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~ Factors Affecting 
the Content of 


ASCORBIC ACID 
IN TOMATOES 


BULLETIN 573 UNIVERSITY OF ILLINOIS 
AGRICULTURAL EXPERIMENT STATION 


CONTENTS 


Page 
REVIEW OF (LITERATURE. ., 00. 24. 1a. 5. eos oo we 3 
MATERIALS ‘AND METHODS... 0. 3. -a02 0 2. es a.) > ee vs 
EXPERIMENTS, AND RESULTS... 5 2 a 8 


Variation in Ascorbic-Acid Content of Shaded and Exposed Fruits. . 8 


Effect of Sunlight on Ascorbic-Acid Content of Fruits 





at Various Stages of Development... ..........). 2 9 

Effect of Bagging on Fruit Development in the Field............. jy 
Greenhouse Experiments... . 2... 00.0% 045 ls 0s eos 13 
Seasonal Variation in Ascorbic-Acid Content.................. ites) 
Seasonal Variation in Number of Exposed and Shaded Fruits..... U7, 
DISGUSSION wes wc Oe Ee a i, 
SUMMARY AND CONCLUSIONS. .2..2..--..0 1. 22 
LITERATURE :CITED ©... ce ces ek es eee elle oe 22 
Urbana, Illinois April, 1954 


Publications in the Bulletin series report the results of investigations made 
or sponsored by the Experiment Station 


Factors Affecting the Content of 
Ascorbic Acid in Tomatoes 


Hussein H. Hassan and J. P. McCo.ttum® 


HE TOMATO (Lycopersicon esculentum) is important in nutri- 

tion primarily because of its ascorbic-acid (vitamin C) content. 
Efforts to increase the ascorbic-acid content of commercial varieties 
by breeding have not been too successful, even with genetically 
superior strains available. The slow progress in increasing the anti- 
scorbutic value of tomatoes has been due primarily to the difficulty of 
comparing strains because of errors in sampling. Such errors are 
indicated by the highly variable and conflicting data in the literature. 

The purpose of this study is to evaluate some of the factors 
affecting the ascorbic-acid content of tomato fruits in an effort to re- 
duce sampling errors and increase the accuracy of strain comparisons. 


REVIEW OF LITERATURE 


The literature dealing with the ascorbic-acid content of tomatoes 
has been well reviewed by Maclinn and Fellers,?** Hamner and May- 
nard,’ and Aberg.t For this reason only representative investigations 
are cited here. 

Maclinn, Fellers, and Buck’? reported on the ascorbic-acid content 
of 98 tomato varieties tested in Massachusetts. They found variations 
among the different varieties ranging from 44 + .03 to 138 + .03 milli- 
grams per 100 grams of fresh weight. They also reported great varia- 
tions among samples of the same variety. For example, they found 
values varying from 19 to 50 milligrams per 100 grams fresh weight 
for the Bonny Best variety, and from 19 to 48 milligrams for John 
Baer. They found Marglobe 28 percent higher in ascorbic acid than 
Prichard. On the other hand, Tripp, Satterfield, and Holmes,*° in a 
varietal test in North Carolina, reported Prichard high in ascorbic 





* Superior figures refer to literature cited on pages 22 to 24. 

“Hussein H. Hassan, formerly graduate student in Horticulture while on 
leave from Fouad First University, Cairo, Egypt; J. P. McCo.titum, Associate 
Professor of Vegetable Crops. This publication is based primarily on a thesis 
by the senior author in partial fulfillment of the requirements for the degree of 
Doctor of Philosophy. 


3 


4 Buuuetin No. 573 [ April, 


acid and as containing 27 percent more than Marglobe. Hamner, 
Bernstein, and Maynard" showed wide variations in the ascorbic-acid 
content of tomato varieties grown at different locations. Fruits of 
Marglobe varied from 14.4 + 2.12 grams of ascorbic acid to 30.6 + 
2.04 grams with location; Rutgers, from 8.4 + 0.50 to 19.7+1.17 
grams; and Prichard, from 10.7 + 0.88 to 29.0 + 1.29 grams. 

Although a number of investigators? * ?* have reported definite 
varietal differences in the ascorbic-acid content of tomatoes, Currence,' 
with samples obtained from a replicated field experiment, showed that 
differences between varieties were indefinite and difficult to demon- 
strate statistically. 

Breeding for tomato varieties with high ascorbic-acid content, 
Shivrina®® reported values as high as 48 milligrams per 100 grams 
fresh weight for cultivated varieties and as high as 80 milligrams in 
some wild varieties. In 1938 Biryukov? crossed varieties having high 
and low potencies and found the first generation to have an ascorbic- 
acid content close to that of the parent with the higher values. In 1942 
Reynard and Kanapaux* reported that single determinations on each 
of 166 second-generation plants from a Red Current tomato « Mar- 
globe cross showed that the ascorbic-acid content in the F, generation 
ranged from about 9 to 42 milligrams per 100 grams fresh weight, 
while the parental lines had 42 and 16 milligrams respectively. 

The influence of chromosome number on the vitamin-C content 
of tomato fruits has been the subject of considerable discussion in the 
literature. In 1933 Key? reported that tomatoes of the same genetic 
constitution, whether of diploid (12-pair) or tetraploid (24-pair) 
plants contained equal quantities of ascorbic acid. Later in the same 
year Sansome and Zilva** reported that tomatoes from tetraploid 
plants contained twice as much ascorbic acid as tomatoes from 
diploid plants. In 1935 McHenry and Graham?* compared tetraploid 
with diploid fruits and reported that the diploid fruits contained about 
84 percent as much ascorbic acid as the tetraploid, a difference con- 
siderably less than that reported by Sansome and Zilva.** However, 
in another report published in 19386 Sansome and Zilva*® stated that 
they were unable to record again such a great inequality between the 
ascorbic-acid contents of tetraploid and diploid forms as they had 
reported in 1933. They suggested that an unknown factor or factors 
must have been responsible for that inconsistency. McHenry and 
Graham’® claimed that the differences reported between tetraploid 
and diploid tomatoes were due to fruit size, as tetraploid tomatoes are 
usually smaller than diploid tomatoes. 


1954| Facrors AFFECTING THE CONTENT OF AscorBic AcID IN ‘TOMATOES 5 

Considerable disagreement is found concerning the relation between 
fruit size and ascorbic-acid content. Maclinn, Fellers, and Buck,”? as 
well as other investigators,” ?* *° reported no correlation between 
ascorbic-acid content and fruit size within a strain or a variety of toma- 
toes. Hallsworth and Lewis!’ found a rapid and highly significant 
increase of ascorbic acid with decreasing weight (correlation coefficient 
— 0.94) for tomato fruits weighing less than 30 grams; whereas fruits 
weighing 30 grams or more gave a nonsignificant coefficient of — 0.03. 
Several investigators,” ?° *? however, found ascorbic acid to be nega- 
tively correlated with fruit size. 

In 1937 Maclinn, Fellers, and Buck’? reported that degree of ripe- 
ness had no significant effect upon the vitamin-C content of fruits 
picked from six tomato varieties. Conversely, Lo Coco?! in 1945 re- 
ported that the ascorbic-acid content was highest near and before the 
ripening stage and lowest in green and overripe tomatoes. 

Conflicting reports have been published on experiments dealing 
with the effect of soil fertility and plant nutrients. Hester and Koh- 
man" reported that tomatoes grown on Sassafras sandy loam soil were 
44 percent higher in ascorbic acid than those on Edgemont stony loam. 
However, the tomatoes on the sandy loam were grown at Moorestown, 
New Jersey, and those on the stony loam at Elverson, Pennsylvania, 
and harvested one month later. Hester and Kohman’® reported that 
the application of potassium fertilizer to certain soils resulted in an 
increase in the yield and in the vitamin-C content of tomato fruits. 
They also reported similar effects for the application of manganese to 
soils deficient in this element.*®? Hamner, Lyon, and Hamner"! showed 
that the ascorbic-acid content of tomatoes was not appreciably 
affected by wide variations in the amounts of macronutrient elements 
supplied to the plant. 

Murphy’”® reported that environmental agencies markedly influence 
the synthesis of vitamin C in tomatoes. She stated that the geographi- 
cal situation is not a contributing factor except insofar as environ- 
mental conditions are consistently characteristic of that situation. 
Hamner, Lyon, and Hamner," working with the Bonny Best variety, 
reported that the location where the crop is grown has an effect upon 
the ascorbie-acid content of the fruits. They found the ascorbic-acid 
content to be associated apparently with differences in the environment 
of the top of the plant but not with differences between soils at the 
several locations. 

Of the various environmental factors that influence the accumu- 
lation of ascorbic acid in plants, light seems to have the greatest 
effect.2® *1 In British Columbia, Harris!® noticed that the warmer 


6 BuuuetIn No. 573 [April, 


districts, with plenty of sunshine, yield tomatoes with the highest 
vitamin-C content. Pepkowitz et al®° found higher ascorbic acid in 
peas associated with the wider spacing, which allowed more light to 
the plants. McCollum‘ reported that fruits picked from defoliated 
tomato plants were remarkably higher in ascorbic acid than those 
from plants with normal foliage. He stated that this difference in the 
ascorbic-acid content was due to the greater exposure of fruits to 
sunlight when the tomato plants were defoliated. 

Clow and Marlatt® found that greenhouse tomatoes allowed to 
ripen on the vine were not quite so potent a source of vitamin C as 
field tomatoes ripened on the vine. 

Brown and Moser‘ reported that tomatoes from vines supported 
on poles were significantly higher in ascorbic acid than those picked 
at the same time from adjacent unsupported vines. Obviously the 
supported vines received more over-all light. 

Currence,’ growing a number of tomato varieties in the greenhouse, 
found significant differences in ascorbic-acid content from week to 
week and noticed that such differences did not appear to be associated 
with percentage of sunshine. 

Somers, Hamner, and Nelson*’ reported that the amount of light 
for 18 days prior to harvest is closely correlated with the ascorbic- 
acid content of tomatoes under field conditions. In a later and more 
extensive experiment, however, by Somers, Hamner, and Kelly,* 
these results were not substantiated. Hamner and Parks,’* working 
with turnip greens, noticed that light intensities Just prior to harvest 
play the dominant role in determining ascorbic-acid level. Similar 
results have been reported by Aberg! for tomato leaves. 

McCollum?* reported that exposed field tomatoes were remarkably 
higher in ascorbic acid than the shaded fruits from the same variety. 
He also showed that the upper half of the tomato fruit which received 
more sunlight was higher in ascorbic acid than the lower half. He 
stated that uniformity to light exposure ought to be considered in 
selecting tomato samples representing different treatments. He sug- 
gested the use of samples composed of equal opposite sectors taken 
from 12 to 15 either shaded or unshaded fruits. 

Hamner, Bernstein, and Maynard** transferred staked tomato 
plants of the Bonny Best variety at different developmental stages 
from sunshine to shade, and others from shade to sunshine, and re- 
ported that shading during the period just prior to ripening of the 
fruits increased the ascorbic-acid content. The effectiveness of illumi- 
nation on the fruit and foliage was not measured separately. They 
also reported an increase in the ascorbic-acid content of the fruits with 


1954] Factors AFFECTING THE CONTENT oF AscorBic AcID IN TOMATOES 7 
an increasing photoperiod in the control chambers. However, they re- 
ported only a 17-percent increase with a 16-hour day in comparison 
with an 8-hour day. 

Hansen and Waldo” reported that strawberries grown and ripened 
under reduced light intensity contained less ascorbic acid than those 
ripened on plants fully exposed to light. They also found that shading 
the entire plants resulted in a much greater reduction in ascorbic acid 
than did shading the berries only. Recently Robinson** showed evi- 
dence that the ascorbic-acid content of strawberry fruits was affected 
by the amount of illumination received by the leaves. 

Veselkine et al,*1 kept some developing tomato fruits in double 
bags of black paper and compared the ascorbic-acid content of the 
bagged fruits with that of comparable light-exposed control fruits. 
Their data were inconclusive but indicated that the light-exposed 
fruits were higher in ascorbic acid. 


MATERIALS AND METHODS 


The experiments reported here were conducted at Urbana, Illinois, 
on both field and greenhouse tomatoes. Two varieties, Illinois T19 and 
Garden State, were used in the field experiments. Seedlings from both 
varieties were transplanted for the crops of 1948 and 1949 on May 21 
and May 19 respectively. In 1949 two additional plantings were made 
on June 14 and July 11. 

For the greenhouse experiments the Lloyd forcing variety was 
used. The plants were transplanted on February 16, 1949, in raised 
benches running east and west. The greenhouse was maintained at day 
temperatures between 70° and 75° F. The plants were pruned to a 
single stem and topped at about 5 feet after producing from four to 
six clusters. 

Light was excluded from fruits at different stages of development 
by enclosing them in bags made from aluminum-covered paper.* The 
bags were then closed from the bottom by means of two or more small 
clips in a way that permitted air exchange inside the bags. 

Fruits for analyses were harvested between 11 and 12 o’clock in 
the morning and analyzed the same day. Unless otherwise specified 
12 to 15 selected fruits were used for each sample. Equal opposite 
sectors were cut from each fruit, making a total of 200 to 250 grams 
for analysis. The whole fruit was used when analyzed individually. 
Each fruit was harvested for analysis when entirely red. 


*Secured from the Tested Papers of America, Inc., Chicago, III. 


8 BuLuetTiIn No. 573 [April, 


For ascorbic-acid analyses the samples were blended for two 
minutes in a Waring blendor with one milliliter of 0.5-percent oxalic 
acid per gram of tomato. The mixture was then allowed to settle, and 
a portion was filtered through Whatman No. 12 filter paper. Dupli- 
eate 3-milliliter aliquots of the filtrate in 5 milliliters of 0.2-oxalic 
acid were titrated with 2,6-dichlorobenzenoneindophenol according to 
the method of Bessey and King.’ 

Total solids were determined by drying duplicate 20-gram samples 
of juice at 80° C. in a Brabender ventilated oven until a constant 
weight was reached. 


EXPERIMENTS AND RESULTS 


Variation in Ascorbic-Acid Content of Shaded 
and Exposed Fruits 
In order to study sample variability, shaded and exposed fruits of 
Illinois T19 and Garden State varieties were analyzed individually 
for ascorbic-acid content. Fruits from the 1948 field crop were used. 


Table 1.— Variability in Ascorbic-Acid Content of Exposed 
and Shaded Tomato Fruits 


(Data are given in milligrams per 100 grams fresh fruit) 








Illinois T19 Garden State 
Number of 
fruits Exposed , Shaded Exposed Shaded 

OR dre i cee Vara! Bs iy’ Ais ok OW a gr Pv’ & Virsa od bg 33.6 +.0,538° Zia 
YR ee eats 3148 OTT 2623 F 0.50 32.6 + 0.638 “21.3 -2O286 
1D ce renee: 36;654,.0' 83° 4926: 2s OS2 34.5 + 0.81 21.8 + 0.83 
LE) 2 tance etc tane ans Soe 37.0 £0.95 26.2 +:0,65 32.5 + 0,89 2205 eeeees 
LOST See Lene go at BS iT 02750. 265850875 30. ae Ute 19.9 + 0.83 
Tho pete. 35/3 er 0599) £2638 251205 34.9+ 1.01 22 sort el4 








Samples of 30 well-exposed fruits of each variety and 30 fruits well 
shaded by foliage were selected at random for analyses. The exposed 
and the shaded fruits of Illinois T19 were harvested on August 18 
and 19, those of Garden State on August 20 and 21. Calculations were 
made of the mean, the standard error of the mean, and the coefficient 
of variation for each of the four 30-fruit groups. Similar calculations 
were made for subsamples of 15 and 10 fruits each. 

The exposed fruits (Table 1) were remarkably higher in ascorbic- 
acid content than the shaded fruits. The differences amounted to 41.4 
percent with Illinois T19 and 55.6 percent with Garden State. In ad- 


1954) Factors AFFECTING THE CoNTENT oF Ascorsic AciD IN TOMATOES 9 


dition, both the exposed and the shaded fruits of Illinois T19 were 
significantly higher in ascorbie acid than the respective exposed and 
shaded fruits of Garden State. The shaded fruits of Garden State were 
more variable than the exposed ones. The difference is especially evi- 
dent if the coefficients of variations are compared. 


Effect of Sunlight on Ascorbic-Acid Content of Fruits 
at Various Stages of Development 


Sinee the exposure of fruits to sunlight increases the ascorbic-acid 
content, experiments were designed to determine the stage of fruit de- 
velopment at which sunlight is most effective. This was done by 
excluding light from fruits at various stages of development with 
aluminum-covered paper. Experiments were conducted on both field 
and greenhouse tomatoes. Date of bagging, date of harvesting, fruit 
weight and diameter, and ascorbic-acid content were recorded. 


Light excluded at turning stage of fruit. On August 9, 1948, a 
number of exposed fruits of the Illinois T19 variety were bagged at 
the turning stage. A number of similar fruits were marked for controls. 
The fruits were harvested when ripe and analyzed for ascorbic-acid 
content. Thirty bagged and thirty control fruits were harvested be- 
tween August 15 and 20 and analyzed individually for ascorbic-acid 
content. The average time required for ripening was 7 to 8 days with 
both the treated and the control fruits. The experiment was repeated 
with the Garden State variety. Fruits were bagged September 12 and 
harvested between September 18 and 24. The results of the analyses 
are shown in Table 2. 

The values for the bagged fruits averaged slightly lower than those 
for the controls, but the difference was not significant. There was no 


Table 2.— Effect of Excluding Light at Turning Stage on 
Ascorbic-Acid Content of Tomato Fruits 
(Data are given in milligrams per 100 grams fresh fruit) 


Illinois T19# Garden State® 
Treatment Ascorbic- Ascorbic- 
acid rites at acid aie at 
content 0 content 0 
[ipqitie #4 ola Ole ULOZ Re, 24.0 £.0.54 i 
Pre GRDOSC0) ok cy 32.2 + 0.49 1.43 266.2 0155 1.54 


® Average of 30 fruits. 


10 Buuuetin No. 5738 [April, 


noticeable effect of bagging on the time required for ripening, on 
diameter, or on weight of fruit. 

Fruits bagged 25 days after flowering. Because of the discrep- 
ancy in the literature®” °° regarding the relation of sunlight during the 
last few weeks before harvest to the ascorbic-acid content, experiments 
were made to study the effect of illumination on fruits in the late 
green stage. Flowers of the Illinois T19 variety were tagged in the 
field on August 1, 1948. Twenty-five days later some of the fruits 
from the tagged flowers were bagged, while others were left exposed to 
sunlight. As the treated and control fruits ripened between September 
12 and October 1, they were harvested and analyzed for ascorbic acid. 
The experiment was repeated with the Garden State variety. Twenty- 
five-day-old fruits were bagged or marked as controls on September 
11 and harvested between September 28 and October 18. 

The average time from flowering to ripening in the control fruits of 
Illinois T19 was 50 days and in the bagged fruits, 51 days; while for 
Garden State the average was 50 days for each treatment. In each 
test the control fruits were significantly higher in ascorbic acid than 
the fruits from which light was excluded (Table 3). The amount in 
the bagged fruits was 17.6 percent lower in Illinois T19 and 14.0 
percent lower in Garden State. 


Light excluded at early green stage of fruit. Although the dif- 
ferences shown in Table 3 are highly significant, they are much less 
so than the differences between the shaded and exposed fruits in 
Table 1. The two groups of data indicated that illumination early 
in the development of tomato fruits might be a factor affecting 
their ultimate ascorbic-acid content. So further experiments with two 
varieties were conducted to study the effect of solar illumination dur- 
ing the early development of field-grown fruit. 


Table 3.— Effect of Bagging Fruits 25 Days After Flowering on 
Ascorbic-Acid Content of Tomato Fruits 
(Data are given in milligrams per 100 grams fresh fruit) 


Illinois T19* Garden State* 
Treatment Ascorbic- Dif- L.8.D.  <Ascorbic- Dif- L.S.D. 
acid fer- at acid fer- at 
content ence 1% content ence 1% 
Fruits bagged.<....--.. "20.0 +0.60 (02. |...” 2374 09/6 
Fruits exposed......... 30.7 + 0.64 5.4 °°2.384 27.2 4.0.45 93 Sees 


a Average of 30 fruits. 


1954) Factors AFFECTING THE CONTENT oF AscorBic AciIp IN TOMATOES 11 


Table 4.— Effect of Excluding Light at Early Green Stage on 
Ascorbic-Acid Content of Tomato Fruits 
(Data are given in milligrams per 100 grams of fruit) 





Illinois T19* Garden State 
Ascorbic- —_L.8..D.¢ Ascorbic-  L.S8.D.° 

acid at acid at 

content La content 1% 
Fruits bagged for 10 days........ Boer USO) meats 22.4+0.67 2.58 
Fruits bagged for 20 days Soe et 23.2+0.58 2.11 20s 0.0589 2537 
Fruits bagged until ripe 2 gay sy) 21628 a: 0231 9) 1290 be 0. Oleg 47 
Fruits exposed (conirol).......... 30.4+40.54 Leen 26.8 + 0.69 Loe 


« Average of 30 fruits. » Average of 25 fruits. * Compared with exposed fruits. 


Since in preliminary tests it had been found that bagging the 
flowers prevented fruit development, this operation was delayed until 
the fruits were between 2 and 3 centimeters in diameter and about 
15 days old. Fruits of Illinois T19 bagged July 14, 1949, were divided 
into three groups: the first group remained bagged for 10 days and 
was then exposed to light until ripe; the second remained covered for 
20 days; and the third was left covered until ripe. Control fruits were 
exposed throughout their development. Thirty fruits each of all four 
light treatments were harvested between August 12 and September 2 
and analyzed separately. The fruits of Garden State were bagged or 
marked August 4 and 25 from each of the four treatments harvested 
between August 27 and September 27. 

In these tests highly significant differences occurred in the ascorbic- 
acid content of bagged compared with exposed fruits (Table 4), and 
the content declined as the period of light exclusion was lengthened. 
When light was excluded for 10, 20, and 39 days, the ascorbic-acid 
content was reduced 17.8, 23.7, and 44.7 percent respectively in fruits 
of Illinois T19, and 16.4, 25.0, and 49.6 in the Garden State fruits. 


Leaves and fruit shaded. The effects of shading the leaves and 
fruits of tomato plants were shown in another experiment. Illinois T19 
transplanted to the field on May 21, 1949, was used for the test. 
Treatments were as follows: (1) fruits were bagged approximately 
15 days after flowering; (2) fruits were bagged as in (1) and the 
plants shaded with a double layer of cheesecloth on July 8; (3) plants 
were shaded as in the previous treatment but fruits were not bagged; 
(4) plants were exposed and fruits were shaded by foliage; (5) plants 
and fruits were exposed to direct sunlight. Two replications of eight- 
plant rows were used for each treatment. Samples of 12 to 15 fruits 


12 Buuuetin No. 573 [April, 


Table 5.— Ascorbic-Acid Content and Total Solids of Tomato 
Fruits Under Different Light Treatments 








Ascorbic- 
Treatment acid Br 
content? 








mgs/100 grams»  perct.» 


1. Fruits bagged, plants unshaded................... 1703 5.3 
2. Fruits bagged, plants shaded with cheesecloth....... 17.35 4.7 
3. Plants shaded with cheesecloth.................... 25.08 4.8 
4. Unshaded plants, shadedifrits.. 2.5 bo. .0 Me ao be 24.25 5.5 
5. Unshaded plants, exposed fruits (control). .......... 33.52 5.6 








#1.8.D. (compared with control): at 5% level 1.90, 1% level 2.59. 
> Values are averages for six samples of 12 to 15 fruits each. 


from each treatment were harvested August 6, 26, and September 11 
and were analyzed for ascorbic acid and total solids. 

No difference was found in the ascorbic-acid content of bagged 
fruits whether the plants were shaded or exposed (Table 5). Fruits 
shaded by cheesecloth which covered the entire plant had about the 
same ascorbic-acid content as fruits shaded by foliage only. The 
highest ascorbic-acid content was found in fruits exposed to direct 
sunlight on unshaded plants. 

The total-solids content of the fruits was reduced slightly by 
shading the plants with cheesecloth, but shading the fruits had no 
significant effect. The cheesecloth reduced the illumination about 75 
percent, as measured by a Weston illumination meter, Model 756. 


Effect of Bagging on Fruit Development in the Field 


Since bagging fruits at the green stage caused a remarkable de- 
crease in ascorbic acid, other effects on the fruit, such as size, color, 
and date of ripening, were determined for individual fruits in the ex- 
periment reported in Table 4. In addition, temperatures of bagged and 


Table 6.—Size of Tomato Fruits and Time Required for Maturity When 
Fruits Were Bagged at Early Green Stage and When Left Exposed 











Illinois T19® Garden State> 


Average per fruit —________ re 
Bagged Exposed Bagged Exposed 





Ween grammori ia (a eee 149 143 110 112 
Diameter in centimeters............. 6.8 6.9 6.3 6.3 
Number of days between flowering 

BNC nad CULILY eee ee ee one ee een 54 51 56 52 








a Average of 30 fruits. » Average of 25 fruits. 


1954) Facrors AFFECTING THE CONTENT oF AscorBic AcID IN TOMATOES 13 


exposed fruits were taken on several cloudless days, readings being 
made every two hours between 10 a.m. and 4 p.m. 

Bagging the fruits proved to have only slight or no effect on the 
average fruit weight and diameter (Table 6). When the fruits were 
covered from the time they were 15 days old (early green stage) until 
maturity they required 3 to 4 days longer to ripen than the controls. 
This difference was found to be significant only at the 5 percent level; 
when the fruits were covered for a shorter period at 25 days after 
flowering there was no significant delay in maturity (see page 10). 

Bagging also caused the disappearance of the green color in the 
developing fruits, but did not prevent the normal development of red 
pigment as indicated by pigment analyses. 

On cloudless days the temperatures of the bagged fruits were 1 to 2 
degrees C. lower than those of fruits exposed to direct sunlight. 


Greenhouse Experiments 


An attempt was made to determine the effect of foliage on the 
ascorbic-acid content of the fruits in the greenhouse during the fall of 
1948. But when the leaves adjacent to a cluster were removed, the 
fruits failed to develop satisfactorily, when they developed at all. It 
was noticed, however, that the fruits on the upper clusters were much 
higher in ascorbic acid than those on the lower clusters. An experiment 
was therefore made to determine whether this difference was due to 
exposure to hght or to position on the plant, or to both. 

Effect of light and position of clusters. Tomatoes of the Lloyd 
forcing variety grown in the spring of 1949 were used. Fruits on the 
experimental plants were thinned to two per cluster. Alternate clusters 
on a plant were bagged approximately 15 days after flowering. On half 
the plants the bagged fruits were uppermost and on the other half 
the exposed fruits were uppermost. Data were taken on the second, 
third, fourth, and fifth clusters. The first two were considered lower 
and the second two upper. Fruits of the lower clusters ripened between 
May 25 and June 27, while those of the upper clusters ripened between 
June 6 and July 8. 

Excluding light from the fruits greatly decreased the ascorbic-acid 
content (Table 7), 33.1 percent in the upper clusters and 24.6 percent 
in the lower ones. The previous finding that fruits highest on the 
plant are also highest in ascorbic acid was confirmed. The upper 
bagged fruits were higher in ascorbic acid than the lower ones. 

Effect of fruits per cluster. Since the number of fruits per cluster 
on greenhouse tomatoes varies widely, the effect of this variation on 


14 Buuietin No. 573 [April, 


Table 7.— Ascorbic-Acid Content of Bagged and Exposed 
Tomato Fruits on Different Parts of the Plant 


(Data are given in milligrams per 100 grams fresh fruit: 
average of 16 analyses) 


Treatments compared 
Ascorbic-acid 


Fruit position and en ane Nos. Difference L.S.D. 
treatment Mean—S.F. in ascorbic- At At 

acid content 5% 1% 

Upper clusters* Bagged vs. exposed 

lL: Bagsed a2 2 ee oe 25.7 + 0.51 1-2 12.7 2.29 3.09 

2, sTUXPOSGG ete 8 peo ee 38.4 + 1.00 3-4 fey) 2.71* 3. 0D 

Lower clusters? Upper vs. lower clusters 

1. BDarrediera. eee 2130 tb Ul 1-3 4.2 2.01 “od 

2. sEIXPOSEC Ae seers 28.5 + 0.86 2-4 9.9 2:10. ($8863 


@ Fourth and fifth clusters. » Second and third clusters. 


the ascorbic-acid content was studied. Eight plants of the Lloyd 
forcing variety in the same row receiving about the same light were 
selected. The fruits on half these plants were thinned to two per 
cluster. Fruits on the other plants were not thinned. The lower fruits 
(Clusters 2 and 3) were harvested between May 16 and June 29, the 
upper fruits (Clusters 4 and 5) between June 4 and July 2. 

Thinning to two fruits per cluster caused a significant increase, 10.8 
percent, in the ascorbic-acid content of the upper clusters, and a very 
significant increase, 19.1 percent, in the content of the lower clusters 
(Table 8). 


Table 8.— Ascorbic-Acid Content of Tomato Fruits From Thinned and 
Unthinned Clusters on Different Parts of the Plant 
(Data are given in milligrams per 100 grams fresh fruit) 


Treatments compared 
Num-__ Ascorbic- 


Fruit position Fruits _ ber of acid Differ- 
and per fruits content Nos. encein _L.8.D._ 
treatment cluster ana- §_Mean— ascorbic- At At 
lyzed S.E. acid 5% 1% 
content 
Upper clusters* Thinned vs. not thinned 
ie Lhinned see 2.0 16. 85:741.138 | 1-2... Sete eee 
2. Not thinned: +. : 7 - Aas 25 $82.3'+ 1.07 | 3-4.... 4.67 93 Geeae. 
Lower clusters® Upper vs. lower clusters 
3. Lhinned te eee 2.0 16.9 28:7 £:1.00 (3.9 9) 7c Oe oe 
4. Not thinned...... Oat 26 24.1.40.72 | 2-4..... 8:2 s2050meeaG 


® Fourth and fifth clusters. »® Second and third clusters. 


1954)  Facrors AFFECTING THE CONTENT oF AscorBic AciIpD IN TOMATOES 15 


Seasonal Variation in Ascorbic-Acid Content 


Fruits of Illinois T19 and Garden State were analyzed weekly 
during the 1948 season for ascorbic-acid content. Samples of 12 to 15 
shaded and the same number of exposed fruits from each variety were 
analyzed separately. Analyses began August 3 and continued to Oc- 
tober 5. 

The exposed fruits of both varieties proved higher in ascorbic acid 
than the naturally shaded fruits (Fig. 1), but the former showed 
greater variation during the season. About the middle of the season 
the ascorbic-acid content of the exposed fruits reached a peak and 
thereafter declined sharply. The fruits of Illinois T19 were signifi- 
cantly higher in ascorbic acid than those of Garden State. 

The study of seasonal variation in ascorbic acid was repeated 
during 1949 with the same varieties. Additional treatments were in- 
cluded to find out whether the decrease in ascorbic acid in the exposed 
fruits at the end of the season might be partly due to deterioration of 





ASCORBIC ACID CONTENT — MGS. PER 100 GMS. FRESH WEJGHT 





3 5 
AUGUST e redeer OCT. 
DATE OF HARVEST 


During the 1948 season, exposed fruits showed a much higher seasonal 
variation in ascorbic-acid content than shaded fruits. (Fig. 1) 


16 Buutuetin No. 573 [April, 


38 rin eal A tr ON a a 















MGS. PER 100 GMS. FRESH WEIGHT 
wow 
+ 














































EXPOSED _ JUNE 14TH PLANTING 
32 
- 30 
28 
fa'6 
ea 
hen 
z 
o 24 
xf ' SHADED 
Ls “i JULY TH 
g 22 , 
o | SHADED_ JUNE 14TH PLANTING 
o 
c 20 
é ILLINOIS TI9 
a 
18 | 
= 10 17 24 31 7 14 2i 28 


AUGUST ; SEPTEMBER 
DIAC ESO Pa HARV bo. 


42 ig -| 
38 ce 


GARDEN STATE 


34 ates, 
_ 


ze 


MAY 20 TH PLANTING 




























EXPOSED — MAY 20TH PLANTING 


mare 


a EXPOSED — JUNE I4 TH PLANTING 








30 
























Ri 


eau 
22 : es 22.2 
18 Po a 

7 14 2i 28 


17 
(RUGUST SEPTEMBER 
DATE OF HARVEST 





SHADED - JUNE I4 TH PLANTING 








ASCORBIC ACID CONTENT — MGS. PER 100 GMS. FRESH WEIGHT 








Physiological condition of the plant resulting from differences in maturity 
had no effect upon ascorbic-acid content. (Fig. 2) 


1954) Facrors AFFECTING THE CONTENT oF AscorBic AcID IN TOMATOES 1, 


the plants. Successive plantings were made on May 21, June 14, and 
July 11. Sampling was done as in the previous season. Harvesting 
of the first planting began on August 3, the second on September 7, and 
the third on September 28, when the season ended. 

There was the same trend as in the previous season. Again an 
increase occurred in the ascorbic-acid content of the unshaded fruits 
until midseason (Fig. 2), followed by a significant decrease toward 
the end of the season. Fruits with similar light exposures from the 
three different plantings were found to have about the same ascorbic- 
acid content at any given time during the season. 


Seasonal Variation in Number of Exposed 
and Shaded Fruits 


The shaded and exposed fruits of Illinois T19 were found to be 
higher in ascorbic acid than the respective shaded and unshaded fruits 
of Garden State. The field-run tomatoes of these varieties should also 
show a difference due to the more dense foliage of Garden State. A 
study was made therefore to determine the percent of exposed fruits in 
these varieties during the season. The number of shaded and exposed 
fruits from 10 plants of each variety were harvested and recorded at 
weekly intervals throughout the 1949 season. 

The percentage of exposed fruits harvested from Illinois T19 during 
the season was 64.6, and from Garden State 41.3. Both varieties, 
especially Illinois T19, showed a strong initial increase in percent of 
exposed fruits, then a leveling off, and then a gradual increase to the 
end of the season (Fig. 3). The total-yield curve of Illinois T19 
showed a sharp peak through August 31, followed by a sharp decrease 
(Fig. 4). Garden State did not show such a sharp peak in yield but 
continued to produce over a longer period than Illinois T19. 


DISCUSSION 


From the data presented it is obvious that the exposure of the fruit 
to sunlight is an important factor affecting the ascorbic-acid content 
of tomatoes. The percentage increase due to light exposure was higher 
with Garden State (55.6) than with Illinois T19 (41.4). The Garden 
State variety has heavier foliage and for this reason its shaded fruits 
perhaps received less illumination than those of Illinois T19. The 
percentage difference between the shaded and exposed fruits of Garden 
State is also higher because of its lower ascorbic-acid content. 


18 Buuuetin No. 573 [April, 


Po 
Sa Ss ae 
| eee 
A Bo. 


100 






80 











60 






— 
are 
NEES, | I 
MWA aes. 

SS os | a 
a Se 
a ee 






40 







{ 


20 


PERCENT OF EXPOSED FRUIT HARVESTED 






28 
AUGUST SEPTEMBER 


DATE OF HARVEST 


The percent of exposed fruit harvested from Illinois T19 during the 1949 
season was higher than that from Garden State. For both varieties the per- 
cent increased toward the end of the season because of defoliation. (Fig. 3) 


ips) 
° 
°o 


a 
° 





ind 
o 





@ 
°o 


fe STATE 


aA 
pel | | | 


b 
ie) 





NO. OF FRUITS HARVESTED WEEKLY FROM 10 PLANTS 








3 ce) 
AUGUST SEPTEMBER 
DATE OF HARVEST 


T19 showed a higher seasonal peak of production than Garden State. With 
both varieties the high peak of production coincided with the high peak of 
ascorbic-acid content (Fig. 2). (Fig. 4) 


1954)  Facrors AFFECTING THE CoNTENT or AscorBic AciD IN TOMATOES 19 


The data are in agreement with those obtained in earlier tests by 
McCollum** *° indicating that sampling error may be greatly reduced 
by selecting fruits according to light exposure. They also suggest that 
many of the discrepancies found in the literature concerning the ascor- 
bic-acid content of tomatoes may be due in part to failure to consider 
light exposures of the fruit. Although the standard error increases 
with a decrease in number of fruits per sample, it is very significant 
that when fruits are selected for light exposure, a difference in ascorbic 
acid of 2 to 3 milligrams per 100 grams of fruit can be measured with 
a 10-fruit sample. 

Fully exposed fruits can be easily selected, but even with careful 
selection there will be some variation in the light exposure of the 
shaded fruits. This is indicated by the higher coefficient of variation 
found in the shaded fruits. The data indicate that more accurate com- 
parisons between varieties may be made by selecting samples from 
fully exposed, rather than from shaded, fruits. The reverse, however, 
might have been true if the samples for the test reported in Table 1, 
page 8, had been taken later in the season after the plants were 
partially defoliated. It would then have been difficult to determine 
whether or not an exposed fruit had formerly been shaded. 

When developing fruits are enclosed with aluminum-covered paper 
to exclude light, they develop normally except for the absence of 
green color. Apparently there is no measurable effect on fruit size, 
but a small delay in maturity. This is perhaps a result of a slightly 
lower temperature of the bagged fruits as compared with that of those 
exposed to direct sunlight. This temperature difference should have 
no measurable effect on ascorbic-acid content. The increased ascorbic- 
acid content of exposed compared with bagged fruits may be at- 
tributed to solar illumination received by the exposed fruits. 

The ascorbic-acid content of tomato fruits appears not to be in- 
creased by light exposure during ripening or after the disappearance 
of chlorophyll from the fruits (Table 2, page 9). The accumulation of 
ascorbic acid can be assumed, then, to be associated with some aspect 
of photosynthesis, as suggested by McCollum.?* This is in line with the 
work of Somers, Kelly, and Hamner,?* who found that ascorbic acid 
in leaves could not be increased by light in the absence of carbon 
dioxide. 

Fruits covered for 10 days early in their development and then ex- 
posed to direct sunlight until ripe were lower in ascorbic acid than 
similar fruits not covered (Table 4, page 11). These data indicate that 
the effect of sunlight is cumulative, and for a fruit to contain the maxi- 
mum amount of ascorbic acid, it must be exposed to sunlight through- 


20 BuLLETIN No. 573 [ April, 


out its development. Somers, Hamner, and Kelly*® found no correlation 
between relative illumination and ascorbic-acid content of tomatoes. 
Since their samples were apparently not selected for hght exposure, 
and since illumination was recorded for only three weeks prior to 
harvest, little if any correlation should have been expected. When 
exposed ripe fruits are used in sampling for ascorbic acid, the prob- 
ability of foliage coverage earlier in their development should be 
considered. 

The data in Table 5, page 12, show that bagged fruits have about 
the same ascorbic-acid content on shaded and exposed plants. The 
same is true for shaded fruits. Ascorbic-acid content closely parallels 
the amount of illumination reaching the fruit and is only slghtly 
affected by that reaching the leaves under field conditions. Similar 
results were also shown by Somers, Hamner, and Kelly.*® Even though 
shading the plants decreases the total solids of the fruits, it apparently 
has no significant effect on ascorbic acid. 

Uppermost fruits on greenhouse plants were found to be highest 
in ascorbic acid (Table 7, page 14). This could have been due in part 
to a difference in light exposure, but it was also true for fruits from 
which light was excluded about 15 days after flowering. Since no 
seasonal trend could be shown in this experiment, it may be assumed 
that this difference is due to position on the plant and related to the 
availability of precursors for the development of ascorbic acid. This 
is also indicated by the fact that thinning the fruit increases the 
ascorbic-acid content. 

When ascorbic acid was determined at intervals throughout the 
seasons of 1948 and 1949, weekly variations but no definite trends were 
found with shaded fruits. However, during the latter season somewhat 
higher values were obtained with the early fruits. At this time the 
plants were still producing new foliage which might have shaded some 
of the sampled fruits only a short time before ripening. These higher 
values might therefore have been due to illumination during early 
development. The exposed fruits, on the other hand, showed a very 
significant peak about the middle of the harvesting season (Figs. 1 
and 2). There is no obvious relation between this trend and the 
weather data (Fig. 5). Since the effect of weather on the ascorbic- 
acid content of tomatoes is cumulative, a close relationship between 
weather at any definite time and the ascorbic-acid content of toma- 
toes 1s not to be expected. A decrease in ascorbic acid toward the end 
of the harvesting season might be expected on the basis of plant 


1954) Facrors AFFECTING THE ConTENT oF AscorBic AcIp IN ‘TOMATOES 21 


MEAN TEMPERATURE °F 
1948 WEEKLY AVERAGE 1949 


HOURS DAILY SUNSHINE — #9 nt lil 
x 


i= 
ie al 
oo 


: 
INCHES OF RAINFALL 
PER WEEK 

% — 

: nH 

Ld 

bei Hie 

, =} | 


15 22 29 6 13 20 27 3 10 Ade Es ae 28 ry rar) 15 22 29 6 = 2027 3 10 17 24 3l 7 14 2128 5 
NE JULY AUGUST SEPTEMBER 0. JUNE JULY AUGUST SEPTEMBER 0. 


1948 WEEK ENDING 1949 
























































Weather conditions during the 1948 and 1949 seasons had no significant 
effect on the ascorbic-acid content of tomatoes. (Fig. 5) 


senility, but fruits from young plants (Fig. 2) showed a trend almost 
identical with those of old plants. These data preclude the possibility 
that this trend could have been due largely to the sampling of fruits that 
were shaded earlier in their development. Differences in ascorbic acid 
between samples of tomatoes harvested one month apart and attributed 
to soil type by Hester and Kohman”™ could just as easily have been ex- 
plained on the basis of seasonal effects. 

Tomato strains may vary in time of maturity, making it difficult 
to sample all for ascorbic acid at one time during the season. When 
this is the case, shaded fruits should give a more accurate sample than 
those exposed to direct sunlight. 

Not only were the respective shaded and exposed fruits of the 
Illinois T19 variety higher in ascorbic acid than those of Garden State, 
but this variety also produced a higher percentage of exposed fruits 
(Fig. 3) and ripened more of them at a time when ascorbic acid was 
highest (Fig. 4). In order, then, to determine the tendency of a strain 
of tomatoes to produce fruits high in ascorbic acid, attention must be 
given to genetical potential, fruit shading, and the yield curve. 


22 BuuuEetTiIn No. 573 | April, 


SUMMARY AND CONCLUSIONS 


Tomato fruits exposed to direct sunlight were found to be signifi- 
cantly higher in ascorbie acid than shaded fruits. The data indicate 
that sampling error can be greatly reduced by selecting fruits with 
regard to light exposure. When a number of treatments are sampled 
at one time for ascorbic acid, more accurate comparisons can be made 
by using fruits exposed to direct sunlight. By selecting fruits in this 
manner, a difference of two to three milligrams of ascorbic acid per 
100 grams of fresh fruit can be measured with a 10-fruit sample. 
During both the 1948 and 1949 season, and with two varieties, exposed 
fruit reached a peak in ascorbic acid about the middle of the harvest- 
ing season and showed greater seasonal variation than shaded fruit. 
Shaded fruit should therefore be used when strains or treatments are 
sampled at different times during the season. 

The uppermost fruit on greenhouse plants are highest in ascorbic 
acid. The location of the fruit on the plant therefore is an important 
factor in sampling for ascorbic-acid content. 

Illumination has a cumulative effect on ascorbic acid throughout the 
ereen stage of the fruit. The maximum ascorbic-acid content is there- 
fore not reached if a fruit is shaded for any length of time during its 
development. Ascorbic-acid content varies with the intensity of the 
illumination reaching the fruits but 1s apparently not affected by that 
reaching the leaves under conditions in the field. 


LITERATURE CITED 


is ABERG, B. Effects of ight and temperature on the ascorbic acid content of 
green plants. Ann. Roy. Agr. Col. Sweden 13, 239-273. 1945. 


2. Bessgy, O. A., and Kine, C. G. The distribution of vitamin C in plant and 
animal tissues, and its determination. Jour. Biol. Chem. 103, 687-698. 1933. 


3. Biryuxov, D. Vitamin C in tomatoes and in pepper. Konserv. Prom. 4, 18- 
19. 1988. (Chem. Abs. 33, 9364; 1939.) 


4. Brown, A. F., and Mossr, Farr. Vitamin C content of tomatoes. Food Res. 
6, 45-55. 1941. 


5. Brown, G. B., and Boon, G. W. Ascorbic acid in fruit of tomato varieties 
and F, hybrids forced in the greenhouse. Amer. Soc. Hort. Sci. Proc. 47, 
255-261. 1946. 

6. Crow, B., and Maruart, A. L. Studies on vitamin C in fresh canned tomatoes. 
Jour. Agr. Res. 40, 767-775. 1930. 

7. Currence, T. M. A comparison of tomato varieties for vitamin C content. 
Amer. Soc. Hort. Sci. Proc. 37, 901-904. 1940. 

8. Currence, T. M., Criacunz, J. A., and IsHam, P. D. Value of commercially 


canned and laboratory prepared tomato juices as antiscorbuties. Jour. 
Home Econ. 27, 447-451. 1935. 


1954) Factors AFFECTING THE CONTENT oF AscorsBic AcID IN TOMATOES 23 


9. Gomoiyako, L. G. Variability in the amount of antiscorbutic vitamin in 
different tomato varieties. Bul. Appl. Bot., Genet. Plant Breeding 
(U.S.S.R.) Sup. 84, Vitamin Prob. 2, 116-128. 1937. (Chem. Abs. 33, 1366; 
1939.) 

10. HatuswortH, I. G., and Lewis, V. M. Variation of ascorbic acid in tomatoes. 
Nature 154, 431-432. 1944. 

11. Hamner, K. C., Lyon, C. B., and Hamner, C. L. Effect of mineral nutrition 
on the ascorbie-acid content of the tomato. Bot. Gaz. 103, 586-616. 1942. 

12. Hamner, K. C., and Maynarp, L. A. Factors influencing the nutritive value 
of the tomato: A review of the literature. U. 8. Dept. Agr. Misc. Pub. 502. 
1942. 

13. Hamner, K. C., and Parks, R. Q. Effect of light intensity on ascorbic acid 
content of turnip greens. Jour. Amer. Soc. Agron. 36, 269-273. 1944. 

14. Hamner, K. C., Bernstein, L., and Maynarp, L. A. Effects of light intensity, 
day length, temperature and other environmental factors on the ascorbic 
acid content of tomatoes. Jour. Nutr. 29, 85-97. 1945. 

15. Hansen, E., and Watpo, C. F. Ascorbic acid content of small fruits in rela- 
tion to genetic and environmental factors. Food Res. 9, 453-461. 1944. 

16. Harris, G. H. The effect of climate in British Columbia on the chemical 
composition of tomatoes. Sci. Agr. 21, 679-683. 1941. 

17. Hester, J. R., and KouHman, E. F. The influence of soil type and fertilization 


upon the yield and composition of tomatoes. Soil Sei. Soc. Amer. Proce. 5, 
281-283. 1940. 

18. Hester, J. R., and Konman, E. F. The influence of potash fertilization upon 
yield and quality of tomatoes. Amer. Fert. 93 (11), 5-8, 24, 26. 1940. 

19. Hester, J. R., and KoHman, E. F. Manganese and vitamin C. Science 93, 
401. 1941. 

20. Key, K. M. The determination of vitamin C in diploid and _ tetraploid 
tomatoes. Biochem. Jour. 27, 153-156. 1933. 

21. Lo Coco, G. Composition of Northern California tomatoes. Food Res. 10, 
114-121. 1945. 

22. Macuinn, W. A., Feviers, C. R., and Buck, R. E. Tomato variety and strain 
differences in ascorbic acid (vitamin C) content. Amer. Soc. Hort. Sci. 
Proc. 34, 543-552. 1937. 

23. Maciinn, W. A., and Fruiers, C. R. Ascorbic acid (vitamin C) in tomatoes 
and tomato products. Mass. Agr. Exp. Sta. Bul. 354. 1988. 

24. McCottum, J. P. Some factors affecting the ascorbic acid content of to- 
matoes. Amer. Soc. Hort. Sei. Proc. 45, 382-386. 1944. 

25. McCoitutum, J. P. Effect of sunlight exposure on the quality constituents of 
tomato fruits. Amer. Soc. Hort. Sci. Proc. 48, 413-416. 1946. 

26. McHenry, E. W., and Granam, M. Observations on the estimation of 
ascorbic acid by titration. Biochem. Jour. 29, 2013-2019. 1935. 

27. McIntosH, JENNIE. Some factors affecting the vitamin C content of tomatoes 
and rutabagas. Maine Agr. Exp. Sta. Bul. 391, 320-321. 1938. 

28. Murnerek, A. E., and Wirrwer, 8. E. Some factors affecting ascorbic acid 
content of apples. Amer. Soc. Hort. Sci. Proc. 51, 97-102. 1948. 

29. Murpuy, ExuizasetH F. The ascorbic acid content of different varieties of 
Maine grown tomatoes and cabbages as influenced by locality, season, and 
stage of maturity. Jour. Agr. Res. 64, 483-502. 1942. 


24 


30. 


3l. 


32. 


33. 


34. 


30. 


36. 


3. 


38. 


3g. 


40. 


41. 


BULLETIN No. 573 


PerxowitTz, L. P., et al. The carotene and ascorbic acid concentration of 
vegetable varieties. Plant Phys. 19, 615-626. 1944. 

Rew, Mary E. The effect of light on the accumulation of ascorbic acid in 
young cowpea plants. Amer. Jour. Bot. 25, 701-711. 1938. 

Reynarb, G. B., and Kanapaux, Marcaret 8. Ascorbic acid (vitamin C) con- 
tent of some tomato varieties and species. Amer. Soc. Hort. Sei. Proc. 41, 
298-300. 1942. 

Rosinson, W. B. The effect of sunlight on the ascorbie acid content of 
strawberries. Jour. Agr. Res. 78, 257-262. 1949. 

SANSOME, F. W., and Zitva, 8. 8. Polyploidy and vitamin C. Biochem. Jour. 
27, 1935-1941. 1933. 

SaNsoME, F. W., and Zitva, 8. 8. Polyploidy and vitamin C. Biochem. Jour. 
30, 54-56. 1936. 

Suivrina, A. W. A study of vitamin C and provitamin A (carotene) in 
tomato varieties. Bul. Appl. Bot., Genet. Plant Breeding (U.S8.8.R.) Sup. 
84, Vitamin Prob. 2, 128-141. 1937. (Chem. Abs. 33, 1366; 1939). 

Somers, G. F., Hamner, K. C., and Netson, W. L. Field wlumination and 
commercial handling as factors in determining the ascorbic acid content of 
tomatoes received at the cannery. Jour. Nutr. 30, 425-433. 1945. 

Somers, G. F., Ketty, W. C., and Hamner, K. C. Changes in ascorbic acid 
content of turnip-leaf discs as influenced by light, temperature, and carbon 
dioxide concentration. Arch. Biochem. 18, 59-67. 1948. 

Somers, G. F., Hamner, K. C., and Keituy, W. C. Further studies on. the 
relationship between illumination and the ascorbic acid content of tomato 
fruits. Jour. Nutr. 40, 133-143. 1950. 

Tree, F., Sarrerrimrp, G. H., and Houmes, A. D. Varietal differences in the 
vitamin C (ascorbic acid) content of tomatoes. Jour. Home Econ. 29, 
258-262. 1937. 

VESELKINE, W. V., et al. Influence de la lumiére sur la synthése des vitamines. 
(Russian with a French summary). Bul. Inst. Sci. Leshaft (Leningrad) 
17-18, 389-404. 1934. 


3M—4-54—54377 


AUTHOR INDEX 


AUTHOR INDEX 


BULLETIN NO. 


Se TEE LDA LONG eet eS ge eee a See a ae Re le”, 564x572 
GS BSS ie a le ie, enn Lae Geary SOR igs TYE 559 
SREP OE ek Si oil's a ose ae hea oslo Dee 560 
eee TR cP tral got Shera oe Vick ol ud Seek Bahl s 6, Pte RO ee 
EE Oe cy Gok Tae a1 SW ete Fa we OR wks 564, 566, 571 
SME Bees ed Sr rye ac ot Re Ge ie Oe Moet aA A ew 568 
See MIE NNO, eee gah oS ik on Me ah oemasaien. ay Alls) lon ah NGMMMLA bowl Moly as 561 
SE OE Lorine Cee Ge Si ee ee OU Nee UN oneins Cte ied 565 
SSE MEN Sn ER, 2. ae oe ae ae oR ee ae 2 ee as 565 
eee ALT e Tete re i a vie shes Kerang: a, muh tom, » § on weal abe ca het 570 
eee Le) Va ee Meee ee eee le tao eee Oe oe 567 
Ney MRE ety AAT ORR OEE dS oc os ie ve ghd oe, bed a OES to tad ee Se 564 
ee laa ay 1 Mpg Pak Sages Boy a ane reas On ees dhe ee 560 
RMS TOSSES See Red oO os oa, ORS gg ad on HOE On ioe 559 
PMO VIA Ee RRR go eel ea ln od kee aL hae Pe EERO cas 561 
Perera PC CGS Ute Lame perme Sr cies Sa og ue w vw nd WR ee ak 573 
Oe ee ee iO ag iw i on ge a ho CS ela Bee J oli 570 
Deas eg ee Ce EO LMT ia eiaF ena sp eccw oO sk ek gee ate 564, 571 
rere eei ee aR FeV Ve ee Ee hg wi ok Sins sage rg atu Ales 563, O72 
Pe eee AY ede ee PR OP od oy tp Ss si alas’ o'eiel oP» PQtetaly Rh vd ene 559 
OEE Esco egg BL Gee Aa a Ae ga ee 567 
ik Wedges o BAL) 68s pai 2 ee ae a rer ee stan ee eee ae ee en 562 
(SN A Sa SMe Ee ee ee ee ee 564, 571 
De ee Ee er hi ee ing again « Rika awate Ba diets wi Slay. 564, 571 
ee ee ae A ee ee is 8 ny yl aAd Sate Ore ae Gam Raw de Dwi se 559 
eR ENON CENT FU LOE ee ee yi han che edt «halk ew igs as ed Piste Fe ee RYE) 
Ok OV MICE 62 Sa aR Se Pea ae rep ee a Ee 558 
Se Se 2th iar) shee) ale! me Rh Tanke oa AIK, woot Gante Ck ae 569 
ENP ae en a ns , s heer. ce Seals Clots PM eee bea ae 567 
EGG ie SINS ER CRY OS RF cand: Po A i Para 564, 571 
ELE Ba aes ee tt ee ENE ee Flies aan w ens a8 566 
Ue ee te ewe ee ay ene yh Se, EP esa, ote ag Mase fi Sie 9) a1 vale, 98 570 
IEE 2 Wet gl met PRI eS Bok eR op eS oa Sp acdreress 558 
RR CPCS 00s Se Orr tn MCE tN Pe i LENG Uh dhl NS gn iy Kk ety ww: 5 562 


Ie (Pity ee eee ty oar eee, ole Dau eS ee 563, 569 


SuBjJEcT INDEX 


UE EE Coles LINGTS) Tee 


Bulletin and page 


ASCORBIC ACID IN TOMATOES, FACTORS AFFECTING THE CONTENT OF......... 573 
effect of bagging on fruit development. ........6.6s...... .. sn 12 
seasonal ‘VariatiOM iy 5 6 65 fe Ge wings ohh © Gd ub.» 9 a Weole ons ws eae IS 
variation between shaded and unshaded fruits.............055. 55 oe ee 8 

ASPARAGUS RUST IN ILLINOIS, AN INVESTIGATION OF ITS CAUSAL 

AGENT AND ITs CONTROL: 22)... 5..0.50 h85 bid bie 5 3 oct ce 559 
research on disease and pathogen under Illinois conditions................... 16 
review of literature. .62..6 48) bk ca 4 ea A ae 3 ee ae ee -) 

Barns, dairy, economic and functional characteristics of.. ..,..., 5 -:)3 eee 570 

BROWN Swiss: BREED, COMPOSITION OF HERD MILK OF... 1 2...2- eee 567 

Buildings, dairy, economic and functional characteristics of................... 570 

Combining sweet corn seed (is... . S240 aoc ek. ees 3 50] mas 

CorRN BORER NUMBERS, REDUCTION OF FROM OCTOBER TO 

JUNE, A/TEN-YEAR STUDY). 22 oc be5 24 dedu le 0.1 ve ob 566 

Corn, developmental morphology of vegetative and floral shoots of............ 568 

CORN HYBRIDS, EXPERIMENTAL, 1952 TESTS. 4.5.0.1... .5 2.55 563 

CORN Hyprins, EXPERIMENTAL,.1953 TESTS. 7.2... 2... se ee 572 

Corn picker 
for harvesting sweet corn seed 5.00... a6 nv a Pe Se eet oo ee 561, 14 
for reducin? numbers of corn borers:, |... =..24.¢...--- 566, 7 

Corn‘sheller damage to sweet: cotn seed. 3.4... feeed xe = er 561523 

CorRN ‘Tests; ILLINOIS, 1952.05 0. on wc 564 
qlis€ases 2 Ok bala oe Ch see ni Sep oe At ee 7 
Insect damage. . g..ws sali uly wd we ton sw chew ee Sea wer ape ae 2 ee 6 
soil and planting rate adaptation test. -.>...........sa2s. 578) 26 
Variety testS 0.6 cb oe ines 2b hous ee ete ee es ard. een ae er 14 

Corn: Tests, ILLInors; 1953 22. nee ceili cee ee ee 571 
CISCASES (0. Siew ki. seca et center is one soe elm anders Wile ad goal orn ee ce rrr 9 
fUNGICIMES bs ono whee ocr daly a's eas Ue ale AR eerative sloth ae errr i 
msect. damage... 6 sels aoe ee ess wie wip ee via mis ele ov os ee 6 
soil and: planting rate adaptation test... ....2........ 2.110.) eee 25 
Variety, CeStS i.e cc, aco Bn winca.s Bele eee el EO Sr cee OS er 16 

Corn, sweet, see Sweet corn 

Crop ‘system, effect on earnings... .. 2.22. se0 98 a4 vee ee 503, 

DaiIRY BUILDINGS, FARM, ECONOMIC AND FUNCTIONAL 

CHARACTERISTICS OF i, 2. sages oy Sharcaety me ns 2 ale ieee aac. le 570 

Diseases: OF COL ties. oc Pk Slows 6 oe ee a ee 564, 7; 571, 9 

|b 6, <a ee ee Ct ee OM ary get Oe 564, 129°S7ive 

EARNINGS: WHY SOME FARMS EARN MorRE THAN OTHERS.................. 558 
efficiency: fACtGrs 2 cc). 8 cs. soas 0 Gps. 40 ho Sse ts va eer ahh oe a 8 
how some increased earnings... 2... ees we ease sus sou ss 30 
volume of business... sii.) os. coe bebe vhs meena aviv ee 28 

FOREST RESOURCES AND INDUSTRIES OF ILLINOIS..,........... 5. 562 
iNCUStTIES 6%. basa as Rolle gate 5d oR 8 She Ree ete 50 
program to increase forest returns.........:..5.¢...+.0.... 5.02 oe Ee 
resOUrCes . . hind Pen PO a eee sls a Deena VS fae ae ee 19 
trends in timber volume and stand composition.:............. 49) e eee 67 

GALVANIZED ROOFING, WEATHERED, DURABILITY OF PAINTS ON............. 565 

Grain crops, effect of yields on earnings................. 0... .. ee 553) aib 

Insects 
attacking: corniin 1952 2.3... wales conn Gate sels ae 564, 6 
attacking corn:in 1953). ¢ 0.0... Avless s slew eas as es er 57150 

Labor costs 
effect: OM GarniNngs 1620s ee kes Lae oh Wed ee ee 558, 18 
requirements‘for milk plants; .viio.. J. i on. woes 6 560, 9 


Livestock, effect of amount and efficiency in producing on earnings......... 558, 14 


Supyect INDEX 


MAIzE, DEVELOPMENTAL MORPHOLOGY OF THE VEGETATIVE 


OE REIS Uae s Cg a ee Seas al id i eR Aen SC oe 568 
Ninmotbrowh owiss breed; Composition Of, 6... cick ace bew Ore vec ey Sakae ete 567 
Mice PLANT OPERATION, MEASURING EFFICIENCY OF. ..;0.6.-0--6.s.00054.! 560 

Creat OCW DIAULS esata £4 ibis i caeck aca eS LA IRRN fay Solt Wah ee es 25 

MRL SE ae re a TENE SNe. gi canis (oozing a auitelard Vince BR Wedel ack 8 ok day 6 

EE PEROT STIL G ee om es kis oe AME re ee. eas renee et RE elt PIR aM alo a 8 
pee ee (LIP Mh e Ue ie ae oko uc ah Se aww ok Nhe ke eA a eae 5042107 laa ke 
Paints, durability of on weathered galvanized roofing................00eeeeee 565 
Plowing, effect on reducing corn borers numbers. ..............0.0 cece eues 566, 8 
Fumeranu machinery costs, effect’on earnings: .. 1.6.35. 6.e8. cee es eae hehe ly 
lereCeIved CileCt ON GAFMINgGS. oi). Andi bia ewe Fb ee eae ew oe 553;315 
ERMINE ENOS OL COTTER kis Fcc Fo2 xt AK ist Mabe a. es Sieve ene Pde wp 3 eRe 564, 7; 571, 9 
PST ARK RU) Ww LT OLS yr os. 2 each nw cs ah ore eos loe Ca Rael cea adh 569 
aeRO Peak, PEM 6 wales, «sin Pik es EKG wow ok 504,010.57 1.512 
SE OHS VERE fe |. oF haba oo ses Roo le Cha we here 5645105575, 10 
SWEET CorRN SEED, PHYSICAL DAMAGE TO CAUSED BY MECHANICAL 

PE VESTING AND SUBSEQUENT PROCESSING. < .¢ .5.406 ose a diese wh wis ae Sms oe 561 
Timber, see B562, FOREST RESOURCES AND INDUSTRIES OF ILLINOIS 
Tomerees; factors affecting content of ascorbic acid In........0..sene- ese aes 573 


Vitamin © itt tomatoes...<.... «. Be gee ey oN ae a oo a, Se eR Ree a 573 


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