ASH CONTENT OF THE AWN, RACHIS PAI.EA, AND 

 KERNEL OF BARLEY DURING GROWTH AND MA- 

 TURATION 



By Harry V. Harlan, Agronomist in Charge of Barley Investigations, and Merritt 

 N. Pope, Assistant Agronomist in Barley Investigations, Office of Cereal Investiga- 

 tions, Bureau of Plant Industry, United States Department of Agriculture 



INTRODUCTION 



The ash determinations here assembled were made with two primary 

 objects in view. Earlier studies had shown that in the varieties under 

 observation the awns possessed a physiological function. When they 

 were removed the kernel development was retarded and the spike became 

 brittle through the greater ash deposit in the rachis. In order to see 

 if usable variations existed in the amount of ash deposited in the rachises 

 and awns, a considerable number of varieties were studied. 



The previous experiments were not as complete as was desired. 

 Mechanical difficulties had prevented the taking of samples to the point 

 of absolute maturity. There thus existed a possible doubt as to the 

 nature of the changes in the days immediately following the date when 

 kernel sampling became impossible. The determination of ash in the 

 awns and rachises was, therefore, continued for some time after maturity 

 in one series of varieties at Chico, Calif. 



The results point a possible way to the securing of desirable non- 

 shattering awnless and hooded varieties. They also throw some light 

 on the ash content of the kernel during growth. 



MATERIAL USED 



Material for the study of ash in the barley spike was collected from 

 several sources. Two series of samples originated at Aberdeen, Idaho. 

 The awns, rachises, and paleas were obtained from the irrigation plots, 

 the kernel studies of which were previously reported. In this series 

 and the one from Minnesota the glumes were forcibly removed from the 

 kernels. To eliminate the possible effect of imperfect separation when 

 the glumes were thus removed, the kernels from a naked barley grown 

 at Aberdeen were included for comparison. 



Two lots of samples were grown at Chico, Calif. The first of these 

 consisted of a collection of varieties embracing a wide range of botanical 

 characters. The second consisted of a lesser number of varieties, which 

 were allowed to stand in the field for a time after ripening. Frequent 

 samples were taken, and the change of ash after maturity was determined. 



Further use also was made of the data from an experiment carried 

 on at St. Paul, Minn. Ash determinations were made on a number of 

 varieties grown at Arlington, Va., the detailed results of which are not 

 included. 



Journal of Agricultural Research. Vol. XXII, No. 8 



Washington, D. C. Nov. 19, 1921 



aao (433) KeyNo. G-2SS 



