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 * 



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)? 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 w^th grapes in Europe. Roux (18) lists a 

 large amount of literature on this subject. Recent papers by Maze", 

 Ruot, Lemoigne (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 (74) 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. 



2 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-s 



(153) 



