 chlorotic leaves do not function in carbon assimilation and death of the 

 plants soon results. 



It has been shown recently that this chlorotic action of manganese 

 is of considerable economic importance. Kelley (1908) attributes the 

 " yellows" of pineapples — a condition that is met with in this crop as 

 grown in certain districts in Hawaii — to the abundance of this element. 

 Analyses of the soils where this trouble occurs show the presence of exces- 

 sive amounts of manganese, as appears on page 172. 



Relation of previous conditions of growth to toxicity. — Pea seedlings 

 that have been grown for ten days in distilled water, tap water, and full 



