TEE RATE OF GROWTH OF GREEN AND ALBINO MAIZH 
SEEDLINGS 1 
By J. H. Kempton 
Assistant Botanist , Biophysical Investigations , United States Department of 
Agriculture 
For several years continuous records 
of elongation of many species of plants 
growing naturally in the field have been 
obtained by means of an auxanometer 
adapted to "field use. 2 Chief among the 
plants measured is maize and from the 
hundreds of records obtained for this 
species it has become increasingly evi¬ 
dent that much individuality exists in 
the responses of plants to meteorological 
changes even where such plants are re¬ 
lated closely and are growing in near 
proximity. These differences in reac¬ 
tion between individuals in many cases 
must result from very small environ¬ 
mental fluctuations, though in others it 
seems more probable that the observed 
behavior is the result of inherent differ¬ 
ences within the plants. In general, 
however, the elongation of all maize 
plants is accelerated by increased tem¬ 
perature, at least below 100° F. and 
probably above this temperature. The 
minimum rate is reached shortly after 
the minimum temperature, usually an 
hour or two before sunrise. In addition, 
maize plants seem not to be sensitive to 
changes in temperature or solar radia¬ 
tion which persist for less than 30 
minutes. 
In connection with the inherent 
differences between plants in their 
response to temperature and solar 
radiation it became of interest to com¬ 
pare the elongation rate of albino 
seedlings with that of their normal 
green sibs. 
As is well known, there are several 
forms of albino seedlings in maize, the 
most extreme of which show no trace 
of chlorophyll. The growth of such 
seedlings should be comparable to 
that made by the sprouts of stored 
tubers or bulbs where the elongation 
results from the transfer of stored 
material. The latter type of elonga¬ 
tion, however, is checked by light, 
whereas albino seedlings growing in 
sunlight continue to increase in size 
until the endosperm is exhausted. 
If solar radiation is a direct factor in the 
elongation of maize (for which there is 
some evidence) albino seedlings would 
be expected to react very differently 
from normal green plants since the 
practically pure white leaves would 
reflect a large part of the light. The 
reflection of light might be expected to 
result in a lower temperature for such 
plants but in reality there can be little 
difference since the leaves of normal 
green plants are maintained at prac¬ 
tically air temperature through the 
effects of transpirations. 
There is little difference in the size of 
normal and albino maize seedlings un¬ 
til three leaves have been produced, but 
after this the normal plants forge rap¬ 
idly ahead while the albinos as rapidly 
decline. It is not unusual to find albino- 
seedlings with four leaves and more 
rarely with five, but for the most part 
the leaves above the third are very 
much smaller than similar leaves of 
normal plants. Normal plants seem 
to derive little benefit from the mate¬ 
rial elaborated by the first few leaves 
unless the size of the root system is in¬ 
creased, though an inspection of the 
roots of albino and normal seedlings of 
the same age reveals no outstanding 
differences. 
The accompanying figure is one of 
several very similar figures obtained 
from sister maize seedlings grown in the 
same hill in the field. The graph shows 
the hourly elongation rate of the second 
leaf in each case, the air temperature, 
and the solar radiation as measured by 
the differential thermograph devised by 
Briggs. 3 
The growth curves are remarkedly 
alike, the greatest difference consisting 
of 0.2 mm., being little larger than the 
experimental error. It is apparent 
from the figure that the maximumi 
hourly rate of elongation is no greater in- 
the green than in the albino plants, and 
that, like the green plants, the albinos- 
have their maximum rate during the- 
1 Received for publication July 29, 1924. Issued January, 1925. 
2 Collins, G. N., and Kempton, J. H. A field auxanometer. Jour. Wash. Acad. Sci. 6:204-209 
illus. 1916. 
3 Briggs, L. J. A mechanical differential tei.ethermograph and some of its applications. 
Jour. Wash. Acad. Sci. 3: 33-35, illus. 1913. 
Journal of Agricultural Research, 
Washington, D. C. 
99183—25t- 
Vol. XXIX, No. 6, 
Sept. 15, 1924. 
Key No. G—428, 
4 
(311) 
