Postharvest Biology and Technology 20 (2000) 151 – 162
www.elsevier.com/locate/postharvbio
Ethylene feedback mechanisms in tomato and strawberry
fruit tissues in relation to fruit ripening and climacteric
patterns
Mordy A. Atta-Aly *, Jeffrey K. Brecht, Donald J. Huber
Horticultural Sciences Department, Uni6ersity of Florida, Gaines6ille, FL 32611 -0690, USA
Received 16 August 1999; accepted 18 May 2000
Abstract
Exposing pericarp tissue excised from immature tomato fruit to 4.5 mmol l − 1 C2H4 revealed a negative C2H4
feedback mechanism in relation to its biosynthesis since ACC concentration and C2H4 production by the tissue were
reduced. An opposite trend (positive C2H4 feedback mechanism) was observed in pericarp tissue excised from fruit at
the pink stage. At the mature-green stage however, tissue showed a transition from negative to positive C2H4 feedback
mechanism with the onset of tissue ripening. In strawberry tissues excised from green, white and half-coloured fruits
however, C2H4 application caused a short-term increase in C2H4 production followed by a sharp reduction to the
control level along with a marked reduction in ACC levels. In both tomato and strawberry fruit tissues, C2H4
application significantly induced ACC oxidase (ACO) activity at all ripening stages, as measured by in vivo ACC
conversion to C2H4. This strongly suggests that ACC synthesis is the limiting step in C2H4 autocatalysis and the only
limiting step in C2H4 autoinhibition. In tomato pericarp tissues, C2H4 autoinhibition and autocatalysis caused by
C2H4 application in immature and pink fruits, respectively, were eliminated when tissues were transferred to air and
re-occurred when tissues were returned back to C2H4. These responses did not occur in all strawberry tissues due to
the sharp reduction in C2H4 production with the time course of C2H4 application. Inhibiting C2H4 action with STS
pretreatment inhibited both negative and positive C2H4 feedback mechanisms in both tomato and strawberry tissues
indicating that C2H4 feedback mechanism is one sort of C2H4 action. In addition, only tomato fruit tissue showed
significant increases in CO2 production with C2H4 application. In contrast to the nonclimacteric behaviour of
strawberry fruit which exhibits only a negative C2H4 feedback mechanism, these data strongly suggest that the
transition of the C2H4 feedback mechanism from negative to positive, which occurs in tomato fruit only with ripening
initiation and progress, may be the reason behind the climacteric behaviour of tomato fruit. © 2000 Elsevier Science
B.V. All rights reserved.
Keywords: Ethylene feedback mechanism; Climacteric behaviour; Tomato fruit; Strawberry fruit
* Corresponding author. Present and permanent address: Department of Horticulture, Faculty of Agriculture, Ain Shams
University, P.O. Box 68, Hadayek Shoubra 11241, Cairo, Egypt. Tel.: + 20-2-4447317; fax: + 20-2-4444460.
0925-5214/00/$ - see front matter © 2000 Elsevier Science B.V. All rights reserved.
PII: S 0 9 2 5 - 5 2 1 4 ( 0 0 ) 0 0 1 2 4 - 1
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1. Introduction
The rate of C2H4 production varies with the
type of plant tissue and its stage of development.
In climacteric fruits, C2H4 is produced at different
rates based on fruit stage of growth. Such fruit is
characterized by a low rate of C2H4 production
during the preclimacteric or unripe stage (basal
C2H4), followed by the climacteric, a sudden increase in C2H4 production during fruit ripening, a
phenomenon referred to as autocatalytic C2H4
(Abeles, 1973). After the climacteric rise, C2H4
production significantly declines during the postclimacteric phase (Hoffman and Yang, 1980).
Nonclimacteric fruits, on the other hand, exhibit
no increase in C2H4 production during maturation and ripening (Knee et al., 1977).
Autocatalytic C2H4 production is a common
feature of ripening in climacteric fruit, in which
increased synthesis of C2H4 is triggered by exogenous C2H4 application (Burg and Burg, 1965;
Abeles, 1973). Several reports however, have
demonstrated autoinhibition of C2H4 production.
McMurchie et al. (1972) reported that C2H4 treatment inhibited C2H4 production of banana pulp
slices. Similarly, propylene treatment, which initiated ripening, suppressed C2H4 production in
intact green bananas. In the non-ripening stages
of sycamore fig, C2H4 acts as an autoinhibitor of
its own production, but this does not occur in the
ripening stages (Zeroni et al., 1976). C2H4 autoinhibition was also noticed in avocado fruit (Zauberman and Fuchs, 1973), immature tomato
locule gel tissue (Atta-Aly et al., 2000) and pea
segments (Saltveit and Dilley, 1978).
It has been suggested that C2H4 autocatalysis
involves increased synthesis of ACC synthase and
the enzyme responsible for the conversion of ACC
to C2H4 (Riov and Yang 1982; Atta-Aly et al.,
2000), whereas autoinhibition involves suppression of the activity of either both enzymes (Riov
and Yang, 1982) or only ACC synthase (Atta-Aly
et al., 2000). Ethylene, therefore, seems to play a
role in regulating its own production (Yang and
Hoffman, 1984). Studies involving treatment with
exogenous ethylene or propylene have indicated
that fruit response to C2H4 may also serve to
distinguish between climacteric and nonclimacteric fruits (McMurchie et al., 1972). The response
of harvested fruit to applied C2H4 depends on
various factors, including tissue sensitivity and
stage of maturation, as well as whether or not the
fruit is climacteric (Biale and Young, 1981).
The objectives of this work, therefore, were to
study C2H4 feedback mechanisms (autocatalysis
and autoinhibition) in tomato and strawberry
fruits at different developmental stages; to determine the step(s) in C2H4 biosynthesis which control C2H4 feedback mechanism; to examine the
relation between C2H4 feedback mechanism and
the behaviour of both tomato and strawberry,
climacteric and nonclimacteric fruit, respectively;
to determine the most suitable stage to induce
fruit ripening with exogenous C2H4 application.
2. Material and methods
2.1. Plant material
Full size tomato (Lycopersicon esculentum Mill
cv. Sunny.) fruits were harvested from a commercial field in south Florida at immature (IM),
mature-green (MG) and pink (P) stages. Blossomend dark and light-green colours were used to
distinguish between IM and MG stages, respectively, since the former has no jelly-like locular
materials in any fruit locules while only one or
two locules of the latter developed jelly-like materials. Strawberry (Fragaria X ananassa) fruits cv.
Chandler, were picked from Gainesville area, FL,
at full size green (G), white (W) and half-coloured
(HC) stages. Tomato and strawberry fruits were
transferred to the laboratory on the same day.
Fruits were washed with chlorinated water (3.4
mM NaOCl), sorted, regarding to size and developmental stage, and kept at 15°C and 95% RH
overnight for treatment preparation. Experiments
were repeated three times using tomato and strawberry fruits from the same sources.
2.2. Tissue sampling
Tomato outer pericarp disks were excised from
M.A. Atta-Aly et al. / Posthar6est Biology and Technology 20 (2000) 151–162
the equator of the fruit using a stainless steel cork
borer at IM, MG and P stages (one disk/fruit).
Disks were trimmed to remove excess jelly-like
locular materials which had developed only in
MG and P fruits. The presence of jelly-like materials was used to distinguish between MG and IM
tomato fruit. Directly after excision, disks were
placed epidermal surface down, inside glass tubes
(17 ml vol.; 2 cm diam.; one disk/tube).
Strawberry flesh cylinders were longitudinally
excised from fruit central flesh using the cork
borer after removing 0.5 cm from blossom and
stem ends to obtain achene-free fleshy cylinders.
This was done to exclude the effect of auxins on
C2H4 biosynthesis since it is known that the achenes are the main source of auxins in strawberry
fruit (Archbold and Dennis, 1985). Excised tissue
cylinders were then placed vertically inside the
tubes, which contained 3-mm glass beads at the
bottom of each tube to protect the tissue base
from anaerobic conditions. Both fruit tissues were
then distributed among chemical solution treatments and exposed thereafter to C2H4 using a
gas-flow system as described below.
2.3. Chemical treatments and tissue analysis
For each treatment, 100 ml of each solution was
applied to the locular surface of tomato disks or
to the vascular tissue of the strawberry flesh cylinders. With the exception of ACC, which was
applied 3 days after continuous C2H4 exposure to
eliminate wound C2H4 interaction, all solutions
were applied immediately after excision. Chemical
solutions were applied to both tomato and strawberry tissues as described below.
2.3.1. Control treatments
These tissues were divided into three groups.
The first group was used to measure initial C2H4
and CO2 production, immediately after excision,
with an incubation period of 30 min. This incubation period was enough for measuring basal C2H4
levels and less than that required for wound C2H4
to be initiated (Atta-Aly, 1992). The second and
the third groups, however, were continuously exposed to an air flow94.5 mmol l − 1 C2H4 for 5
days, either for monitoring C2H4 and CO2 pro-
153
duction 3, 4 and 5 days after excision or for ACC
analysis 4 days after excision. Plant tissue produces a large amount of wound C2H4 which diminishes within 72 h of excision (Atta-Aly et al.,
1987). The gas flow system removed wound C2H4
produced during the duration of the experiment
and the first C2H4 analysis, therefore, was carried
out after 3 days of excision.
2.3.2. In 6i6o estimation of ACC oxidase (ACO)
acti6ity
Tissues were treated with water or 0.5 mM
AVG directly after excision and then exposed to
C2H4 for 3 days, when water or 100 mM ACC was
added to the tissues 2 h before measuring C2H4
production as an indicator of ACO activity.
2.3.3. C2H4 action
This was achieved in two different ways as
follows:
1. Tissues were treated with water and then divided into two groups. The first group was
exposed to air for 3 days, then transferred to
the 4.5 mmol l − 1 C2H4 atmosphere for 1 day,
then returned to air for another day, while the
second group was exposed to the above atmospheres in the opposite order. C2H4 and CO2
production were analyzed at the time of each
atmosphere transfer.
2. STS (silver thiosulfate; 0.5 mM) was applied
to the tissues while water was the control
treatment. After 3 days of gas treatments,
C2H4 and CO2 produced by the tissues were
analyzed.
2.4. Ethylene treatments
Based on the highest respiratory levels of excised tomato and strawberry fruit tissues, measured 1 day ahead, an air flow system was
calculated and adjusted to a rate of 3.5 l h − 1 for
supplying normal O2 levels around the tissue. CO2
levels in the air flow were checked twice per day
and its concentration was always below 0.5%
throughout the experiment. The air flow94.5
mmol l − 1 (100 ml l − l) C2H4 was passed through
water flasks twice before passing through tissue
containers (RH 98%).
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M.A. Atta-Aly et al. / Posthar6est Biology and Technology 20 (2000) 151–162
Excised tissues were placed inside the 17-ml
volume glass tubes, chemically treated and then
divided into two groups for either air or C2H4
treatment. Each group was placed inside 10-l gasflow containers. The containers were kept at 20°C
and 95% RH throughout the experiment. Time
between tissue excision and gas exposure for each
treatment was less than 30 min.
Since applied C2H4 may emanate during tissue
incubation and interfere with the measurement of
endogenous levels, 100 g of tomato and strawberry fruit tissues, excised at each developmental
stage, were exposed to the air flow94.5 mmol l − 1
C2H4 for 3 days, thoroughly flushed with C2H4free air for 60 s and exposed to the vacuum
procedure described by Saltveit (1982) for measuring internal C2H4 concentrations. No significant
differences were found between air and C2H4treated tissues in internal C2H4 levels at each
developmental stage of both fruits. All tissues,
therefore, were thoroughly flushed for 60 s with
C2H4-free air prior to each C2H4 analysis.
In a separate experiment, tissue was exposed to
580 mmol l − 1 propylene gas instead of 4.5 mmol
l − 1 ethylene. C2H4 production by both tomato
and strawberry fruit tissues was similar to that
obtained with C2H4 application when the tissue
was flushed with C2H4-free air for 60 s before
incubation.
2.5. C2H4, CO2 and ACC analysis
At each sampling time, the tubes were removed,
thoroughly flushed with C2H4-free air for 60 s,
and then sealed with rubber stoppers. After 30
min of incubation at 20°C, 1-ml gas samples were
withdrawn and used for C2H4 and CO2 measurements. A Hewlett Packard gas chromatograph
Model 5080A with FID was used for C2H4 analysis, while a Gow Mac Model 60, with TCD (Gow
Mac Instrument Co., NJ) was used for CO2 measurements. After withdrawing the gas samples the
tubes holding tissues were unsealed and returned
to the gas flow containers.
For ACC analysis, fruit tissues were removed
after 4 days of continuous exposure, frozen in
liquid nitrogen and kept at −20°C. Two grams
of the frozen tissues were homogenized in 10 ml
0.2 mM trichloroacetic acid (TCA) (Atta-Aly et
al., 1987). The mixture was centrifuged at 1000×
g for 10 min and the supernatant decanted.
Aliquots were assayed for ACC with a modified
version of the procedure used by Lizada and
Yang (1979).
2.6. Experimental design and statistical analysis
Experiments were designed as factorial arrangements in completely randomized designs with five
replicates each consisting of 15 samples. Experiments were repeated three times and data were
subjected to combined analysis. Means were analyzed for statistically significant differences using
the LSD test at the 5% level (Little and Hills,
1978).
3. Results and discussion
Immature tomato fruit tissue showed a pattern
of C2H4 autoinhibition (negative C2H4 feedback
mechanism) since C2H4 production by such tissue
was strongly inhibited upon exposure to exogenously applied C2H4 (Fig. l). An opposite trend
(C2H4 autocatalysis or positive feedback mechanism) however, was observed when tomato fruit
tissue at the pink stage was used (Fig. l). With the
first visual sign of red colour which occurred in
MG tissue 4 days after exogenous C2H4 exposure,
a transition phase from C2H4 autoinhibition to
autocatalysis was detected (Fig. 1). All developmental stages of strawberry fruit tissues, on the
other hand, showed a short-term increase in C2H4
production upon exogenous C2H4 application followed by a dramatic reduction to that of control
levels after 4 days of continuous C2H4 application
(Fig. 1). Since 5.8 mmol l − 1 propylene has the
same impact on fruit ripening as 0.045 mmol l − 1
C2H4 (McMurchie et al., 1972), separate tests with
tomato and strawberry tissues were also carried
out using propylene rather than C2H4. Results
showed similar levels of C2H4 production in both
treatments.
Since ACC formation and its conversion to
C2H4 are the two main limiting steps in C2H4
biosynthesis (Yang, 1980; Yang and Hoffman,
M.A. Atta-Aly et al. / Posthar6est Biology and Technology 20 (2000) 151–162
155
Fig. 1. Effect of exogenous ethylene treatment on ethylene production by tomato and strawberry fruit tissues at different
developmental stages. Vertical bars superimposed on datapoints at each sampling date represent the L.S.D. values at the 5% level.
1984) and also in C2H4 feedback mechanism
(Nakatsuka et al., 1998; Atta-Aly et al., 2000),
both ACC concentration and in vivo ACO activity were determined in both fruit tissues at all
developmental stages. While ACO activity signifi-
cantly increased in both fruit tissues at all developmental stages with exogenous C2H4 treatment
(Table 1), ACC concentration showed a different
pattern of response (Fig. 2). ACC increased in
tomato fruit tissues as ripening initiated and de-
M.A. Atta-Aly et al. / Posthar6est Biology and Technology 20 (2000) 151–162
156
Table 1
ACC oxidase activity (C2H4 nmol g−1 h−1) in tomato pericarp and strawberry flesh tissues exposed to exogenous C2H4 treatmenta
Treatment
C2H4 exposure
Fruit developmental stages
Tomato
H2O
AVG
ACC
AVG+ACC
Air
C2H4
Air
C2H4
Air
C2H4
Air
C2H4
Strawberry
Immature
Mature green
Pink
Green
White
Half coloured
0.12a
0.09b
0.04a
0.03a
2.15b
5.17a
0.78b
2.15a
0.78b
0.92a
0.18a
0.13a
1.88b
2.80a
0.94b
1.47a
0.73b
0.88a
0.31a
0.39a
2.07b
2.52a
0.19b
1.73a
0.04b
0.09a
0.01a
0.01a
0.38b
0.90a
0.36b
0.53a
0.02b
0.07a
0.01a
0.01a
0.14b
0.36a
0.10b
0.19a
0.02b
0.06a
0.01a
0.01a
0.20b
0.32a
0.10b
0.21a
Fruit tissues were treated with either H2O or 0.5 mM AVG immediately after excision and then exposed to either air or 4.5 mmol
l C2H4 for 3 days with H2O or 100 mM ACC application 2 h before C2H4 measurements. Values within each treatment for each
fruit developmental stage followed by the same letter are not statistically different at the 5% level.
a
−1
veloped, but decreased in immature tomato fruit
tissue and in all developmental stages of strawberry fruit (Fig. 2). Regardless of C2H4 application, ACC concentration increased the maturation
of both fruit tissues (Fig. 2). A short-term increase
in C2H4 production occurred in all developmental
stages of strawberry fruit tissues upon C2H4 treat-
Fig. 2. Effect of exogenous ethylene treatment for 4 days on
ACC concentration in tomato and strawberry fruit tissues at
different developmental stages. IM, MG and P are immature,
mature-green and pink tomato while G, W and HC are green,
white and half-coloured strawberry fruits, respectively. At each
developmental stage, significant differences are presented at
the 5% level.
ment, due mainly to induced ACO activity. This
increase was diminished thereafter when ACC
concentration became limiting. The reduction in
ACC concentration which occurred in strawberry
fruit tissues (Fig. 2) may be due not only to the
high level of its consumption during the first 3
days as a result of induced ACO activity (Table
1), but also to the reduction in tissue ACC synthesis, since after the first 3 days, C2H4-treated tissue
contained lower ACC concentrations but produced C2H4 levels at a rate equal to that of
air-treated ones (Figs. 1 and 2). These data suggest that both ACC and its conversion to C2H4
are limiting steps in C2H4 autocatalysis, while
only ACC is the controlling step in C2H4 autoinhibition.
Riov and Yang (1982) suggested that autoinhibition of C2H4 production in wounded citrus peel
tissue is attributable to the suppression of ACC
formation due to the inhibition of ACC synthase
formation and activity. Since the in vivo activity
of the ACO enzyme relies on the available level of
ACC in the tissue (Yang, 1980), it could be suggested that in the long term, ACC synthesis is the
limiting step in C2H4 feedback mechanism.
Thus the climacteric behaviour of tomato fruit
M.A. Atta-Aly et al. / Posthar6est Biology and Technology 20 (2000) 151–162
during ripening initiation and development may
be due mainly to the presence of C2H4 catalysis,
while the absence of this mechanism and the
157
presence of C2H4 autoinhibition are the reasons
for the nonclimacteric behaviour occurring in
strawberry fruit and during the nonripening
Fig. 3. Effect of transferring tomato and strawberry fruit tissues, excised at different developmental stages from air to ethylene and
back to air [air – ethylene–air; starting with 3 days in air (A) to 1 day in ethylene (B) and back to air for another day (C)] or to an
opposite sequence of exposure [ethylene–air–ethylene; starting with 3 days in ethylene (D) to 1 day in air (E) and back to ethylene
for another day (F)] on the levels of ethylene production at each atmosphere change. Significant differences are presented for each
sampling date at the 5% level.
158
M.A. Atta-Aly et al. / Posthar6est Biology and Technology 20 (2000) 151–162
stages of tomato fruit. Zeroni et al. (1976) reported
that C2H4 acts as an autoinhibitor of its own
production in the immature stages of sycamore fig
but not during ripening. Studies involving treatment of fruit with exogenous ethylene or propylene
indicated that fruit response to C2H4 may also
serve to distinguish between climacteric and nonclimacteric fruit (McMurchie et al., 1972). The
response of harvested fruit to applied C2H4 depends on various features, including tissue sensitivity and stage of maturation, as well as whether or
not the fruit is climacteric (Biale and Young, 1981).
These data suggest that exogenous C2H4 application to climacteric fruit should not be applied until
fruit become mature to obtain acceptable ripening
uniformity and quality, since positive C2H4 feedback mechanism does not occur at earlier stages.
To test the impact of C2H4 feedback mechanism
on C2H4 production in relation to fruit developmental stage and its climacteric pattern, both
tomato and strawberry fruit tissues at three specific
developmental stages were transferred between air
and C2H4 atmospheres. This was carried out in two
opposite sequences: air – C2H4 – air, or C2H4 – air –
C2H4, starting with 3 days in the first atmosphere
to eliminate wound C2H4 followed by one additional day for each subsequent atmosphere change.
During the immature stage of tomato fruit development, C2H4 production was significantly reduced when tissue was exposed to C2H4 or
transferred from air to C2H4 in comparison with
that exposed to air or transferred from C2H4 to air
(Fig. 3). As maturation progressed, exposure to
exogenous C2H4 significantly induced C2H4 production. This induction was eliminated upon transferring the tissue to air and re-occurred when tissue
was returned back to C2H4 (Fig. 3). The same
pattern of response was also obtained using
tomato locule gel tissue (Atta-Aly et al., 2000).
In strawberry fruit tissues however, C2H4 production strongly increased during the 3rd day of
exposure to exogenous C2H4 compared with those
exposed to air. After those first 3 days however, the
impact on C2H4 production of transferring tissues
between air and C2H4 atmospheres was diminished
(Fig. 3). Zauberman and Fuchs (1973) reported
that C2H4 feedback mechanisms may last after
removing the tissue from an C2H4 atmosphere.
Table 2
C2H4 and CO2 production by tomato pericarp and strawberry flesh tissue excised from fruits at different developmental stages and
exposed, for 3 days, to exogenous air 94.5 mmol l−1 C2H4 immediately after H2O or 0.5 mM STS applicationa
Treatment
C2H4 exposure
Fruit developmental stages
Tomato
C2H4 (nmol g−1 h−1)
H2O
STS
CO2 (mmol g−1 h−1)
H2O
STS
Strawberry
Immature
Mature green
Pink
Green
White
Half coloured
Air
C2H4
Air
C2H4
0.13a
0.09b
0.12a
0.14a
0.89b
1.04a
0.84a
0.80a
0.77b
0.92a
0.84a
0.76a
0.08a
0.09a
0.14a
0.11a
0.02b
0.07a
0.09a
0.09a
0.02b
0.06a
0.05a
0.04a
Air
C2H4
Air
C2H4
0.68b
0.87a
0.86a
0.80a
1.01b
1.52a
0.91a
0.89a
1.29b
1.55a
1.01a
1.04a
1.96a
1.95a
1.91a
1.88a
1.08a
1.19a
1.57a
1.64a
1.72a
1.81a
1.95a
1.74a
a
Values within each treatment for each fruit developmental stage followed by the same letter are not statistically different at the
5% level.
M.A. Atta-Aly et al. / Posthar6est Biology and Technology 20 (2000) 151–162
To test that a C2H4 feedback mechanism is
dependent on C2H4 sensitivity, STS was used to
inhibit C2H4 action before exposing both fruit
tissues either to air or C2H4 atmosphere. Data
159
presented in Table 2 show C2H4 autoinhibition in
immature tomato tissue but C2H4 autocatalysis in
mature-green and pink tomato as well as in white
and half-coloured strawberry fruit tissues after the
Fig. 4. Effect of exogenous ethylene treatment on CO2 production by tomato and strawberry fruit tissues at different developmental
stages. Vertical bars superimposed on data points at each sampling date represent the L.S.D. values at the 5% level.
160
M.A. Atta-Aly et al. / Posthar6est Biology and Technology 20 (2000) 151–162
Fig. 5. Effect of transferring tomato and strawberry fruit tissues, excised at different developmental stages from air to ethylene and
back to air [air – ethylene –air; starting with 3 days in air (A) to 1 day in ethylene (B) and back to air for another day (C)] or to an
opposite sequence of exposure [ethylene–air–ethylene; starting with 3 days in ethylene (D) to 1 day in air (E) and back to ethylene
for another day (F)] on the levels of CO2 production at each atmosphere change. Significant differences are presented for each
sampling date at the 5% level.
3 days of continuous C2H4 exposure. Both C2H4
autoinhibition and autocatalysis were diminished
when STS was used. Riov and Yang (1982) reported that silver ion blocked the autocatalytic
effect of C2H4. Inhibiting C2H4 action in the
climacteric tomato fruit with diazocyclopentadiene (DACP) application at different ripening
stages depressed C2H4 production (Sisler and
M.A. Atta-Aly et al. / Posthar6est Biology and Technology 20 (2000) 151–162
Lallu, 1994; Tian et al., 1997a), while opposite
results were obtained in the nonclimacteric
strawberry fruit (Tian et al., 1997b). It was also
evident that C2H4 autoinhibition is shifted to
C2H4 autocatalysis in tomato fruit as ripening is
initiated and progresses by stimulating both
ACC synthase and ACO (Nakatsuka et al.,
1998; Atta-Aly et al., 2000). Data presented in
this work, therefore, indicate that inhibiting
C2H4 action using silver ion blocks both C2H4
positive and negative feedback mechanisms.
Since the pattern of fruit respiration during
ripening initiation and development is another
strong feature to distinguish between climacteric
and nonclimacteric fruit behaviour, CO2 production therefore, was determined in both fruit tissues at three developmental stages during
continuous exposure to either air or C2H4 atmosphere. Exogenous C2H4 application induced
CO2 production by tomato fruit tissue while it
had no effect on strawberry as ripening progressed (Fig. 4). Inhibiting C2H4 action with
DACP application reduced tomato fruit respiration (Sisler and Lallu, 1994; Tian et al., 1997a),
while no effect was found in strawberry (Tian et
al., 1997b). When both fruit tissues were transferred between air and C2H4 atmospheres, CO2
production by tomato significantly increased in
the exogenous C2H4 atmosphere. This increase
diminished upon transfer to air and re-occurred
when tissues were returned to the C2H4 atmosphere. In strawberry however, none of these
differences occurred (Fig. 5). The stimulation of
tomato fruit respiration caused by exogenous
C2H4 application did not occur when C2H4 action and subsequently its feedback mechanism
was blocked by STS application (Table 2). This
means that during tomato fruit ripening there
was a positive correlation between a positive
C2H4 feedback mechanism and fruit climacteric
respiration. This correlation was absent in the
nonclimacteric strawberry fruit.
In conclusion, it is suggested that a negative
C2H4 feedback mechanism may be the reason
for the nonclimacteric behaviour of strawberry
fruit and immature tomato fruit, while a positive C2H4 feedback mechanism is the reason for
tomato fruit climacteric behaviour during ripen-
.
161
ing initiation and development. ACC formation
is possibly the limiting step for either positive or
negative C2H4 feedback mechanisms, since exogenous C2H4 treatment induced ACO activity
regardless of fruit species and physiological age.
References
Abeles, F.B., 1973. Ethylene in Plant Biology. Academic Press,
New York, p. 302.
Archbold, D.D., Dennis, F.G., 1985. Strawberry receptacle
growth and endogenous IAA content as affected by growth
regulator application and achene removal. J. Am. Soc.
Hort. Sci. 110, 816 – 820.
Atta-Aly, M.A., 1992. Ethylene production by different
tomato fruit tissues at different ripening stages. Egypt. J.
Hort. 19, 137 – 147.
Atta-Aly, M.A., Saltveit, M.E., Hobson, G.E., 1987. Effect of
silver ions on ethylene biosynthesis by tomato fruit tissue.
Plant Physiol. 83, 44 – 48.
Atta-Aly, M.A., Brecht, J.K., Huber, D.J., 2000. Ripening of
tomato locule gel tissue in response to ethylene, Postharvest Biol. Technol. 19 (3), 239 – 244.
Biale, J.B., Young, R.E., 1981. Respiration and ripening in
fruits retrospect and prospect. In: Friend, J., Rhodes, M.J.
(Eds.), Recent Advances in the Biochemistry of Fruits and
Vegetables. Academic Press, New York, pp. 1 – 40.
Burg, S.P., Burg, E.A., 1965. Ethylene action and the ripening
of fruit. Science 148, 1190 – 1196.
Hoffman, N.E., Yang, S.F., 1980. Changes in L-aminocyclopropane-L-carboxylic acid content in ripening fruits in
relation to their ethylene production rates. J. Am. Soc.
Hort. Sci. 105, 492 – 495.
Knee, M., Sargent, J.A., Osborne, D.J., 1977. Cell wall
metabolism in developing strawberry fruit. J. Exp. Bot. 28,
377 – 396.
Little, T.M., Hills, F.J., 1978. Agricultural Experimentation.
Wiley, New York, pp. 31 – 52.
Lizada, C., Yang, S.F., 1979. A simple and sensitive assay for
L-amino cyclopropane-L-carboxylic acid. Anal. Biochem.
100, 140 – 145.
McMurchie, E.J., McGlasson, W.B., Eaks, I.L., 1972. Treatment of fruit with propylene gives information about the
biogenesis of ethylene. Nature (Lond.) 235, 237.
Nakatsuka, A., Murachi, S., Okunishi, H., Shiomi, S.,
Nakano, R., Kubo, Y., Inaba, A., 1998. Differential expression and internal feedback regulation of 1-aminocyclopropane-1-carboxylate synthase, 1-aminocyclopropane-1carboxylate oxidase, and ethylene receptor genes in tomato
fruit during development and ripening. Plant Physiol. 118,
1295 – 1305.
Riov, J., Yang, S.F., 1982. Autoinhibition of ethylene production in citrus peel disks: suppression of L-aminocyclopropane-L-carboxylic acid synthesis. Plant Physiol. 69,
687 – 690.
162
M.A. Atta-Aly et al. / Posthar6est Biology and Technology 20 (2000) 151–162
Saltveit, M.E., 1982. Procedures for extracting and analyzing
internal gas samples from plant tissue by gas chromatograph. HortScience 17, 878–881.
Saltveit, M.E., Dilley, D.R., 1978. Rapidly induced wound
ethylene from excised segments of etiolated Pisum sati6um
L. cv Alaska. II. Oxygen and temperature dependency. Plant
Physiol. 61, 675 – 679.
Sisler, E.C., Lallu, N., 1994. Effect of diazocyclopentadiene
(DACP) on tomato fruits harvested at different ripening
stages. Postharvest Biol. Technol. 4, 245–254.
Tian, M.S., Bowen, J.H., Bauchot, A.D., Gong, Y.P., Lallu, N.,
1997a. Recovery of ethylene biosynthesis in diazocyclopentadiene (DACP)-treated tomato fruit. Plant Growth Regul.
22, 73 – 78.
Tian, M.S., Gong, Y.P., Bauchot, A.D., 1997b. Ethylene
.
biosynthesis and respiration in strawberry fruit treated with
diazocyclopentadiene and IAA. Plant Growth Regul. 23,
195 – 200.
Yang, S.F., 1980. Regulation of ethylene biosynthesis.
HortScience 15, 238 – 243.
Yang, S.F., Hoffman, N.E., 1984. Ethylene biosynthesis and its
regulation in higher plants. Annu. Rev. Plant Physiol. 35,
155 – 189.
Zauberman, G., Fuchs, Y., 1973. Ripening processes in avocado
stored in ethylene atmosphere in cold storage. J. Am. Soc.
Hort. Sci. 98, 477 – 480.
Zeroni, M., Galil, I., Ben-Yehoshua, S., 1976. Autoinhibition
of ethylene formation in nonripening stages of the fruit of
sycamore fig (Ficus sycomorus L.). Plant Physiol. 57, 647 –
650.