immobility of iron in the plant 
By P. L. GilE, Chemist , and J. O. CarrERO, Assistant Chemist , Porto Rico Agricultural 
Experiment Station 
INTRODUCTION 
Work at the Porto Rico Experiment Station on the assimilation of 
iron by certain plants, including rice (Oryza sativa ), has afforded results 
which seem to show that iron is relatively immobile in the plant after it 
has once been transported to the leaves. In respect to mobility in the 
plant iron would thus be similar to silicon and calcium and different 
from nitrogen, phosphorus, potassium, and magnesium, which are 
generally considered mobile. 
These observations on the immobility of iron are chiefly concerned with 
the nontransference of iron from leaf to leaf under conditions where the 
plant was insufficiently supplied with iron. That the mobile mineral 
elements and nitrogen are translocated from leaf to leaf under such con¬ 
ditions seems proved by Schimper (8) 1 as well as by observations on the 
growth of plants in media lacking one of these elements. The translo¬ 
cation of nitrogen, potassium, and phosphorus from old leaves and 
stems to the fruiting parts has, of course, been well established by ash 
analyses of plants during maturation and by direct experiments (6, p. 
585-586). This, however, is not different in principle from the translo¬ 
cation of these elements from old to new leaves, as the constituents 
must in this case also pass from the old leaf into the stem. 
The various facts which seem to point to iron being relatively immo¬ 
bile in the plant are given below. 
OBSERVATIONS ON RICE GROWN IN NUTRIENT SOLUTIONS LACKING 
IRON 
Rice grown in nutrient solutions without iron is quite different in 
appearance from rice grown without nitrogen or phosphorus. In iron- 
free solutions the leaves of the plants commence to die at the top rather 
than at the base of the plant. The newer leaves that are formed are 
almost pure white, very thin, and generally wither before the old leaves. 
The phenomena in rice grown in absolutely iron-free solutions are not so 
marked as in plants grown for a time with iron and then transferred to 
an iron-free solution; since either the amount of iron in the seed does 
not suffice for the needs of the first leaves or it is incompletely translo¬ 
cated, so that even the first two or three leaves formed are yellowish 
green in color. 
1 Reference is made by number to “literature cited,” p. 87. 
Journal of Agricultural Research, 
Dept, of Agriculture, Washington, D. C. 
fp 
(83) 
Vol. VII, No. 3 
Oct. 9,1916 
B—11 
