George Harlan Dungan.

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drolyzable in 2.5-percent hydrochloric acid and low in ether extract
and insoluble starch. When the breaking of the shanks was delayed
until the grain was in the soft-dough stage, the proportion of total ni-



1926}



INFLUENCE OF PLANT INJURY ON COMPOSITION OF CORN



265



trogen, hemicellulose, and non-hydrolyzable material was not so high
as when the breaking was done earlier, but it still was considerably
higher than in the normally matured ears. There was also a signifi-
cant increase in the relative amount of ether extract and insoluble
starch as the grain developed from the milk to the soft-dough stage.

The breaking of the stalk did not affect the composition of the
grain so much as did the constriction of the shank, altho it did result
in a slight increase in total nitrogen and non-hydrolyzable material, as
well as in a small decrease in ether extract and insoluble starch. The
time of breaking the stalks had very little effect on the relative quan-
tity of these materials in the grain. It appears that either the plant
above the constriction contained a sufficient amount of previously
elaborated food materials to fill out the grain to an almost normal de-
gree, or the bending of the vascular elements in the stalk was not
acute enough to prevent the passage of solutions for synthetic pur-



TABLE 3. EFFECT OF THE BREAKING OF THE SHANKS AND STALKS OF CORN ON THE

CHEMICAL COMPOSITION OF THE CORN GRAIN

(Amounts expressed in percentages)



















Material












Dextrins






non-hy-


3




Total


Ether


Total


and


Insolu-


Hemi-


drolyz-




Treatment


nitro-


ex-


sugar


solu-


ble


cellu-


able in


O




gen


tract




ble


starch


lose


2. 5- per-












starch






cent


















HC1


A


Parent ears


2.07


4.83


1.32


2 01


53.17


6.62


6.16


B


Shank broken when grain was


















in milk stage


3.40


3. 16


1. 17


1.76


39.76


9.55


9.90


C


Shank broken when grain was


















in soft-dough stage


2.27


3.92


1.54


1.44


44.71


9.04


7.68


D


Stalk broken when grain was


















in milk stage


1.90


4. 18


1.05


1.78


51.85


6.65


6.19


E


Stalk broken when grain was in
soft-dough stage


1.85


4.38


1.53


1.77


51.61


7.25


6.81


F


Ears from erect plants and from
unbroken shanks


1.66


4.56


1.61


2.67


54.35


6.66


5.95



poses into the lodged plant. It is very likely that both the transloca-
tion of storage material already in the stalk and the deposition of re-
serves synthesized after the stalk was broken were contributing factors
in producing grain of a practically normal composition. Even tho the
relative amounts of materials in the grain produced on broken stalks
closely approached that of the checks, the total weights of ears and
grains were considerably below those of the checks (Table 1).

A comparison of the data presented in Table 2 with that in Table
3 brings out the fact that the condition of the corn grain which has so
often been described by the term "starchy" is not necessarily associ-
ated with a higher percentage of starch in the grain, but that, on the



266



BULLETIN No. 284



[December,



contrary, there is a slight suggestion that the ears which are more
"starchy" in appearance may actually contain less starch hydrolyzable
with saliva than horny ears of the same variety.

EFFECT OF PLANT INFECTION WITH CORN ROOT
ROT ORGANISMS

Not all the plants that were inoculated with the four corn root
parasites gave evidence of being injured appreciably by these organ-
isms. In order to obtain data on the effectiveness of the inoculation,
both shelled grain weights and root anchorage figures were taken. The



TABLE 4. SPECIFIC GRAVITY OF THE GRAIN PRODUCED FROM INOCULATED HILLS

COMPARED WITH THAT OF GRAIN FROM PLANTS IN ADJACENT,

UNINOCULATED HILLS





Number
by which


Specific g
grain f


ravity of
rom


Difference


Organism with which seed was
inoculated


inoculated
plant was
designated


Inoculated
hill


Adjoining
uninocu-
lated
hill


uninocu-
lated
hill


Diplodia zeae . ...


2b..


1.111


1.116


.005




9b


1.096


1.042


054




27b


1.085


1.126


.041




37b


1.132


1.161


.029




55b


1.053


1.188


.135




Average. .


1.095


1.127


.032


Fusarium moniliforme


3a. .


1.222


1.302


.080




lOa


1.217


1.243


.026




28a. . .


1.214


1.245


.031




56a


1.312


1.302


-.010




3b


1.090


1.100


.010




lOb


1.127


1.117


-.010


: f^J


17b


1.066


1.040


- .026




28b. ..


1.167


1.196


.029




38b


1.193


1.298


.105




Average. .


1.178


1.205


.027


Gibber eUa saubinetii


54a. .


1.281


1.293


.012




12b. .


1.047


1.069


.022




19b


1.142


1.132


-.010




40b


1.188


1.239


.051




54b


1.233


1.320


.087




Average. .


1.178


1.211


.033


Rhizopus spp


18a. .


1.243


1.243


.000




25a


1.173


1.226


.053




4b


1.063


1.066


.003




25b


1.040


1.040


.000




32b


1.219


1.239


.020




Average. .


1.148


1.163


.015


Grand average




1.154


1.181


.027 .



Odds that the average difference is not due to chance = 302:1



1926]



INFLUENCE OF PLANT INJURY ON COMPOSITION OF CORN



267



root anchorage was determined by measuring the pulling resistance of
the hills at harvest time. Grain from only those plants that yielded
less, or that had a root anchorage below that of the adjoining uninocu-
lated check, was selected for analysis. The yield, however, was given
primary consideration in making this selection. No ear was taken for
this study unless its weight was less than its check.

It was possible in many instances by visual comparison to detect
a slightly greater proportion of soft starch in the corn from the inoc-
ulated hills. This was not possible, however, in every case. In order
to determine more accurately the influence that infection had upon
the density of the grain, specific gravity determinations by displace-
ment in 95-percent alcohol were made. The results of this experiment
are given in Table 4.

In only five cases out of the twenty- four sets tested did the grain

TABLE 5. PERCENTAGE OF WATER ABSORBED BY GRAIN PRODUCED ON CORN PLANTS

GROWN FROM INOCULATED SEED, COMPARED WITH THAT ABSORBED BY

GRAIN PRODUCED ON PLANTS FROM UNINOCULATED SEED



Organism- with which seed
was inoculated


Number
by which
inoculated
plant
was
designated


Amount of water
absorbed in 24 hours
by grain produced on
plants from


Difference
in favor
of corn
from
inoculated
seed


Inoculated
seed


Adjoining
uninocu-
lated seed


Diplodia zeae


27b. .


perct.
72.53
64.27
67.82
68.21


perct.
64.16
63.09
62.28
63.18


perct.
8.37
1.18
5.54
5.03




37b


55b


Average. .


Fusarium moniliforme


3a


53.09
51.40
55.41
65.26
61.32
73.06
54.87
59.20


49.26
44.89
49.42
58.97
62,57
54.53
47.86
52.50


3.83
6.51
5.99
6.29
-1.25
18.53
7.01
6.70




28a


56a


3b


lOb. .


28b


38b


Average. .


Gibberella saubinetii


54a..
12b


47.58
72.03
67.57
62.91
56.62
61.34


48.34
63.12
64.97
54.66
48.59
55.93


- .76
8.91
2.60
8.25
8.03
5.41


19b


40b


54b


Average. .


Rhizopus spp


4b.


72.04
56.99
64.52


65.04
54.66
59.85


7.00
2.33
4.67




32b


Average. .


Grand average


62.04


56.26


5.78



Odds that this difference is due to inoculation > 9999:1



268



BULLETIN No. 284



[December,



from the inoculated plant exceed that of the check in specific gravity.
This occurred once with Diplodia, three times with Fusarium, and
once with Gibberella. In every case, however, the average specific
gravity was higher for the corn from uninoculated plants, and
when the results from all the organisms were averaged the grain from
uninoculated plants was found to be .207 higher than the specific grav-
ity of the infected plants, with odds of 302 to 1 that this difference was
not due to chance.

In some previous work by the author 8 it was shown that corn pos-
sessing a high proportion of soft starch in the endosperm is capable of

TABLE 6. RESULTS OF CHEMICAL ANALYSES OF CORN GRAIN PRODUCED BY PLANTS

GROWN FROM INOCULATED AND FROM UNINOCULATED SEED

(Results expressed in percentages)



Kind of corn


Plant
No.


Total
nitro-
gen


Ether
extract


Total
sugar


Dextrins
and solu-
ble
starch


Insol-
uble
starch


Hemi-
cellu-
lose


Non-hy-
drolyza-
ble
residue


Diplodia-inoculated. . . .
Adjacent check


2b.. .
6b....


2.77
2.22


4.26
4.70


1.32
1.68


2.58
3.15


48.22
50.06


7.72
7.91


5.94
5.32


Diplodia-inoculated. . . .
Adjacent check


9b...
13b


2.26
1.81


4.67
4.61


1.13
1.39


1.89
1.75


51.23
52.92


7.67
7.36


5.87
6.49


Fusarium-inoculated. . .
Adjacent check


lOa. . .
14a


2.31
1.99


4.07
4.42


1.23
1.53


2.48
2.67


48.93
51.30


6.13
6 46


4.52
4.35


Fusarium-inoculated. . .
Adjacent check


17b...
21b


1.64
1.84


4.45
4.74


1 32
1.34


1.73
1.82


53.32
53.21


8.29
7.53


6.33
5.95


Gibberella-inoculated . .
Adjacent check


la..
5a


1.55
1.68


3.73
4.12


.95
.95


3.07
2.43


61.96
55.76


5.85
5.91


5.33
5.56


Gibberella-inoculated . .
Adjacent check


Ib...
5b.. ..


2.92
1.79


4.44
5.16


1.03
1.24


2.71
2.76


45.65
56.97


8.16
7.45


7.76
6.25


Rhizopus-inoculated . . .
Adjacent check


ISa
14a


2.02
1.99


5.01
4.42


1.70
1.53


3.92
2.67


52.94
51.30


5.74
6.46


4.81
4.35


Rhizopus-inoculated. . .
Adjacent check


25a
21a....


2.37
.2.09


4.02
4.38


1.08
1.13


2.30
2.43


52.58
55.28


6.57
6.79


7.29
4.70


Rhizopus-inoculated. . .
Adjacent check


25b...
21b....


1.87
1.84


4.65
4.74


1.29
1.34


2.01
1.82


53.92
53.21


6.94
7.53


5.14
5.95


Average difference in
favor of inoculated
plant




+ 31


22


12


+ 13


-1 14


- .14


+ .45




















Odds that above dif-
ference is not due to
chance




44:1


57:1


57:1


4:1


4:1


5:1


18:1





















more rapid water absorption than corn containing a less amount of
this material. Accordingly, the water-absorptive capacity of the corn
in the present experiment was determined with a view to applying the
results as a measure of soft-starch content. The data included in Table
5 were obtained by soaking samples of corn produced by inoculated
and check plants, in distilled water, under the same conditions, for a
period of twenty-four hours. The percentages are based on the water-
free weight of the sample.



1926}



INFLUENCE OF PLANT INJURY ON COMPOSITION OF CORN



269



In every instance except two one with Fusarium and one with
Gibberella the corn from infected plants absorbed more water than
that from the adjoining checks. When all the determinations with
corn from plants inoculated with the four organisms were averaged,
the difference between the percentage of water absorbed by the grain
from inoculated plants and that by grain from the checks was 5.78,
and the odds were greater than 9999 to 1 against a difference as great
as this being due merely to chance.

Notwithstanding this conclusive evidence, the results of the chem-
ical analyses of representative samples, as presented in Table 6, do
not show any marked differences between corn grain produced by
plants from inoculated seed and those from uninoculated seed.

When the differences between the two types of grain in all the nine
pairs of determinations are averaged, it is found that the corn from
the inoculated plants contained .31 percent more nitrogen, .13 percent
more soluble starch and dextrins, and .45 percent more non-hydroly-
zable substance than the accompanying checks. The odds that these
average differences were not due to chance were 44 to 1, 4 to 1, and
18 to 1, respectively. The corn from the uninoculated plants exceeded
that from the inoculated plants in ether extract by .22 percent, with
odds of 57 to 1. The average difference in total sugar was .12 percent
in favor of the uninoculated checks, and this result also carried odds
of 57 to 1. Insoluble starch and hemicellulose averaged slightly higher
for the check corn, but the significance of these results as measured by
odds is very low.

CHEMICAL CHANGES OCCURRING IN "STARCHY" AND HORNY
CORN DURING THE GERMINATIVE PROCESS

A preliminary analysis of the four lots of Learning corn repre-
sented in Figs. 1 and 2 showed that the "starchy" lots, B and D, had
practically the same percentage composition as the horny lots, A and
C. That there was a marked difference in these lots of corn may be
seen from their specific gravity, a record of which is given in Table 7.

TABLE 7. SPECIFIC GRAVITY OF THE GRAIN OF LEAMING CORN, Two LOTS OF
WHICH WERE HORNY AND Two "STARCHY"











Average










specific


Type of corn


Lot


Weight of
20 kernels


Specific
gravity


gravity of
the two lots










of the










same type






(grams)






Horny


A..


7.85


1.312


1.292




C


7.87


1.271




"Starchy".. .


B..


6.54


1.208


1.204




D


6.40


1.199





270



BULLETIN No. 284



[December,



In order to obtain data on the difference in quality of the mater-
ials contained in these two types of seed, a germination test of both
was made at 16 C., and the kernels and the seedlings with grains
attached were sampled for analysis every two days. The degree of
development is illustrated in Fig. 4. The results obtained are presented
in Table 8. The data from Lots A and C and from Lots B and D
are averaged and set forth in this table under the descriptive heads,
horny and "starchy," respectively.

TABLE 8. CHEMICAL COMPOSITION OF THE CoRfr, GRAIN, AND SEEDLINGS OF HORNY
AND "STARCHY" CORN DURING THE PROCESS OF GERMINATION AT A
CONSTANT TEMPERATURE OF 16 C.



Material


Type of
corn


Percentage composition of seedlings after being
on the germinator for different numbers of days




days


2
days


4
days


6

days


8
days


10

days


Ether extract


Horny. . . .
"Starchy" .


4.81
4.96


4.81
4.95


4.74
4.87


4.58
4.64


4.21
4.31


4.03
4.00




Total nitrogen ....


Horny. . . .
"Starchy" .


1.94
1.89


1.94

1.85


1.94

1.88


1.93
1.85


1.90
1.79


1.91
1.85


Soluble nitrogen. . .
Total sugar


Horny. . . .
"Starchy" .

Horny. . . .
"Starchy" .


.24
.25

1.27
1.26


.19
.20

1.34
1.26


.21
.24

' 1.66

1.27


.33
.35

2.91
3.00


.41

.42

3.87
3.42


.53
.53

5.66
6.10




Reducing sugar. . .


Horny. . . .
"Starchy" .


.15

.02


.68
.57


1.47
1.04


1.84
1.92


2.53
2.40


3.71
3.98


Dextrins and solu-
ble starch


Horny. . . .

"Starchy".

Horny. . . .

"Starchy" .


2.73
2.90

51.52
50.91


2.67
1.92

50.16
50.45


2.92
2.52

50.54
50.82


3.22
2.41

49.49
50.06


3.76
2.64

47.23

47.78


3.20
2.45

45.57
46.48


Insoluble starch . . .


Hemicellulose


Horny. . . .
"Starchy" .


6.96
7.15


7.12
7.34


7.13

7.51


7.10

7.48


7.26
7.34


7.35

7.82



From the second day to the end of the period there was a grad-
ual but distinct reduction in the percentage of ether extract in both
the horny and the "starchy" groups. This decrease is illustrated
graphically in Fig. 5. These data harmonize with the results obtained
by Toole, 37 who found that the fat in the maize embryo was rapidly
oxidized during the germinative process.

The fact that the "starchy" corn possessed a slightly greater per-
centage of ether extract than the horny ears should not be taken as of
any particular significance, for the "starchy" Lot B contained some-
what less fat than either Lots A or C. Lot D, however, was abnor-
mally high in fat, and this contributed to the slightly superior average



INFLUENCE OF PLANT INJURY ON COMPOSITION OF CORN



271



of the "starchy" group over the horny group. It is also probable that
the more rapid exhaustion of the fat of the "starchy" kernels is of
doubtful import, since the differences between these percentages are
well within the error common to these determinations.

There was a very slight, tho fluctuating, reduction of total nitro-
gen during germination. The proportion of soluble nitrogen, however,





FIG. 4. APPROXIMATE AVERAGE GROWTH OF THE SEEDLINGS
TAKEN FROM THE GERMINATOR AT TWO-DAY INTERVALS



5.00



4.75



4.50



4.25



4.00



- *>Sf-arch y" corn
-Horny corn







Days on cferminator at /6"C

FIG. 5. PERCENTAGES OF ETHER EXTRACT IN HORNY AND IN
"STARCHY" CORN AT DIFFERENT STAGES OF GERMINATION



272



BULLETIN No. 284



[December,



after a small decrease at the end of the second day, increased appre-
ciably thereafter. It is worthy of note that the soluble nitrogen was
consistently higher in the "starchy" than in the horny corn. When the
soluble nitrogen was calculated as a percentage of the total nitrogen,
the greater solubility of the nitrogen of the "starchy" type of corn is
more strikingly emphasized. Fig. 6 was prepared from such a calcula-
tion.



Percentage of nitrogen that was water
so/ub/e
* fe <5 5 % *<










/'

//


~ IS 1


Tarchy" corn
>rny corn


>
/
/

f

''A


f /
* /
t /


H








/
/

/
,


/ /








/ /

/ /
/ /
/ /
/ /
/ /
/ /
/






^ON


^.x

^**


/






) 2 4 C 6 /<

Days on cjerminator at /6"C



FIG. 6. PROPORTIONS OF TOTAL NITROGEN THAT WERE WATER-
SOLUBLE IN HORNY AND IN "STARCHY" CORN AT DIF-
FERENT STAGES OF GERMINATION

A larger quantity of the nitrogen contained in the
"starchy" corn was in a soluble form than that in the horny
corn. In this respect the "starchy" corn resembles grain
lacking in maturity. There is the suggestion that the nitro-
gen of the "starchy" corn is more readily converted to the
soluble form during the process of germination than is the
case with horny corn.



The amount of total sugar in the horny corn increased from the
very beginning of germination. The rise was more gradual, however,
during the early than during the later stages of germination. The in-
crease of sugar in the "starchy" corn was initiated somewhat more
slowly than that in the horny corn, altho at the end of the sixth day
the amount of total sugar in the "starchy" corn slightly exceeded that



INFLUENCE OF PLANT INJURY ON COMPOSITION OF CORN



273



in the horny corn. A comparison of these two types of corn in respect
to total sugar content may be made from Fig. 7.

The increase in reducing sugar was much more marked from the
very beginning of germination than was the case with total sugar. At
the end of the second day, when the total sugar was increased only .07



I

c:






"t!
6

5
4
3
2


(












Joto ' \


Horni.


/ corn
hy corn




i




[


Horntj


i corn
-hy corn




/










/..-


i ,






i


^.


/


k


^^


^/^


ir






/


^


'"'








924 6 8 /(.
Days on germ/nator af /6C



FIG. 7. PERCENTAGES OF TOTAL AND REDUCING SUGARS IN
HORNY AND IN "STARCHY" CORN AT DIFFERENT

STAGES OF GERMINATION

There was no uniform difference in the sugar content
of the horny and starchy corn during the process of ger-
mination. On the 6th and 10th days of germination the
percentages both of total and of reducing sugars were
higher in the "starchy" corn than in the horny corn. The
reverse was true at the beginning of the test and at the
end of the 2d, 4th, and 8th days of germination.



of one percent in the horny corn, and not at all in the "starchy" corn,
the amount of reducing sugar was multiplied 4% times in the horny



274



BULLETIN No. 284



[December,



corn and 28 times in the "starchy" corn. Fig. 7 shows that the rela-
tion of the quantity of reducing sugar in the two types of corn was
roughly the same as that of the total sugar. It is evident from this
chart that the proportion of reducing sugar to total sugar increased
markedly until the fourth day of germination, after which time there
was a reduction in this proportion. The ratio of reducing sugar to total
sugar approached the 65-percent mark on the sixth day of germination,
and remained there with minor variations to the end of the period.

It is significant that the soluble starch and dextrins were consist-
ently higher in the horny group than in the "starchy" lot. The quan-
tity of these materials was somewhat greater in the "starchy" lots,



So/ub/e starch and dextrins
in percent

^ I\J Co -t


HA


rny corn
jrchy'corn




^


\


._"<?/;




V-


"^^

^

+


+**^^


- '"''















2 4 6 8 /t

Days on germ/nator at /6'C



FIG. 8. SOLUBLE STARCH AND DEXTRINS IN HORNY AND IN
"STARCHY" CORN AT DIFFERENT STAGES

OF GERMINATION

Soluble starch and dextrins are intermediate products
in the conversion of starch to sugar. Their accumulation
in greater quantities in the horny corn during germination
is suggestive either of a greater ease of starch hydrolysis
or of a less rapid utilization of the final products of hy-
drolysis by the growing seedling. The evidence here pre-
sented indicates that the former is nearer the truth than
the latter.



however, at the beginning of the germination test. The uniform con-
tinuity of this greater proportion of soluble starch and dextrins in the
horny group is shown in Fig. 8.

The reduction in percentage of insoluble starch is represented in
Fig. 9. From this it is evident that the digestion of starch reserves in
the endosperm of the horny grain progressed at a slightly more rapid
rate than in the "starchy" grain. This difference in unhydrolyzed
starch in the two types of corn is in accord with the data already pre-



1926}



INFLUENCE OF PLANT INJURY ON COMPOSITION OF CORN



275



sented, showing the greater proportion of soluble starch and dextrins in
the horny than in the "starchy" corn. Holbert and associates 13 and
Trost 38 have reported that the seedlings and plants produced from



51



ft



a

<0



47



45



- "31-arch y " corn
.Horny corn



8



10



Days on germinator at /6'C

FIG. 9. PERCENTAGES OF INSOLUBLE STARCH IN HORNY AND
IN "STARCHY" CORN AT DIFFERENT STAGES

OF GERMINATION

Striking as it may seem, the horny corn contained
slightly more starch at the beginning of the test than the
"starchy" corn. From the 2d until the 10th day of germi-
nation, however, the "starchy" corn contained a greater
percentage of starch than the horny. This suggests that
the starch of the horny corn is more readily hydrolyzed
to soluble forms than that of the "starchy" corn.



seed corn having a horny composition were superior in vigor and pos-
sessed a greater resistance to certain corn diseases than seed corn hav-
ing a "starchy" composition. The more ready solubility of the starch in



276 BULLETIN No. 284 [December,

the horny endosperm corn than in the "starchy" corn is believed to be
an important contributing factor to this difference in vigor and disease
resistance.

The data on the quantity of hemicellulose fail to show any uni-
form change in this material during germination, altho on the whole
it did increase proportionately, owing in all probability to the oxida-
tive consumption of other carbohydrate materials.



DISCUSSION

A comparison of the composition of the grain from the broken
stalks and ear shanks in the present experiment with the results ob-
tained by Hornberger and Raumer, 15 Schweitzer, 28 Jones and Huston, 1 *
and Smith 32 shows that this treatment had essentially the same effect
upon the grain as premature harvesting. There was an increase in
starch content as a result of allowing the ears to remain on unbroken
shanks from the milk stage to the soft-dough stage, and a still greater
starch deposition when the ears were permitted to go to maturity with-
out shank mutilation (Table 3) .

It is striking, however, that in those samples broken at the inter-
mediate stage, the physical appearance of the corn was such as to be
classed as 100-percent "starchy," whereas those ears which contained
more real starch were apparently not so "starchy" (Table 2). Further-
more from the results presented in Table 8 it is plain that corn with a
high proportion of soft starch in the endosperm is not necessarily high


2

Online LibraryGeorge Harlan DunganThe influence of plant injury and the root rot diseases upon the physical and chemical composition of corn grain → online text (page 2 of 3)