AMERICAN 
JOURNAL OF BOTANY 
Vol. X June, 1923 No. 6 
SOME EFFECTS OF PHYSIOLOGICAL CONDITIONS ON GENETIC 
CHARACTERS OF WHEAT 
W. F. Gericke 
(Received for publication September 20, 1922) 
The relative earliness or lateness of maturation of wheat (comparing one 
variety with another) and the awned or awnless form of the spikelets are 
two classes of genetic characters used by agronomists to distinguish dif¬ 
ferent varieties. Under the usual conditions of field culture, such as 
prevail in any wheat-growing section, these characters have a considerable 
degree of fixity in pure-line strains. That they are not immutable, but 
change with conditions that concern both the nutrition and the external 
environment of the plants, has become apparent from some recent investiga¬ 
tions of the writer. 
Pertaining to that investigation, nine different varieties of spring wheat, 
representing a range from early to late wheats, were planted and grown to 
maturity in a fertile soil. The seeding was made December 15, and the 
cultures were exposed to greenhouse conditions for the entire growing period 
of the plants. They ripened in due course of time, and in such order and 
with such characters as would be expected from the known behavior and 
properties of these wheats. The earliest variety matured in the last week 
of April and the latest seven weeks thereafter. 
On March 20, another test was begun with these same varieties, but 
using tap water as the growth medium. Previous tests by the writer had 
shown that wheat could be grown to maturity in tap water. This medium 
is markedly deficient in the essential salt nutrients, the total salt concentra¬ 
tion being approximately 0.12 atmospheres osmotic value. The usual 
method employed for culture solution experimentation was followed in 
these tests. This consisted in germinating the seed on cloth netting 
suspended over, and in contact with, water. When the plants were 6 to 
8 cm. high, they were set into cork supports fitted in two-quart containers 
(Mason jars) filled with tap water. Twenty cultures of five plants each 
were used for each variety tested. All cultures were then subjected to the 
same climatic conditions, being placed on a centrally located table in the 
greenhouse and there allowed to grow as they would without further treat¬ 
ment. There was no renewal of tap water during the entire growing period, 
[The Journal for May (io : 221—274) was issued May 10, 1923.] 
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