818 
Journal o f Agricultural Research 
Yol. XXX, No. 9 
influence of minor factors can be con¬ 
sidered. The best results are obtained 
when sound beets of good physical con¬ 
dition are planted early in the season. 
At this time the cold-air temperature 
inhibits seed-stalk and seed production 
and favors vegetative leaf production, 
while the cold-soil temperature is favor¬ 
able for side-root production and food- 
mobilization processes in the beet. At 
this favorable soil temperature for side- 
root production the mother beet often 
shows extended enlargement with an 
abundant formation of new roots. This 
extended root system is necessary to 
supply water for the transpiration 
stream during the seed production 
period. In early spring the roots 
probably absorb limiting food materials 
from the soil which aid materially in 
the further development of the beets 
and especially the seed, as it is under¬ 
stood that the amount of available food 
materials in the soil varies considerably 
during the season. There is a further 
accumulation of available food ma¬ 
terials in the beet by the digestion of 
the stored sucrose. These progressive 
changes are also accompanied by a 
vegetative leaf production, which un¬ 
doubtedly aids in the accumulation of 
new food materials. As the season 
advances, the temperature of the soil 
rises to a point which is unfavorable for 
root production, while the temperature 
of the air rises to the optimum for seed- 
stalk and seed production. Under 
these conditions maximum seed pro¬ 
duction occurs, because the beet has 
an abundance of available food and 
absorption organs provided by the 
earlier development. 
On the other hand, if beets are 
planted during midsummer, when the 
temperature of the soil is inhibitive to 
root growth and the temperature of 
the air is favorable for seed production, 
the beets are forced to immediate re¬ 
production or death, and there is very 
little or no seed produced. In this 
case, all conditions are similar and 
favorable for maximum seed produc¬ 
tion, except that the beet has not 
previously passed through a period of 
food mobilization and vegetative de¬ 
velopment which is necessary to sus¬ 
tain the reproductive development. 
SUMMARY 
These investigations indicate that 
the second year’s development of the 
mother beet should be divided into 
two distinct periods: The first period 
being characterized by food mobiliz¬ 
ation, vegetative foliage development, 
new root production, and absorption of 
soil nutrients; the second period by 
rapid utilization of mobilized food, 
development of seed stalks, and pro¬ 
duction of seed. 
The optimum temperature for seed- 
stalk and seed development is higher 
than the optimum temperature for 
vegetative leaf and root development. 
The cold air and soil temperatures 
during the first period inhibit the re¬ 
productive development, while these 
temperatures favor complete vegeta¬ 
tive development. 
The higher temperatures of the 
second period favor rapid reproductive 
development and result in the retard¬ 
ing of the vegetative development. 
There is maximum reproduction 
when a plant passes through a first 
period of complete vegetative develop¬ 
ment in which the reproductive de¬ 
velopment is inhibited, followed by 
a second period of forced reproductive 
development in which the vegetative 
development is largely inhibited. 
The first period is an essential pre¬ 
requisite to the second. 
The seed produced during the second 
period is directly proportional to the 
extent of development of the beet 
during the first period. 
