A STUDY OF
THE PROPAGATION OF THE WALNUT

Thesis for the Degree of M. 5.

Benjamin Gaillard Sitton
‘ 1928

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A STUDY OF THE PROPAGATION OF THE WALNUT

With Special Consideration of the
Role of Carbohydrates and
nitrogen and Their Re-

lation to Grafting.

_v_

A Preliminary Report
Thesis

Submitted to the Faculty of the Michigan State
College of Agriculture and Applied Sci-
ence in partial fulfillment of the
requirements for the degree
of master of Science.

by
Benjamin Gaillard Sitton
>9 “M”

177/7 June 1928

THES‘S

 

 

 

INTRODUCTION

 

The native black walnut (guglans nigrg) is
assuming increasing importance in recent years as
a producer of edible nuts. The meats of the black
walnut are in special demand for candy manufacture
and confectioners are willing to pay 25 per cent
more for them than for those of the English.walnut.
However, nuts from most seedling trees are so hard
to crack that the meats are broken into small pieces.
Occasionally a seedling tree which bears nuts that
crack so that the meats come out in halves has been
located and some are being propagated as named varieties.

It is true with the black walnut, as with most
other fruits, that sexual reproduction usually does
not produce fruit like that of the parent tree, there-
fore asexual propagation must be invoked for multiplica-
tion of desirable trees. Vegetative propagation of the
walnut is very difficult and uncertain. Apparently this
difficulty of vegetative propagation is at present the
chief obstacle to the development of a considerable
industry.

It is desirable to know Why the walnut is so
difficult to propagate vegetatively and to find some
means of increasing the degree of success, if possible.
With these considerations in mind, the work reported

herein was undertaken.

1-025134%)

REVIEW OF LITERATURE

 

Asexual propagation of the Persian or English
walnut (nglans Eggigl seems to have received atten-
tion some time ago. In the early writings of Thomas
Andrew Knight a discussion of the budding of the
walnut appears. He was entirely unsuccessful in his
first trials and discouraged the attempt to propagate
the walnut by methods other than by seed. Later and
more successful efforts were reported before the
London Herticultural Society in 1818 (6). He said
that the walnut bud, when inserted into the shoot of
the same season's growth, fails, possibly because
the branch into which the buds are inserted had
stopped growth long before any of the buds were
mature enough for use. To obviate this difficulty he.
retarded the growth of the stock (probably by placing
it in a pot in a cool place) and when the bud was
ready the stock was allowed to vegetate. In this
manner he secured fair success. In another experiment
he inserted one of the minute buds from near the base
and one of the larger ones from the middle portion of
one year wood into the same stock. The small buds
took freely while the larger buds failed entirely.

Later (1853) Knight (7) stated that the follow-

ing mode of grafting succeeded under many unfavorable

circumstances: Allow the primary buds to unfold on
both stock and cion, then remove all the open buds.
After the small buds, which have previously been
almost invisible , begin to swell, take off the cion
and immediately insert upon the stock which should be
wood of the previous year. He reported saddle or cleft
graft equally successful.

Baltet in 1869 (1) recommended crown grafting
and flute budding. He said the cion should be out
obliquely, exposing the pith on one side only. He
advised the use of cions whose base consists of two
year old wood.

Oliver (1902) (12) recommended the patch bud
method of propagating pecans. He advised the use of
buds from near the base of the past season's growth,
from shoots of large diameter with short plump buds.
He gives the following directions: A rectangular piece
of bark, with the bud near the center, is removed from
the bud stick. The outer bark at the sides of the bud
is shaved off so that the edges will make a perfect
fit. Hake an.I cut in the stock, the distance between
the horizontal cuts being the same as the length of
the bud piece, raise the top portion of the flaps
slightly and insert the bud. The flaps are pressed

down snugly, tied and the whole covered with a wax.

Kraus (1911) (8) reports good results from using a
similar method in.walnut propagation.

Lake (1913) (9) assembled all the ideas on
walnut propagation to date and gave a description
of desirable cion wood: from suitable trees take
normal one year old wood from the middle more or
less erect portion of the tree. Under no circumstance
use suckers. Cion wood should be one-fourth to three-
eights of an inch in diameter, with small pith, round,
not angular, thrifty, plump about the buds, with short
internodes, straight, preferably not over a foot long.
The terminal portion is unfit, because its buds are
immature. Cions should be out during the period of
dormancy, probably two or three weeks before vegeta-
tion is due to begin. The cut ends should be dipped
promptly in melted paraffin so that evaporation from
the cut ends may not reduce the vitality of the cion.
Batchelor (2), Fuller (5), Iewis (10), Reed (13),
Stuckey and Kyle (14), Woolsey (15) and others give
much the same general directions; apparently all draw
their information from the same original source.

Cooper quotes H.E.Dosch who in turn quotes
Professor Lechemby as saying that 90% of walnut grafts
will grow if these directions are followed: use one

gallon of water with four teaspoons of sulphate of

quinine. The cions should be out submerged in this
solution and the cut tree should be washed at once
to prevent it from turning black; then the cion is
to be inserted as on other fruit trees.

There seems to be a dearth of original thought
on the subject of vegetative propagation of the walnut
and indeed of the nuts in general. Writers have passed
the opinions of others on without actually trying out
the methods advocated. With a few exceptions, careful
investigation of the propagation of the walnut seems

to have been neglected.

EKPmeIMENTAL METHOD

 

This problem has been approached from three
angles: first, field or nursery trials; second,

chemical analyses; and third, anatomical examinations.

1.. Field Work

 

Cion wood was obtained from a block of seedling
trees in the nursery of the Fbrestry Department of
this college, which were probably twelve years old
and 10 to 15 feet high. They were moderately vigorous,
making a growth of about 12 inches a year, although
they were not uniform. Cion.wood was selected from

those in the best state of vigor and was usually

obtained from the lower portion of the trees. A
small lot of cion wood was obtained from a block

of seedling trees at the Graham Horticultural
Experiment Station, near Grand Rapids. These seedl-
ings were grown from nuts from a single tree, were
very uniform, and were making from 18 to 24 inches
growth per year. Some of these had been ringed, some
girdled, and others left in the natural condition.

The stock into which grafts were set consisted
of a block of seedling trees in the Forestry nursery,
about five years old, four feet high, low in vigor
and not uniform.

In the hope of securing varying chemical condi-
tions of wood to be used as cion and stock, and in
that manner, to secure various degrees of success in
grafting, both cion and stock were treated in five
ways.

One lot was left in the natural condition with-
out treatment; a portion of this lot was collected
in the fall and a portion in the spring. These are
designated "Natural-fall" and "natural-spring"
respectively. Each of these portions was divided into
five lots:- 1. apical portion of one year wood, 2.
basal portion of one year wood, 3. apical portion of
two year wood, 4. basal portion of two year wood, and

5. apical portion of three year wood. Lot 4 corresponds

to the portion above the girdle and Lot 5 to the
portion below the girdle as mentioned below.

In the latter part of August 1926 a wire was
twisted tightly around the stem at the base of the
two year wood on another lot of cions, which are
referred to as "Girdled".

A fourth lot was partly defoliated by cutting
the mid-rib of the compound leaves so that approximate-
ly half of the leaf area was removed. This lot is
called "Defoliated." '

A fifth lot received an application of sulphate
of ammonia about the middle of September, after growth
had ceased. This did not cause a resumption of growth
but caused.the trees to retain their leaves later than
those not receiving the treatment, and to begin growth
earlier in the spring. This treatment is designated
by the word "Nitrate."

Seedling trees to be used as stocks were given
the same treatment except that the girdle was placed
about 18 inches from the ground.

Cion wood from the "nitrated" class was gathered
December 11, 1926 and buried about 18 inches deep in
a well drained place. Cion wood from the "nitrated"
and other classes was gathered April 6, 1927, packed
in moist sawdust, and placed in cold storage until

needed. Samples for chemical analysis were taken at

the time of collecting cion wood.

Grafting began on April 25 and was completed
may 4. Various combinations of the treated and the
untreated cion with those of the stock were made.
These combinations, together with the number of
grafts and the percentages of successful unions are
presented in Table l. The whip or tongue graft, made
in the usual way, was used. The cion was fitted to
the stock, tied with cotton string and the entire
union and the tip of the cion was covered with a
brush wax, the formula for which is found in Michigan
Experiment Station Special Bulletin 142 (e). The
entire cion and union was covered with a kraft paper

bag.

Budding

A limited amount of budding was done and,
though no detailed study was given this method of
propagation, it seems very promising. The patch bud
method, as described by Stuckey and Kyle (14) was
followed fairly closely. The budding knife described
by them under the name of "Texas Agie" was used in
this budding. Budswere obtained from one year wood

cut in spring before growth began.

Root grafting

 

On February 6 to 8, natural cions, nitrate
cions, girdled cions and some which had special
treatment were whip grafted on pieces of walnut
root. Special treatment was given some of the
natural cions as follows: the cions were placed into
three suction flasks, containing respectively a 3%
solution of sucrose, a 5% solution of dextrose and
a 2% solution of potassium nitrate. The flasks were
then evacuated for 20 minutes and the cions allowed
to remain in the solution for two hours. A fourth
lot was placed in a Mason Jar and enough other added
to saturate the air of the Jar. The jar was then
sealed and allowed to stand for 16 hours.

Natural walnut cions were placed on apple roots,
apple cions on walnut roots, apple cions on apple
roots and apple cuttings similar to the cions were
made. All grafts were packed in moist sawdust and

placed in storage at about 40°F.
CHEMICAL

garbohydrate Analysis

 

Samples for chemical analysis were cut into
half inch pieces, weighed in a tared sample bottle

and heated to 95°C. for one hour. Later they were

10

dried at 90°C., ground to pass a 60-mesh sieve and

an aliquot dried to a constant weight at 95°C. Two
grams of the dry ground material were placed in a

250 ml. Erlenmeyer flask and extracted with five

80 ml. portions of 80% alcohol. The alcohol was
brought to boiling and boiled for five minutes, cooled

' and filtered. After the last extraction the residue

was washed several times with 80% alcohol.

The alcohol was evaporated at reduced pressure
at 50°C. and the residue taken up with about 150 ml.
water. The extract was clarified with lead acetate
and deleaded with diabasic sodium phosphate. The
reducing power of an aliquot was determined and
expressed as dextrose.

The Shaffer and Hartman iodine titration method
was used to determine the reducing power. Twenty-five
ml. each of copper sulphate and Rochelle salts solution
were placed in a 500 ml. Erlenmeyer flask and 50 ml.
sugar solution added from a pipette. This was brought
to boil in four minutes and boiled two minutes, cooled
to 40°C. Twenty-five ml. iodine-iodate solution (60 gms.
potassium iodide and 5.4 gms. potassium iodate to one
liter) added and mixed, 17 ml. H2804 (175 m1. concen-
trated acid to one liter) added and then 20 ml. saturat-

ed potassium oxolate solution. The excess iodine was

11

titrated with 0.1N sodium thio-sulphate. The difference
between the amount of thio-sulphate used and that used
in a blank determination multiplied by 6.56 equals
milligrams copper reduced by the sugar solution. Dupli-
cate determinations were made which checked to 0.1 ml.
this-sulphate.

One hundred ml. of the clarified extract was
hydrolyzed by adding 10 m1. concentrated HCl and hold-
ing at 70°C. for 10 minutes. This was cooled, neutralized,

and the reducing power of an aliquot determined and
expressed as total sugars.

The residue from the alcohol extraction was
washed into the Erlenmeyer, heated for 50 minutes over
a water bath, cooled and a 1% solution of taka-diastase
added. This was digested for 36 hours at 58°C., filtered,
washed with enough water to make 150 ml., then 8 ml.
concentrated H01 added and refluxed over a water bath
for two and one half hours. It was cooled, neutralized,
made up to 250 ml. and the reducing power determined
without previous clarification. From this the starch
content was calculated.

The residue from the taka—diastase digestion
was washed into the Erlenmeyer with dilute HCl (8 ml.
to 150 ml. water) and hydrolyzed for two and one half

hours, cooled, neutralized, filtered, and made up to

12

250 m1. and the reducing power determined. From this,
calculations were made for acid hydrolyzable poly-

saccharides other than starch, presumably hemi-cellulose.

Nitrogen Analysis

 

Soluble, insoluble, and total nitrogen were
determined by the Experiment Station Chemist, using
the Heldahl-Gunning method.

Histological

 

Sections were made from girdled and natural
stems, of successful and unsuccessful grafts, and
also of pruning wounds which had begun to heal.

Fresh material was sectioned on a sliding microtome
set to cut 20 microns. They were stained by a
modification of a method described in Turtox news:-
sections were placed in an alcoholic solution of
safranine for 50 minutes to several hours. They were
destained in acidified 50% alcohol and transferred

to 50%, 70%, 95% and 100% alcohol, standing in each
only a few minutes. They were then passed through

75% xylol, into xylol in which a small amount of
gentian violet was dissolved, allowed to remain there
until the cellulose tissue was stained, then transferred

to pure xylol and mounted in balsam.

. l3
PRESENTATION AND DISCUSSION OF DATA

Counts of grafts growing, live and dead were
made on June 28 and August 9. On the earlier date
many cions were still alive but it was impossible to
tell whether or not union was established. 0n the
later date, however, all cions were either growing or
dead. Table 1 gives the results of the August count.

When the count was made, several cases of defec-
tive waxing were discovered; these were discarded
from the record.

It will be observed from this table that the
stock apparently is not the controlling factor in
the process of uniting of the graft. The degree of
success on the natural stock varied from 0 to 52.7
per cent. The stock above the girdle showed varying
success from 12.5 to 58.8 per cent and the stock
below the girdle varied from 15.0 to 61.6 per cent
living. The nitrate stock gave more uniform results
but in this case the cions used were the types which
gave approximately the same percentages on other
types of stock. These data substantiate field observa-
tions. All grafts which failed to unite were examined
and in practically every case the stock formed callus
quite freely but the cion did not; apparently it was
the failure of the cion to form callus which was

responsible for the failure to establish union.

14

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There does seem to be some influence of the
condition of the cion upon the degree to which grafting
is successful. With the natural cions, there was an
increase in the percentage of success with increased
age of cion wood. Spring cut cion woodgave considerably
better results than fall out cion.wood. This difference
might appear to be due to the size of the buds and the
readiness with which they begin growth. Supposidly the
early growth would cause excessive drain on the cion
before union was formed and thus prevent the union. This
was not the case, however, for cions of the one year
old wood where the buds were the largest did not start
to grow and die later, the cion apparently died before
the buds could begin to grow.

Cions treated by girdling, defoliation, and nitrogen
application gave inconsistent results when grafted on
various stocks.

Carbohydrate and nitrogen analyses of the cion
wood, with the percentages of success in grafting are
presented in Table 2. In this table the results of the
nitrate cion upon various stocks are averaged, which is
true of those of above the girdle, below the girdle and
defoliated cions. It will be noted that the c/N ratio
in the "Natural-fall" cion increases with the age of the

wood and that the degree of success also increases in

16

 

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17

the same direction. The same holds true also in the
"Natural-spring".cion, but comparison of the fall and
spring ratios show that the fall ratio is larger than
the spring ratio for the same type of wood in every

case except one, If increased success in grafting is
associated with increased C/H ratio, the fall cut cion
should be superior to the spring out cion, but this is
not the case. This ratio is higher also in the girdled
and defoliated cion but the percentage of success is
smaller. In the nitrate cion, the ratio is smaller

while the percentage successful grafts is not materially
changed. In the same manner, no single class of carbohy-
drates or nitrogen varies consistently with or inversely
to the degree of success in grafting.

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appear in Table 5 and here again there is no consistent
nor significant variation.

Chemical analyses and field results of the cion
wood from the Graham Station are given in Table 4. These
cions were treated about a month before those from the
Ferestry nursery and showed considerable swelling above
the girdle and ring, Figure 1. They were grafted on
natural stock in the Ferestry nursery in the same manner
as the other cions. It was expected that the results

from this lot of cions would show marked differences.

18

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B B 0. T. B.L T. 0
.e T. .L n I
as e 0. u
8 fl. 9

’r?

yeaaasa ensue .awaeeem.T
Banana son“ soao Ho madness dang“ use momhamss somonpun use epsnchnopuso t.¢ edema

20

There are some differences both in field results and
in carbohydrate content but they do not tend in the
same direction in the girdled and ringed cion nor are

the results of grafting consistent with the analyses.

Histological

 

The most striking aspect in the sections of
walnut grafts (Figures 2 and 5) is the large size and
number of the vessels, and of the large proportion of
the old xylem tissue which is dead. The vessels had
not become plugged with gum, as is common in tissues
of the apple (Figures 4 and 5).

Sections of pruning wounds on walnut stems
(Figures 6 and 7) show some degree of closure of the
vessels due to the formation of tyloses (Figure 8)
but little or no gum formation. The degree to which
the vessels are closed is considerably less than in
apple wounds. The tracheids and vascular rays seem to
be plugged. These observations may be significant in
partially explaining the difficulty in propagating the
walnut by grafting. If the vessels remain.open so that
rapid loss of water takes place and the tracheids and
rays become plugged, making translocation of stored
food materials difficult, active division of the cambium

cells would be limited or prevented, thus reducing the

21

amount of wound meristem formed. Since union of stock
and cion results from the meeting and fusion of the
wound meristem arising from each, no union could take
place if the meristem were not formed by the cion.
Since the cion is severed from its water supply some
time before it is placed on the stock it suffers more

from the loss of water than the stock does.

Root Grafting

Y fivvavvfi

 

A few rather interesting observations were made
regarding the root grafts. Cions treated with sucrose,
dextrose, and those from above the girdle remained
alive longer than other cions, although no successful
unions were obtained; treatment with sugar solution
seems promising for further study. Treatments with
potassium nitrate and other were very injurious; the
cions turned black and died in a very short time.

Walnut cions depressed callus formation by the
apple roots and walnut roots depressed callus formation
in the apple cions placed on them (Figures 9 and 10).
This suggests the possibility that the walnut contains

some substance inhibitory to callus formation.

22

QONCLUSIONS

v" vvwfi

 

At the present stage of the experiment, the
condition of the cion wood seems to be the limiting
factor in successful propagation of the walnut by
grafting. The carbohydrate and nitrogen content of
the cion does not seem to have the controlling
influence. It may be possible that some other sub-
stance, not taken into consideration in the present
work does exert more influence.

The anatomical and morphological relations
seem to be very important and deserve more study.
Treatments of the cion with sucrose and other

solutions should receive further attention.

25

SUMMARY

1. The stock of the walnut seems to be the
least variable of the two symbionts in behavior
in grafting.

2. The percentage of success in grafting

increases with age of wood, up to three years old.

5. Cion.wood cut in spring seems to be superior

to that cut in fall.

4. Girdling of the stem and application of a
nitrate fertilizer do not seem to influence greatly

the degree of success in grafting.

5. Plugging of tracheids and vascular rays,
associated with the failure of vessels to become
plugged, seems to limit callus formation and

success in grafting.

24

i4.5112110ijr)G s GENTS

 

The writer wishes to express his thanks to
Messrs. V.R.Gardner, F.C.Bradford and J.W.Crist
for many valuable suggestions and helpful criticisms
offered during the progress of this work and to
Hessrs. W.C.Dutton and L.P.Watson for help with photo-
graphic work, and to Mr.W.E.Thrun for the nitrogen

analyses.

25

 

' Fig. l.- Walnut branches from the Graham I
Horticultural Experiment Station, hear
Grand Rapids showing girdle and ring.

26

‘ :. C. '0. . ‘.
e‘-’ ..'. I. .f O J
.3 .. | ‘

 

 

,Jig. 2.-Cross section of whip graft of walnut.
{ost of old xylem in both cion and stock is
dead. The vessels are large and not plugged.

27

A

. . .
a I s
o .04...
. .

..- ..e.n . ., o!

e Ease _ _
.. knew/he“ .e a... fin! .. ..

. ... .. .e.... .. u. \xuawks .. W.

. Fig. 5.-,Cross section of whip graft of walnut.

. -.. _ 4.. ”
1.x?

I: (’1'. .V:‘. L!

 

 

the regeneration in the tongue of the stock was

There is very little callus tissue on cion and
very weak until union became established.

28

z; "b (H): .
9):)! 3”“ ' "Hi

' .

:1 (TN)

e my ti

)
l T

H
I“ fly“ Q

': :2 9'!" ‘1 (13::
Iwhmtfi¥‘("ufi

i“ ,

K , A

, Fig. 4.- Longitudinal section of amputation,
wound on apple stem. Vessels are completely
plugged near cut surface and walling over
callus plentiful.

 

 

29

.modmmfip mnflhanodqfi mpoopoum mdommo> Ho
wdamwdam and dopHaHH hAo> mu aoahx doom .ofimmfip Bodhx wqdoh on» knew
muammnom and Mann on» mqa>oaon an odds Boom magma do undom I.m .mHm .

 

 

 

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30

/3 the circumference. ’
Tracheids are plugged, vessels are open except for occasional

ones having tyloses.

- Fig. 6.- Amputation wound on walnut stem, slightly below the
injury. Xylem is dead for nearly 1

31

 

 

 

.onw mHHoo has and mdwonownp hams asp domoao and

maommo> Bow knob .npaq on» on and dado; mo unopxo onfiuso
on» used ma aloN o .n ohdMam spas anomaoo .wqapd>flpadw
non: gasp Ho Hm>oaou n odds Boom pdfiHmB no dudes I.> .mam

. v II . t I I.“ I .
I. . u\3¢....W4.LLflf' \

W. ....
Q

!

‘..I‘..Il’rmo

 

32

 

Fig. 8.- Higher magnification of a portion
of Figure 6 showing tyloses in a few vessels.

33

.deHwo mnwsonm mmaappdo mamas daemon I.m .MHm

 

54

.nnmmnw no Mao; kno> neapwaao% deHwo
.mpoon unmask so doomam soon was moans muoao oammd I.oa .mflm .

 

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$4.4

 

 
 

 

l.

2.

5.

4.

6.

9.

10.

35

Bibliography

Baltet, Charles. L'Art de Greffer, 7th edition
Paris 1902 (lst. ed. 1869).

Batehelor, L.D.., Walnut Culture in California.
California Agri. EXP. Sta. Bul. 579. 1924

Cardinell, H.A. and F.C.Bradford, Grafting in the
Apple Orchard. Iieh.Agri.Exp.Sta.Bu1.l4z. 1925

Cooper, J.C., Walnut Growing in Oregon.-Bu1. Pass. Dept.
Oreg. RR. & Navig.Co. Portland. 1910

Fuller. Andrew 3., The Nut Culturist,- Orange-Judd
New York. 1896

Knight, Thomas Andrew, Physiological and Horticultural
Papers p. 231. London. 1841

Ibid p. 326

Kraus, E.J., A Method of Budding the Walnut.
Greg. Agri. EXP. Sta. Ciro Bule 160 1911

Lake, E.R., The Persian Walnut Industry of the United
States. U.S.D.A.,Bur.Pl.Ind.Bul.254. 1913

Iowis, C.I., Walnut Culture in Western and Southern
Oregon., Gen. Pass. Dept. Sou. Pacific Ry.
Portland. Oreg. (no date)

11. massey, A.B.. Antagonism of the walnut in Certain

Plant Associations. Phytopath. 15:773. 1925

12.

15.

l4.

l5.

56

Oliver, George W., Budding the Pecan. U.S.D.A.,
3111‘. P1. Ind. 31.110 300 1902

Reed, C.A., Nut-Tree Propagation. U.S.D.A.,Farmers
Bul. 1501. 1926

Stuckey, H.P. and E.J.Kyle., Pecan Growing.
EacMillian, Iew Yerk. 1925

Woolsey, 0., Pecan Growing and Propagation in
Arkansas. Univ. Ark. Ext. Cir. 228. 1927

 

 

 

 

 

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