A CHLOROSIS OF CONIFERS CORRECTED BY SPRAY¬ 
ING WITH FERROUS SULPHATE 
By Clarence F. Korstian, Forest Examiner , Carl Hartley, Pathologist, Lyle F. 
Watts, Forest Examiner, and Glenn G. Hahn, Scientific Assistant, Forest Service 
and Bureau of Plant Industry, United States Department of Agriculture 1 
INTRODUCTION 
In plants the term “chlorosis" is commonly applied to any abnormal 
condition whose most conspicuous symptom is a deficiency of green 
pigment. An exception to this general statement is perhaps the albin¬ 
ism of seedlings of oak, pine, and other plants which are from the first 
entirely lacking in chlorophyll, or, as sometimes happens in the conifers, 
have green cotyledons but no green in the leaves formed later. While 
such plants have always, so far as the writers' experience goes, died in 
the seedling stage, and the phenomenon must therefore be regarded as 
strictly pathological, the condition is not ordinarily spoken of as chlo¬ 
rosis. The inherited tendency on the part of healthy plants of horti¬ 
cultural varieties to grow leaves or parts of leaves lacking in chlorophyll 
is not usually considered pathological, and is better known as “varie¬ 
gation" than as chlorosis. True chlorosis may be due to a number of 
causes, such as low temperature, which hinders the formation of pigment, 
or lack of nitrates, which, according to Crocker { 2 ), 2 at least in one of 
the algae, is associated with a rapid decomposition of chlorophyll. 
Plants in full sunlight are often less green than those less exposed, 
probably because of the rapid disintegration of the pigment in strong 
light. High temperatures very likely have the same effect (Black¬ 
man's “time factor"). Plants with deficient water supply are, on the 
other hand, liable to chlorosis caused by difficulty in pigment synthesis. 
Much study has been given to the chlorosis of plants on calcareous 
soils, especially in connection with grapes in Europe. Roux ( 18 ) lists a 
large amount of literature on this subject. Recent papers by Maz£, 
Ruot, Eemoigne (jj), and Gile (6) are well worth attention. The favor¬ 
able effect of iron on plants affected with certain types of chlorosis was 
discovered before the middle of the last century, spraying a solution of an 
iron salt on chlorotic leaves having resulted in correcting the chlorotic 
appearance ( 24 ). Molisch ( 14 ) discusses many of the earlier experiments 
with iron. In a recent interesting paper, Johnson ( 12 ) states that spraying 
with iron salts is helpful for a chlorosis associated with extremely high 
1 The writers wish to acknowledge helpful suggestions from Dr. C. B. Lipman and Dr. Howard E. Pulling. 
8 Reference is made by number (italic) to “Literature cited,” p. 170-171. 
Journal of Agricultural Research, Vol. XXI, No. 3 
Washington, D. C. May 2, 1921 
xp Key No. F-5 
( I S3) 
30731°—21-4 
