May 1,1925 
815 
Planting Mother Beets for Seed Production 
September. The root development of 
beets planted March 1 was similar to 
that of beets planted April 1. Beets 
planted in April and May showed some 
enlargement of the old root and especi¬ 
ally a marked development of new side 
roots. These side roots on the beets 
planted early are many and robust, 
while they are few, very fine, and 
threadlike on the beets planted later 
in the season. In this connection it 
was learned from the soil and air 
thermograph records that the enlarged 
root systems were developed at a time 
when the soil and air temperatures 
were low, and that the meager thread¬ 
like root systems were developed when 
the soil temperature and air tempera¬ 
ture were high. The mean air and 
soil temperatures for the year 1923 are 
given in Table III. Plate 3, C, shows 
extensive root development of beets 
planted in September, at a time when 
soil temperature corresponded to the 
soil temperature of May. It is prob¬ 
able that these beets would produce an 
abundance of seed if September and 
October were followed by months of 
high temperatures, such as June and 
July. 
Table III. — Mean air and soil ( 6-inch 
depth) temperatures for 1923 
Month 
Mean air 
Mean soil 
Mar__ 
°C. 
3.9 
°C. 
3.0 
Apr__ 
9.8 
9.0 
May_ 
16.7 
14.8 
June_ 
18.2 
16.2 
July_ 
i 24.5 
21.5 
Aug--- 
! 22.6 
20.7 
Sept_ 
i 18.1 
15.6 
Oct___ 
11.6 
9.7 
In order to verify this effect of 
temperature more carefully, beets were 
planted under controlled moisture and 
temperature conditions ranging from 
15° to 30° C. The result was that the 
more marked side-root development 
occurred between 15° and 30°. The 
side roots developed at higher tem¬ 
peratures were thin and threadlike, 
as shown in Plates 2, B, and 3 A, B. 
In order to verify more carefully the 
effect of illumination on side-root de¬ 
velopment, and indirectly on seed 
development, beets were planted under 
controlled moisture and temperature 
conditions favorable for side-root de¬ 
velopment, and the quantity of illumi¬ 
nation varied. Beets exposed to short 
or long illumination periods produced 
more robust and more numerous side 
roots than beets exposed to darkness 
(pi. 4, A and B). The beets planted 
April 1, in the field and exposed to 
24-hour illumination until June 1, 
showed no greater root development 
than a similarly planted lot exposed to 
only 12-hour illumination. It appears 
that under favorable temperature con¬ 
ditions the usual day illumination of 
April and May is quite sufficient for 
maximum side-root development, and 
that the amount of illumination may 
not be as important as the presence or 
absence of illumination. 
It was learned that an abundant 
root-bud and side-root development 
could be forced under controlled tem¬ 
perature and moisture conditions by 
removing crown buds (pi. 4, C). It 
was also possible to force crown develop¬ 
ment by removing root-bud tissues. 
It was further noted that temperatures 
of 15° and 20° C. inhibited seed-stalk 
development, while these same tem¬ 
peratures favored the development of 
side roots and vegetative leaves. 
Likewise, temperatures of 25° C. re¬ 
tarded the development of side roots 
and vegetative leaves, due to the fact 
that it forced seed-stalk development. 
Even though vegetative organs, such 
as leaves and side roots, may lengthen 
faster at higher temperatures, these 
same organs develop best at lower 
temperatures. 
DISCUSSION 
In explanation of this increased seed 
production resulting from early plant¬ 
ing, Briem 4 states that the growth 
period of the beet from planting to 
blossoming time should be twice as 
long as the period from blossoming to 
ripening of seed, and that this period 
must have a slow, steady rise of temper¬ 
ature. Shaw 5 concluded from his ex¬ 
periments that the beets must pass 
through a period of restrained growth, 
at a temperature between 2.75° and 
10° C., in order for the flower buds to 
develop. That this is not necessary is 
shown by the fact that beets stored at 
1.7° or above 15° C.,and planted under 
high temperatures in June, July, and 
August were not “trotzers” and pro¬ 
duced seed. 
The true explanation of the relation 
of increased seed production with early 
planting of beets will probably be 
found in many influencing factors. It 
seems that certain fundamental factors, 
such as moisture, temperature, and 
aeration, must be supplied before the 
4 Briem, H. zeit des auspflanzens und der samenertrag bei mutterruben. Osterr. CJngar. 
Ztschr. Zuckerindus. u. Landw. 27: 685-690. 1898. 
s Shaw, II. B. climatic control of the morphology and physiology of beets. Sugar 19 : 387-391, 
431-434, illus., 1917; 20: 23-27, 68-70, 109-112, 150-154, illus., 1918. 1917-18. 
