86 
Journal of Agricultural Research 
Vol. VII t No. 2 
With respect to the accumulation in old leaves, iron is similar to 
silicon and calcium, which also seem immobile in the plant when once 
transported to the leaves. Young leaves are generally relatively higher 
in the mobile elements than old leaves. This parallelism, however, 
really affords little proof, as the relative amount of the different ash 
constituents present in young and old leaves is probably governed more 
by the function than the mobility of the elements. Also the accumula- 
tion of iron in the old leaves of plants well supplied with iron may merely 
show that a functioning leaf has a continual need of iron. As iron is in 
some way associated with the formation of chlorophyll and as chloro¬ 
phyll is apparently undergoing a continual formation and destruction 
under the.influence of light (2, p. 193; 5) and enzyms (10, p. 746), one 
can conceive of a physiological necessity for an accumulation of iron in 
old leaves. 
The most that can be said concerning the evidence of ash analyses is 
that the results are such as one would expect if iron were immobile 
after being located in the leaf. 
DISCUSSION OF RESULTS 
The only references to the mobility of iron in the plant which the 
authors have found in the literature are a discussion by Sachs (7) and 
a statement by Pfeffer that “in a starved green plant, as well as in a 
fungus, the iron and potassium may be removed from the older dying 
organs and transferred to the younger growing parts so that the growth 
may not immediately cease” (6, p. 417). No data or reference are given 
in support of this statement. While the movement of potassium under 
such conditions is generally recognized, the same can hardly be said 
of iron. 
Lack of information on the movement of iron is partially due to the 
fact that iron has ordinarily been considered of so little interest in plant 
nutrition as to be disregarded in ash analyses. Also, as already pointed 
out, the usual method of determining iron in plant analyses is probably 
not sufficiently accurate to show significant changes. 
Sachs, in his interesting discussion of the chlorosis of various plants 
grown under garden conditions (on a calcareous soil), points out the 
apparent slowness with which iron moves in plants (7). 
From the data presented it is not intended to assert that the non¬ 
translocation of iron from leaves is an absolutely general rule for all 
plants, since the foregoing observations were based chiefly on rice and 
pineapples. 
Various observations on rice and pineapples grown with insufficient 
iron seem to show that iron after once being transported to the leaves 
is immobile. 
