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thesis entitled

EFFECT OF STRESSES ON GROWTH AND

YIELD OF ASPARAGUS (APARAGUS OFFICINALIS L.)

 

 

presented by
Daniel R. Shelton

has been accepted towards fulfillment l
of the requirements for

M.S. degree in Botany & Plant Path". |

 

 

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Date 4/25/78

 

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EFFECT OF STRESSES ON GROWTH AND

YIELD OF ASPARAGUS (ASPARAGUS OFFICINALIS L.)

 

By

Daniel R. Shelton

A Thesis

Submitted to
Michigan State University
in partial fulfillment of the
requirements for the degree of

Master of Science

Department of Botany and Plant Pathology

1978

(
K ,
\/

ABSTRACT

EFFECT OF STRESSES ON GROWTH AND
YIELD OF ASPARAGUS (ASPARAGUS OFFICINALIS L.)

 

By

Daniel R. Shelton

One-year-old a5paragus plants held for two months under a constant
16 hour photoperiod and temperatures of 20°-28°C in the greenhouse, dif-
ferentiated buds and storage roots throughout the growing season. Growth
of two-year-old asparagus crowns in the field was unaffected by length
of harvest duration. Average weight of stalks produced per crown by the
end of the season was also unaffected by length of harvest, although tim—
ing and rates of spear and fern production were affected by weather condi-
tions and length of harvest. Extreme variability in growth and develop-
ment among plants was observed.

In the first year of harvest, marketable yields from four-year-old
asparagus plants increased throughout the six weeks of harvest. In the
second year of harvest, marketable yields remained about the same during
the first six weeks of harvest, then decreased drastically thereafter.
Percent marketable spears and average weight of spears declined through-
out harvest in both years. In general, two years of yield data were
insufficient to determine the effect of length of harvest on long term
yields of asparagus.

Soluble storage carbohydrate levels of asparagus plants decreased

Daniel R. Shelton

during harvest and after harvest as spears and stalks were produced. Car-
bohydrate levels increased after stalks had matured, and plants regained
original levels of carbohydrate by mid- to late summer. Extending the
harvest period resulted in increased time and severity of carbohydrate
depletion, although all plants, regardless of length of harvest, possessed
comparable levels of storage carbohydrate by the end of the season.
Asparagus plants replenished the supply of carbohydrate in established
storage roots before producing new storage roots.

Asparagus storage carbohydrates were identified as fructose-oligosac-
charides, which varied considerably in size, mobility, and percent fructose'
and glucose. The largest oligosaccharides were composed of 90% fructose
and 10% glucose and had a molecular weight of approximately 3200 (18
molecules of fructose and 2 molecules of glucose).

Treatment of asparagus plants with the herbicides, simazine, linuron,

or terbacil, either inoculated with Fusarium oxysporum f. sp. asparagi

 

and F. moniliforme or uninoculated, resulted in increased crown survival

 

and increased total yields. Treatment with field rates of simazine re~
sulted in higher total yields per crown than with other herbicides; mar-
ketable yields were not affected. Soil populations of E3 oxysporum and

E, moniliforme were not significantly different in any of the treatments

 

by the end of the second season after inoculation.

To Roland and Bobby

ii

ACKNOWLEDGMENTS

To Dr. Melvyn L. Lacy, I express appreciation for his guidance
during this project, and for his assistance in the preparation of this
manuscript.

To the members of my guidance committee: Dr. John Lockwood, Dr.
Alan Putnam, and Dr. Hugh Price, I extend my thanks for their suggestions
and critical evaluation of the manuscript.

To all those individuals, too numerous to mention, who have provided

me with financial, physical, and/or moral support, my deepest thanks.

iii

TABLE OF CONTENTS

LIST OF TABLES .
LIST OF FIGURES
INTRODUCTION .
LITERATURE REVIEW

1. Growth and Bud Formation in Asparagus .
II. Effect of Length of Harvest on Yields . .
III. Effect of Length of Harvest on Seasonal Fluctuations
of Storage Carbohydrates .
IV. Characterization of Asparagus Storage Carbohydrates .
V. Effect of Three Herbicides on Spear and Stalk Production
and Crown Survival in Natural and Artificially
Infested Soil .

METHODS AND MATERIALS

I. Growth and Bud Formation in Asparagus .

II.-III. Effect of Length of Harvest on Yields and Seasonal

Fluctuations of Storage Carbohydrates . .
IV. Characterization of Asparagus Storage Carbohydrates .
V. Effect of Three Herbicides on Spear and Stalk Production
and Crown Survival in Natural and Artificially
Infested Soil .

RESULTS

I. Growth and Bud Formation in Asparagus .
II. Effect of Length of Harvest on Yields . .
III. Effect of Length of Harvest on Seasonal Fluctuations

of Storage Carbohydrates . .

IV. Characterization of Asparagus Storage Carbohydrates .

V. Effect of Three Herbicides on Spear and Stalk Production
and Crown Survival in Natural and Artificially
Infested Soil

DISCUSSION .

LITERATURE CITED .

iv

11
13
13
I4
15

18

. 20

20

. 23
. 30
. 44
. 49
. 62

. 69

Table

10.

11.

LIST OF TABLES

Initial yields from asparagus plots harvested for 2, 4,
or 6 weeks

Yields from asparagus plots harvested for 0, 2, 4, or 6
weeks the previous year .

Effect of length of harvest on levels of soluble storage
carbohydrate and percent storage root dry matter (1976)

Effect of length of harvest on levels of soluble storage
carbohydrate, total carbohydrate per storage root system,
dry weight of storage roots, and percent storage root
dry matter (1977)

Ratios of fructosezglucose in hydrolyzates of oligosac-
charides eluted from chromatograms developed for 4, 12,
or 24 days

Molecular weight determination of oligosaccharides extracted
from asparagus storage roots

Effect of three herbicides on crown survival and stalk
production in natural and Fusarium infested soil

Effect of three herbicides on yields of asparagus per plot
in natural and Fusarium infested soil .

Effect of three herbicides on yields of asparagus per crown
in natural and Fusarium infested soil .

Orthogonal comparisons of the effects of three herbicides

on crown survival, asparagus yields per plot, and asparagus
. 60

yields per crown in natural and Fusarium infested soil

Effect of three herbicides on soil populations of f:
oxysporum and E: Moniliforme in natural and artificially
infested soil . .

 

29

. 35

. 4S

. 50

SS

56

. 58

. 59

. 61

Figure

10.

11.

LIST OF FIGURES

Production of spears, buds, and new storage roots by one-
year—old plants held under a constant 16 hour photOperiod
and soil temperatures of 20°-28°C .

Marketable yields from asparagus plots harvested for 2, 4,
or 6 weeks

Marketable yields from asparagus plots harvested for 4, 5,
8, or 10 weeks. Plots were harvested for O, 2, 4, or 6
weeks the previous year .

Percentage of marketable spears produced by asparagus
plants harvested over a 10 week period

Effect of length of harvest on levels of soluble storage
carbohydrate (1976)

Effect of length of harvest on levels of soluble storage
carbohydrate (1977)

Effect of length of harvest on storage root growth

Effect of length of harvest on total soluble carbohydrate
per storage root system . . .

Representation of paper chromatograms developed for 4, 12,
or 24 days, drawn to 0.5 scale lengthwise. Numbers
identify bands of carbohydrate eluted from undeveloped
portions of the chromatograms for analysis

Gas chromatogram of trimethylsilyl derivatives of oligosac-
charide hydrolyzates (band #1, Figure 9). Peaks are: 1.

fructose; 2. fructose; 3. glucose; 4. fructose; 5. unknown;

and 6. glucose

Gas chromatogram of trimethylsily derivatives of oligosac-
charide hydrolyzates (band #10, Figure 9). Peaks are: 1.
fructose; 2. fructose; 3. glucose; 4. frucose; 5. unknown;
and 6. glucose

vi

Page

. 21

. 24

. 27

. 31

33

. 4O

. 42

. 47

51

INTRODUCTION

Commercial asparagus production in Michigan is a multimillion dollar
industry (30). Michigan presently ranks third among states in asparagus
production, behind California and Washington (30), and acreage planted
to asparagus continues to increase (19). Despite increased production
due to increased acreage, yields of asparagus have been in a general
decline since 1970 (19), causing great consternation within the asparagus
industry. Although the exact reasons for the decline in yields are not
known, stress factors———cu1tura1, biological, and environmental———are un—
doubtedly involved. The general scope and purpose of these investigations
was to examine the effect of stresses on the growth and yield of asparagus.

In order to understand the effects of stresses on the growth and
yield of asparagus it is important to have an understanding of those fac-
tors———genetic, physiological, and environmental-——which affect its de-
velopment. It is generally accepted that the growth and marketable yield
of asparagus is closely related to reserve carbohydrate materials pro-
duced and stored during the fern period of the preceeding year. It is
also agreed that marketable yields are directly related to bud size and
spear size. Many stresses may be imposed on asparagus plants which affect
levels of storage carbohydrate and/or bud and spear size. These include:
spring freezes, extended harvest periods, drought, weed competition, and
damage from insects, disease, tillage, and herbicides. Many of these

stresses can be ameliorated to a greater or lesser extent. Damage from

weeds, insects, and disease can be minimized through the use of pesticides
and resistant asparagus varieties. Tillage damage can be eliminated with
zero-tillage cultural practices. Even spring freezing and drought can be
ameliorated to some extent through the use of irrigation. The one stress
which cannot be avoided isharvestingcfi?asparagus. It is necessary,
therefore, to have a precise understanding of how length of harvest affects
levels of storage carbohydrate and bud and spear size in order to optimize
yields without adversely affecting plant vigor. The major thrust of this
research was to investigate the effect of length of harvest on yields

and seasonal fluctuations of storage carbohydrates. Investigations were
also initiated to observe the effect of length of harvest on growth and
development of asparagus plants, to elucidate the structure and composi-
tion of storage carbohydrates, and to examine the effect of different
herbicide treatments on yields of asparagus and their interaction with

asparagus root rot fungi.

LITERATURE REVIEW

1. Growth and Bud Formation in Asparagus

Individual asparagus plants, even of the same cultivar, differ con-
siderably in their growth patterns (35). This variability is due to
the fact that asparagus is dioecious; plants of the same variety are not
isogenetic. Male crowns, on the average, are larger than female crowns
and are of greater longevity (35). Male plants produce fewer but larger
spears (35,12). Sawada (ZS) calculated that mature male plants produced
28% more carbohydrate, on a daily basis, than female plants.

An understanding of bud formation and subsequent spear formation is
prerequisite to understanding growth and development of asparagus. Buds
are produced in terminal clusters, and the clusters Operate independently
(23). Buds produced one season give rise to spears the next season (35,
3). Bud size diminishes from larger buds near the stalks to smaller buds
near the periphery of the crown (35,23). Spear size is directly related
to bud size (3,23), although Tiedjens (35) observed that large buds did
occasionally give rise to small spears. Rajzer (23) studied the rela-
tionship of bud dominance and size to spear size. He observed that the
primary bud (the first to break dormancy) produced the largest spear in
the cluster, that the secondary bud produced the second largest spear,
that the tertiary bud produced the third largest spear, etc. There seemed
to be a direct correlation between the size of buds and the size of the

stalks which furnished the carbohydrate for their formation (36). The

production of small spears during late harvest, the production of small
stalks after harvest, and the subsequent production of small buds seemed
to be a result of reduced carbohydrate levels (36). Spear diameter one
season was positively correlated with stalk diameter the preceeding sea—
son (7).

Depth of plant and/or soil temperatures have an effect on spear num-
ber and size. The deeper asparagus crowns were planted (up to 30 cm)
the fewer but larger the spears they produced (33). Soil temperatures
of between 19° and 24°C produced the largest spears, while 26°C produced
maximum yields (9). No studies have been conducted concerning the effect

of temperature on bud size.

11. Effect of Length of Harvest on Yields

 

Several studies have been conducted during the past 50 years concern-
ing the effect of length of harvest on asparagus yields. Jones (12)
studied the effect of two lengths of harvest on the yields of male and
female 'Palmetto' asparagus plants in California. One set of plots was
cut for approximately 9 weeks in 1926 when plants were four years old,
11 weeks in 1927-28, and 12 weeks in 1929-31: another set of plots was
cut for approximately 4 weeks in 1925 when plants were three years old,
11 weeks in 1926, 13 weeks in 1927—28, and 14 weeks in 1929-31. While
both male and female plants yielded a significantly greater number of
spears in the longer harvest plots, only the male plants yielded a signi-
ficantly greater weight of spears. The average spear weight for plots
harvested for the longer period was significantly lower than plots har-
vested for the shorter period. Although there were no significant dif-

ferences in number of stalks produced, stalks of plants in the longer

harvest weighed significantly less than those in the shorter harvest.

Haber (11) studied the effect of harvesting for different periods of
time on the yields of 'Mary Washington' asparagus plants in Iowa. Plots
were harvested for periods of l, 3, 5, 7, 9, or 11 weeks, beginning when
the plants were four years old (1929). In the first year, due to the
long harvest, the plots harvested for 11 weeks yielded the greatest num-
ber and weight of spears. In 1920, plots harvested for 9 or 11 weeks
yielded equal numbers and weights of spears. Plants harvested for 11
weeks declined in vigor from year to year; after five years the majority
of plants were dead. From 1930-34, plots harvested for 9 weeks yielded
a greater number of spears than any of the other plots; however, only in
1931 did they yield the greatest weight of spears. In 1932 and 1933
plots harvested for 7 or 9 weeks produced approximately equal weights of
spears; in 1934 plots harvested for 7 weeks produced the greatest weight
of spears. Spear size in plots harvested for l or 3 weeks increased
from 1929-34 in comparable fashion: spear size in plots harvested for 5
weeks also increased in size, but to a lesser extent. Spear size in plots
harvested for 7 weeks remained approximately the same or increased gradu-
ally. Spear size in plots harvested for 9 weeks declined.

Williams and Garthwaite (39) studied the effect of three lengths of
harvest on the yields of 'Giant Mammoth' asparagus plants in England.
Plots were harvested for periods of 6, 8, or 10 weeks, beginning when the
plots were five years old (1964), with the exception of the plots harvested
for 6 weeks which were first cut when four years old (1963). In the first
two years of harvest, plots harvested for 10 weeks produced a significantly
greater number of spears than plots harvested for 6 or 8 weeks. In 1966

and 1967 plots harvested for 8 or 10 weeks produced approximately equal

numbers of spears. In 1968 plots harvested for 8 weeks significantly out-
yielded plots harvested for 6 or 10 weeks. Weights of spears were not
reported. Percentage of large spears in the 6 and 8 week harvest periods
was comparable and declined gradually from 1964-68; percentage of large
spears in the 10 week harvest period declined drastically. The plots
harvested for 6 weeks consistently produced a greater number of early
spears than the plots harvested for 8 weeks, which in general, produced

a greater number of early spears than the plots harvested for 10 weeks.
Monetary return fOr each of the harvest periods was averaged over the
five year period. Taking into account total number of spears, size of
spears, and earliness of spears, the plots harvested for 8 weeks yielded
a significantly greater monetary return than those harvested for 6 or 10
weeks.

' Deonier and Hoffman (5) studied the effect of six lengths of har-
vest and times of harvest on the yields of 'Mary Washington' asparagus
plants in Mississippi. Plots were harvested for periods of 4, 8, or 12
weeks in the spring, 4 or 6 weeks in the fall, or 4 weeks both in the
spring and fall; plants were first harvested when four years old (1937).
The best marketable yields, averaged over the five year period, were from
plots harvested continuously for 8 weeks in the spring. Plots harvested
for 12 weeks in the spring yielded well from 1937-39, but by 1940-41
yields had dropped off drastically. Yields from plots harvested for 4
weeks in the spring increased from year to year and by 1941 were only
slightly less than those from plots harvested for 8 weeks. Yields from
plots harvested only in the fall, or in both spring and fall, were small.
Percentage of marketable spears produced in 1941 was greatest in the 4

week spring harvest, followed by the 8 and 12 week spring harvests, and

was least in the fall and spring-fall harvests.

Takatori, et a1. (30) studied the effect of several lengths of har-
vest and times of harvest on the yields of asparagus plants in California.
Plots were harvested for 4 weeks (Feb. - March), 8 1/2 weeks (Feb. -
April), 13 weeks (Feb. - May), or 17 weeks (Feb. - June) in the spring;

8 l/2 weeks (June - July, July - Aug., Aug. - Sept., or Sept. - Oct.) in
the summer or fall; or 4 weeks in the spring and fall (Feb. - April and
Aug. - Sept., or Feb. - April and Sept. - Oct). From 1966-68 best over-
all yields (numbers and weights of marketable spears) were obtained from
the plots harvested for 8 1/2 weeks in the spring. Decreases in yields
from the plots harvested for 13 or 17 weeks in the spring during 1966
were caused by losses in spear size. During 1967 and 1968 both weights
and numbers of spears decreased. The reduction in numbers of spears pro-
duced was a result of loss in stand. In 1969, all plots were harvested
for 8 1/2 weeks in the spring. Plots previously harvested for 4 weeks

in the spring yielded the greatest weight of marketable spears, followed
by the plots harvested for 8 1/2 weeks in the spring and the plots har-
vested for 4 weeks in the spring and fall (Feb. - April and Sept. - Oct).
The plots harvested in the fall (Sept. - Oct.) and spring and fall (Feb. -
April and Aug. - Sept.) yielded moderately well, while the plots harvested
for 13 or 17 weeks in the spring and the plots harvested in the summer
yielded very poorly.

Lewis (17) studied the effect of time of initiation of harvest on
subsequent yields of 'Mary Washington' asparagus plants in Illinois.

Six harvest treatments were carried out:

 

 

Treatment Weeks Harvested
Number 1927 1928 1929 1930 1931-33
1 0 O 4 6 8
2 0 2 4 8 8
3 0 4 6 8 8
4 2 4 8 8 8
5 4 6 8 8 8
6 6 8 8 8 8

From 1931-33, when all plots were harvested for an 8 week period, treatment
two produced both the greatest number and weight of spears, followed close-
ly by treatment one. Treatments three and four yielded approximately equal
numbers and weights of spears, while treatments five and six lagged far
behind the other treatments. Treatment two produced the highest percent-
age of large spears and greatest average spear weight, averaged over the
seven year period, followed by treatments one and three. Lewis calculated
monetary return per acre for each of the treatments, based on total spear
weight and spear size, and found that treatment two yielded the greatest
monetary return over the seven year period. Lloyd and McCollum (18)
continued Lewis' study from 1933-37. They found that the trends dis-
cussed above continued through 1937 (all plots were cut for 8 weeks from
1931-37). Treatment two continued to yield the greatest total number and
weight of spears as well as greatest number and weight of large spears,

followed closely by treatment one.

111. Effect of Length of Harvest on Seasonal Fluctuations of Storage

 

Carbohydrates

 

One previous study was conducted in North Carolina on the effect of

length of harvest period on fluctuations of storage carbohydrates in
asparagus (27). Asparagus plants were periodically sampled and assayed
using harvest periods of 4 or 6 weeks. Reducing sugars, non-reducing
sugars, starch, and total nitrogen were determined. Large fluctuations

in levels of non-reducing sugars were found throughout the season, while
levels of reducing sugars and starch fluctuated very little. Concentra-
tions of non-reducing sugars decreased at a moderate rate from beginning
to end of harvest, after which concentrations decreased dramatically.

Sugar levels reached a minimum about a month after the end of harvest,

then increased rapidly for about two months, regaining levels comparable
to those of early spring by late summer. Lengthening the harvest period
from 4 to 6 weeks caused a greater depletion of carbohydrate reserves,

and a longer period for carbohydrate accumulation after the end of harvest
was required, than with the shorter harvest. Harvesting for 6 weeks did
not appear to permanently affect the carbohydrate composition of the crown.
Scott et a1. (27) also followed carbohydrate fluctuations in asparagus
plants harvested in the fall. They found a similar pattern of cyclic
depletion and replenishment of storage carbohydrate, except that the pattern
was shifted by about six months. Carbohydrate reserves began to decline
in early fall as harvesting began, remained at moderate levels through

the winter, and declined further during the spring as fern was being pro-
duced. Carbohydrate reserves were replenished by early summar and remained
so until harvesting began again in early fall. Plants harvested in the
spring were in a state of carbohydrate depletion only about three months
out of the year, while plants harvested in the fall were in a state of

depletion or semi-depletion about nine months out of the year.

10

IV. Characterization of Asparagus Storage Carbohydrates

 

Carbohydrates from asparagus storage roots were first isolated in
1909 (34). When sections of asparagus storage root were treated with
95% ethanol a milky white precipitate was formed. The precipitate was
composed, in part, of an inulin—like carbohydrate which was termed
asparagose. Upon hydrolysis asparagose yielded 93% fructose and 7% glu-
cose.

A storage carbohydrate was isolated from asparagus in 1937 which was
termed asparagosin (26). The asparagosin molecule was estimated to be
composed of 13-14 fructose residues. Hydrolysis of the methylated deri-
vative yielded dimethyl-, trimethyl-, and tetramethyl-fructose; the
trimethyl-D-fructose was identified as 3, 4, 6- trimethyl-D-fructofuranose.
Whether glucose was present in the molecule was not determined.

Sucrose was reported as the storage carbohydrate of asparagus by
Scott et a1. (27). Since no quantitative data were presented, it appeared
that the investigators presumed (without direct evidence) that the non-
reducing portion of the carbohydrate present was sucrose.

Shiomi et a1. (29) isolated and characterized eight fructo-oligosac-
charides from asparagus. Oligosaccharides were exhaustively methylated
and hydrolyzed, and methylated derivatives analyzed by gas-liquid chroma-
tography. Identification of constituent monosaccharides and glycosidic
bonds were deduced by comparing retention times of the methylated deri-
vatives with retention times of methylated sugars of known composition
and structure; mass spectrometry was not used. The eight fructo-oligisac-
charides were tentatively identified as 1F(l-B-fructofuranosyl)1 sucrose
{l-kestose}: lF(l-B-fructofuranosyl)2 sucrose {nystose}: lF(l-B-fructo-

furanosyl)3 sucrose: 6G(I-B-fructofuranosyl)1 sucrose {neokestose}:

ll

6G(l-B-fructofuranosyl)2 sucrose: 66(1-B-fructofuranosyl)3 sucrose: and

1F(l-B-fructofuranosyl)2-6G-B-fructofuranosyl sucrose.

V. Effect of Three Herbicides on Spear and Stalk Production, and Crown

Survival in Natural and Artificially Infested Soil

Herbicides are known to have a wide variety of effects on soil micro-
organisms and plants, resulting in both increased and decreased disease
incidence and severity (2,13,15). Herbicides may directly affect popula-
tion levels or activities of pathogens in the soil, affect levels or acti-
vities of microorganisms antagonistic to soil-borne pathogens, or somehow
affect resistance or predisposition of plants to disease (13).

Fusarium oxysporum f. sp. asparagi Cohen and Heald and Fusarium

 

moniliforme (Sheld.) emend. Snyd. and Hans. are the causal agents of the

 

wilt and root rot diseases of asparagus (10). Kaufman (14) found that
treatment of soybean-cropped soils with the phenylurea herbicides linuron
and diuron caused a decrease in the total number of Fusarium propagules
in those soils, but that there was no effect on Fusarium populations in
corn-cropped soils. Percich and Lockwood (21) demonstrated that popula-
tions of Fusarium in Conover atrazine amended loam soil were increased 4-

fold. Population levels and activities of propagules of Fusarium solani,

 

f. sp. pisi and Fusarium roseum f. sp. cerealis 'Culmorum', as well as

 

incidence of pea root rot and corn seedling blight, were enhanced by
atrazine.

Simazine-treated plots have occasionally been observed to yield a
greater total weight of spears than weeded check plots (Putnam, personal
communication). However, Welker and Brogdon (38) did not obtain higher

yields from simazine-treated plots than from weeded controls. Dry weight

12

of asparagus plants from soils treated with simazine at 4.4 kg/ha (for

two years) or DMPA at 16.5 kg/ha was significantly greater than from un-
treated plants or plants treated with a number of other herbicides (24).
This was attributed to superior weed control by simazine; however, other
investigators (22,38) did not find simazine superior to other herbicides

in controlling weeds in asparagus.

METHODS AND MATERIALS

I. Growth and Bud Formation in Asparagus

Ten one-year-old 'Mary Washington' asparagus crowns were planted in
wooden boxes (three crowns each in two lO7xSlx46 cm boxes, 2 crowns each
in two 81x4lx46 cm boxes), filled to a depth of 28 cm with steamed soil,
and placed in the greenhouse. Crowns were placed on the surface of soil
in the boxes, then covered with 10-15 cm of expanded silica (Perlite).
Plants were held under a constant 16 hour photoperiod. Soil temperatures
ranged from 20°-28°C. Periodically, the Perlite was removed to observe
growth and development of the crowns, and to record numbers of buds,
spears, and new storage roots after which the Perlite was replaced.

A two-year-old asparagus plot at the Botany and Plant Pathology Farm
was divided into 1.5 x 18 meter replicated plots arranged in a completely
randomized design which were harvested for periods of O, 3, or 6 weeks, re-
spectively. Periodically (4/14/77 through 9/7/77) three to six complete
crowns and storage root systems from each of the plots were removed from
the soil. Plants were taken to the laboratory, washed free from soil, and
divided into spears and/or stalks, crowns, and storage roots. Plant parts
not immediately processed were stored at m5°C. Crowns, spears, and por-
tions of stalks were weighed, dried at 96°C for approximately 12 hours,
and reweighed to determine dry weight. Dry weight of whole stalks was
computed by extrapolating percent dry matter of stalk portions to the en-
tire stalk. Observations concerning growth and development of plants

were noted.
13

14

II.-III. Effect of Length of Harvest on Yields and Seasonal Fluctuations

 

of Storage Carbohydrates

 

A three-year-old asparagus plot at the Botany and Plant Pathology
Farm was divided into 1.5 x 7.7 meter replicated plots arranged in a ran-
domized complete block design which were harvested for periods of 0, 2, 4,
or 6 weeks, respectively. Storage roots from plants in each treatment
were sampled periodically from 4/9/77 through 10/29/77 by collecting a 15-
20 cm soil core containing root segments approximately 15 cm from the cen-
ter of the crowns with a 70 cm soil probe. Two to three plants from each
plot were sampled on each sampling date and four core samples were taken
per plant. Storage root segments were weighed and dried at 96°C for
approximately 12 hours, reweighed to determine dry weight, and then ground
in a Wiley Mill using a screen with 0.40 mm openings. Particles retained
and passed through the sieve were collected for analysis. Soluble storage
carbohydrates were extracted from one gram dried ground tissue in a
Sorvall Omni-mixer (Ivan Sorvall, Inc., Norwalk, CT) bucket containing
100 ml distilled water for two minutes at 4,400 rpm. Solutions were
centrifuged for 15 minutes at 4,000 rpm in a Universal Model U-V
International centrifuge (International Equipment Co., Needham, MA) to
remove emulsions, then filtered through Whatman glass-fiber filter paper.
Extract solutions were diluted 50-100 fold and total carbohydrates deter-
mined by a modified anthrone analysis (20). One ml of extract solution
was mixed with 9 ml of anthrone reagent (0.2 grams of anthrone dissolved
in 100 ml of 95% sulfuric acid), placed in a boiling water bath for 15
minutes, then immediately cooled in an ice bath. After the solutions had
warmed to room temperature, optical density was measured at 620 nm with

a Bausch and Lomb Spectronic 20 spectrophotometer (Bausch and Lomb,

15

Rochester, New York). Carbohydrate concentrations were determined using
a standard curve derived from sucrose.

In the following year, the harvest period was extended for 4 weeks
for each of the plots, resulting in harvest periods of 4, 6, 8, or 10
weeks corresponding to the 0, 2, 4, or 6 week harvest periods of the
previous year. Storage roots were not sampled in these plots the second
year.

In the two-year-old asparagus plot (page 16), three to six complete
crowns and storage root systems from each of the plots were removed
periodically from 4/14/77 through 9/7/77 from the soil for analysis of
storage carbohydrate levels. An attempt was made to obtain as much of
the storage root system as was possible, although small quantities of
roots were inevitably lost. Plants were taken to the laboratory, washed
free from soil, and divided into spears and/or stalks, crowns, and
storage roots. Storage roots were washed and stored at m5°C until further
processing. Randomly chosen storage roots were cut into 2.5 - 4.0 cm
segments, weighed, dried at 96°C for approximately 12 hours, reweighed to
determine dry weight, and then ground in a Wiley Mill as before. Carbo-
hydrate determinations were performed using the anthrone method as previ-
ously described, with the exception that fructose was substituted for

sucrose in deriving the standard curve.

IV. Characterization of Asparagus Storage Carbohydrates

 

One half gram of dried ground storage root tissue was extracted with
100 ml of boiling 80% ethanol in a Sorvall Omni-mixer for five minutes
at 10,800 rpm. The carbohydrate solution was filtered through Whatman

glass-fiber filter paper, taken to dryness in a flash evaporator,

l6

redissolved in distilled water, filtered through a 0.22 pm pore size micro-
filter (Millipore Corp., Bedford, MA), and again taken to dryness in a
flash evaporator. The residue was redissolved in 1-2 ml of distilled

water and stored in vials at WS°C until analyzed.

Aliquots of extract solution were streaked on Whatman 3MM chromato-
graphy paper and developed in propanolzethyl acetatezwater (7:1:2) (8)
for periods of 4, 12, or 24 days using a descending technique. Sucrose
and/or raffinose were used as reference sugars for the chromatograms
developed for 4 or 12 days. One of the carbohydrate bands eluted from
the chromatogram developed for 12 days, and subsequently characterized,
was used as a reference sugar for the chromatogram developed for 24 days,
by which time sucrose and raffinose had been eluted off the chromatogram.
Oligosaccharides were detected by spraying a small longitudinal strip of
the chromatogram with ketose sugar-specific NEP indicator (1% w/v a-
napthol in ethanol with 10:1 v/v 80% H3P04) (1), then heating at 100°C
for 2 minutes. Oligosaccharides were eluted from the undeveloped portions
of chromatograms. Sections containing specific oligosaccharides were cut
into small squares and extracted with 50 ml of double distilled water
for 30 minutes on a reciprocal shaker (115 cycles/minute). Carbohydrate
solutions were filtered through a 0.22 pm pore size microfilter, taken
to dryness in a flash evaporator, redissolved in 1 ml of double distilled
water, and stored at ~5°C until analyzed.

Fructose and glucose were determined via gas-liquid chromatography
(31,4,28). Quantities of carbohydrate solution containing 50-100 ug of
oligosaccharide were freeze-dried, then hydrolyzed with 1N HCl at 52°-
54°C for one hour in Kimax vials covered with teflon-lined caps. HCl

was neutralized with AgCO and the precipitate washed once with 100 ul ?;

3

17

acetic anhydride and twice with 1 m1 of dry methanol. All fractions were
collected and taken to dryness in a vacuum desiccator. Hydrolyzed samples
were trimethyl-silylated overnight with 50 ul of Tri-Sil Z (Pierce Chemical
Co., Rockford, IL). Samples were injected into either a Perkin Elmer 900
gas chromatograph equipped with a 3.7 m glass column (3% 85-30 stationary
phase, 100-120 mesh Chromosorb Q packing) or Perkin Elmer 910 gas chroma-
tograph equipped with a 3.7 m glass column (3% SP-2100 stationary phase,
100-120 mesh Chromosorb Q packing), both with hydrogen flame ionization
detectors. Separation of monosaccharides was accomplished using a tempera-
ture-programmed analysis of 140°-200°C (4 minutes at 140°C followed by
increases of 2°C min-1) for the 900 model and 120°-180°C (4 minutes at
120°C followed by increases of 2°C min-1) for the 910 model. The flow

rate of nitrogen carrier gas was 50 ml/min; injection port and detector
temperatures were 260°C. Peak areas were determined electronically with

a Spectra-Physics Autolab System IV interfaced with the gas chromatographs.
Standards of inulin and sucrose were included with each batch of samples
analyzed.

Total galactose was determined with a Galactostat Reagent Set
(Worthington Biochemical Corp., Freehold, N.J.).

Molecular weight was estimated using gel exclusion chromatography
(37). Bio-Gel P-4 and P-6 400 mesh beads (Bio-Rad Laboratories, Richmond,
CA) were packed in 1 cm diameter columns to a bed height of 23 cm. With
a head of 80 cm, flow rate was 3.2 ml/hour and the void volume was 3.6 m1
as determined with blue dextran. One mg of storage carbohydrate was
applied to the top of the columns in 0.1 ml of distilled water. Frac-
tions collected were analyzed for total carbohydrate using the anthrone

method, as previously described.

18

V. Effect of Three Herbicides on Spear and Stalk Production.and Crown

Survival in Natural and Artificially Infested Soil

 

One-year-old 'Mary Washington' crowns were planted at the Botany and
Plant Pathology Farm. Prior to covering the crowns, half of the plots
were inoculated in the row with 50 grams/25 foot row colonized wheat seed

inoculum containing both Fusarium oxysporum f. sp. asparagi and F:

 

moniliforme. Simazine (4.4 kg/ha), linuron (2.2 kg/ha), or terbacil (2.2

 

kg/ha) were applied in the spring prior to spear emergence in 1975, 1976,
and 1977 using a COZ-powered small plot sprayer (AZ Field Test Service,
Accord, N.Y.). One set of plots was left untreated and was weeded by
hand or with a rototiller as needed. Crown survival and stalk production
were recorded in October, 1976. In the spring of 1977, all plots were
harvested for four weeks. Crown survival and stalk production were re-
corded in September, 1977.

Soil samples were taken on October S, 1976 and July 25, 1977, by
obtaining three 2.5 x 10-13 cm soil cores per plot from between crowns
within the row. Population levels were determined using the selective
medium and plating techniques of Komada (16). The basal medium contained
(per liter) 1 gram KZHPO4, 0.5 grams KCl, 0.5 grams Mgso4 - 7H20, 0.01
grams Fe-Na-EDTA, 2.0 grams L-asparagine, 20.0 grams D-galactase, and
15.0 grams of agar. The antimicrobial supplement consisted of (per liter)
1.0 grams of PCNB, 0.5 grams Oxgall, 1.0 gram Na2B4O7 ' lOHZO, and 0.25
grams of chloramphenicol. All materials were mixed and autoclaved for
one hour to sterilize and melt the agar, cooled to 50°C in a water bath,
the pH adjusted to 3.8-4.0 with a 10% solution of phosphoric acid, then

poured into sterile disposable Petri dishes.

Soil suspensions were prepared by adding 10 grams of soil to 90 m1

19

of 0.1% sterile water agar, followed by shaking for 15 minutes on a
reciprocal shaker (170 cycles/minute). Further dilutions were made with
0.1% sterile water agar, and 0.5 m1 of soil suspension diluted 1000-fold
was pipetted onto each of 5 pre-poured plates. After incubation for 8-

9 days, colony counts of F: oxysporum and F, moniliforme were made on

 

the basis of colony morphology and pigmentation, and microscopic observa-
tions of microconidiophores. Soil moisture was determined by drying 10
grams of soil in tared aluminum soil canisters at 100°C for 24 hours,

reweighing and calculating % moisture.

RESULTS

1. Growth and Bud Formation in Asparagus

 

Spear growth was initiated 2-3 days after planting on crowns planted
in boxes in the greenhouse and covered with Perlite. Spears were pro-
duced throughout the growing season (Figure 1). New buds and storage
roots appeared within two weeks after planting of crowns and also were
found throughout the growing season. The average number of buds per crown
approximately doubled from mid-June through mid-August. Five plants
flowered during the course of the season and were male; five plants did
not flower and were presumed to be female. Overall growth and development
varied considerably from crown to crown.

In the field, dry weight of crowns from plots harvested for periods
of 0, 3, or 6 weeks approximately doubled through the course of the sea-
son, although crown sizefluctuatedconsiderably from sampling date to
sampling date. In the unharvested plots, stalks grew and matured quickly;
average dry weight of all stalks on each crown reached a maximum of approxi-
mately 34-36 grams by mid-July. In the plots harvested for 3 weeks, stalks
also grew and matured quickly after the end of harvest (5/9/77); average
dry weight of all stalks on each crown reached a maximum of approximately
34-36 grams by early July. In the plots harvested for 6 weeks, stalks
grew more slowly than in the other harvest periods after the end of har-
vest (5/30/77) (two weeks of cool temperatures in mid-July undoubtedly

affected growth rates of spears). However, there was an average of 32

20

Figure 1.--Production of spears, buds, and new storage roots by one-year-
old plants held under a constant 16-hour photoperiod and soil
temperature of 20°-28°C.

22

  
  

         

   
  

      

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23

grams (dry weight) of stalks on each crown by the last sampling date
(9/7/77). A light freeze in early May, approximately one week after har-

vesting began, killed a number of spears in the unharvested plots.

II. Effect of Length of Harvest on Yields

 

During the first year of harvest (1976), yields from all three plots
were similar on any given harvest date (Figure 2). Total and marketable
spear production (numbers and weights) in plots harvested for 4 or 6 weeks
increased through the third and fourth weeks of harvest surpassing spear
production during the first two weeks of harvest (Table 1). Total and
marketable numbers of spears produced during the last two weeks of har-
vest were approximately double that of the middle two weeks of harvest
in plots harvested for 6 weeks; total and marketable weights of spears
also increased sharply. Percent marketable spears decreased in all plots
throughout the harvest periods (Table l). The average weight of spears
increased during the third and fourth weeks of harvest in plots harvested
for 4 or 6 weeks, then declined during the last two weeks of harvest in
plots harvested for 6 weeks.

During the second harvest season (1977), plots harvested for 10 weeks
(harvested for 6 weeks the preceeding year) out-yielded all other plots
on any given harvest date (Figure 3). The total number of spears produced
during the fifth and sixth weeks of harvest was almost equal to the total
number of spears produced during the first four weeks of harvest in plots
harvested for 6, 8, or 10 weeks; total weight of spears also increased
sharply (Table 2). Total numbers and weights of spears produced decreased
dramatically after the sixth week of harvest in plots harvested for 8 or

10 weeks. Percent marketable spears and the average weight of spears

Figure 2.--Marketable yields from asparagus plots harvested for 2, 4, or
6 weeks.

25

 

 

 

 

 

 

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Figure 3.--Marketable yields from asparagus plots harvested for 4, 6, 8,
or 10 weeks. Plots were harvested for 0, 2, 4, or 6 weeks
the previous year.

28

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30

decreased in all plots throughout harvest. Numbers and weights of mar-
ketable spears remained about the same in all plots harvested through
the first six weeks of harvest, then decreased dramatically thereafter
(Table 2). Percentage of marketable spears produced by plots harvested
for 10 weeks fluctuated between 65 and 75% during the first three weeks
of harvest, decreased rapidly during the fourth week of harvest, then
fluctuated between 25 and 40% through the duration of harvest (Figure 4).
Total and marketable spear production (numbers and weights) during
the second year of harvest, 4 years after planting, was approximately

double that of the first year during any given time period.

111. Effect of Length of Harvest on Seasonal Fluctuations of Storage

Carbohydrates

 

In 1976, percent storage carbohydrate in four-year-old plants de-
creased gradually through the harvest periods (April-May) and slightly
beyond (Figure 5). One to two weeks after the end of harvest, carbohy-
drate levels decreased at a more rapid rate (as ferns were produced) than
during harvest, reaching a low ebb in early June. Then carbohydrate
levels increased rapidly, reaching peak levels in mid- to late August.
Thereafter, carbohydrate levels gradually decreased. Unfortunately, the
integrity of the different harvest periods was disrupted due to a freeze
in mid-April, approximately one week after harvesting began, which lasted
for approximately two weeks. The full effects of this cold period on
storage carbohydrate production are not known. Only between the 6 week
harvest and the other three harvest periods could statistically signifi-
cant differences in percent storage carbohydrate be demonstrated (Table 3),

and then, only during that part of the season when carbohydrate levels

Figure 4.--Percentage of marketable spears produced by asparagus plants
harvested over a 10 week period.

32

 

 

 

 

 

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33

Figure 5.--Effect of length of harvest on levels of soluble storage
carbohydrate (1976).

34

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35

Table 3.--Effect of length of harvest on levels of soluble storage carbo-
hydrate and percent storage root dry matter (1976).

 

 

Total
Sampling Length of Carbohydratea Percent
Date Harvest (weeks) % of dry weight) Dry Matter
b

4/9 0 62.9 A 21.3 A
2 61.5 A 21.9 A

(4/18 - harvest 4 63.6 A 22.1 A
initiated) 6 60.5 A 22.0 A
4/23 0 60.9 A 21.0 AB
2 64.3 A 22.9 B
4 64.7 A 21.6 AB

6 60.9 A 20.2 A

5/21 0 55.6 A 17.6 A
2 58.7 A 17.8 A

4 57.2 A 17.1 A

6 61.2 A 19.0 A

5/28 0 46.3 AB 15.6 A
2 37.5 A 14.7 A

(5/31 - harvest 4 49.2 A 14.6 A
terminated) 6 54.6 B 17.9 B
6/4 0 26.0 A 12.1 A
2 28.4 A 12.2 A

4 31.6 A 12.7 A

6 43.3 B 14.5 B

6/11 0 19.6 A 11.9 AB
2 19.9 A 11.4 A

4 24.6 A 11.5 A

6 33.9 A 14.0 B

6/25 0 37.4 A 14.6 A
2 27.5 A 12.1 A

4 25.9 A 13.9 A

6 27.7 A 13.1 A

7/9 0 50.4 A 15.2 A
2 49.8 A 16.8 A

4 48.2 A 14.8 A

6 42.6 A 14.8 A

7/23 0 68.4 A 22.2 B
2 61.8 A 18.8 AB

4 61.4 A 17.4 A

6 56.3 A 19.0 AB

36

Table 3.--(cont.)

 

 

Total
Sampling Length of Carbohydratea Percent
Date Harvest (weeks) (% of dry weight) Dry Matter
8/6 0 70.5 A 21.4 A
2 73.3 A 22.1 A
4 64.1 A 21.2 A
6 69.5 A 22.5 A
9/3 0 69.7 A 25.8 A
2 70.7 A 24.7 A
4 70.4 A 24.5 A
6 68.8 A 25.1 A
10/29 0 66.6 A 24.8 A
2 68.9 A 25.7 A
4 67.6 A 25.5 A
6 68.9 A 25.8 A

 

aCarbohydrate was measured by the anthrone method and is expressed as
sucrose equivalents.

37

were declining rapidly (early June). Carbohydrate levels in plants har-
vested for 6 weeks were consistently higher during harvest and bottomed
out one to two weeks later than carbohydrate levels in plants which

were harvested for 0, 2, or 4 weeks. Fluctuations in percent storage
root dry matter closely followed fluctuations in percent storage carbo-
hydrate (Table 3).

In 1977, fluctuations in percent storage carbohydrate in three-year-
old asparagus crowns were nearly identical to those of the preceeding
year (Figure 6). In general, carbohydrate levels of plants in all three
harvest periods decreased through harvest and after harvest during fern
production, then increased rapidly, reaching peal levels in mid- to late
summer. Percent storage carbohydrate of plants harvested for 0 or 3
weeks bottomed out in late May to early June and peaked in late July to
early August, while percent storage carbohydrate of plants harvested for
6 weeks bottomed out two to three weeks later than plants harvested for
0 or 3 weeks (mid-June) and did not regain levels of carbohydrate com-
parable to plants harvested for 0 or 3 weeks until early August. Fluc-
tuations in total carbohydrate per storage root system (Figure 7) and
dry weight of storage roots (Figure 8) were similar in direction and
magnitude to fluctuations in percent storage carbohydrate (Figure 6),
reflecting the pattern of storage carbohydrate utilization by asparagus
crowns. Plants harvested for 6 weeks experienced a more severe depletion
of total carbohydrate per storage root system and a greater loss in dry
weight of storage roots than plants harvested for 0 or 3 weeks, and also
required a considerably longer period of time to replenish their supply
of storage carbohydrate and dry root matter. With the exception of the

first week in June, there were no statistically significant differences

38

Figure 6.--Effect of length of harvest on levels of soluble storage
carbohydrate (1977).

39

 

 

      
 

 

 

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41

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43

 

 

 

 

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44

in percent storage carbohydrate, total carbohydrate per storage root sys-
tem, or dry weight of storage roots between the 0 or 3 week harvest peri-
ods (Table 4). There were dramatic differences between the 0 or 3 week
harvest periods and the 6 week harvest period. Plots harvested for 6
weeks had significantly less percent storage carbohydrate from early June
through mid-July, significantly less total carbohydrate per storage root
system from early June through late August, and significantly less dry
weight of storage roots from mid-June through late August, but there

were no significant differences thereafter. Values for percent storage
carbohydrate, total carbohydrate per storage root system, and dry weight
of storage roots were approximately the same for all three harvest periods
at the first (4/14/77) and last (9/7/77) sampling dates. Fluctuations

in percent storage root dry matter closely followed fluctuations in per-

cent storage carbohydrate (Table 4).

IV. Characterization of Asparagus Storage Carbohydrates

 

Asparagus storage carbohydrates were readily soluble in 80% ethanol.
Re-extraction of tissue with distilled water revealed only trace quanti-
ties of soluble carbohydrate remaining.

Paper chromatography revealed a plethora of oligosaccharides varying
in size and mobility, all containing ketose sugars (Figure 9). Twelve
distinct oligosaccharide bands were eluted from one or more of the
chromatograms: two bands (nos. 1 and 2) could be distinguished on the
chromatogram developed for 4 days, eight bands (nos. 3, 4, 5, 6, 7, 8, 9,
and 10) on the chromatogram developed for 12 days, and eight bands (nos.
4A, 4B, 5A, 5B, 6, 7, 8, and 10) on the chromatogram developed for 24

days. Bands 4 and 5 on the chromatogram developed for 12 days separated

4S

 

< w.mH < ~.m < o.H < m.- o

m v.m~ m< v.- m< m.m m n.0m m

u m.m~ m m.o~ m ~.v m o.m~ o oH\o
< o.m~ < v.m < v.~ < m.m~ o

m m.w~ < o.m~ m m.m m ~.o~ m

m o.om < m.e~ m m.v m c.n~ o m\o
< a.NH < w.- < ~.~ < m.u~ o

< o.m~ < o.c~ < o.~ < o.- m

< o.m~ < m.- m e.m m w.om o N\c
< m.om < m.mH < o.m < a.vm a aeouacaswop

< m.o~ < m.HH < m.~ < ~.mm m amo>paa - OM\mV
< m.oH < n.m~ < m.N < n.5H o om\m
< m.om < w.m~ < o.m < m.vm o

< v.m~ < n.m~ < m.m < m.mm m

< v.- < m.~m < v.m < m.0m o m~\m
< o.om < m.n~ < 0.9 < n.5m c

< m.~m < m.m~ < o.w < m.nm m

< ~.N~ < H.em < H.m < H.5m o wm\e
< H.4N < m.- < m.a < A.He o Aeooaauaca

< a.mm < m.mm < o.v~ < m.~v m amo>waa - w~\ev
< a.m~ < «.mm < a.v~ n< m.vq o 4~\v

pouumz xpa A.wv onmmwh poem A.wv Ecumxm AugmMoz x96 we xv Amxoozv umo>pmz open
ucoopoa usage: xno woo: ewmaoum woo moumwexgonhmu mo sumac; mcflfimEmm
cumuexzonumu Hmuoe ~mu0h

 

.Annmfiv Rename xuu Hock ommHOHm acoupom ecu .muoOH owmhoum mo usage: ape .Eoumxm peep ommHOHm
Hem eunucxzonumo amuoa .oumhcxnonpmo omeOHm mansfiom mo m~o>o~ co umo>nms mo :umcoH mo uoommmnu.v manna

46

.umou emcee oamwuflas m.:mo::a >3 amo. u my xaucmowmflcmwm HoMMMc no: ow Hopuo~ oemm on» xn eozoafiom mosfim>

.mucofim>fi:co omouoshm mm

a

commouaxo me one venues ocouzwem one xn nopsmmoe mm: oumhwxconpmum

 

 

< o.om < v.v~ < o.o~ < o.vv o
< m.- < «.mm < v.- < m.mv m
< «.mm < o.mm < c.mH < v.vv o m\m
< a.>~ < o.v~ < m.v < H.vm o
< n.om m m.n~ m m.m < m.mm m
< w.H~ m m.m~ m v.~H < m.am o oa\w
< N.Hm < m.m~ < m.w < w.mv o
< o.m~ m m.vm m H.m~ < m.mv m
< o.mm m m.Hm m “.mH < o.mv o m\m
< o.om < m.m~ < m.m < o.mm o
< o.mm m o.mm m m.m~ < c.~v m
< m.mm m o.om m v.m~ < v.vv o Hm\n
< v.o~ < v.5H < m.m < o.mm o
< v.om < o.vm m m.m m w.mm m
< m.m~ < o.~m m ~.m m v.ov o m\n
< N.NH < n.@ < m.~ < o.vH o
m m.om m w.oH m H.> m m.mm m
m ~.~N m o.- m a.m m m.om o mm\o
soups: xuo a.wv osmmflk poem m.mv Ecumxm nunwwoz xhn mo xv nmxoozv umo>nmz mama
ucoohoa uswwoz xho poem omeOHm Mom moumncxxophmo mo cameo; wcw~oEmm
opmhuxnoppmu Hooch “much

 

fi.o=oov--.v algae

Figure 9.--Representation of paper chromatograms developed for 4, 12,
or 24 days, drawn to 0.5 scale lengthwise. Numbers identify
bands of carbohydrate eluted from undeveloped portions of
the chromatograms for analysis.

48

4 DAYS 12 DAYS 24 DAYS
Rofl‘lnou
4A
Sucrose
4B
m'4
3
I
, 5A
.,1 SB
4
Raflimu 5 ~

     

IO 0 IO .
Inulln lnulln

49

into two distinct bands (4A and 48, 5A and SB) when time of development
was extended to 24 days. Bands 6, 7, 8, and 10 were eluted from chroma-
tograms developed for both 12 and 24 days. Band no. 9 was not eluted
from the chromatogram developed for 24 days due to its heterogeneous
nature.

Gas chromatography of hydrolyzates revealed that the eluted
oligosaccharides were composed predominantly of fructose and, to a lesser
extent, glucose (Table 5). Ratios of fructose to glucose ranged from 2:1
(Figure 10) for the oligosaccharide with the greatest mobility to 9:1
(Figure 11) for the oligosaccharide with the least mobility (no movement
from the origin). Unfortunately, exact ratios for most of the oligosac-
charides were impossible to estimate due to the heterogenity of oligosac-
charides within bands and the lability of fructose during acid hydrolysis.

Only trace quantities of galactose were detected.

Gel exclusion chromatography indicated the molecular weight of the
largest oligosaccharides to be between 3,000 and 4,000 (Table 6). The
0.7 ml fraction collected immediately after the void volume contained

approximately 10% of the applied material.

V. Effect of Three Herbicides on Spear and Stalk Production.and Crown

 

Survival in Natural and Artificially Infested Soil

 

The inoculated plots receiving no herbicide contained significantly
fewer crowns by October, 1976 than the uninoculated non-herbicide-treated
plots or the herbicide-treated plots, inoculated or uninoculated (Table
7). Non-herbicide-treated plots produced significantly fewer stalks per
plot than the herbicide-treated plots. By September, 1977, the untreated

plots inoculated or uninoculated, contained significantly fewer crowns

50

Table 5.--Ratios of fructosezglucose in hydrolyzates of oligosaccharides
eluted from chromatograms developed for 4, 12, or 24 days.

 

 

Band Eluted from a Estimated Ratio of
Chromatogram Percent Glucose Fructosezclucose
1 33 2:1
2 26 3:1
3 22 4:1
4A 25 -°
48 26 -
5A . 20 -

SB 21 -
6b 15 -

7 15 -

8 15 -

9 14 -

10 10 9:1

 

3Loss of fructose during acid hydrolysis necessitated multiplying levels
of percent fructose by a constant derived from loss of fructose from a
molecule (sucrose and/or inulin) of known composition.

bBands 6, 7, 8, and 10 were eluted from both 12 and 24 day developed
chromatograms. Values are the average of both determinations.

CRatios of glucosezfructose not estimated due to suspected oligosaccharide
heterogeneity and fructose lability.

51

Figure 10.--Gas chromatogram of trimethylsilyl derivatives of
oligosaccharide hydrolyzates (band #1, Figure 9). Peaks
are: l. fructose; 2. fructose; 3. glucose; 4. fructose;
5. unknown; and 6. glucose.

52

mg
mm

NC
on

N9
mm

N9
ON

NS
@—

m9.

0.

NS
m

y-

om.

 

 

 

 

 

00
2:4

33N08838 83080038

53

Figure 11.--Gas chromatogram of trimethylsilyl derivatives of
oligosaccharide hydrolyzates (band #10, Figure 9). Peaks
are: l. fructose; 2. fructose; 3. glucose; 4. fructose;
5. unknown; and 6. glucose.

mm. NC mm: mm. NS mm. mm: ON. 00
mm 00 mm ON m. 0. m 0 2:).

 

S4

 

 

l a

 

3SNOdS38 83080038

 

 

 

 

 

55

Table 6.--Molecular weight determination of oligosaccharides extracted
from asparagus storage roots.

 

Exclusion Limit

 

Fraction Collecteda 4000 6000

 

Optical Densityb

 

3 ml 0 0
0.7 m1° o o
0.7 m1 ' 0.27s 0

 

aOne mg of material in 0.1 ml of distilled water was applied to the t0p
of the column.

bCarbohydrates were detected by the anthrone method. Optical density of
solutions was read at 620 nm in a Bausch and Lomb Spectronic 20 spectro-
photometer.

CApproximates the void volume.

dEach value is the average of two determinations.

S6

.umou owcmh ofimwugoe m.:mo::a x2 mmo. u av xfiucmofimficwwm acouomwfio Ho: on Houuoa osom ozu x2 oozogfiom moofio>o

thommxxo um MCACMoucoo EsfisoOCM poem

woos: wouwcofioo mo ohzuxwe m we manna om oo>wooop uofim oouoHSoocfl comm

 

.osuomflfiflcoe am ocm MmeoMmm .mm .m

n

.mczoho om oocwoucoo xHHocwwwno uon comma

 

 

 

 

< mm.m < o.om~ < m.~w m< N.n~ m w.w~ oz

< oa.m < w.mm~ < w.mo < o.m~ < o.o~ mo> noumopuca

m mm.m~ m ~.mvm m 0.0HH m o.w~ m o.m~ oz

m mm.m~ m v.~mm m v.vHH m w.m~ m o.m~ mo> N.N Hfiomneob

m ov.- m o.mm~ m v.mo~ m w.w~ m o.o~ oz

m No.H~ m o.v- m v.oo~ m o.w~ m v.w~ mo> ~.~ :onocfio

m mn.m~ m N.mmm m w.oo~ m o.w~ m o.m~ oz

m mw.m~ m w.mmm m N.mcH m w.n~ om «.mH we» v.v ocflwoewm
nnmfi puma ommfi nnmfi onmg

czohu Hem uoHo pom mxaoum muofia you oo~o~=oo=~ Am;\wxv ucoaumoae
mxfimpm mo Honeoz Hooch mczopo mcfi>fi>nom mama

 

.Hoom

topmomcw Ezmummzm ocm Hopouo: cm :owwoooOHm xfimum woo ~o>w>nam :3oho no moomownpo; omega mo uoommmun.n manna

57

(Tables 7, 10) and produced significantly fewer stalks per plot and stalks
per crown than the herbicide-treated plots, inoculated or uninoculated
(Table 7).

Yields were computed both on a plot (Table 8) and a plant basis
(Table 9). Untreated plots yielded significantly fewer total numbers
and less total weight of spears than herbicide-treated plots (Table 10).
There was a significant interaction between inoculum level and herbicide
treatment affecting marketable spear production (Table 10). The inocu-
lated untreated plots yielded significantly fewer numbers and less weight
of marketable spears than the inoculated herbicide-treated plots, while
the uninoculated untreated plots yielded significantly higher numbers
and greater weight of marketable spears than the uninoculated herbicide-
treated plots. There were no significant differences between non-herbicide
and herbicide-treated plots on a per plant basis (Tables 9, 10); however,
plots treated with simazine (4.4 kg/ha) yielded significantly greater
numbers and weights of total spears than plots treated with linuron (2.2
kg/ha) or terbacil (2.2 kg/ha) (Table 10). Simazine treatment did not
affect yields of marketable spears.

There were no significant differences between soil populations of

Fusarium oxysporum and E, moniliforme in any of the treatments on either

 

 

of the sampling dates (Table 11). The majority of isolates were F,

oxysporum.

58

.umou emcee vanguass m.:oo::o xn Ame. u my xaucoowmflcmHm wommflo yo: om popped meow osu xn oozofiaom mo=Ho>

 

n

.oshomfldficos am one wwmhmmmm

.om .m Espommeo am wcflcwoucoo Eofizoocw poem woos: nonwcofioo mo ououxfle a mo msmhw cm oo>wooou wean :oomm

 

 

o.~mo.~ m.~mm.a ~.Hm o.wv m< w.mm~ oz

m.mon ~.~mo.~ m.n~ N.mm < «.mmm mo> noumopucs

m.amm o.m-.~ e.e~ o.Hv m c.5o3 oz

m.~wm n.5mo.m m.mm v.mv m m.mo~ mo» ~.N Hwomnhoh

w.wmm H.cwm.~ m.nm o.mv m m.oo~ oz

~.ovo.~ m.m~o.m m.om N.wv m N.~oH mo» m.m :oaocwq

m.wmm a.m~o.~ e.mm o.m¢ m m.oa~ oz

m.omo.H m.vm~.m H.0N c.0v am o.mn~ moo» v.v ocflNmem
Aewv memoom flamv whoomm mpaomm memoom memoom oopoaooocH no;\mxv wooEuoohe
ofinmuoxhoz u:m«oz oaseooxeoz ofinmuoxyoz Honsoz oumz

uswwo: Hence unoohoo Honsoz Hooch

 

.Hflom ooymomcw ezmummom one “ensue: :« uoam woo mommemmmm mo moHomx :o mooflomnno; ooucu mo uoommmlu.m ofinmh

59

.umoo owcow ofimwuaoe m.:mo::a >9 Amo. u my xfiucooflmflcmMm nommfio Ho: oo wouuoa osom one x: ooonHow mozflm>

a

 

.thomwfiocoE am new mehmmmo

.om .m thommxxo um wcwcfloucoo ESHSUOCM voom woos: oouwcofioo mo oHSwaE m mo manna om oo>fioooh “can :oomo

 

 

< o.mm < n.no~ mo.m Hv.m oz

< ~.~v < n.~o~ mH.m Hm.w mo» oopooppcs

< w.mv < m.mo~ HN.N om.w oz

< o.~m < a.mm om.~ Hm.m mo» N.~ HHoonooe

< o.mv < H.ooH am.~ me.m oz

< m.wm < m.m- ou.m oH.m mo» N.~ zopocfia

< v.mm < m.-~ ev.m Hm.a oz

< m.nm < m.m- vm.m vw.m omo> v.v ocwumefim
mamv memomm namg whoomm whooom mpooom ooumaooocm Ho;\mxv acoEumowa
ofinmuoxpoz pgwfioz ofipouoxamz Honesz oumm

oswwoz Hooch Homeoz Hmpoe

 

.Hfiom powwomcfi sowummom use Monauo: :fl czouo you mowomommm mo moaomx :o moofiownuo: ooenu mo Hoommmlu.o ofinme

6O

.flmo.
.floo.

ao oaaoaomcwom saoaoaomaoaom

n

ao oaaoooficwam saoaowomooaoma

 

.mcmoe How m o~nob oom
.mcmoe How m oanmb oom
.mcmoe wow w oHAmE oom
.mcooe Mom w ognmh oom
.mcooe how w omnoh oom
.mcooe pom w ofinmb oom
.mcmos now u oanmb oom

mm.mm

.czonu non mumoom mo ucwfioz Hooch
.czonu pom whoomm mo ponszz Houob u om:
.uofia pom memoom odnmuoxamz mo uzwwoz u mm:
.uofia pom mnmoam oHnouoxaoz wo Honsoz u :m:
.poHo woo whoomm mo uswwoz Hooch H mm:
.uoHo poo muoomm mo poneoz Houoe u «m:
.Aunmav pogo Mom mczoho mcw>w>uom n am:

am:

 

~.aao me.o ovm.4o www.cma m.mmm mh.H mm Hosea
e.mmm Hw.o Nao.m Hw.m~ omm.vm om.~ A_.~ Ame Aoasefimoao
N.~m~ mH.o .omo.aHm .o.oae mo~.emN m.mmw ov.4 ASS flaoooaosooco
x fiQHmOHF
.m> nouoohuczv
m COMHNHDUOCH
x HCGEHNOHH
m.~a o~.o awa.m N~.a oum.wa o.~a~ No.~ a cohoaasooco
ov.o o~.o ama oo.o oov.am m.omN m~.o aao Aaazeomomo
.~.mom .ao.o mmo.o oo.o Hom.o~ H.cmo mm.~ moo Aooumauoe
w COHSCMA
.m> ocfluoswmv
A.Ho~ ov.m com.mm «.mm n.mwm.amm ..m.moa.4 a..o~.mm flog Aeouaowo
.m> ooumowuczv
m HCGEHGOHP
n.4oH Hm.o NHm.m~ mo.4m wov.va o.ma~ om.o 4 avg
Nmz am: mm: mm: mm: «m: .m: .o.e oowsom
.Hmom woumomcfl Eowhmmzm ocm Hogans: ca =3ono Mom mofiowx mnwmuommo one .uon
#09 momma» msmwhmnmm .Hm>w>H3m £30Ho :0 mmfiwanHon OQHSH mo mwuowmo 0:9 we mcommHmQEoo automocuhO|u.oH QHDGP

61

Table ll.--Effect of three herbicides on soil populations of E, oxysporum
and F: monoliforme in natural and artificially infested soil.

 

 

 

 

Rate

Treatment (kg/ha) Inoculated Number of Propagules/Gram of Soil
10/5/76 7/25/77d
Simazine 4.4 Yesa 5,516b Ac 6,708 A
No 5,464 A 6,684 A
Linuron 2.2 Yes 4,896 A 9,140 A
No 5,744 A 5,290 A
Terbacil 2.2 Yes 5,922 A 8,310 A
No 5,276 A 8,670 A
Untreated Yes 6,544 A 6,864 A
No 5,844 A 8,460 A

 

aEach inoculated plot received 50 grams of a mixture of colonized wheat
seed inoculum containing 5, oxysporum f. sp. asparagi and f3 monoliforme.

 

bEach value is the average of two determinations.

cValues followed by the same letter do not differ statistically (P = .05)
by Duncan's multiple range test.

jThere were no statistically significant differences using Orthogonal
Comparisons.

DISCUSSION

The ultimate goal of a length of harvest study is the determination
of the optimum harvest period(s) which will result in maximum yields and
profits over the lifetime of an asparagus planting. In order to maximize
yields, a compromise must be made between maximizing spear numbers by
extending harvest, and maximizing spear size by shortening harvest. All
spears less than one cm in diameter are discarded as culls, and yet each
spear represents an expenditure of energy by the plant. While growers
wish to obtain maximum yields, it is also recognized that larger spears
are produced earlier in the season and that average spear size and plant
vigor decrease as the harvest season progresses. This was most eloquently
demonstrated in the study of Williams and Garwaithe (39). Plots harvested
for 10 weeks yielded the greatest number of spears while plots harvested
for 6 weeks yielded the highest percentage of marketable and early spears,
but plots harvested for 8 weeks were the most profitable because they
yielded both a resonable quantity of spears and a relatively high quality
of spear, averaged over a 5 year period. On the basis of several studies
(5,11,32,39) a spring harvest of 7-9 weeks is recommended for obtaining
maximum yields and profits from asparagus plantings over an extended
period of time. Harvesting of asparagus before the 3rd year after
planting is not recommended.

Two years of yield data were insufficient in arriving at conclusions

concerning the effect of length of harvest on subsequent yields of

62

63

asparagus, although it is apparent that harvesting of a four-year-old
field should not be continued beyond 6 weeks. Yields of marketable spears
decreased dramatically after the 6th week.

Results concerning the effect of length of harvest on seasonal fluc-
tuations of storage carbohydrates agreed closely with those of Scott et
a1. (27). Production of spears, and subsequently stalks, by asparagus
plants required the utilization of carbohydrates produced by the fern and
stored in the roots the preceeding year. In the spring, spears were pro-
duced at the expense of these stored carbohydrates. Not until the pre-
fern stage did stalks begin to photosynthesize more carbohydrate than
they respired (6), and not until stalks were almost mature did they pro-
duce sufficient carbohydrate to translocate to the roots to replenish
the diminished supply. The effect of extending harvest was to lengthen
the time and increase the severity of carbohydrate depletion, and to
decrease the number of days available through the rest of the season for
the production of storage carbohydrates for the succeeding year's growth.
Measurement of percent carbohydrate alone can be misleading. Asparagus
plants replenished their supply of storage carbohydrate in established
storage roots before investing heavily in new storage root growth. There
continued to be significant differences in total carbohydrate per storage
root system between plants harvested for 0 or 3 weeks and plants harvested
for 6 weeks up to six weeks after there ceased to be significant differ-
ences in percent storage carbohydrate.

The absence of significant differences between carbohydrate levels
in plants harvested for 0 or 6 weeks in 1976 was probably due to low
temperatures beginning one week after harvesting began, which lasted for

two weeks and resulted in several killing frosts. Spears produced by

64

plants in unharvested plots were killed and as a result, the carbohydrate
which had been invested in spear growth was lost. The absence of signifi-
cant differences in percent storage carbohydrate, total carbohydrate per
storage root system, and dry weight of storage roots between plants har-
vested for 0, 3, or 6 weeks by early fall (9/7/77), and absence of differ-
ences in carbohydrate levels and storage root dry weight between plants
sampled in early spring and those sampled in early fall could be due, in
part, to the fact that it was impossible to retrieve entire storage root
systems intact from the soil.

Although it is generally agreed that storage carbohydrate levels are
directly related to plant vigor, i.e. extensive harvesting leads to car-
bohydrate exhaustion which in turn leads to plant death, it is not known
how carbohydrate levels affect quantity or quality of asparagus yields.
Takatori et a1. (32) reported that plants harvested for 13 or 17 weeks
produced smaller spears in the second harvest season and both smaller
and fewer spears in the third and fourth harvest seasons; and that loss
in yields was due to a loss in stand. Haber (11) found that plants
harvested for l, 3, or 5 weeks produced spears of increasing size from
year to year, and that plants harvested for 7 weeks produced spears of
equal size, while plants harvested for 9 or 11 weeks produced spears
which decreased in size from year to year and had a high mortality rate.
Plant death in both studies was inevitably the result of carbohydrate
exhaustion; however, the effect of length of harvest on bud size and sub-
sequently spear size, involved genetic, physiological and environmental
factors. Primary buds produced the largest spears while secondary, ter-
tiary, etc. buds produced progressively smaller spears (35,23). The size

of buds was related to the size of the stalks which supplied the

65

carbohydrate for their formation (36). A positive correlation was found
between the diameter of spears one season and the diameter of stalks the
preceeding season (7). Plants harvested for shorter periods of time
produced consistently larger spears because larger primary and secondary
buds gave rise to larger spears and subsequently larger stalks, which in
turn gave rise to larger buds for the succeeding year's growth. As
length of harvest was extended, plants produced progressively smaller
spears because smaller tertiary and quaternary buds gave rise to smaller
spears and also, as a result of carbohydrate depletion, smaller stalks,
which in turn gave rise to smaller buds for the succeeding year's growth.

Soil temperatures are known to affect size and number of spears (9).
It seems probable then that soil temperatures also affect size and number
of buds. Although uncut plants produced buds continuously, timing of
bud formation under field conditions is not known. If bud formation
occurred predominantly after the end of harvest, then plants harvested for
shorter periods of time would produce larger buds due to cooler soil
temperatures, whereas plants harvested for longer periods of time would
produce smaller buds to warmer soil temperatures.

There can be no question that asparagus storage carbohydrates are
fructans of variable size. Gas chromatography revealed that oligosac-
charides were composed predominantly of fructose and to a lesser extent
glucose, although ratios varied considerably. Several other investiga-
tors have reported isolating fructans from asparagus storage roots (34,
37,29). The report by Scott et a1. (27) that asparagus storage carbohy-
drate was sucrose was in error. Since the investigators did not state
their method(s) of analysis, it appears that they presumed the soluble

nonreducing sugars which they isolated from asparagus roots to be sucrose.

 

66

Asparagus oligosaccharides possess an inulin-like structure: molecules
of fructose are polymerized to 8,1-6 fructosyl-glucopyranose, either
through the l-carbon of fructose or the 6-carbon of glucose (29). The
largest oligosaccharides were composed of approximately 90% fructose and
10% glucose and had a molecular weight of approximately 3200, consisting
of 18 molecules of fructose and 2 molecules of glucose. There exists not
one but a great many asparagus storage carbohydrates. Paper chromatography
revealed a plethora of oligosaccharides ranging in size from sucrose up
to oligosaccharides which did not move from the origin on the chromato-
grams. The first carbohydrate fraction collected from the Bio-Gel P-4
column contained only about 10% of the total material applied. Since
these carbohydrates were extracted from the storage roots of crowns which
were dormant, it would appear that asparagus plants normally possess
oligosaccharides of varying size and composition throughout the year.

Although certain herbicides stimulated levels and activities of
Fusarium spp. in the soil, resulting in increased disease incidence in
the field (21), this did not occur in asparagus plots with any of the
three herbicides tested. Herbicide treatment was conducive to increased
crown survival in both natural and Fusarium-infested soil. It was impos-
sible to ascertain the exact nature of the herbicide effect. Data were
not available on initial populations levels of F: oxysporum and F.

moniliforme, for crown survival for the fall of 1975, or for weed infesta-

 

tions in plots not treated with herbicides. Although attempts were made
to keep non-herbicide treated plots free from weeds, a weed problem
existed in these plots the latter part of 1976 and 1977. If increased
crown survival was the result of a plant- and/or pathogen-herbicide in-

teraction several explanations are possible: the herbicides may have

67

been inhibitory or toxic to Fusarium in the soil, or they may have been
stimulatory to microorganisms antagonistic to Fusarium, resulting in
decreased disease incidence. The herbicides may have been taken up by
asparagus plants resulting in increased disease resistance, either by
stimulating plant resistance mechanism, or by acting fungistically, inhi-
biting the growth of invading fungi.

Decreased stalk production per crown (1977) by plants in untreated
plots was probably the result of a weed problem in these plots and acci-
dental chopping down of stalks while rototilling. Untreated control
plots (containing significant fewer crowns) yielded significantly fewer
total spears and weight of spears than the herbicide treated plots. The
interaction of inoculum level with herbicide treatment with regard to
numbers and weight of marketable spears is difficult to explain. Why
herbicide-treated inoculated plants would yield significantly greater
numbers and weights of marketable spears than herbicide-treated uninocu-
lated plots, and why non-herbicide-treated uninoculated plots would yield
significantly greater numbers and weights of marketable spears than non-
herbicide-treated inoculated plots is not known. More data are needed
in order to adequately assess the situation.

Simazine appears to possess growth regulating properties on asparagus.
Simazine-treated plots yielded significantly higher numbers and greater
weights ot total spears than plots treated with linuron or terbacil.
Apparently, secondary buds were being forced to break dormancy sooner
than normally would occur. Sandhu and Grieg (24) reported that simazine
(4.4 kg/ha) caused a significant increase in plant dry weight compared
to a weeded check and several other herbicides in two years' time. Dr.

A. R. Putnam (personal communication) has observed an apparent increase

68

in yields from simazine-treated plots relative to hand-weeded controls,
but could not rule out the possibility of a decrease in yields in control
plots due to presence of weeds. In the present study, simazine caused

an increase in yields relative to linuron and terbacil, all of which gave
comparable weed control. Welker and Brogdon (38) did not observe an
effect of simazine on yields, however, the investigators had many treat-
ments and few replications in their experiment and analyzed their data
using Duncan's multiple range test. The author also was unable to
demonstrate significant differences using Duncan's multiple range test.
Only through the use of orthoganol comparisons, a more powerful statisti-
cal technique, could significant differences be demonstrated. Other
factors——soi1 type, organic matter content, rainfall, cultivar type,
etc.-—could also play a role in determining the simazine effect. The

effects of extended use of simazine on asparagus yields are not known.

10.

11.

12.

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