THE EFFECTS OF FIELD SPRAYS' OF MALEIC HYDRAIIDE
ON THE STORAGE LOSSES AND COOKlNG
QUALITY OF PQTATO TUBERS

M for flu Dean. of Ph. D.

MICHIGAN STATE UNIVERSITY

E. Lalekan Ayokunnu Art
1962

 

fESlS

0-169

This is to certify that the
thesis entitled
The Effects of Field Sprays of Maleic
Hydrazide on the Storage Losses and

Cooking Quality of Potato Tubers.

presented by

E. Lalekan Ayokunnu Are

has been accepted towards fulfillment
of the requirements for

Ph.D. degree in Farm Crops

,fl/Qz:

Major professor

Ma1612

 

     
 

LIBRARY

Michigan State
University

    

 

 

 

 

THE EFFECTS OF FIELD SPRAYS OF MALEIC HYDRAZIDE
ON THE STORAGE LOSSES AND COOKING

QUALITY OF POTATO TUBERS

By ‘

M
E. Lalekan Ayokunnu Are

AN ABSTRACT

Submitted to
Michigan State University
al fulfillment of the requirements
for the degree of

in parti

DOCTOR OF PHILOSOPHY
Department of Farm Crops

Year 1962

Approved W

 

ABSTRACT

QUALITY OF POTATO TUBERS
By E. Lalekan Ayokunnu Are

The objectives of the investigation were to determine:
the types of weight losses in stored potato tubers from
maleic hydrazide treated plants, and the effect of maleic
hydrazide on the cooking quality of such tubers.

Kennebec and Russet Rural potatoes were grown in several
plots in 1960 and 1961. Half of the plots were sprayed with
the diethanolamine salt of 6—hydroxy-3—(2H)—pyridazinone,
i.e. MH—30, at blossom drop.

Yields and specific gravity of harvested tubers were not
altered by MH-30.

Tubers from untreated and maleic hydrazide-treated
plants stored at 410 F. lost 6.5% and 4% dry matter, re—
spectively. Few sprouts were formed. At 600 F., tubers
from maleic hydrazide-treated plants where few sprouts were
formed and untreated plants with many sprouts lost 5% and
22% of their dry matter, respectively. Half of the dry

matter loss in control tubers was due to sprouts. About

 

 

 

 

E. Lalekan Ayokunnu Are

19% of the initial crude protein content of tubers from

untreated plants was lost in sprouts. Maleic hydrazide did

stored at 410 and 700 F. In limited trials, maleic hydra—
zide-treated tubers conditioned a week faster than untreated
tubers at 700 F. There was a direct correlation between

the amount of total sugar in the tuber and the color of
potato chips produced from such tubers. Chips of acceptable
light color could only be made from tubers containing 0.05%

or less of total sugar.

 

 

 

 

THE EFFECTS OF FIELD SPRAYS OF MALEIC HYDRAZIDE
ON THE STORAGE LOSSES AND COOKING

QUALITY OF POTATO TUBERS

BY

E. Lalekan Ayokunnu Are

A THESIS

Submitted to
Michigan State University
al fulfillment of the requirements
for the degree of

in parti

DOCTOR OF PHILOSOPHY
Department of Farm Crops

Year 1962

VQ‘O

Io[ Islez.

Dedicated
to
my mother, Christiana Nihinlola Alabi
who encouraged me as a boy
and to
my cousin, Amusa Olaniyi Lawal Are

who inspired me as a man.

 

 

 

 

ACKNOWLEDGEMENT

The author wishes to express his profound gratitude to
Dr. S. T. Dexter and Dr. D. R. Isleib for their valuable
assistance, suggestions and interest throughout the inves—
tigation and their helpful advice in preparing this thesis.
The author is also very grateful to Drs. D. H. Dewey,
E. J. Benne and C. L. Bedford for their kindness in allow-
ing me the use of their laboratory facilities.
Sincere thanks are also extended to Dr. N. R.
Thompson, Dr. R. S. Baudurski, Dr. C. M. Harrison, Dr.
R. R. Dedolph, Dave Maclean, Leslie Wilcox and John Showers
for the various assistance rendered and to Mrs. Jody Levi
who typed the first copy of the thesis.
Finally, immense gratitude is extended to the manage-
ment of the Western Nigeria Development Cooperation,
Ibadan, Nigeria, for their generous scholarship which made
the study possible and to the chairman, Mr. Alfred Ogbeyiwa
Rewane, for his encouragement throughout my stay in the

U.S.A.

   

 

 

 

 

 

 

TABLE OF CONTENTS

Page
LIST OF TABLES . . . . . . . . . . . . . . . . v
LIST OF FIGURES . . . . . . . . . . . . . . . . viii
INTRODUCTION . . . . . . . . . . . . . . . . . 1
REVIEW OF LITERATURE . . . . . . . . . . . . . 4
MATERIALS AND METHODS . . . . . . . . . . . . 24
RESULTS . . . . . . . . . . . . . . . . . . . . 33
DISCUSSION . . . . . . . . . . . . . . . . . . 89
SUMMARY AND CONCLUSIONS . . . . . . . . . . . . 95
LITERATURE CITED . . . . . . . . . . . . . . . 98

iv

 

 

 

 

 

 

LIST OF TABLES

Table Page

la The weight of sprouts expressed in grams
per kilogram initial fresh weight, after
various periods of storage . . . . . . . . . . . 34

lb Sum of evaporation and respiration losses from
tubers and weight of sprouts expressed in grams
per kilogram initial fresh weight, after
various periods of storage . . . . . . . . . . . 43

2a Chemical composition of potato tubers and
sprouts from untreated and treated plants
determined between the third and sixth months
of storage and expressed in grams per kilogram
of initial fresh weight of sample . . . . . . . . 45

2b Chemical composition of potato tubers and
sprouts from untreated and treated plants
determined between the third and sixth months
of storage and expressed in grams per kilogram

of initial fresh weight of sample . . . . . . . . 47
3 Yield and specific gravity of Kennebec and

Russet Rural tubers from plots sprayed and

unsprayed with MH-3O . . . . . . . . . . . . . . 49

4a The weight of sprouts expressed in grams per
kilogram initial fresh weight, after various
periods of storage . . . . . . . . . . . . . . . 50

4b Evaporation and respiration losses from tubers
expressed in grams per kilogram initial fresh
weight, after various periods of storage . . . . 52

40 Sum of evaporation and respiration losses from
tubers and weight of sprouts expressed in grams
per kilogram initial fresh weight, after
various periods of storage . . . . . . . . . . . 53

   

 

 

 

 

 

Table Page

5 Evaporation and respiration losses from
tubers stored at 41° F. and 90-95% relative
humidity for 15 weeks in respiration pails
expressed in grams per kilogram initial fresh
weight, after various periods of storage . . . . 60

6 Evaporation and respiration losses from tubers
stored at 70° F. and 70% relative humidity for
15 weeks in respiration pails expressed in
grams per kilogram initial fresh weight, after
various periods of storage . . . . . . . . . . . 61

7 The weight of sprouts from tubers stored for
15 weeks in respiration pails expressed in
grams per kilogram initial fresh weight, after
various periods of storage . . . . . . . . . . . 61

8 Components of weight lost by tubers during the
15 weeks of storage in respiration pails
expressed in grams per kilogram initial fresh
weight and expressed as percent of total
weight loss . . . . . . . . . . . . . . . . . . . 63

9 The effect of tuber size on the rate of respi—
ration of potato tubers stored at 700 F. and .
70% relative humidity . . . . . . . . . . . . . . 64

10 Evaluation of potato chips made from potato
tubers from treated and untreated plants during
the storage period . . . . . . . . . . . . . . . 72

ll Potato chip color score during conditioning at
700 F. and 70% relative humidity of tubers pre—
viously kept at 41° F. and 90—95% relative
himidity for 15 weeks . . . . . . . . . . . . . . 73

12 Evaporation and respiration losses from tubers
and weight of sprouts produced during the con—
ditioning period at 700 F. and 70% relative
humidity of tubers previously stored at 41° F.
and 90-95% relative humidity for 15 weeks . . . . 78

vi

   

 

 

 

 

Table

13

14

15

16

17

18

 

Page

Components of weight loss during the condi—

tioning period at 70° F. and 70% relative

humidity of tubers previously held at 41° F.

and 90—95% relative humidity for 15 weeks . . . . 78

The relationship between the amount of total

sugar expressed as percent of fresh weight of

tuber and potato chip color score, at the

beginning and end of conditioning at 70° F.

and 70% relative humidity of tubers previously

stored at 41° F. and 90—95% relative humidity

for 15 weeks . . . . . . . . . . . . . . . . . . 82

Color, flavor and texture scores of boiled

potato tubers made at monthly intervals from

tubers stored at 41° and 700 F. for 5 and 3

months respectively . . . . . . . . . . . . . . . 83

Dry matter losses from tubers and sprouts from

the end of the third month to the end of the

sixth month in storage at 410 F. i 2° and 600 F.

in the 1960-61 experiments . . . . . . . . . . . 85

Dry matter losses from tubers in respiration

and from sprouts in 15 weeks at 41° F. and

90—95% relative humidity and 70° F. and 70%

relative humidity expressed in grams per kilo—

gram initial fresh weight and as percent of

total dry matter loss . . . . . . . . . . . . . . 86

Dry matter loss from tubers during conditioning

at 70° F. and 70% relative humidity expressed

in grams per kilogram initial fresh weight and

as percent of total dry matter loss . . . . . . . 87

 

LIST OF FIGURES

Figure Page
1 Apparatus for measuring CO2 production of
potato tubers . . . . . . . . . . . . . . . . . . 35
2 A comparison of the condition of Russet Rural

and Kennebec MH—tubers and control tubers after
6 months of storage at 60° F. and 70% relative
humidity . . . . . . . . . . . . . . . . . . . . 36

3 A comparison of the condition of Kennebec and
Russet Rural MH-tubers and control tubers after
6 months of storage at 410 F. t 2° and 85—90%
relative humidity . . . . . . . . . . . . . . . . 36

4 The condition of Russet Rural tubers after 6
months of storage at 600 F. and 70% relative
humidity and 41° F. t 2° and 85—90% relative

humidity . . . . . . . . . . . . . . . . . . . . 38
5 The condition of Kennebec tubers after 6 months

of storage at 410 F. i 20 and 85—90% relative

humidity and 600 F. and 70% relative humidity . . 38

6a Evaporation and respiration losses from tubers
stored at 410 F. i 2° expressed in grams per
kilogram initial fresh weight after various

periods of storage . . . . 41

6b Evaporation and respiration losses from tubers
stored at 600 F. expressed in grams per
kilogram initial fresh weight after various

periods of storage . . . . . . . . . . . . . . . 42

7 The condition of Russet Rural tubers at the end
of 3 months storage at 700 F. and 70 _ 2%

relative humidity . . . . . . . . 54

8 The condition of Kennebec tubers at the end of
3 months storage at 70° F. and 70 I 2% relative

humidity . . . . . . . . . . . . . . 54

viii

 

 

 

 

 

Figure

9a

9b

10a

10b

11a

llb

12a

12b

l3

14

Page

The effect of MH—3O on the respiration rate
of Kennebec tubers stored at 700 F. and 70%
relative humidity for 15 weeks . . . . . . . . . 56

relative humidity for 15 weeks . . . . . . . . . 57

. . . 58

The effect of MH-30 on the respiration rate of
Russet Rural tubers stored at 410 F. and 90—95%
relative humidity for 15 weeks . . . . . . . . . 59

The condition of Kennebec tubers stored at 410
F. and 90-95% relative humidity at the end of
15 weeks. Photographed on 2-27-62 . . . . .

The condition of Russet Rural tubers stored at
41° F. and 90-95% relative humidity at the end
of 15 weeks. Photographed on 2—27-62 . . . .

The condition of Kennebec tubers stored at
700 F. and 70% relative humidity at the end of
15 weeks. Photographed on 2—27—62. . . . . . . . 67

The condition of Russet Rural tubers stored at
70° F. and 70% relative humidity at the end of
15 weeks. Photographed on 2-27—62 . . . . . . . 67

Potato tubers photographed at the end of 3
months in storage at 700 F. and 70 i 2% relative
humidity to illustrate the loss of apical

dominance by MH—tubers . . . . . . . . 7O

Potato chips from Russet Rural tubers made at
the beginning of conditioning and at 2, 3 and 4
weeks later to show the trend in chip color

change . . . . . 74

ix

 

 

 

 

 

Figure page

15 Potato chips from Kennebec tubers made at the
beginning of conditioning and at 2, 3 and 4
weeks later to show the trend in chip color

change . . . . . . . . . . . . . . . . . . . . . 74
16 The condition of Kennebec MH-tubers and control

tubers at the end of conditioning at 700 F. and

70% relative humidity . . . . . . . . . . . . . . 76
17 The condition of Russet Rural MH—tubers and

control tubers at the end of conditioning at

70° F. and 70% relative humidity . . . . . . . . 76

18a The effect of MH—3O on the respiration rate of
Kennebec tubers during 4 weeks of conditioning
at 700 F., following storage at 41° F. for 15

weeks . . . . 79
18b The effect of MH—3O on the respiration rate of

Russet Rural tubers during 4 weeks of condition-

ing at 700 F., following storage at 410 F. for

15 weeks . . . . . . . . . . . . . . . . . . . . 80

 

 

 

 

INTRODUCTION

In the regions of the United States where the bulk of
the nation's supply of potatoes is grown, harvest shortly
precedes freezing weather, and the portions of the crop
that are utilized during the following months-—October to
May—-come from storage. Potatoes planted in spring and
harvested in fall constitute about 66.4% of the total crop
in the United States (72). About 75—80% of this crop is
stored for direct consumer use and for processing into
potato chips, french fries, and dehydrated potatoes. In
many parts of the world, storage facilities are crude and
haphazard even in regions where the tubers may constitute
a large part of the diet, and deterioration in storage may
lead to a greatly restricted food supply.

In general, potato tubers are stored to preserve their
market and culinary qualities for consumption beyond the
9rOWing season. In order to prevent the development of
Certain fungous and bacterial diseases which induce rotting,
and to retard shrinkage and sprouting, low temperatures of
380-400 F. have been generally recommended for potato

storage (67). Low temperatures slow the rate of metabolic

 

 

 

 

 

 

 

 

processes within the tuber, and there is an accumulation of
sugar, which can be rapidly decreased by re—transformation
to starch and by loss in respiration at higher tempera-
tures, e.g., 600-70o F. The accumulated sugar affects
cooking quality by causing a sweet flavor and produces dark
brown chips unacceptable to the potato chip industry.

Regardless of the varied attempts being made to pro—
perly store potato tubers, millions of dollars worth are
lost annually. Loss of weight in the stored potato tubers
is the result of desiccation, respiration and sprout growth.
Sprouting is objectionable in that it decreases the carbo—
hydrate and protein contents of the original tuber. More—
over, it also causes difficulties in washing potatoes (71).
Sprouting can be controlled by proper temperature or by
the use of chemical sprout inhibitors.

It has been claimed that maleic hydrazide is effective
in inhibiting sprouting and reducing total weight loss of
pOtato tubers in storage (35, 56). In the latter case,
fresh weight loss of the edible tuber is sometimes as great
as in the sprouted controls. Apparently, either increased
deSiccation or respiration of the treated tubers increases

loss in fresh weight and compensates for the sprout loss.

 

 

 

 

 

 

The objective of this investigation was to determine: 1)
the types of weight losses in stored potato tubers, 2) the
relative magnitude of each type of weight loss, 3) the
influence of maleic hydrazide and storage environment on
these types of weight losses, and 4) the effect of maleic

hydrazide on the cooking quality of the stored tubers.

 

 

 

 

 

 

 

REVIEW OF LITERATURE

Fundamentals of Storage of Potatoes

The dietary importance of potato tubers has led to
many investigations seeking to determine the best means of
preserving their culinary quality during storage periods.

Thompson and Kelly (70) summarized investigations in
this area. They reported that to prevent excessive shrink—
age and rotting, potato tubers should be held at 500-600 F,
and 85-95% relative humidity during the first week after
harvest to heal the bruises. After this, storage at 380—400
F. is desirable to extend the rest period and to prevent
sprouting when the rest period is over. They also reported
that the greatest shrinkage in storage occurs when sprouts
appear, due to the translocation of carbohydrates from the
tuber into the sprouts, increase in respiration rate and
large increase in water loss from the sprouts.

During storage at low temperatures, the rate of respir—
ation is reduced more than is the rate of conversion of
Starch to sugar, thus leading to sugar accumulation (67).

According to Appleman (4), good, vigorous tubers of
most potato varieties sprout first from the buds on the
terminal or seed end of the tuber. This inhibiting

4

 

 

 

 

 

 

 

 

influence of the terminal sprouts on the growth of sprouts
from the other eyes on the tuber is known as "apical
dominance.” Appleman suggested that the cause of apical
dominance was inherent in the tuber and that the degree of
apical dominance might be employed as a practical index of
vitality in seed tubers. In fact, he suggested a direct
relationship between sprout vigor and the degree of apical

dominance.

Storage in Relation To Cooking Quality

Wright §£_§1. (73) reported an increase in sugar content
as the storage temperature was lowered. This was accompanied
by the lowering of cooking quality as denoted by flavor and
texture. At temperatures below 500 and 600 F., sugars in—
creased while starch decreased. They also stored potato
tubers at 40°, 360 and 320 F. and after 6 weeks, transferred
them to 700 F. for another period of 6 weeks. They noticed
that the sugar content of those tubers previously stored at
400 F. was similar to what it had been when they were first
put in storage, while those at 360 and 320 F. had relatively
high sugar content.

Treadway et_§1, (71) observed that Katahdin potatoes

stored at 340-380 F. lost 3.8% of their starch during the

 

 

 

 

 

first 7 weeks of storage: but experienced only little addi-
tional loss as the duration of storage or temperature in—
creased. A large increase in total sugars (primarily in
reducing sugars) was found in potatoes stored at 34° and

36° F.; the greatest change taking place during the first

13 weeks in storage. Little sugar accumulation was recorded
at 38°~42° F., whereas some decrease occurred between 50°
and 60° F. With conditioning at 70° F., however, the sugar
levels became lower in those samples from warmer storage
than the levels of those stored at low temperatures.

The amount of sugars formed during cold storage of
potatoes varies with variety as well as temperature (27).
The extent of sugar disappearance which occurred on expo-
sure to higher temperature was also found to be different
in different varieties.

Appleman (3L studying the changes occurring in potatoes
during storage reported that potato tubers which accumulated

sugar during low temperature storage lost about 4/5 of that

 

sugar through reconversion to starch and only 1/5 through
respiration. (3
Appleman and Smith (5) proved conclusively that the

initial high liberation of CO2 from potatoes after a period J

 

 

 

of cold storage was due to actual respiration and not
simply to the output of excess CO2 which was dissolved in
the cold sap of the potato tissue. They also observed that
during the period of the most rapid decline in the respira-
tion rate at 86° F. of tubers previously held in cold
storage, the percentage of both total and reducing sugars
in the tubers was actually increasing. Further studies (5)
by both men revealed that in potatoes, the shifting equili—
brium between sugar and starch tended to attain stability
with widely different percentages of sugar characteristic
of the different temperature ranges. They inferred that
these carbohydrate transformations in potatoes with tem—
perature changes were the cause of the characteristic res-
piratory response with the same temperature changes. They
concluded that the high initial respiration rate in potatoes
when suddenly changed from a lower to a higher temperature
was due to the "change of temperature effect.” They

showed by experiments that this "change of temperature affect"
could be reproduced in the same lot of potatoes at least 3

times over a period of 5 months without much change in the

typical respiratory response.

 

 

 

 

 

 

 

 

 

Treadway et al. (71) confirmed that sugar disappearance
during conditioning was accompanied by gain in starch.
However, they also pointed out that the total starch con-
tent of tubers decreased progressively.

Sweetman (67) noticed that boiling, as well as chipping
quality of potatoes decreased at 400 F. storage, but that
both qualities could be partially restored after 21 days
at 68° F. The sweet flavor and off color in the chips were
attributed to sugar accumulation at levels of 0.5% or
higher of the fresh weight.

Denny and Thornton (26) found a direct correlation be-
tween the amount of reducing sugar rather than total sugars,
in the juice of potato tubers and the extent of browning
when chips were made from them.

Alexander gt_§l, (1) reported that potatoes with higher
specific gravity lost sugar more quickly than those with
lower specific gravity.

Fischnich and Heilinger (34) observed that the chemi-
cal constituents of the potato tuber were primarily related
to variety, both quantitatively and qualitatively, but that
they could also be influenced by soil fertility, climate,

disease, growing seaSOn and storage conditions. The organic

 

 

 

 

 

acid components are malic, lactic, succinic, tartaric,
citric and oxalic. The protein content of the tuber, al—
though only about 2%, was said to be highly nutritious.
Starch was suggested as the primary material respired
at a rate of 1.2 to 2.5 milligrams dry matter per kilogram
per hour (12). Changes in the starch—sugar ratio in the .
potato tubers were reported to be controlled by 3 factors:
(1) hydrolysis of starch to sugar,
(2) condensation of sugar back to starch, and
(3) oxidation of sugar during respiration.
Hensen (41) used the CO2 liberated from potato tubers
as an index of the intensity of their respiration. He
pointed out that losses in tuber weight due to respiration
were much smaller than those due to evaporation; he even
suggested a ratio of 1:10, but gave no data on the dry mat—
ter content to substantiate this ratio. Starch loss was
said to be responsible for tuber weight loss as a result
of respiration. Moisture loss was thought to depend on the
evaporation of water from the tuber skin and on the thickness

of the cork layer of the tuber.

 

 

 

 

 

 

10

Chemical Sprout Inhibitors

Chemical inhibitors have been available for commercial
application since about 1947 (68). Interest in the use of
chemical inhibitors was stimulated by the work of Elmer
(30), who discovered that volatile gases given off by
apples applied to potato tubers, produced sprouts which
developed abnormally. Several factors prompted the use of
chemical inhibitors, viz.:

a) The need for keeping potatoes sprout—free while in
transit during World War II, other than by
refrigeration (68).

b) Potato processors using deep fat frying like to
store their produce at 50° F. or higher for curing
and color control. This puts a serious limitation
on the use of temperature alone for the control of
sprouting (68).

c) Potato processors buying their produce at periods
of peak supply when prices tend to be low, need
some method other than temperature manipulation to

keep these potatoes relatively sprout-free (68).

 

d) Some high yielding potato varieties which also pos-
sess good cooking qualities have a short rest period

(69).

 

 

 

 

 

 

11

Chemical inhibitors applied as dusts on tubers or as
sprays to potato foliage have found commercial acceptance.
Numerous chemicals which are effective for this purpose
have not as yet been cleared by the federal government for
commercial use; however, maleic hydrazide was recently
given such clearance. It is noteworthy that maleic hydra-
zide has been tested more and has received a wider range of
acceptance than any other commercial inhibitor in the
United States. The greatest use of this chemical has been
with potato processors (68).

The most promising chemical inhibitors in potato re—
search programs are: tetrachloronitrobenzene (TCNB), maleic
hydrazide (MH), methyl-ester of alpha naphthalene acetic
acid (MENA), isopropyl-N-chlorophenyl carbamate (CIPC) and
amyl and nonyl alcohols (68). Irradiation is also a very
potent sprout inhibitor (68).

MH was reported to be effective for inhibiting sprout
growth only if applied during the growing season (35).
MENA, CIPC and TCNB, on the other hand, can be applied as
dusts or sprays to potatoes going into storage. Amyl and
nonyl alcohols, as well as MENA and CIPC have been applied

as gases to potatoes after they are in storage. Irradiation

 

 

 

 

 

 

 

12

has a disadvantage in that it cannot be applied to potato
tubers in the bin.

Denny et al. (25) used MENA incorporated into filter

 

papers distributed among potato tubers stored in earthen—
ware containers which were not tightly closed. The chemi-
cal was reported to inhibit the sprouting of the tubers.
Sprouting was completely prevented for 1 year by an unin-
terrupted application of 400 milligrams per kilogram of
tubers while inhibition was only barely perceptible with
10 milligrams per kilogram. The filter papers were found
effective a second time in closed containers. For one year
at 500 F., there was neither shrivelling of the tubers nor
sprouting. The treated tubers made good chips, but it
could not be recommended then for commercial use as the
amount of the chemical in the tuber was not known.

Denny (24) in a later experiment found that not more
than 5 mg. of the MENA was taken up by the tissues treated
with 100 mg. per kilogram for 5 months. Of the 5 mg., 4/5
was in or on the skin of the tubers. The tubers, however,
did not sprout properly when cut and planted, not even when
treated with ethylene chlorhydrin.

Sawyer and Dallyn (62) showed that the application of

 

 

 

 

 

 

 

l3

vaporized chemical inhibitors gave excellent sprout con—
trol with potatoes. Good results were obtained with CIPC

at 250 mg. per bushel and with MENA at 500 mg. per bushel.
Gaseous application was less expensive and gave better
control of shrinkage and less sprouting than dust or aerosol
application. It is free from dust, which is a problem with
aerosol formulations.

Talburt and Smith (68) summarized that a gas applica—
tion of MENA, CIPC and the alcohols (amyl and nonyl), had
many advantages over the other methods of sprout control
since the application may be delayed until a definite need
arose for sprout control. The effects were longer lasting
with such delayed application in storage than from an appli-
cation of the same material at harvest. They further
pointed out that all of the other methods of sprout control,
which required an application before a need arose, were
wasted during years when the rest period and cool storage
temperatures were sufficient to keep the tubers in good
condition for the storage period.

A characteristic common to all chemical inhibitors is
that the mechanism that prevents cell division for sprout—
ing, also prevents cell division for wound periderm forma-

tion (68).

 

 

 

 

 

 

l4

ggperal Effects of Maleic Hydrazide

Maleic hydrazide (MH) is commonly used in the form of
the diethanolamine salt (MH-30) or as the sodium salt
(ME-40) of 6-hydroxy—3-(2H)—pyridazinone. MH has been
extensively evaluated and found to:

a) inhibit cell division but not cell expansion (31),

b) reduce respiration rate (44, 55),

c) destroy apical dominance (47, 56), and

d) to behave as an anti-auxin (7).

Schoene and Hoffman (63), working on tomatoes, turf
and corn, described maleic hydrazide as a unique growth
regulant. Since their work, many experiments have been
performed and MH-3O has been shown to be both a plant growth
inhibitor and a herbicide (75). It has found extensive use
on many crops and was found to be relatively non—toxic to
mammalian tissue (75). In fact, MH—30 applied at a rate of

1 gallon per acre on potatoes, showed no diethanolamine

 

residue in the tubers (14).

MH functions as a herbicide by preventing the regrowth
of rhizomes (ll), preventing flowering and inhibiting ger—
mination to control annual weeds such as sandbur grass and

Wild oats (13, 53). Since MH is most active against young

 

 

15

vigorously growing plants, it exerts selective control on
young weeds among mature plants.
As a growth inhibitor, MH inhibits cell division with-

out affecting cell expansion (31). It also prevents the

 

growth of suckers in tobacco and increases the yield of
tobacco leaves (10). It finds application on lawn grasses
where it reduces the frequency of mowing by reducing grass
growth (76). Inhibition in grasses (22), however, shows
variable response possibly due to the differences in rate
of absorption which can be correlated with relative

humidity (65).

 

MH inhibits sprouting of radish (28), sugar beets (74),
potatoes (56) and onions (56). Other effects of MH include:
inhibition of terminal growth to force axillary buds for
increased flower production of Chrysanthemums (9), reduc-
tion of respiration to decrease storage losses of sugar in
sugar beets (74), suppression of apical dominance and bolt-
ing in vegetables (7), increase in percentage of protein in
forage grass (64) and production of male sterile cucurbits

(43), sorghum (52) and corn (54).

 

 

16

Effects of MB on Potatoes

Many papers have reported the effects of MH on potato
tubers. Dipping potatoes in MH solution was demonstrated
to be ineffective in reducing sprout growth although it
checked fungous infestation (16, 32). This indicated that
the chemical was probably not absorbed by the tubers.
Marshall and Smith (51),however, working with Green Moun—
tain potatoes, reported that a toothpick application of
0.25% MH by puncturing the tuber prevented any sprout from
developing.

Experiments indicated that only a field spray appli—
cation on potato vines was effective in retarding sprout
growth of tubers in storage (35, 56). Later work showed
that the time of application was very critical. Kennedy
and Smith (47) observed that sprays applied early in the
growing season caused increased tuber set and decreased
yield. Other workers (56, 58) reported that satisfactory
sprout control could be obtained from MH sprays applied
several weeks before harvest. Sawyer and Dallyn (62) and
Denisen (23) found a blossom drop (i.e., 8 days after full
bloom) application most satisfactory as it gave less

detrimental effects to the tubers than earlier sprays.

 

 

 

 

 

 

 

 

 

l7

Isleib (45) working with Arenac, Kennebec, Russet Rural,
Merrimack and Golden Chipper, observed that spraying 7—12
days after full bloom led to no reduction of yield or
specific gravity of the tubers. In general, foliar spray
applications of MH applied at blossom drop or 6 weeks
before harvest of the tubers have been found to inhibit
sprouting in tubers and to give no reduction in yields and
no significant difference in the specific gravity of the
tubers either before or after 5 months of storage (23, 35,
47, 58). A few workers (8, 15), however, did not obtain
the above mentioned effects.

Accompanying a reduction in sprout growth and total
weight loss in storage was the fact that there was an in-
crease in the number of buds showing activity (47).

Paterson (56L applying a foliar spray of 500, 1000 and
2500 ppm of MH 1-7 weeks prior to harvest to Irish Cobbler,
Pontiac, Russet Rural and Sebago potatoes observed that
apical dominance of both tubers and individual sprouts on
the tubers was destroyed. Paterson and Rao (56, 58) re-
ported that the apical region of each tuber had complete
Sprout inhibition as contrasted with the basal region where

incomplete inhibition was observed.

 

 

 

 

 

 

 

18

Highlands et al. (42) treated Kennebec and Katahdin
potatoes in Maine with 1000 and 2500 ppm MH,37, 27 and 20
days prior to harvest. After storing the tubers at 40° F.
for 6 months, he found no significant differences in chip
color or in reducing sugar content in tubers from treated
and untreated plants. These results were confirmed by
other researchers (48, 56).

Salunkhe and Wittwer (61) failed to obtain the above
mentioned results. They reported potatoes treated with MH
yielded golden yellow chips of good flavor and texture as
compared with the burnt, dark brown and bitter chips pro—
duced from control tubers.

Klein and Leopold (49) suggested that MH acted as an
auxin competitor in the presence of true growth regulators
(indole acetic acid for example), increasing growth by as
much as 30% at 1 ppm and inhibiting growth at high con— '
centrations. PaterSOn (56) confirmed the growth promoting
aspect of MH when he observed that low concentrations of
MH applied shortly before harvest, in fact, stimulated
Sprout growth on potato tubers.

Greulach and Haesloop (38) reported that inhibition of

cell division by MH accounted for practically all the

 

 

19

observed growth inhibition. Further work by Greulach (37)
showed that MH definitely inhibited cell division but that
'I
its effects on cell enlargement were varied, gfthough the
cells in treated plants were often larger than those in
controls. The amount of xylem and lignified interfasci-
cular tissue was also greatly reduced, due to the inhibi—
tion of secondary meristematic activity. Maleic hydrazide
may also have an effect on cell differentiation, as indi- 5
cated by the fact that Greulach found guard cells ceased
growing in various stages of ontogeny in treated bean and
sunflower leaves, as well as a greatly reduced number of
stomates per unit area. Other physiological effects of MH
reported include: accumulation of carbohydrates, lowering
of protein content and increasing non-protein nitrogen
compounds, particularly leucine, and reducing the rate of
transpiration from leaves.

Darlington and McLeish (20) working with MH on the
mitosis of Vicia faba roots reported complete cessation of
mitosis for 2 days in roots in water solution concentrations
above 0.0005 M NH for 24 hours at 53.60—60.8O F. Lower concen—
trations, however, did not stop mitosis, but breakage of

chromosomes at mitosis was seen.

 

 

 

 

 

 

20

Inhibition of respiration by MH was reported by Naylor
and Davis (55). Working with the root tips of peas, sun-
flower, corn, barley, tomato, oats and wheat, they sug-
gested that MH possibly exerted its influence on growth by
inhibiting respiration perhaps by affecting the normal
function of dehydrogenase.

The results of Isenberg's study (44) support the con-
clusion that the principal effect of MH is the modifica-
tion of the respiratory activity of the plant. The
modification is said to be twofold in nature: low concen—
tration of applied sprays stimulate respiratory activity,
while high concentrations reduce or inhibit respiratory
activity. This change in respiratory rate is generally
accompanied by undesirable morphological changes in actively
growing plants. These changes were not apparent in storage
organs such as tubers and bulbs, although respiratory
changes were detectable.

iFischnich et a1. (33), working with potatoes and
Jerusalem artichoke sprayed with MH before or during bloom,
concluded that MH exerted a strong retardation effect upon
growth and development of plants. The action presumably

depends upon a strong inhibition of metabolic processes,

 

 

 

 

 

 

21

of respiration, as well as upon the inactivation or de-
struction of natural growth substances.

An anti—auxin action has been suggested by Audus (7)
for MH. He also reported that growth inhibition caused
by ME was relieved only by high concentration of IAA,
indicating a mutual competition for the growth centers.
MH was also found to inhibit cell division but not cell
extension, and had no significant effect on indole acetic
acid levels in growing tissues except at 10°3 M concen—
tration. Audus also stated that many observations showed
thatAcarbohydrate metabolism was seriously disturbed by
MH treatment in many different tissues. Such disturbed
metabolism was usually characterized by an increase in
sugars at the expense of polysaccharide reserves. It was
also reported that some workers, however, showed that in—
crease in sugars had no direct connection with growth in-
hibition. Petersen and Naylor (57) working on some meta-
bolic changes in tobacco stem tips treated with MH proposed
that a blockage of carbohydrate utilization might necessi-
tate drawing on proteins as a source of respiratory fuel
and so disturb protein metabolism and cell division.

{
Inhibition of protein formation was also suspected.

 

 

 

 

 

 

22

Greulach (36) described work on starch metabolism of
plants treated with MH. He found that MH did not block
starch breakdown processes. He also suggested that MH
blocked either hydrolysis or phosphorolysis, but certainly
not both processes. In his second experiment, he found
that MH did not block starch synthesis in bean and tomato
plants.

Some enzyme systems are reported to be affected by MH.
These include succinnic dehydrogenase (44), peroxidase,
phosphatase and polyphenolase (40).

Inhibition of differentiation of tissue in the buds
and root primordia of tubers and bulbs was reported (58).
Sections of Irish cobbler tubers prepared after 5 months of
storage at 55° F. showed no evidence of meristematic
(phellogen) tissue in the periderm following treatment with
MH. Comparatively little activity was seen in the buds (59).

The relative humidity of the atmosphere at the time of
application markedly affected the rate of absorption of MH
(65). The most rapid absorption occurred when leaf cells
were turgid under high humidity conditions. MH from the
diethanolamine salt formulation was better absorbed than

the corresponding sodium salt at humidities above 40%.

 

 

 

 

 

 

 

 

 

23

This was probably due to the ability of the amine salt to
absorb water from the atmosphere (21).

MH moves in the phloem (19) and translocation occurs
both in an upward and downward direction from the point of
application (50).

All the investigations have shown that MH is primar-
ily an inducer of dormancy in potatoes. There are, how-
ever, conflicting reports on its mode of action, although
it appears to inhibit cell division in the meristematic
regions but not cell enlargement. A precocious maturation

of tissues also occurs (31).

 

 

 

 

 

 

 

MATERIALS AND METHODS

The experiments were conducted between May 1960 and
May 1962. Two recommended potato varieties in Michigan,
Kennebec and Russet Rural, were selected for use in the
experiments. They were grown at the Lake City experi—
mental station during both 1960 and 1961. The potato
vines were hand sprayed with MH—30 at a rate of 1 gallon
MH-30 in 100 gallons of water d.e., 3 lbs. active MH) per.
acre on August 4, 1960 and August 6, 1961. Each year
the potato tubers were harvested in October and brought
from the Lake City station to the Michigan State University

campus at East Lansing in November where they were stored.

1960/1961 Experiments

A quantity of potato tubers from the 1960 crop, care—
fully selected for lack of bruising, rot, injuries or
disease, were placed in storage for 6 months from November
17, 1960 to May 20, 1961, in the Farm Crops field labora-
tOry. There were 2 storage environments:

a) A large room in the basement of the laboratory with

a temperature of 600 F. and relative humidity of

about 70% at the start of the experiment. (In April

24

 

 

 

 

 

 

25

and May 1961, however, the temperature rose to an
average of 62° F. while the relative humidity fell
to 46%).

b) A controlled temperature room at 41° F. t2 , with
a relative humidity of 85—90%.

Each sample in storage weighed about 2500 grams. There
were 2 replications. The samples were placed in mesh bags,
which were in turn carefully placed in wooden boxes with
openings at the sides, bottom and top to permit free air
circulation in storage. Each mesh bag was numbered.

Gross weight readings were recorded at the beginning
and at monthly intervals until the end of the sixth month.
Sprout weight was obtained by difference by first weighing
all the tubers with their sprouts intact, then breaking off
all sprouts and reweighing the tubers alone. Observations
were made as regards the nature of the sprouts and the con-
dition of the tubers.

From the end of the third month in storage, a proximate
feed analysis was made on each potato sample. This
included determinations for ash, water, ether extract,
crude protein, crude fiber and nitrogen free extract (NFE).

Both tubers and sprouts were analyzed for these constituents.

 

 

 

 

 

 

 

26

In order to obtain a representative portion for chem—
ical analyses, each sample was divided into 2 lots by count,
based on the size of the individual tubers it contained.
One lot was then thoroughly cleaned with a clean,
soft cloth to remove all soil and sand particles in par—
ticular. The tubers were then cut into thin slices and
weighed to determine their fresh weight. They were placed
on trays and put in the drying oven at about 185°F. for 24
hours. After drying, the samples were again weighed to
determine the loss in weight which was expressed as
moisture loss. The dry samples were finely ground in a
Wiley mill, thoroughly mixed, and stored in bottles with
tight lids. This material was used for all chemical
analyses.

The analytical methods used were standard laboratory
procedures as described by the Association of Official

Agricultural Chemists (6).

1961/1962 Experiments

On May 9, 1961, Kennebec and Russet Rural tubers were
each planted in 11 ranges at the Lake City experimental

station. Each plot, made up of 3 rows, was 9 feet by 24

 

 

 

 

 

 

27

feet and was approximately 1/200 acre. One plot out of
every 2 was randomly chosen and was hand sprayed with
MH-30 on August 6, 1961, 10 days after full bloom. The
rate of maleic hydrazide application was, as in 1960, 1
gallon MH—30 in 100 gallons of water per acre.

At harvest in October 1961, only tubers from the middle
row of each plot were collected, tagged and bagged for
yield records. The tubers were later sorted and graded
into US No. l (1 7/8 inch minimum diameter) and the B group
(less than 1 7/8 inch). Specific gravity determinations
were made, by weighing the tubers in air and then in water,
using only US No. l tubers from each plot (46).

The tubers were put in 41° F. storage at East Lansing
on the 12th and those at 700 F. on the 20th of November
1961. Each storage sample was about 2000 grams. Only
healthy tubers were used.

Both storages had automatic devices for maintaining
temperatures at 41° and 700 F., respectively. The 41° F.
controlled temperature room operated at an average relative
humidity of 85-90%, while the 70° F. cabinets averaged a
relative humidity of 70% i 2 for the storage period.

Weighings were carried out at monthly intervals. The

 

 

 

 

 

 

28

weight of tubers and sprouts was also determined.

Storage of tubers in the 700 F. cabinets was terminated
at the end of the third month owing to excessive sprout
growth. However, tubers in the 410 F. room were held there

until April 21, 1962, i.e., for 5 months.

Respiration Studies

The method used in this experiment to measure the
quantity of CO2 evolved by the tubers was an adaptation
of the Claypool—Keefer method (17, 29). The method and the
apparatus used have been described in detail by Eaks and
Pratt, with additions by Clerx and Dewey (Fig. 1). Healthy
Kennebec and Russet Rural tubers were used. The experi-
ments were conducted in 2 controlled temperature rooms.

10,000—gram samples of US No. 1 potatoes were placed
in closed plastic pails for storage at 41° F. and 5000
grams for storage at 700 F. Each pail was fitted with
hose connections to permit an air flow rate of about 200
ml./min. over the tubers. Air from each pail was run
through the indicator solution (dilute NaHCO3 contain—
ing bromthymol blue dye) to measure CO2 production.

-Blanks were run for each period. Samples were examined

 

 

 

 

 

 

 

 

29

periodically for sprouting, mold growth and spoilage. Tuber
weights were taken and corrections made whenever a spoiled
tuber was removed. The amount of CO2 evolved was computed
and expressed as mg. COZ/Kg-hr.

The respiration experiments were started on November 13,
1961, but no reading was taken until November 20, 1961,
after which further readings were taken every 3 1/2 days-—
one at 11 p.m. on Mondays and the other at 11 a.m. on
Fridays of each week.

After 10 weeks in storage, the sprouts of all the tubers
kept at 700 F. were removed and weighed. Respiration data
were recorded for another 5 weeks before the experiment
was terminated after 15 weeks. The final weight of each
sample was recorded. The newly regenerated sprouts were
broken off from each sample and their weights recorded. The
samples (tubers and sprouts separately) were then analyzed
for dry matter content.

The respiration measurements for the tubers stored at
410 F. were also terminated after 15 weeks of storage.

Final weight readings were made for each sample. However,

a 4000—gram sample was taken from each lot and was continued

. , 0
1n respiration studies at 70 F.

 

 

 

 

 

30

When the plastic pails were opened to examine and
weigh the tubers, a tuber was removed from each sample for
cooking to determine potato chip quality. This was done
with a view of relating the respiration rate of each sample
to the rapidity of conditioning for making potato chips.

Portions were removed with a cork borer from each of
6-7 tubers. This material was preserved in 80% ethanol
for subsequent sugar analyses. A total sugar analysis was
made using the pickled tuber samples at the beginning and

at the end of the conditioning period.

Cooking Quality

This experiment was done in order to find out what
effect maleic hydrazide had on cooking quality of potatoes;
The tubers were washed with water and were cut longitudi—
nally into halves, i.e. along the axis from the apex to
the basal end. One of the 2 halves from each sample was
boiled in water for about 25 minutes. They were pierced
With a pointed instrument to determine when they were well
cooked. Samples stored under the same storage conditions
were all cooked together in one big aluminum pot divided

into 8 compartments, one for each sample. When they were

done, each sample was peeled and scored for color, flavor

 

 

 

 

 

 

31

and texture. The other half of the cut tuber was sliced
with a chip slicer. Six or seven slices were picked from
each sample and were soaked in cold water for about 10
minutes to remove adhering starch and to separate the
slices (60). Then the slices were fried until they were
sufficiently cooked in oil which had been preheated to
375° F. The slices were judged to be well fried when
bubbling stopped in the oil. That was an indication of
complete removal of water from the slices. During the
rapid evaporation of water from the chips in the frying
oil, the temperature of the oil fell rapidly to about

350° F.

Anatomical Studies
___________________

The purpose of this study was to ascertain whether
the difference in loss of water and inhibition of sprouts
in tubers from potato plants treated with MH—3O is due to
the degree of cell differentiation. After 3 months of
Storage at 70° F., 10 potato tubers showing the typical
maleic hydrazide effect of bunchy, rosette—like tiny sprouts
were selected from treated tubers. Ten tubers were also

chosen at random from the controls. All tubers were waShed

 

 

 

 

 

32 t

and scrubbed with a soft, clean cloth to remove soil and

sand particles.

With a 7/16 inch cork borer, 1/2 inch long pieces were
taken from each of the 10 tubers in each sample, usually
through the bud. After fixation and embedding, the
pieces were sliced to a 12 micron thickness with a micro—
tome, and were stained with safranine I'O," crystal violet

and orange G for microscopic examinations.

 

 

 

 

 

RESULTS
1960-61 Experiments

The results of the experiments conducted from November
17, 1960, to May 20, 1961, are shown in Tables 1a, lb, 2a
and 2b and Figs. 6a and 6b. From now on, potato tubers from
MH treated plants will be designated MH tubers; while those

from untreated plants shall be known as the control tubers.

MH Effects on Sprouting

Sprout weights expressed in grams per kilogram initial
fresh weight of the tuber samples were recorded throughout
the 6 month storage period as shown in Table 1a. Sprouting
was effectively inhibited by MH when the tubers were stored
at 41° and 60° F.

The effectiveness of MH in retarding sprout growth is
also shown in Figs. 2, 3, 4, and 5. The photographs were
taken on May 31, 1961, at the end of the storage period.
Apical dominance was lost in MH—tubers. Sprouts of MH—tubers
Were rosette—like and bunchy as contrasted with the l or 2
The basal sprouts

Vigorous apical sprouts of control tubers.

of MH—tubers were the most vigorous.

33

 

 

 

 

--—‘Ir

34

 

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named? Smwum HmfluHcH EmumoHflx Mom mEmHm CH commoHQXw musoumm mo ucmflwz wSB .MH wanme

 

 

 

 

 

 

 

 

 

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Fig. 1. Apparatus for measuring CO2 production of
potato tubers.

 

 

 

 

 

 

 

 

 

 

36

Fig. 2. A comparison of the condition of Russet Rural
and Kennebec MH—tubers and control tubers after 6 months
of storage at 60° F. and 70% relative humidity.

Fig. 3. A comparison of the condition of Kennebec and
Russet Rural MH—tubers and control tubers after 6 months
of storage at 41° F. i 2° and 85-90% relative humidity.

 

 

 

RR. MH-tubers

Ken. MH-tubers

 

RR. Ebntrol tubers Ken. control tubers

Ker MH-tubers

control tubers

Ken. control tubers RR. MH-tubers

‘ \
l
I

   

 

   

 

 

 

 

 

 

 

38

Fig. 4. The condition of Russet Rural tubers after 6
months of storage at 600 F. and 70% relative humidity and
41° F. ”5 2° and 85-90% relative humidity.

Fig. 5. Theocondition of Kennebec tubers after 6 months
ofostorage at 41 F. _ 2° and 85—90% relative humidity and
60 F. and 70% relative humidity.

 

 

 

Control tubers Control tubers

MH-Lubers MM-tubers

. . \._f‘\ ...

h1°1=. - . . .. 60°F.-

\ .‘
s l . .
l l . .
. . I a
u“ _ . I\".
l
O . .
I '- '
I. o I 1 I '

Control tubers

     

3‘.

 

.’J

     

ontrol tuber

 

 

 

 

 

4O

Wei ht Loss

Weight loss due to water evaporation and respiration

were measured by weighing the samples at monthly intervals.

The results obtained are shown in Figs. 6a and 6b.

When stored at 600 F., weight loss from the control
tubers was greater than that from the MH—tubers only after
the fourth month, but generally MH-tubers lost slightly
more weight than the control tubers when stored at 410 F.

o . .
+ 2 Higher losses were experienced by Russet Rural con-

trol and MH-tubers than their Kennebec counterparts at both

storage temperatures. However, both varieties lost more

weight at 600 F. than at 41° F. The larger weight loss of

MH—tubers stored at 41° F. i 2° appeared to have compensated

for sprout loss from control tubers. A combination of

weight loss from dessication, respiration and sprout growth

gave the total weight loss or shrinkage during the storage
period. (See Table lb.) Total weight loss was greater at

the warmer storage temperature for both varieties. The

control tubers lost more weight than the MH tubers.

The conditions of the tubers at the end of the 6 month

storage period are illustrated by Figs. 2, 3, 4, and 5.

 

 

 

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41

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HHM Hod mEmum CH commmumxw
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(Bx/5)

 

42

32° O—————4> Kennebec control tubers

A——--fl Kennebec MH—tubers

300
x—---—x Russet Rural control tubers

Russet Rural MH-tubers

Weight loss (g/kg)

 

 

Storage time in months

 

Fig. 6b. Evaporation and respiration losses from tubers
Stored at 600 F. expressed in grams per kilogram initial
fresh weight after various periods of storage.

 

‘f

 

43

 

 

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44

o
Tubers at 41 F. were firm and fresh; whereas, those at 60°
F. were wrinkled although MH tubers had a better appear-

ance than control tubers.

Chemical Composition of Tuber and Sprouts

A proximate feed analyses were made on tubers and sprouts

 

at monthly intervals starting from the end of the third
month. The results (see Tables 2a and 2b) indicated that
weight loss from tubers was primarily a result of water eva-
poration, crude protein loss and the disappearance of NFE,
i.e., the easily hydrolyzable carbohydrates.

No chemical analyses were made of sprouts from MH tubers
or from control tubers stored at 41° F. i 2°, since the
quantity of sprout produced in each case was not enough for

a proximate feed analysis.

1961-62 Experiments

Yield and Specific Gravity
Yield records and specific gravity measurements are

shown in Table 3. Results obtained showed that the MH

treatment neither reduced the total and U.S. No. 1 yield of

tubers, nor did it have any effect on their specific gravity.

 

 

 

 

 

45

Table 2a. Chemical composition of potato tubers and sprouts
from untreated and treated plants determined be-
tween the third and sixth months of storage and
expressed in grams per kilogram of initial fresh
weight of sample.

 

 

 

 

 

STORAGE Varieties ASH
and
Temp. % treatment 3rd 4th 5th 6th
oF relative month month month month
' humidity
TUBERS g/kg g/kg g/kg g/kg
41° 85—90 Kennebec control 9,4 9.,1 8.5 9.1
i: 2°
" MH—3O 9°6 9.2* 962 9.3
Russet Rural control 909 959 908 9.8
" " MH—3O 10.1 10.2 9.8 10.0
TUBERS
O
60 7O Kennebec control 9.1 808 7,9 7.3
" MH—3O 9.4* 1000* 902* -**
Russet Rural control 1000 906 8.6 8-2
" " MH—3O 1005* 9.6* 9.8 10.0*
SPROUTS
o
60 70 Kennebec control 003 008 1 2 1.5
Russet Rural control 0:4 094 1.1 1°6
* Only 1 sample available for data. ** No sample.

 

b ‘

 

46

 

 

 

 

CRUDE FIBER ETHER EXTRACT

3rd 4th 5th 6th 3rd 4th 5th 6th
month month month month month month month month
g/kg g/kg g/kg g/kg g/kg g/kg g/kg g/kg
3.9 3.4 3.8 3.6 1.5 0.9 0.7 0.9
4.1 3.6* 3.7 3 9 0.9 0.9* 1.0 0.8
5.2 4.7 4.5 4.6 1.1 1.2 0.8 1.0
4.8 5.1* 4 5 4.1* 1.3 0.8* 0.8 1.0*
4.0 3.9 3 4 3 8 0.9 0.8 0.9 1.6
4.1* 3.8-k 3.6* _~k* 008* 007* 1°8* _**
4.9 4.7 4.7 4.5 1.2 0.9 0.7 1.3
4.8* 4.5* 4.5 4.4* 1.1* 0.8* 0.6 2.3*
0.4 1.3 2.0 2.7 0.1 0.1 0.1 0.2

 

 

 

 

 

 

 

47
Table 2b. Chemical composition of potato tubers and sprouts
from untreated and treated plants determined betweai
the third and sixth months of storage and expressed
in grams per kilogram of initial fresh weight of
sample.
STORAGE . WATER
7 Varieties
Temp. . and 3rd 4th 5th 6th
relative
o . . treatment month month month monfli
F. humidity
TUBERS g/kg g/kg g/kg g/kg
o
41 85-90 Kennebec control 784.5 785.0 777.2 750.6
+ 20
" MH-30 777.8 765.7* 762.4 737.1
Russet Rural control 765.7 758.7 740.9 697.8
" " MH—30 753.0 741.5* 737.9 732.9*
TUBERS
o
60 70 Kennebec control 683.0 652.1 488.8 418.7
" MH—3O 738.8* 683.1 651.2* —**
Russet Rural control 661.2 611,8 490.1 402.1
" " MH—30 690.6* 646.5* 616.5 580.4*
SPROUTS
60°
70 Kennebec control 23.6 24,4 109°7 106.0
Russet Rural control 1609 45°1 103.3 108.6
* .
- Only 1 sample available for data. ** No sample.

 

 

48

 

 

 

 

NITROGEN FREE EXTRACT CRUDE PROTEIN

3rd 4th 5th 6th 3rd 4th 5th 6th
month month month month month month month month
g/kg g/kg 9/kg g/kg g/kg g/kg g/kg g/kg
153.5 143.7 143.8 142.1 20.1 21.1 20.1 20.7
154.1 146.4* 148.8 147.0 19.7 20.0* 20.3 19.2
159.2 152.8 148.4 146.9 17.1 17.5 17.8 17.9
153.5 157.5* 148.0 145.4* 17.8 17.9* 19.0 18.5*
146.0 138.7 128.2 112.2 19.4 18.5 16.0 15.3
133.1* 136.8* 138.3* —** 19.5* 21.8* 20.7* —**
160.4 143.9 137.4 124.2 16.2 16.8 16.0 14.1
153.9* 158.5* 153.0 144.6* 17.3* 18.9* 18.4 19.1*

2.2 6.0 9.1 12.0 0.8 2.3 2.3 4.4

3.2 2.8 8.0 13.0 0.9 0.9 2.6 3.8

 

 

 

 

 

 

49

Table 3. Yield and specific gravity of Kennebec and Russet
Rural tubers from plots sprayed and unsprayed with

 

 

 

 

MH-30

Varieties YIELD PER PLOT (LBS.) . .
SpeCific

and US B ra it
treatment No. 1 Group Total g V Y

Kennebec control 48.9 3.3 52.2 1.077

" MH-30 48.4 3.5 51.9 1.076

Russet Rural control 48.2 4.7 52.9 1.077

" ” MH—30 45.3 4.6 49.9 1.077

 

Total yield was, however, slightly decreased by the MH
treatment in the Russet Rural. The above observations con-
firm the findings of the earlier researchers in this field

(23, 45, 47, 58).

Weight Losses

Sprout weights were recorded for both storage environ-
ments. The results are shown in Table 4a. MH was effective

OF It
in prolonging the rest period of the tubers at 41 .

0
also reduced the amount of sprout growth at both 41 F. and

70° F.

 

 

50

 

 

.mes wHQEmm H hHQO «

 

 

 

 

 

 

 

 

 

 

 

 

k.m m.m o.o omumz = =
m.va v.m o.o Houucoo Hmnsm ummmom
o.o *m.oa o.o omlmz z
o.ov m.vH o.o Houucoo umnmocmx m w on oos
o.o o.o o.o o.o o.o omumz z =
m.H o.o o.o o.o o.o Houocoo Hmuom ummmsm
o.o o.o o.o o.o o.o omumz =
o.H o.o o.o o.o o.o Houusoo ownwcowx ooumm oHv

mxxo mx\o ox\m ox\o ox\m

wuapaesn .m
mnucoe msucoe mQuCOE wzusoE fluCOE . .

o
ucwEumeu w>aumawm
m v m N H Ucm X musumnwmfimfi
mmfluwaum>
mo sz mmB B< emonZ 930mmm . mo<moem

 

 

 

.meHOum mo mUOAHmQ mDOAHm> kumm .uanwB
Smwuw HMHuflce EmHmoHflx mom mEmum ca pwmmmumxm muDOHmm mo unmflwk was .wv wHQmB

 

 

 

51

Weight losses due to water evaporation and respiration
were also measured. The results (see Table 4b) indicated
that weight losses by MH-tubers and control tubers were
similar.

The total weight loss or shrinkage was the same in both
MH tubers and the control tubers at 700 F. up to the end of
the second month in storage (see Table 4c). At 410 F., the
MH tubers lost slightly more weight than the control tubers
except in the first and fifth months.

The 700 F. experiment was terminated at the end of the
third month due to excessive sprout growth of the tubers as
shown in Figs. 7 and 8. By that time, the tubers at 700 F.
were wrinkled. The appearance of the tubers stored at 410 F.
for 5 months was good, but most of the tubers were beginning

to lose their firmness.

Respiration Data

The CO2 evolved was measured every 3 1/2 days. It was
expressed as mg. COZ/kg.—hr. The results obtained are shown
in Figs. 9a, 9b, 10a and 10b. The rate of respiration of

the tubers was higher at the warmer temperature than at the

COld temperature as expected. The respiration rates of MH

 

 

 

 

 

52

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

m.oOH H.Hn o.Hv omumz = =
m.mm H.on o.ov Honecoo Honem emmmsm
o.on m.mo o.mm omumz =
H.mm m.nm o.om Honocoo ownoccwx m H On ooh
o.om a.mm m.mm n.ns m.m emumz = =
m.mm m.mm a.mm o.oH H.o Houucoo Hmuom pommom
m.mm m.om m.km a.mm m.NH omnmz =
m.Ho m.mm a.mm m.mm m.ma Houucoo ownwocwx ooumm 0H6

mx\o mx\m mx\m mx\o ox\m

mfluCOE zuCOE ucwEumeu w>auMHmm o
m v m m H ppm . o musumuwmfiwe
IIIIlIIlIlllIlIIlIlllllllllllllllllllllll meuwHHm> IIIIKWIIIIIIIIIIIIIIII
mo sz mme Ed mmoq Bmemz mwdmoem

 

.mmmuoum mo mpOHuwm msoHum> kuwm .uanw3 Smwuw HmHuHCH EmumoHHx
uwm mEmum CH Ummmwumxm mumflsu Eouw wwwmoH COHuMHHQmmH paw coHumuomm>m .Qv wHQmB

 

 

 

53

 

 

 

 

 

 

 

 

 

 

 

 

 

a.mOH o.mm o.Hv : =
m.vHH m.mn o.ov Houucoo Hmusm uwmmsm
o.om p.mn o.mm omumz =
H.0NH H.me o.om Houucoo owanst N H on ooe
o.om a.mm m.mm n.5H m.m omlmz : :
o.mm m.mm v.mm o.oH H.m Houucoo Hmusm uwmmsm
N.mm m.om m.nm a.mm m.NH omlmz :
m.mv h.mm a.mm m.mm m.mH Houucoo ownwscmx omlmm OHv
918 or}... oxxo or} 93...
wuapafidfl .m
maucoe wzucos wzucoe mgucoe nucoE ucwsumwuu w>+ m w o
m v m m H Cam .uoH m wusumuwmfiwe
meuwHum> 8
mo sz mme B< mmoq BmOHmz m0¢moem

 

Hmuwm .usme3 fimwuw HMHuHcH EmumoHHx Mom
mo uzme3 paw muonsu EOHM mommoH COHumuHm

.wmmuoum mo mUOHHwQ mSOHHm>

mEmum CH memmumxw muzoumw
mwu paw coHumnomm>w mo Esw .Uv wHQMB

 

 

 

 

 

54

Fig. 7. The condition of Russet Rural tubers at the
end of 3 months storage at 700 F. and 70 i 2% relative
humidity.

Fig. 8. The condition of Kennebec tubers at the end

of 3 months storage at 700 F. and 70 1 2% relative
humidity.

 

 

 

2‘?!

Control tubers

 

Control tubers

 

MH-tubers

 

MH-tubers

 

 

56

 

um Uwuoum muons» owflwccwm mo mums soHum
mxmwB CH

mH vH NH OH
F|\ _ _ _

Uw>OEwH
mucouam

 

 

.mxmwz mH you muflonsos m>numeu Ron oem .m oon

gnomes one no omnmz no uowmum one .mo

wEHu wmmuowm

m w
1 _

V
N

 

wHwqu Houucoo so mudoumm who: u m
mcHuSOHQm umsm Honuaoo H 4

mumnouumz elliulle

mequ Houucoo @llllllO

.mHm

I
O
v-i

I
N
H
'1q—‘6x/ZOQ '6m 9391 uorqexrdsau

 

mH

 

 

 

57

 

.m
pwuoum muonsu Hmusm uwmmsm mo mama coHu

xwwz mH sou munonsss w>flumen Ron out .m com um
muHommH one so omnmz mo uomnmo one .nm .mHm

mxwa CH wEHu wmmuoum

 

 

 

    

 

mH vH NH OH m o v N
VII111 1 1 1 1 1 1111L Ill
m <
e e - .
I o
\3 Nine/ow u m
&\ muonsu Houucoo co musoumm who: I OH
mcHuzoumm umsfl Houucoo H <
3661311: T .II@
I NH
mumpsu Houucoo mTllllllO
pw>OEwH
wusoumm

 

VH

‘1q-‘6x/Zoo 'Bm age: uorqexrdseg

 

 

 

 

 

.81me 3 How 3825.1 9.3.33 .8.3.8 on...
Umuoum muons» ownwsswx mo wumu c

.m 0.3V um
oflmfiowmn one so omnmz mo uowmmw mes. .m. S .65

mxw03 CH wEHu womuoum

mH vH NH OH O O

1 1 1 ~

1 1 1

I
r-I

58
7
N

I
m

I
v
'1q-‘6x/ZOQ 'bm age; uorqelrdsag

 

 

3813-112 T . Ila

muonsu Houusoo mTllllIlG

 

59

 

.mxooz mH new abscess: w>eumaon xmouom new .

OOHOum mHmQDu Hohsm uwmmsm mo mums coHumuHmmmH map so Omnmz mo uummww 0:8 .QOH

mxwos CH wEHu mmmuoum

mH vH NH OH O O v N
VIII 1 1 1 1 1

.—

 

mumnsuumz eIII.III8

meQSu HOHuGOU

m oHv um
.63

I I
m N

I
fl
‘1q-‘6x/ZOQ 'bw age: uorqelrdssg

 

 

 

 

 

60

tubers and control tubers at the same temperature were

similar until the control tubers began to sprout excessively.

After the sprouts were removed, the respiration rates of

both control and MH—tubers again became identical, until

new sprouts showed up on control tubers.

0
At 41 F., where there were no sprouts, the respiration
rates of MH-tubers and control tubers were similar.

Records of weight loss during the respiration experiment

were kept. The results are shown in Tables 5, 6

and 7.

 

Table 5. Evaporation and respiration losses from tubers
stored at 41° F. and 90-95% relative humidity for
15 weeks in respiration pails expressed in grams

per kilogram initial fresh weight,

periods of storage.

after various

 

VARIETIES AND TREATMENT

WEEKS IN STORAGE

 

 

4 8 12 15
g/kg g/kg g/kg g/kg
Kennebec control 3.4 8.0 12.9 16.4
" MH-30 3.2 7.9 13.2 16.6
Russet Rural control 3.2 8.0 13.1 16.7
" " MH-30 3.0 7.7 12.9 16.6

 

 

 

 

 

61

Table 6. Evaporation and respiration losses from tubers stored
at 700 F. and 70% relative humidity for 15 weeks in
respiration pails expressed in grams per kilogram
initial fresh weight, after various periods of storage.

 

VARIETIES AND WEEKS IN STORAGE

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

TREATMENT
4 6 8 10 12 13 15
g/kg 9/kg g/kg g/kg g/kg g/kg g/kg g/kg

Kennebec;

control 10.3 20.8 33.9 45.7 58.6 75.3 83.9 103.8

MH-3O 13.3 24.3 36.8 48.0 59.8 72.2 80.8 100.5
Russet Rural:

Control 11.9 23.2 38.5 51.6 65.7 90.0 96.6 117.4

MH~30 12.2 23.2 38.2 51.7 65.2 83.4 92.0 110.3

 

Table 7. The weight of sprouts from tubers stored for 15 weeks
in respiration pails expressed in grams per kilogram
initial fresh weight, after various periods of storage.

 

 

 

 

STORAGE

 

Varieties lst Next T
O—
T % and 10 5 tal
emperature Relative treatment weeks weeks
OF. humidity
g/kg g/kg g/kg
41 90-95 Kennebec control 0.0 0.0* 0.0*
" MH—30 0.0 0.0 0.0
Russet Rural control 0.0 0.0 0.0
” " MH—30 0.0 0.0 0.0
70 70 Kennebec control 14.8 34.4 49.2
" MH-30 6.4 3.3 9.7
Russet Rural control 5.9 16.2 22.1
" " MH-30 0.6 1.6 2.2

 

 

* Tiny sprouts.

 

 

 

 

 

62

The following equation was used to convert the CO2
production of the tubers to grams starch per kilogram fresh

material:

C6(H1005)n + (602)n “————'.’ (6C02)n + (6H20)n

162 grams -————*>- 264 grams

Table 8 shows the pattern of weight loss by the tubers

. . . . 0
during the respiration experiment. At 41 F., water eva-
poration and respiration accounted for all losses since no

sprouts developed.

Tuber Size and Respiration Rate

An experiment was conducted between February 15 and
February 22, 1962, to determine the effect of size of
potato tubers on the rate of respiration. The tubers were
sorted into small (less than 3 1/2 inch diameter) and large
(3 1/2 inch minimum diameter) sizes and each tuber was
numbered for its identity. The respiration data obtained
are shown in Table 9.

The respiration rates of the small and large tubers were

similar except in Russet Rural MH-tubers where the large

 

63

 

 

 

 

 

 

 

.mucwHwMMHp hm mm .mon Aoumum mm Ummmmumxw ppm GOHHUDOOHQ N00 Scum UquHSUHmo m
m.OH h.hw O.N O.HH n.mm N.N m.NHH omumz : =

o.m O.v> m.mH «.mH O.¢OH H.NN m.OMH Hosucoo Hmudm pwmmsm

m.m n.Hw m.m m.OH o.om o.o N.OHH Omlmz :

N.m o.om N.Nm m.NH m.Hm N.mv O.mmH Honusoo omflwsswx on Oh
N.NN m.Nn o.o o.o O.NH o.o 0.0H omlmz : :

h.mN m4: o.o mfv v.NH 0.0 h.OH HOHuCOU HMHDm uwmmdm

m.Hm n.mo o.o N.m ¢.HH 0.0 m.wH Omlmz :

a.mN H.On o.o m.v m.HH o.o v.0H Houucou ownwcsmm mmIOO oHv
.8 .x. x 918 918 1918 93...

NW u
codumu .coaumu sou ucwfiumwuu wWMMMflMM mo
. t . 8* . .

IHmmmm umumz usoumm IHmmmm um: usoumm Hmuoe paw x QEwB
meuwHHw>
mmoq EOHHB mwflmoem
.mmOH uanm3 Hmuou mo ucwouwm mm
UmmmeQXm paw pamHmB nmwuw HmfluHCH EMHOOHHX me mEmum CH mewwumxw mHHmm GOHumu
IHmmwu

CH wmwuoum mo mxwm3 mH wflu OGHHDU muons» >9 umoH uflmeB mo mucmcomfiou .m wHQmB

 

 

64

Table 9. The effect of tuber size on the rate of respiration
of potato tubers stored at 700 F. and 70% relative

 

 

 

 

humidity.
Varieties AVERAGE RESPIRATION RATE IN MG. COz/KG.-HR.
and
treatment 2—15—62 2-19—62 2—22—62
Small Large Small Large Small Large
tubers tubers tubers tubers tubers tubers
Kennebec:
Control 14.41 14.68 12.18 12.12 14.34 14.33
MH—30 9.77 8.94 8.04 7.15 7.92 8.59

Russet Rural
Control 11.61 12.25 10.67 11.00 13.00 14.29
MH-30 3.53 11.01 7.42 10.07 8.74 7.84

 

tubers respired faster than the small ones on the 15th and

19th of February 1962.

Condition of the Tubers
At the end of 15 weeks of the respiration experiment,

the tuber samples were photographed (see Figs. 11a and llb

o
and 12a and 12b). Tubers stored at 41 F. were fresh and

firm. The MH tubers had no sprouts, but the control tubers,

eSpecially the Kennebecs, had tiny visible sprouts. Tubers

 

 

 

65

Fig. 11a. The condition of Kennebec tubers stored at
410 F. and 90—95% relative humidity at the end of 15 weeks.
Photographed on 2—27-62.

Fig. 11b. The condition of Russet Rural tubers stored
at 41° F. and 90—95% relative humidity at the end 0f 15
weeks. Photographed on 2—27—62.

 

 

. .
I.
J

n-
In:

Control tubers

MH-tubers

 

 

4 .
a:
v

 

Control tubers

MH-tubers

 

 

 

67

Fig. 12a. The condition of Kennebec tubers stored at
700 F. and 70% relative humidity at the end of 15 weeks.
Photographed on 2—27—62.

Fig~ 12b. The condition of Russet Rural tubers stored

at 700 F. and 70% relative humidity at the end of 15 weeks.
Photographed on 2—27-62.

 

 

  

MH-tubers

Control tubers

 

MH-tubers Control tubers

 

 

 

 

 

69

o .
at 70 F. were wrinkled and flabby. The control tubers
sprouted more heavily than MH tubers. Sprouting was most

pronounced on Kennebec control tubers.

Apical Dominance

Fig. 13 confirmed the results of the 1960—61 experiments
in which apical dominance was destroyed in MH tubers. Careful
examinations of the MH—tubers when they sprouted revealed that:
a) the apical dominance of each sprout was also lost, since

the lateral buds grew rather than the apical bud;

b) the basal end sprout was the most vigorous, and
c) the vigor of the sprouts produced decreased progressively

from the basal end to the apical end of the tuber.

Cooking Quality

Potato chips and boiled potatoes were evaluated.

Potato chips:

The potato chips produced were scored using the proposed
color reference standard obtained from the Potato Chip Insti—
tute International of Cleveland, Ohio (18). The averages of 2
The

Scores from 2 replications are presented in Table 10.

scores were judged on a scale from 1 to 10. The evaluation

of the scores is as follows:

 

 

 

I‘M-tubers Control tubers

Fig. 13. Potato tubers photographed at the end of 3
months in storage at 700 F. and 70 t 2% relative humidity
to illustrate the loss of apical dominance by MH—tubers.

'N

 

 

 

 

 

71
l ‘ 4 = Very good
5 = Good
6 - 7 = Fair
8 - 10 = Poor

Acceptable chips have scores of l to 5; l to 4 being the most
desirable. The results (see Table 10) indicated that MH did
not improve the color of the potato chips from MH tubers over
the color of chips from control tubers stored at 410 or 700 F.
Acceptable chips were produced only from potatoes stored at

70° F.

Conditioning:

Potato chips were made at the beginning of conditioning
at 700 F. and at 2, 3 and 4 weeks later using 2 tuber sam-
ples. Table 11 shows the average score from 2 replications.
The color reference standard (18) was used to evaluate the
quality of the potato chips. MH was effective in bringing
the potato chips from MH tubers to a desirable color a week
earlier than those from the control tubers.

At the end of the conditioning period, Russet Rural MH
tubers made chips scored at 5.5. This score was an average
Of 4 scores of 4, 4, 6 and 8. This incidentally confirms
the views of people in the potato chip industry that Russet

Rural tubers do not always condition.

 

 

 

 

 

72

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

m.m o.m o.h OMIEZ : :

 

 

 

 

 

 

 

 

o.m o.v o.m Houusoo amusm uwmmsm
o.m o.m m.m omnmz :
o.m m.m m.v Honucoo ownmccmx N H on on
OnOH mow 000 Oak. OMIMIHE : :
m.m m.m o.o m.n Houucou Hausa uwmwsm
o.o o.o o.oH m.n omlmz :
m.m o.oa o.oa m.n Honucou omnwccwx omlmm Gav
squHEsg .m
mnucoe mzucoe mauCOE zucoe ucwEuwwuu o
w>aumawm
m m m H paw . o wusumnwmfiwa
mwfluwflum> a
mo sz mm& 94 mmoom moqoo mHmo mo<moem

 

 

 

 

 

.UOHMGQ mmmuoum wflu mCflHsp muCMHQ pwumwuucs
pcm Uwummhu EOHM muonsu oumuom Scum wows mmflno Cumuom mo COAHMSHm>m .OH wHQmB

 

 

 

73

Table 11. Potato chip color score* during conditioning at
700 F. and 70% relative humidity of tubers pre—
viously kept at 41° F. and 90—95% relative
humidity for 15 weeks.

 

Varieties AFTER
and . .
treatment Inltlal 2 3 4

weeks weeks weeks

 

Kennebec control 10.0 9.5 8.0 4.5

" MH—30 10.0 8.0 4.0 3.0
Russet Rural control 9.5 8.0 7.5 5.0

" " MH—30 9.0 8.0 3.5 5.5**

 

* Average of 4 scores.

** Average of 4, 4, 6 and 8.

The potato chips produced were photographed in series
at the end of the experiment to show the change in color of
the chips during conditioning. The photographs are shown
in Figs. 14 and 15.

The condition of the tubers and weight losses by them
are shown in Figs. 16 and 17 and Tables 12 and 13.
Respiration measurements were made during conditioning.

The respiration data are presented in Figs.18aand 18b.

 

 

 

 

74

Fig. 14. Potato chips from Russet Rural tubers made
at the beginning of conditioning and at 2, 3 and 4 weeks
later to show the trend in chip color change.

 

Fig. 15. Potato chips from Kennebec tubers made at
the beginning of conditioning and at 2, 3 and 4 weeks later
to show the trend in chip color change.

 

 

..RUSSEI Rum .Rvssn

 

BTCON ROL 3CONTR0L DEEDSHRURAL
- 2NTRO
-2.'7 .. I3 “62 2-0 62 L
343nm ~
J ., ,K‘xl‘ \‘\
3 x I ‘ k
\g , -‘ , 71 '\ . .
l “ :\ \ ‘. l. x
- @I I/ (A ‘. - ;
mi ‘/. \ ‘ .-

 

2 27 62

E”Russnw RURAL uRUSSEI 3m I,RuSSEI RURAL ‘RUMSSEI 3Rum

I,3- Mzo- 3962 3-273 (,2

      

DKENNEBEC EJKENNEBEC ;.,KENNEBEC KENNEBEC

CONTROL CONTROL
CONTRoL - _ -2 4,2 CONTROL

     

5
3- lg 322 3-20-62

     

DKENNEBEC ..,KENNEBEC _KE§\‘§SE8EC
DEEJ’EEEEC '7 MH- 0 flangflgz

;.
‘\

E55: ‘\
9%}:

   

 

 

 

 

 

 

76

Fig. 16. The condition of Kennebec MH-tubers and
control tubers at the end of conditioning at 700 F. and
70% relative humidity.

Fig. 17. The condition of Russet Rural MH—tubers and
control tubers at the end of conditioning at 700 F. and
70% relative humidity.

 

 
     

Mil-tubers Control tubers

 

 

MH-tubers Control tubers

Table 12. Evaporation and respiration losses from tubers and
weight of sprouts produced during the conditioning
period at 700 F. and 70% relative humidity of tubers
previously stored at 41° F. and 90-95% relative

humidity for 15 weeks.

 

 

 

Varities TUBER WEIGHT LOSS IN Total
d Sprout _
an . ht weight
treatment 2 weig loss
weeks
g/kg g/ kg g/kg
Kennebec:
control 14.8 9.5 39.6
MH-30 14.8 3.2 32.2
Russet Rural:
control 14.8 6.9 26.6
MH-30 16.1 1.0 32.6

 

Table 13. Components of weight loss during the conditioning

period at 700 F. and 70% relative humidity of

tubers previously held at 410 F. and 90—95% rela—

tive humidity for 15 weeks.

 

WEIGHT LOSS

 

ter** ration*

Wa—
ter

Respi—
ration

 

Varieties
and To—
treatment tal Sprout
g/kg g/kg
Kennebec:
control 39.6 9.
MHbBO 32.2 3.
Russet Rural:
control 36.6 6.
MH-30 32.6 1.

NW

OKO

%

%

 

 

 

*Calculated from CO2 production and expresse

**By difference.

d as starch loss.

 

79

 

 

 

16 -
o————O Kennebec control tubers
@F*"—@ Kennebec MH—tubers

l4 -
L;
.1:
|
3‘12-
\
N
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w 10 -
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88—
H
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m
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6 - .
Sprouting
started
4
l I ' ’
1 2 3 4

Storage time in weeks

Fig. 18a. The effect of MH-30 on the respiration rate

of Kennebec tubers during 4 weeks of conditioning at
700 F., following storage at 410 F. for 15 weeks.

 

 

80

   

 

 

16-
' 0——————0 Russet Rural control tubers
8——-°——0 Russet Rural MH-tubers
14—
I1
.1:
I
m
{f 12-
N
O
U |
I
6 I
E
3 10-
m
H
a
o
H
4.)
a I
.H 8“
m
m
a) ‘.
£11 1\ ‘
6~ Sprouting I
started '
4 .1
[ l I I
1 2 3 4

Storage time in weeks

Fig. 18b. The effect of MH-3O on the respiration
rate of Russet Rural tubers during 4 weeks of con—
ditioning at 700 F., following storage at 410 F. for E
15 weeks. 1

..-u-.-_ in...- .

 

 

 

 

81

High and similar initial respiration rates were record—
ed for both MH-tubers and control tubers. As conditioning
continued, the respiration rates of the tubers declined
sharply but began to rise again after 2 1/2 weeks by which
time the tubers had started to sprout.

The results of the sugar analyses made at the beginning
and end of conditioning are shown in Table 14. The results
indicate that tubers had to have less than 0.05% total

sugar in order to make acceptable chips.

Boiled potato:

Potato tubers boiled for 25 minutes were scored for
color, flavor and texture (see Table 15). Scores of l to
10 were assigned for each of the cooking quality items
evaluated.

For color evaluation a whitish tuber flesh was most
desirable and 10 points were awarded for that. The more
yellow the color, the less the number of points scored. As
for the flavor, a tasteless, i.e., flat potato scored 10
The score of tubers with taste decreased the

points.

sharper the taste. For texture, a crumbly dry tuber scored

10 points. Water logged sticky moist potatoes scored very

low.

 

 

 

 

 

82

 

 

 

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A good comparative study of the boiled potato tubers
could not be made owing to the arbitrary nature of the
method of evaluation. In fact, each group of 8 samples
was evaluated independent of the next group. Despite the
weakness of this test, MH tubers had better flavor and

texture than the control tubers.

Anatomical Studies
Slides of the longitudinal sections of MH tubers and
control tubers did not show any anatomical differences,

especially as regards cell differentiation and the thickness

of the cork layer.

Dry Matter Losses
Summary tables of dry matter losses from potato tubers
and the dry matter showing up in sprouts are presented in

Tables 16, 17 and 18. NFE and crude protein accounted

for most of the losses.
MH—tubers lost less dry matter than the control tubers

stored at 410, 600 or 700 F. Also, use of MH reduced crude

protein loss in MH—tubers as storage continued.

During conditioning, loss of dry matter due to respira-

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88

loss of dry matter in 15 weeks at 410 F. MH-tubers lost
less dry matter through sprout growth than the control
tubers which sprouted more, but both MH—tubers and control

tubers lost identical amounts of dry matter in respiration.

 

 

 

 

 

 

DISCUSSION

Sprout Growth

Treatment with maleic hydrazide reduced sprout growth
markedly, and at the same time eliminated or even reversed
apical dominance. Since sprouting was associated with
removal of protein from the tubers, it is suggested that MH
interferes with the mobility of the protein. Since apical
dominance is commonly associated with auxin concentration,
it may be inferred that MH treatment led to auxin

redistribution.

Respiration

In all cases with either MH—tubers or control tubers,
the rate of respiration tended to decrease as the duration
of storage was prolonged whether sugar contents of the
tubers were increasing or decreasing. Whenever sprouts
appeared, however, this downward trend was interrupted, and
as sprouts became abundant, respiration rate was greatly
increased. All or most of the differences in respiration
of tubers, regardless of variety, may be attributed to
differences in the occurrence of sprouts. Similarly, dif—
ferences in respiration of MH tubers and control tubers were
closely related to sprout growth.

89

 

 

 

90

The high initial respiration rates recorded for both
MH-tubers and control tubers when transfered from 410 to
700 F. agree with the findings of Appleman and Smith (5).
Since the respiration rate of the tubers was low at 410 F.
compared with the high initial respiration rate when the

o .
same tubers were transfered to 70 F., and Since the sugar

content of the tubers was the same, this proves that there

is no direct correlation between sugar content and respi—
ration rate of the tubers. Therefore, the high initial

respiration rates observed at 700 F. could only be due to

the change in temperature (5).

The decline in the respiration rate of these tubers
that followed the initial rise was probably due to the
reconversion of about 4/5 of the accumulated sugar to

starch (3). This decreased concentration of available

sugars in the tubers was insufficient to support the high

. O . . .
rate of respiration at 70 F. The increased respiration

rate when sprouts appeared was due to the translocation of
carbohydrate from the tuber into the sprouts in order to

supply adequate amounts of energy for the metabolic pro—

cesses of the developing sprout tissue (70). Sprout tissues

being very young compared with those of the tubers, respire

much faster (70).

 

 

 

 

 

 

91

Cells of potato tubers are packed closely together (45).

This limits ready access of air and may account in part for

their relatively low rate of respiration (39). These fac—

tors combined should explain why the size of tubers did not

affect their respiration rate.

Losses in Weight

Losses in weight, either as water or as dry matter,
were reduced either by low temperature storage or by the
use of maleic hydrazide, alone or in combination. However,
although maleic hydrazide greatly reduced sprouting, even

at 600 or 700 F., the losses of water at the higher tem-
peratures resulted in shriveled and unsaleable potatoes.
Dry matter losses in the period from 3 to 6 months storage,
however, present quite a different contrast between MH—
tubers and control tubers. Whereas control tubers of

both varieties lost about 22% of their total dry matter in 3—

6 months, MH tubers lost only 5%. Not only were losses in

sprouts greatly reduced, but respiratory loss was decreased

by the MH treatment. Protein losses in sprouts amounted to

about 19% of the total protein in the control tubers, while

the MH tubers showed no loss. Since potato protein is

highly nutritious (34) this saving of protein could add to

 

 

 

 

 

 

92

the food value of such potatoes.
In the limited trial, MH—tubers conditioned a week

earlier than the control tubers. This would have prevented

the loss of 25% of the total dry matter lost in 4 weeks

during the conditioning period (see Table 18). Since in

potato chip manufacture the greater the dry matter the

better the chips (45), the use of MH for conditioning of

potato tubers may be recommended.
The quantity of dry matter remaining in the tubers,
after storage at 700 F. was greatly affected by MH treat—

ment as indicated above. In the case of conditioning at

700 F. after storage at 410 F., differences in loss of dry

matter after 4 weeks of conditioning were relatively small,

but still less in MH—tubers than in the control tubers. The

slightly higher loss of dry matter by control tubers is
attributable to the larger sprouts of the control tubers.

Water loss from Russet Rural tubers was greater than

in their Kennebec counterparts at both temperatures. Since

Russet Rural tubers were in general much smaller than

Kennebec tubers, and since water evaporation from a material

depends among other things on the surface area to volume

ratio of the material (66), it is expected that the Russet

 

 

 

 

 

 

93

Rural tubers with the larger surface area to volume ratio
than Kennebec tubers should have lost more water.

The ratio of weight losses of water to dry matter in

o
respiration was about 3:1 at 410 F. and 9:1 at 70 F. A

ratio of 10:1 at the warmer temperature was reported by

Hensen (41). The bulk of the weight loss was through

water evaporation.

Color of Potato Chips

As shown in Table 14, there is a correlation between
the amount of total sugar in tubers and the color of chips
made from them. Hence, tubers stored at 410 F. made poor
chips owing to sugar accumulation (67, 73), while those
stored at 700 F. produced acceptable chips, because the

high respiration rate at that temperature not only prevented

sugar accumulation, but also depleted the sugar content of

the tubers.

Similarly, the faster respiration rate of the tubers,
and the reconversion of most of the sugars in the tubers to
. . . . . O .
starch during the conditioning period at 70 F. (3), explain

why acceptable chips were produced from conditioned tubers.

 

 

 

 

 

 

94

Treatment with MH may have accelerated conditioning
slightly, but in either case, low content of total sugars

was necessary to produce good chips.

 

 

inn-fin.-—

 

 

SUMMARY AND CONCLUSIONS

Kennebec and Russet Rural potato vines were sprayed
in the field 10-12 days after full bloom with 1 gallon MH-30
in 100 gallons of water per acre. Potato tubers were har—
vested and stored at 410 F., 600 F., and 700 F. at high
relative humidity (about 70-90%) for periods up to 5 or 6
months, or until sprouting became excessive.

Weight losses due to the different storage environments
were computed.

Chemical analyses were made of tubers harvested in 1960
to determine the variations in their chemical constituents
during the storage period.

Respiration measurements of tubers were made every 3 1/2
days during storage at 410 F., and 700 F. Similar measure—
ments were made during conditioning of tubers previously
stored at 410 F.

Cooking quality was evaluated with potato chips and
boiled potatoes. Sugar was determined in tuber samples
collected at the beginning and end of the conditioning
period. Anatomical studies were also made on the tubers at

the end of the storage period.

95

 

96

MH inhibited sprout growth of both varieties and
destroyed their apical dominance.

Yield and specific gravity of tubers were unaffected
by MH treatment.

The key effect of MH was the prolonging of the rest
period and especially the inhibition of sprout growth.
Fresh weight losses from MH—tubers and control tubers were
identical as long as the sprout growth of control tubers
was small. MH—tubers, however, lost less dry matter than
control tubers.

Weight loss from tubers was a result of water evapora—
tion, losses of protein and carbohydrate due to sprout
growth and losses due to respiration. Water loss contrib—
uted the highest percentage of weight loss.

MH—tubers stored at 600 F. lost less hydrolyzable car—
bohydrate than the control tubers——5% versus 22% respec—
tively, and had no loss in crude protein while the control
tubers lost 20—25% of their crude protein.

The respiration rates of MH—tubers and control tubers
were identical as long as the control tubers did not sprout.

There was no direct correlation between the sugar con-

tent and the respiration rate of the tubers.

 

 

97

MH-tubers did not make better potato chips than the
control tubers when stored at 410 and 700 F. In limited
trials, MH—tubers, however, conditioned a week faster than
the control tubers. Tubers made acceptable chips only if
their total sugar content was 0.05% or less.

Boiled MH—tubers had better flavor and texture than
boiled control tubers.

High weight losses at 600 and 700 F. indicate that MH
should be used as an accessory to regulation of temperature

and relative humidity in order to keep losses at a minimum.

 

 

bun—o. -

 

 

10.

 

LITERATURE CITED

Alexander, L. M., Schopmeyer, G. E. and Anderson, R. B.
Potato storage and quality of french fries. Amer.
Potato Jour. 26: 439-445, 1949.

Anderson, R. L. and Houseman, E. E. Table of ortho—
gonal polynomial values extended to N = 104. Iowa
State College Research Bull. 297, April 1942.

Appleman, C. 0. Changes in potatoes during storage.
Md. Agr. Exp. Sta., Bull. 167:327-334, 1912.

. Potato sprouts as an index of seed value.
Md. Agr. Exp. Sta., Bull. 265, 1924.

and Smith, C. L. Effect of previous cold
storage on the respiration of vegetables at higher
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Association of Official Agricultural Chemists. Offi—
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Andus, L. J. Plant Growth Substances. University
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Barnard, E. E. and Warden, R. L. The effects of var—
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of Netted Gem potatoes. North Central Weed Con-
trol Conference, p. 145, 1950.

Beach, R. G. and Leopold, A. C. The use of maleic
hydrazide to break apical dominance of Chrysan-
themum morifolium. Am. Soc. for Hort. Sci. 61:
543—549, 1933.

 

Bennett, R. B. et a1. Topping flue-cured tobacco and
sucker control. Mimeo sheet, 9 pp., 1956 (North
Carolina State College).

98

 

 

 

 

 

11.

12.

l3.

14.

15.

16.

17.

18.

19.

20.

99

Buchholtz, K. P. Dalapon and maleic hydrazide for
control of quackgrass. Proc. North Central Weed
Control Conference, pp. 62—63, December 1954.

Burton, W. G. The Potato. Chapman and Hall, Ltd.,
London, 1948.

Carder, A. C. The selective control of wild oats in
cereal crops by use of maleic hydrazide. North
Central Weed Control Conference, p. 50, 1954.

Carroll, R. B. Analyses of diethanolamine in cigar—
ettes and potato tubers treated with MH-30.
Unpublished report, Apr. 1957, Consulting Chemist,
Greenwich, Conn.

Cibes, H. et al. Influence of preharvest sprays with
maleic hydrazide on the sprouting of potatoes.
Jour. of Agriculture of the Univ. of Puerto Rico
39: 92—99, 1955.

Ciferri, R. The prevension of sprouting of potato
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Claypool, L. L. and Keefer, R. M. A colorimeter method
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Coughlin, F. J. Quality control in potato chip manu-
facturing. Proposed color reference standard. A
talk presented at the production and technical
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25, 1954.

Crafts, A. S. et a1. Comparative studies on herbicide
transport. Research Report Western Weed Control
Conference, p. 97, March, 1957.

Darlington, C. D. and McLeish, John. Action of maleic
hydrazide on the cell. Nature 167: 407-408, 1951.

 

 

 

 

21.

22.

23.

24.

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26.

27.

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29.

100

Davies, M. E. Effect of relative humidity on a gram
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Bethany, Conn.

DeFrance, J. A. and Hart, S. W. The effect of maleic
hydrazide on the growth of lawn turf grasses. Paper
presented Northwestern Section Am. Soc. for Hort.
Sci., Cambridge, Mass., Jan. 1954.

Denisen, E. L. Response of Kennebec potatoes to maleic
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Denny, F. E. The use of methyl ester of d—naphthalene
acetic acid for inhibiting sprouting of potato
tubers, and an estimate of the amount of chemical
retained by tubers. Contrib. Boyce Thompson Inst.
12: 387—403, 1942.

Denny, F. E. et al. Effect of the vapor of the methyl
ester of d-naphthalene acetic acid on the sprouting
and the sugar content of potato tubers. Contrib.
Boyce Thompson Inst. 12: 253-268, 1942.

 

Denny, F. E. and Thornton, N. C. Factors for color in
the production of potato chips. Contrib. Boyce.
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The third year's results on storage of potato
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405—430, 1942.

Dewey, D. H. and Wittwer, S. H. Chemical control of
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Eaks, I. L., Pratt, H. K., with additions by Clerx,
W. A. and Dewey, D. H. Adaptation of the Claypool—
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Personal communication with Dewey, D. H., Mich.
State Univ.

 

 

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32.

33.

34.

35.

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37.

38.

39.

101

Elmer, O. H. Growth inhibition of potato sprouts by
the volatile products of apples. Sci. 75: 193,
1932.

Esau, Katherine. Anatomic effects of barley yellow—
dwarf virus and maleic hydrazide on certain Gramineae.
Hilgardia (in press) manuscript 70 pages with 46
references.

Findlen, H. Effect of several chemicals on sprouting
of stored table—stock potatoes. Am. Potato Jour.
32: 159-167, 1955.

Fischnich, O. et a1. Application of maleic hydrazide
to some cultivated plants. Angew. Botanik 28:
88-113, 1954.

Fischnich, O. and Heilinger, F. The chemical consti—
tuents of the potato; formation, utilization, pre—
servation. Land ban forschung. 9 (1959) 1: 15-16,
1959.

Franklin, E. W. and Thompson, N. R. Some effects of
maleic hydrazide on stored potatoes. Am. Potato
Jour., 30: 289-295, 1953.

Greulach, Victor A. Notes on the starch metabolism of
plants treated with maleic hydrazide. Bot. Gaz.
114: 480—481, 1953.

Recent work on maleic hydrazide as a plant
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and Haesloop, John G. Some effects of maleic
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50, 1954.

Hardenburg, R. E. How to ventilate packaged produce.
Pre-Pack-Age, Vol. 7, No. 6, pp. 14—17, Feb. 1954.

 

 

 

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41.

42.

43.

44.

45.

46.

47.

48.

49.

50.

102

Haskins, F. A. and Chapman, H. W. Effects of irradi—
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enzyme activity in seedlings of corn, Egg mays L.
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