"Ii-IE RELATIVE VITAMIN A CONTENT
V or LEAF AND HEAD LETTUCF.

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The Relative Vitamin A Content
of Leaf and Head Lettuce

THESIS

 

Submitted to the Faculty of the Michigan State
College of agriculture and Applied Science
in partial fulfillment of the require-
ments for the degree of
Master of Science

by
Olin Campbell Medlock
‘h—u—I"
June 1927

THESIS

-1-
INTRODUCTION

Some investigations have yielded results which
indicate that the vitamin A content of plant and animal
tissues is correlated positively with the degrees of
their pigmentation. This being true a fresh vegetable
plant which contains small amounts, or none, of the pigb
ments would also be low in vitamin a.

This is an important question with many vegetable
craps since they are marketed in both green and blanched
states. The older standards of quality for salad craps
were mainly appearance, crispness, and palatability.
However, there is an increasing tendency to recognise
the vitamin content of such crops in determining their
quality, thus including their food value in the concept
of quality. Hence, if a vegetable which contains small
amounts of pigments also contains less vitamin A than
those more pigmented, it would rate lower in quality
according to the more modern standard.

Since lettuce is an important salad crOp, ex-
periments aimed to determine whether or not head and
leaf lettuce which differ very materially in the amount
of pigment contained also differ in vitamin A.content
were undertaken and completed. Experiments were also
conducted to determine the relative vitamin.a content
of parts of the same plant which differed greatly in the

amount of chlorOphyll contained and also to determine the

.2-

effect growing plants under glass would have on the

vitamin A content. The results are reported herein.

Review of Literature

In 1920 Steenback and Gross “Ma examined a
number of plants for their fat-soluble vitamin content
and concluded that the leaves are richer in this vitamin
than any of the other structures of the plant. They found
that the white leaves of cabbage and the somewhat etiolated
leaves of lettuce were poorest in vitamin A.content of
all the plants they examined. They assumed as a working
hypothesis for further investigations that where yellow
pigments are found in plants one may look fer the pre-
sence of the fat-soluble vitamin.

Delf (3) is quoted as saying, that same year,
that the inner white leaves of cabbage do not contain
growth promoting vitamins.

Osborn and Kendall (10) reported orperiments
in which white rats were fed oily residues from other
extracts of dried spinach leaves, young clover, alfalfa,
and grass. The residues when fedtdaily‘in quantities
equivalent to l to 2 grams of the dried plant promoted
recovery and renewal of growth in rats that were de-
clining in weight on diets deficient in the fat-soluble
vitamin.

Coward and Drummond (l) in 1921 while working
with cabbage, etiolated seedlings, dried seed, algae,

-3-
and fungi found that dried seed generally are deficient
in vitamin a.and that the amount does not appear to be
increased by germination. Etiolated seedlings and white
leaves of cabbage apparently did not synthesize the
vitamin. Green leaves from the outside of cabbage heads
were found to contain large amounts of vitamin a. Lower
plants containing chlorOphyll (marine algael were found
to synthesize this dietary factor while those (mushrooms)
devoid of pigments which play a role in photosynthesis
were found to be almost completely deficient in the
vitamin.

.In 1921 Drummond, Coward, and Watson ‘4)
stated that the diet of a cow is undoubtedly the chief
cause of variation in the amount of vitamin A.in the milk
and butter. The butter was richer in this vitamin when
the cow was on good pasture than when stall-fed on dry
feeds of hay, roots, and cake. Even the drying up of the
pasture in summer lowered the vitamin.a content of the
butter, This indicated that drying green plants in sun-
shine reduced the vitamin a content of the foliage.

Wilson (17) reported in 1922 that rats grew as
well when fed on wheat seedlings sprouted in the dark as
on those sprouted in the light. Ehe seedlings were dried.
powdered, and fed in quantity equal to 5 per cent of the
diet. This amount represented a quantity of seed that
would be inadequate as a source of vitamin A. He concluded

that "vitamin A.is produced in the growing plant with or

-4-

without accompanying photosynthesisI'He criticized Coward
and Drummond's work :1) stating that it only showed that
green tissue synthesized the vitamin more rapidly than

the etiolated tissue and that the quantity of etiolated
tissue which they fed the animals was insufficient to show
the smaller production in these plants. It was noticed,
however, that etiolated tissues were slightly active even
in the small quantities used by them.

In 1922 Steenback and Sell (13) found that the
green inside leaves of cabbage, which had failed to head
properly, contained ten times as much green pigment as
leaves on the inside of good heads and were far richer
in vitamin a, although the white leaves gave considerable
growth when fed in amounts equal to 10 per cent of the diet.
They concluded that the fat-soluble vitamin is present in
more than the minimal demonstrable amounts in the white
leaves of cabbage heads.

The work of Coward ‘2) in 1925 showed that
light is necessary fer the synthesis of vitamin A. fhe
synthesis takes place in the light from an electricllight
bulb. ChlorOphyll does not seem to be necessary for the
synthesis of this food factor and the synthesis will be
carried on in an atmosphere which does not contain either
oxygen or carbon dioxide. The almost complete absence of
calcium from the water solution did not prevent the formap

tion of vitamin A.in the plants. Plants synthesized the

 

‘e

-5-

vitamin in sunlight that had passed through a plate glass
window and a glass bell Jar which probably removed most
of the ultra-violet rays. The results from this work re-
confirmed her previous work showing that etiolated plants
contain much smaller amounts of vitamin a than green plants.
This worker commenting on the work of Wilson pointed out
the fact that the amounts fed by him were more than the
minimal required to produce growth therefore there was:
no difference in rate of growth on the two kinds of tissues.
fhe conclusions drawn from the experiments reported in
Coward's paper show that the conditions for the synthesis
of vitamin.a are not the same as the conditions necessary
for photosynthesis. However, it seems that the conclusions
were based on insufficient evidence. The number of animals
used in each experiment'was usually small and the experi»
ments were very seldom continued for more than four weeks.
The plants grown in atmospheres devoid of oxygen and
carbon dioxide wergisflyto be abnormal and the amounts fed
were not weighed quantities. It seems that there is need
of more investigation along this line before the conditions
necessary for the synthesis of this vitamin are definitely
known.

In 1925 Steenbcok, Bell, and Boutwell (14)
reported work in which six samples of peas were investigat-

ed and it was found that those of green color and carrying

 

.J

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-6-

considerable yellow pigment were far richer in their fat-
soluble vitamin content than yellow peas which contained
much less yellow pigment. They supported the theory ad-
vanced by Steenbock and Gross in 1920, that the fat-
soluble vitamin is biologically related to certain yellow
plant pigments. They disregarded the green pigments whose
presence was much more evident than that of the yellow
pigments. It seems that they might as surely be associated
with the vitamin.a.

The available experimental evidence does not
permit a positive conclusion regarding the relationship
between the vitamin A content of plant tissues and the
intensity of their pigmentation. It can not be said, as
has been pointed out by other investigators, that the
vitamin is always associated with certain yellow or green
pigments. however, it can be said safely that the vitamin
is usually very abundant in tissues containing large

amounts cf such pigments.

Materials and Methods

In determining the vitamin a.content of a _
substance, the general method is to feed a weighed quantity
of the material to be tested to a standard animal fed on
a basal diet adequate in all other respects for a standard
time. The animals used in all the experiments reported in
this paper were albino rats of high grade stock and known
pedigree. The young animals were from families fed on the

 

 

-7-

following stock ration:

Whole milk powder 15 per cent
Cracked wheat 25 per cent
Oat meal 25 per cent
Yellow corn meal 25 per cent
flax seed meal 10 per cent

Fresh lettuce daily, except Sunday (not a weighed
‘amount).

The above ration is the one used by Drem.Dye of
the Home Economics Department, Michigan State College,in
growing stock and experimental animals. It provides enough
vitamin a to produce strong, healthy litters and yet not
enough to enable the young animals to store large amounts
in their bodies.

The test animals were selected at weaning time
from uniform litters of from five to ten animals when they
were 28 to 30 days old and weighed from 28 to 50 grams each.
These were placed in separate wire cages in a well lighted,
ventilated, and heated laboratory. Each rat was fed on a
well balanced basal diet, complete in every respect except
that it contained no vitamin A. This basal diet was com-
posed of the following ingredients:

Irradiated cornstarch 78 per cent
purified casein 18 per cent
salt mixture (McCallum's No.52: 4 per cent

dried yeast about 500 mg. daily, except Sundays.

-8-
Commercial "Cream" cornstarch Was activated by
exposing it to the actinic rays of a 110 volt, 4 ampere,
alternating current Cepper Hewitt quartz mercury vapor
lamp for 15 minutes at a distance of 14 inches. The
cornstarch was put in a layer about one inch deep, in
large shallow zinc pans and was stirred well every four
or five minutes during the process of irradiation. Enough
was irradiated each time to last two weeks. Hess and
Yienstock (7) stated that vegetable oil became actiVated
on eXposure to the mercury vapor lamp for two minutes, or
less, and retained its protective power for at least six
months. Dutcher and Kruger (5) showed that dextrine, made
from commercial cornstarch possessed marked calcifying
preperties.after being treated with ultra-violet light.
Steenbock and others (16) observed that starch became
activated when treated with ultra-violet light while
antirathitic activation could not be induced in purified
protein. some investigators dextrinize their cornstarch
but in these experiments it was fed raw and was relished
by the animals. The actiVation seemdio be sufficient,for
none of the animals showed any symptoms of rickets.
The casein was purified by Sherman and munsell's
(11) method, with slight modifications. 800 grams of finely
ground, dry, crude casein was placed in a three liter flask,
two liters of ethyl alcohol was added and this was boiled
under a reflux condenser for one and one-half hours and

quickly filtered, while still hot, through a suction filter.

-9-

This operation was repeated twice, the casein thereby re-
ceiving three one and one-half hour extractions with boil-
ing alcohol. after having been filtered the third time it
was left in the Buchner funnel and washed with two liters
of hot alcohol. When the alcohol had ceased dripping from
the funnel, the casein was spread in layers about one-half
inch deep in shallow pans and left in a warm room until the
alcohol evaporated. It was then placed in a gas oven and
heated at a temperature of 100 degrees C. for eight hours,
being well stirred every two or three hours so that all of
it would be exposed to the oxygen of the air while being
heated. Finally it was removed from the oven and ground to
a fine powder in a Hobart pulverizer.

The salt mixture used in the basal diet was
HcCcllum's number 32 mixture composed of the following

ingredients:
Sodium chloride 4.7 per cent
Magnesium sulphate 7.2 per cent
Sodium di-hydrogen phosphate 9.4 per cent

Potassium monoehydrogen phosphate 25.8 per cent

Mono-calcium phosphate 14.6 per cent
Calcium lactate 55.1 per cent
Ferric citrate 3.2 per cent

The yeast was prepared by crumbling up Fleischman‘s
yeast cake and heating it in an oven at 100 degrees 0. for
several hours, until perfectly dry, and then grinding it to

(1'

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-10-
a fine powder. The amount fed was not weighed but measured

in a ladle that held approximately 500 milligrams.

After being placed on a vitamin A deficient ration
the animals continued to grOW'fOD from five to eight
weeks, usually seven weezs. When their weight remained con-
stant for a week or two, or they were losing weight, they
were given the lettuce which was to be tested. hany of the
animals at that time had xerophthalmia, an eye disease
caused by the deficiency of vitamin A in the diet, before
they were given the vitamin containing food. Some of the
animals continued to gain in weight after showing definite
symptoms of xerophthalmia. All of them showed that they were
suffering from a deficiency of this vitamin by the color of th
the skin of their ears and tails and by the appearance of
their fur in addition to the fact that they had ceased gain-
ing and most of them were losing weight.

One animal from each litter was retained on a vitamin
A deficient ration and used as a negative control, or check
animal. Sherman and Hunsell (ll) stressed the importance
of negative controls in determining whether the basal diet
is free from vitamin A.

The materials tested in these experiments are leaf
lettuce (Lactuca sativa var. criSpa ) .and head lettuce
(Lactuca satiya var. capitdta). Leaf lettuce of the Grand
Rapids Forcing variety was used in all experiments with
leaf lettuce, while all the head lettuce was of the Iceberg
type. The head lettuce was purchased on the local market,

it being impossible to grow satisfactory

-11-

heads in this locality either in the field or the green-
house.

Fresh lettuce was secured from one to three
times each week, or as often as necessary to avoid the use
of wilted leaves. Data are not available on the effect of
storage on the vitamin.a content of vegetables. In an
effort to eliminate that factor, as much as possible, the
leaf lettuce was harvested and stored in an ice box with
the head lettuce each time a new supply was purchased. The
portion of lettuce that was fed to rats was taken from about
an inch margin of green leaves of leaf lettuce and the well
blanched, inside leaves of firm heads of lettuce, so that
the large midribs would not be contained. The green outside
leaves of head lettuce were discarded except in experiment
three where both blanched and green parts of this plant
were fed. Any variation from the above procedure will be
stated later.

Preltminary experiments were carried on to
determine the amount of lettuce to feed each day to secure
an average weekly gain of three grams. Sherman and Muneell
(11) suggested three grams per week as a suitable standard
for the gain an animal should make. Eddy (6) shows that
work done by Munsell indicates that 600 to 700 mg. of lettuce
daily is necessary to produce 25 grams gain in eight weeks.
The type of lettuce fed by Munsell was not mentioned. Using
JMunsell’s figures as a basis the animals were placed in
eight groups and fed the following amounts: Groupil} 500 mg.
leafelsttuce;agroupaz,500 mg. head lettuce; group 3,700 mg.

leaf lettuce; group 4, 700 mg. head lettuce; group 5,
1 gram leaf lettuce; group 6,1 gram head lettuce; group 7,
2 grams leaf lettuce: group 8, 2 grams head lettuce.
The results from this.test showed that all the animals
had made excessive gains and from the gains made it
seemed the amount necessary to secure the desired growth
was about 300 mg. So this amount was fed in experiments
one and two. ‘
In all experiments an abundance of the basal
diet and water were kept constantly before the animals.
The lettuce, a fresh supply of food, and fresh water

were supplied daily, except Sundays.

PRESENTATION OF DATA

 

Experiment 1.

This experiment was designed to determine
if there is any difference in the vitamin A-oontent
of leaf lettuce and the blanched, inside leaves of
head lettuce. Each animal receiving lettuce was fed
500 mg. of fresh tissue daily, except Sunday. Thirteen
animals were fed leaf lettuce, twelve head lettuce,
and eight ( negative controls) were given no lettuce.
The control animals were the last to cease gaining in
weight on the basal diet which indicates that they were
probably a little more vigorous than the other animals.
The experiment was continued for a period of eight weeks.
The data are set forth in tables 1, 2. and 3 and are

shown graphically in Figure 1.

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Figure l
16F
146
156
12 Leaf Lettuce
112
Head Lettuce
100
88
gggntrols ___
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76
64
5a
4

1 2 5 4 5 6

Time in ”cake
Figure l.- Graphs of data shown in Tables 1, 2 and 3.

The rats having xerOphthalmia. soon recovered
and all resumed growth promptly when the feeding of
lettuce was started. Qhe graph shows very clearly that
leaf lettuce was much superior to head lettuce as a
source of vitamin a. The animals getting 300 mg. of leaf
lettuce daily had an average weekly gain of 8 grams
while those receiving an equal quantity of the inside
leaves of head lettuce had an average weekly gain of
only 4.2 grams. ”he gain of the animals fed leaf lettuce
was practically twice that of the animals fed head
lettuce. The control animals averaged a loss in weight
of 1.06 grams per week and before the end of the OX9

periment one-half of them had died.
Experiment 2.

White rate, even when of the highest grades,show
considerable individual variation under the best experi-
mental conditions. In order to offset the influence of
this variation it was deemed necessary to:oarry on an
experiment in which the sources of vitamin A would be
interchanged at the end of eight weeks and the experi-
ment continued for eight weeks longer. Twelve animals
received 300 mg. of leaf lettuce daily for eight weeks
and then were given 300 mg. of'head lettuce daily for
the remaining eight weeks. Nine animals were fed head
lettuce the first eight weeks and were likewise changed
to leaf lettuce for an equal period. flight control animals

were used in this experiment. The data are given in Tables

4.
5, and 6 and are shown graphically in figure 2.

 

 

Table 4,-

~18-
Record of Animals on Head Lettuce Eight Weeks,

?ollowed by leaf Lettuce for Eight “eeks

 

 

Animal Origin— WEEKLY GLITS (in grams)
and al Istfiwfind 5rd‘fifith ‘Sth 6th 7th 5th Ist 2nd 3rd 45h “5th 6th 7th 8th
Sex weight ween week week week week week week week week week week week week week week week
(grams)
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Sim-9 '77 2o 7 7 6 '7 4. 2 l 4. e 2 2 ~23 .5 .5 --.5
251-5,? ? 1 5 a 4. o 23 l -1 o 10 9 5 -1 l o .5
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Average Weights in Grams

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F igure 2 e-

 

160

124

 

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Head Lettuce

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1 2 5 4 5 6 7 8 , 9 10 11 12 13 14 15 1-
Time in ”cake

Figure 2.- Graphs of data shown in Tables 4. 5 and 6°

-22-

is in experiment-one the animals fed leaf lettuce
made much greater gains than those given an equal quantity
of blanched head lettuce. During the first eight weeks
the rats on the leaf lettuce diet gained more than twice
as much as those on head lettuce, but when they were
fed head lettuce the next eight weeks they gained less
than one-fifth as much as the other lot which received
leaf lettuce. The animals when Changed from head to leaf
lettuce made a very rapid gain in weight the following
three weeks and a substantial, but slower, gain during
the remaining five weeks. Those on the head lettuce
ration made only a very slight gain during the entire
eight weeks and were losing weight at the end of the
experiment.

The control animals averaged a very slight gain
during the first five weeks of the experiment. after
that time there was a continuous and increasing loss
of weight until the eleventh week when the last animal
died. Half of the control animals died before the end
of the seventh week. all of them lost weight and showed
definite symptoms of xerOphthalmia before dying.

This GXperiment shows very clearly that the same
animals gain much more rapidly on leaf lettuce than on
an equal quantity of head lettuce. as the animals grow
larger the rate of gain is less, due to the fact that
more vitamin a is required to maintain the larger animal,

and toward the end of the eXQeriment the head lettuce

H252

did not furnish quite enough of this food factor to

maintain the animals at a constant weight.
Experiment 3.

The object of this experiment was to determine
the difference in the vitamin A content of the very in-
side yellowish leaves of head lettuce and the outside,
green leaves of the same heads. The samples. of the green
lettuce were taken from the outside leaves of good com-
mercial heads which contained much chlorOphyll. Even
though these leaves were quite green they were notioably
less green than the leaf lettuce. The blanched leaves
were taken from the hearts of the same heads.

In experiments one and two the animals had
grown more rapidly than the desired rate, so it was
decided that the amount of lettuce fed daily should be
200 mg. instead of 300 mg. The basal diet and method
of sampling the lettuce was the same as was used in the
previous experiments.

There were ten animals on each kind of lettuce
and six were used as negative controls. The eXperiment
was continued for eight weeks. The data are given in
tables 7, 8, and 9 and are shown graphically in figure 5.
Experiment 4 was under way at the same time, thus per-
mitting the inclusion of a curve showing the growth of

animals on leaf lettuce.

 

 

 

 

 

 

 

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Average weights in Grams

160

148

156

112

100

88

76

64

52

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figure 5e

   

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Leaf Lettuce

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1 2 3 4 5 6 7 6
Time in Weeks
and ll.

Figure 3.- Graphs of data shown in rJ'3ables 7, 8, 9, 10

-27-

The animals fed the green outside leaves of
head lettuce made an average gain in weight of over
34 grams during the eight weeks while those on the in-
side, yellowish leaves of the head had an average loss
in weight of almost seven grams during the same length
of time. The animals receiving an equal amount of leaf
lettuce made an average gain of 43 grams. All of the
negative control animals were dead before the seventh
week of the experiment. Most of these were affected
with xerOphthalmia: before dying' and all had the ap-
pearance of animals suffering from vitamin A deficiency.
Two of the animals fed on inside leaves of head lettuce
died bifore the eighth.week. Four of the animals given
this part of the head lettuce had xerophthalmia. when
the vitamin containing food was first given them, but
none of them recovered from the disease. Seven of the
animals that were fed the outside leaves of the head
were afflicted with xerophthalmia when they came to
constant weight, but all recovered proyptly when they
were given lettuce. '

The data show that animals receiving leaf
lettuce as a source of vitamin a made better growth
than those fed green leaves of head lettuce and that
both of these lots made decidedly better gains than
animals on the leaves of the inner part of head lettuce.
in fact, the inside part of the head when fed in

-08-

quantities of 200 mg. daily did not furnish enough of
this food factor to maintain the animals’constant
weight.

The green leaves of head lettuce that were
fed in this exPeriment are very seldom eaten for they
are usually discarded in preparing lettuce for the table.
It is very evident that head lettuce as consumed hy
human beings is much inferior to leaf lettuce as a source

of vitamin a.
Experiment 4.

Within the last few years the question of
the vitamin content of plants grown under glass has
become of vital interest to vegetable forcers. “coord-
ingly an experiment was conducted to determine if there
is any difference in the vitamin A.content of leaf
lettuce grown in the greenhouse and that grown out in
the field.

Grand Rapids Forcing lettuce was planted
in the field and also in benches in the greenhouse the
same day. This experiment was started in the autumn and
the lettuce in the field did not grow as fast as that in
the greenhouse. When there was danger of frost the out-
door grown lettuce was transplanted to-a protected cold
frame where it was covered with sash during the night
and left uncovered during the day. The experiment was

ended at the end of the seventh week because the lettuce

(a
I r

(a

-29..

in the cold frame was killed by freezing. As in the
previous experiment 200 mg. of lettuce was fed daily.

Eleven animals were fed the outdoor lettuce
while ten were given lettucengrown in the greenhouse.
The controls are the same as in Experiment 5. The data
are given in tables 9. 10. and 11 and are shown
graphically in figure 4.

The data show that lettuce grown under glass
gives practically the same amount of growth as that
grown where it is exposed to the direct rays of the sun.
at least the differences are negligible for they are
within the limits of experimental error. The fact that
animals grew well on lettuce grown under glass shows
that the untra-violet rays that are filtered out by
greenhouse glass are not necessary for the synthesis
of vitamin a. These results are in harmony with those

obtained by Coward (2) with wheat seedlings in 1923.

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-35-

 

 
    

 

 

 

Figure 4.
16
148
156
Outdoor leaf
lettuce
124
112
100
a"' \s
b" \.\
88 ~\\
\Q
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76'- \
\\
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64

52

40

l 2 3 4 5 6

Figure 4.-Graphs of data in Tables 9, 10, and 11.

-'LII)

_5%_
DISCUSSION

The results from the four experiments reported

in this paper clearly indicate that leaf lettuce con-

tains more vitamin A than head lettuce. It is superior,

in this respect, to even the outside, green leaves of
the head lettuce which contain much larger amounts of
this vitamin than the inside yellowish portion of the
head. That the blanched portion, or hearts of head
lettuce, contains some vitamin A is also shown by the
data. When fed in amounts of 200 mg. daily this kind
of lettuce Just about enabled the animals weighing
around 90 grams to maintain their weight for eight
weeks. There was a very slight average loss in weight
by the animals fed on that amount in this experiment.
The data submitted show that there is a cor-
relation between the amount of vitamin a present and
the greenness of lettuce leaves. However, it would be

unsafe to infer either a causal relationship on an

indissoluble association of these two things. available

data clearly show that etiolated seedlings and white
or yellow ”hearts“ of lettuce and cabbage contain some
vitamin.a, but this amount is very small in preportion
to the amount contained in the green parts of the same,
or similar plants.

The investigations of Monteverde and Lubimenkfi

-55-
(18) some years ago led them to state that a pigment
called ”chlorcphyllogen" is formed, independentlzflgf
light, in the chromatophdes of all potentially green
plants. This pigment or "mother substance" of chloro-
phyll is immediately connerted into chlorophyll on
exposure to light, but in some species, (ferns and
evergreen seedlings (Larix, Pinus, Picea) , it becomes
chlorophyll in darkness, but according to Lubimenkol9)
conifer seedlings form less chlorcphyll in darkness
than in light. Issachenko,and Liro (8’ showed that
oxygen and carbohydrates were not necessary for the
transformation of chlorcphyllogen into chlorcphyll
under favorable temperature conditions. Lire (8)
claimed to have killed etiolated seedlings in a care-
ful manner so as to save some of the chlorcphyllogen,
when some formation of chlorophyll was still observed
on exposure to light.

In 1859 Sachs ‘8) mentioned a colorless chro-
mogen called lencOphyll from which chlorcphyllogen is
said to arise. In the June and July numbers of "Revue
Gbnbrale de Botanigue" for 1926 Lubimenko, u.v.(9)
has summarized his extensive investigations and also
the present situation regarding the pigments of the
plastids and photosynthesis. He strongly reaffirms his
position concerning chlorcphyllogen and certain other

phenomena of the plastids and pigments. Most embryos

develop a green color during the first stages of their
develOpment after fertilization and green color was
found to be present in a few of them even after full
maturity of the seed. in the mature cucurbits a rich
store of chlorophyllogen is found in what was the inner
integument. of the ovule. In speaking of chlorophyllogen
in seedlings of angiesperms grown in the dark Lubimenke
makes the following statements: "The seedlings of an-
giesperms produced in the dark accumulate the yellow
pigments and a very small quantity of pigment called
chlorcphyllogen”. "as a general rule, the quantity of
chlorophyllogen in seedlings is so small in proportion
to the quantity of yellow pigments that this pigment

has no sensible influence on the color of the seedlings".
"With angiOSperms the chlorophyll is replaced in the
dark by the chlorophyllogen of which the accumulation,
as in case of the chlorophyll, depends primarily on

the organic nutrition of the plastid."

In his entire summation of the evidence he
endeavors to establish the proposition that the develOp-
ment of the plastids as well as the various pigments
in these structures is more dependent on the organic
nutrition of the cells than any other factor, light
included. In light of these considerations it may be
possible that in apparently chlorcphyll free tissues

there are substances that are closely related to chloro-

D f. .
.
§ .
- .
..
n. - ~
. . - e
. -
r t. .
’
- i 14A
p e.
. . a
. v w. I .
r
- (
- .
e a
,
. .
- ..
.
..
a . -
~ 1 n;
, . .
n. O
a .
a
.
.
H u o
O
I
.. .
.
- . _
4 n . t
,
.
.-

O

-57-
phyll, that is substances from which chlor0phyll is
formed, such as chlorcphyllogen and lencophyll, which

could be related to vitamin A in a very significant

manner.
SUMMARY

1. Leaf lettuce contains more vitamin a.than head

lettuce.
2. The green, outside leaves of head lettuce con-

tain larger amounts of this vitamin than the yellow, or

blanched, portion of the head sometimes called "the

hearts of lettuce."
3. The blanched head lettuce contains some vitamin

A but this occurs in relatively small amounts.

4. Leaf lettuce grown in the greenhouse contains
practically the same amount of this growth promoting
vitamin as that grown in the field where it gets the

direct sun rays.
5. Evidence points toward a close relationship

between chlorophyll, or some of its primary phases

and vitamin A.in lettuce tissue, but this relationship

has not been definitely proved.

‘ L'J‘L

r-i-H \A u)‘_-.'_ z .W‘
‘4 ‘ <4 H lea

H ' V... r
“whmjljkm” ., _ ‘ __ .- . -

. .
Pal-nus 3..

(1'8
-0 -

‘ "‘.' "VT '7‘“ "I? "'1‘°'“ 'V
JiCdrjs-N-L‘ |IOLA 4' In _-J— J- )

 

The writer wishes to express his appreciation
to Dr. J.W.Crist and Dr. Karie Dye for suggestions in

planning and conducting the experiments and for assis-

-pJvQ—

H.-

tance in preparation 0 this manuscript, and to Kr.
G.J.3tout for assisting in caring.for the animals dur-

ing preliminary work on the problem.

1.

2.

5.

6.

7.

9.

-39-

LITBRaTUJB CITED

 

Coward,K.H. and J.C.Drummond. The formation of
vitamin a in living plant tissues. Biochem. Jour.
15: 530, 1921.

Coward, K.H. The formation of vitamin a in plant
tissues 2. Biochem. Jour. 17: 135, 1923.

Delf, E.M. 30. African Jour. Sci. 17: 121, 1920,
Chem. absts. 15: 1154, 1921.

Drummond, J.C., L.A.Coward and a.F.Watson. Notes
on the factors influencing the value of milk and
butter as sources of vitamin a. Biochem. Jour. 15:
540, 1921.

butcher, 2.x. Influence of ultra-violet light on
the anthrgohitio properties of purified rations
used in the study of vitamin n.

Eddy, Y.h. The vitamin content of foodstuffs.
amer. Jour. of Pub. health. 16 Ho. 2: 1926.

Hess, a.F. and M.Wienstock. Imparting of anti?»

rachitio properties to invert substances by ultra-

violet irradiation. Jour. Biol. Chem. 63: 297, 1925.
Liro, J.I., B.Issachenko, h.a.Monteverde, V.N.
Lubimenko, and.J.Sachs. Palladins Plant Physiology.
Lubimenko, m.V. Recherches sur les pigments des
plastes et sur la photosynthise. hevue Generals de

Botanique. 38: 307, 1926.

IPIIIL'IE

10.

11.

12.

13.

14.

15.

17.

-40-
Osborn, T.B. and L.B.Mende11. Nutrition factors

in plant tissues. 4. Fat-soluble vitamin. Jour.

of Biol. Chem. 41: 549, 1920.

Sherman, H.C. and H.E.Munsell. The quantitative
determination of vitamin A. Jour. Amer. Chem. Soc.
47: 1639, 1925.

steenhack, H. and E.G.Gross. The fat-soluble
vitamin content of green plant tissues together
with some observations on their water-soluble
vitamin content. Jour. of Bio. Chem. 413149, 1920.
Steenbeck, H. and M.T.Sell X. Further observations
on the occurrence of the fat-soluble vitamin with
yellow plant pigments.

Steenback, H., M.T.Se11, and P.W.Boutwell. The

fat soluble vitamin content of peas in relation

to their pigmentation. Jour. Biol.Chem. 47: 303,
1925.

Steenback, H., M.T.Helson, and A.Black. A modified
techinique for determination of vitamin A. Jour.
Biol. Chem. 62: 275, 1924.

Steenhack, H.,.A.Black, E.M. Nelson, and C.A.H0ppert.
Jour. Biol. Chem. 63: 25, 1925.

Wilson, J.W. The relation of photosynthesis to

the production of vitamin a in plants. Jour. of

Biale Chemo 51: 455, 1922c

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