Journal of Experimental Botany, Vol. 50, No. 335, pp. 837–844, June 1999
Carbon dioxide and 1-MCP inhibit ethylene production
and respiration of pear fruit by different mechanisms
Hans P.J. de Wild, Ernst J. Woltering and Herman W. Peppelenbos1
Agrotechnological Research Institute (ATO-DLO), PO Box 17, 6700 AA Wageningen, The Netherlands
Received 6 October 1998; Accepted 18 January 1999
Abstract
Ethylene production in relation to O partial pressure
2
of whole pear fruit stored at 2 °C could be described
by a Michaelis–Menten equation. This was indicated
by the use of a gas exchange model. The maximum
ethylene production rate was strongly inhibited while
the K
value (1.25 kPa) was not affected by elevated
mO2
CO . Ethylene
production was also inhibited by 1-MCP,
2
an inhibitor of ethylene perception. The reduction in
ethylene production by CO was similar for 1-MCP
2
treated and untreated pears. Elevated CO , therefore,
2
must have had an influence on ethylene production
other than through ethylene perception. A possible
site of inhibition by CO is the conversion of ACC to
2
ethylene. The O uptake rate in relation to O partial
2
2
pressure of whole pear fruit could be described by a
Michaelis–Menten equation. The O uptake rate was
2
inhibited by elevated CO at a level similar to the
2
inhibition of ethylene production. Again the K
value
mO
(0.68 kPa) was not affected by CO . Using 1-MCP2 treat2
ments it was shown that there was no direct effect of
inhibited ethylene production on O uptake rate.
2
Key words: Gas exchange models, inhibition, Michaelis–
Menten kinetics, pear, Pyrus communis L.
Introduction
Respiration and ethylene biosynthesis are basic physiological processes in plants, which have been extensively
studied. These processes can either be inhibited or stimulated by elevated CO . Recent reviews on respiration
2
(Mathooko, 1996) and on ethylene biosynthesis and
action (John, 1997; Lelièvre et al., 1997) point out that
the precise modes of action of CO on both processes is
2
still not fully understood.
Burg and Burg (1967) proposed that inhibition of
ethylene biosynthesis by reduced O and elevated CO is
2
2
mediated through the receptor site. Gorny and Kader
(1996) supported this hypothesis by demonstrating that
reduced O and/or elevated CO inhibited ethylene pro2
2
duction rate by suppressing abundance of ACC synthase
transcripts. While Burg and Burg (1967) proposed that
CO is a competitive inhibitor of ethylene binding, other
2
experiments suggested the inhibition of ethylene binding
may be indirect or due to secondary effects such as pH
changes (Sisler, 1979; Sisler and Wood, 1988). Rothan
and Nicolas (1994) demonstrated that the reduction in
ethylene production rate by CO might be due to an
2
effect on ACC oxidase. Although elevated CO may
2
inhibit ethylene production, it is required for activation
of ACC oxidase (Dong et al., 1992) and CO may thus
2
promote ethylene biosynthesis. In pear, ethylene production was stimulated by 1% CO and inhibited by 5–20%
2
CO (Chavez-Franco and Kader, 1993).
2
Under aerobic conditions, elevated CO can stimulate,
2
inhibit, or have no effect on respiratory metabolism of
harvested plant parts, depending on the commodity and
the CO level ( Kader et al., 1989; Kubo et al., 1990;
2
Peppelenbos and van ’t Leven, 1996). Inhibition of respiration by CO may be due to reduced activity or
2
synthesis of various enzymes of the respiratory metabolism ( Kerbel et al., 1988; Lange and Kader, 1997a) and
the uncoupling effect of CO on oxidative phosphoryl2
ation (Shipway and Bramlage, 1973). Elevated CO may
2
influence respiration by a change in intracellular pH
(Bown, 1985; Siriphanich and Kader, 1986; Lange and
Kader, 1997b). There are some indications that ethylene
is involved in the inhibitory effect of CO on respiration.
2
Kubo et al. (1990) studied the respiratory responses of
several harvested horticultural crops to high CO and
2
suggested that different responses might be mediated by
the effect of CO on ethylene synthesis and/or action.
2
1 To whom correspondence should be addressed. Fax: +31 317 475347. E-mail: [email protected]
© Oxford University Press 1999
838 de Wild et al.
At present little information is available about actual
ethylene production rates together with actual respiration
rates in whole plant organs at various O and CO levels.
2
2
Most of the research on CO effect on ethylene production
2
has been done in vitro or on excised tissues in vivo. In the
present experiments, a system was used that enables the
study of whole plant organ responses to CO at various
2
O levels. To study the site of inhibition by CO ,
2
2
1-methylcyclopropene (1-MCP) was used. 1-MCP is an
effective inhibitor of ethylene responses because it blocks
the receptor (Sisler and Serek, 1997). It protects against
ethylene binding for many days and is already effective
at low concentrations (0.5–40 ppb at 24 h treatment).
Both ethylene production and O consumption were
2
investigated at 2 °C.
Materials and methods
Plant material
Pears (Pyrus communis L. cv. Conference) were harvested in
September 1997 at a pre-climacteric stage. Fruits were stored
for 3 months under controlled atmosphere conditions (1 °C,
2.0 kPa O and 0.7 kPa CO ) before the experiments started.
2
2
Treatments
The fresh weight and the volume of each individual pear were
measured. Volume was estimated by water displacement
(Baumann and Henze, 1983). The fruits were placed in 1.8 l
cuvettes (two fruits per cuvette). The free volume of the cuvettes
was calculated by subtracting the product volume from the
cuvette volume. The cuvettes were stored in a temperaturecontrolled room at 2 °C and connected to a flow-through
system. At this low temperature physiological change of the
product is minimal. In the flow-through system, pure N , O
2 2
and CO were mixed using mass flow controllers. A range of
2
gas conditions was selected (0, 0.5, 1, 2.5, 6, and 21 kPa O
2
combined with 0 and 5 kPa CO ). Two replicates were used
2
per treatment. The flow rate used in the experiments was
400 ml min−1. The gas entering each cuvette was directed
through a water flask, resulting in a relative humidity close to
saturation (97–99%).
In a second type of experiment the effect of elevated CO on
2
ethylene production and respiration was compared to the effect
of 1-MCP. Pears were left overnight at 2 °C and some pears
were stored in a desiccator with 280 ppb 1-MCP. During the
next 5 d pears were exposed to 6 and 21 kPa O combined with
2
0 and 5 kPa CO At days 3 and 5, respiration and ethylene
2.
production were measured. Two replicates were used per
treatment.
To test the effects of 1-MCP and CO at higher concentrations,
2
pears were treated with 1750 ppb 1-MCP for 18 h. During the
following days, pears were exposed to 21 kPa O combined
2
with 0, 5 (only 1-MCP treated pears) or 20 kPa CO . At days
2
3 and 7, respiration and ethylene production were measured.
At day 9 only ethylene production was measured. Four
replicates were used per treatment.
Measurements of respiration and ethylene production
The respiration of the fruits was measured after 5 d of treatment.
For measuring gas exchange, the gas stream through the
cuvettes was temporary stopped. Headspace O , CO and N
2
2
2
concentrations were measured with a Chrompack CP 2002 gas
chromatograph (GC ) equipped with an automatic sample
system. Gas was sampled directly from the cuvettes. The exact
time of measurement was logged. For every measurement two
samples were taken, and only the second sample was used. The
time period between the first and second measurement was
4.5 h so that the difference in partial pressure between the two
measurements never exceeded 0.3 kPa O or CO at high O
2
2
2
and 0.1 kPa at low O levels.
2
To convert gas levels from percentages to partial pressures,
total pressure in the cuvettes was measured directly after the
first measurement and before the second measurement (with a
Druck PDI 265). After the second measurement, cuvettes were
connected to the flow-through system again.
The next day (day 6), the ethylene production of the fruits
was measured. The air-stream through the cuvettes was stopped
and headspace ethylene concentrations were analysed by
withdrawing 2.5 ml samples from the cuvettes, and injecting
them into a gas chromatograph (Chrompack model 437 A).
After 1 h a second sample was taken. Total pressure in the
cuvettes was measured after the first and before the second
sample withdrawal.
The difference in gas partial pressures between the first and
the second measurement was converted to moles according to
the Ideal Gas Law. Gas exchange rates were calculated by
expressing the mol differences between the two measurements
per unit time (s) and per unit weight (kg fresh weight at the
start of the experiment).
Gas exchange models
The most widely used and accepted equation to describe
respiration at fruit level is based on a mathematical description
of the kinetics at enzyme level (Cameron et al., 1995). This
Michaelis–Menten type of kinetics have been used by several
authors (Chevillotte, 1973; Banks et al., 1989; Lee et al., 1991;
Peppelenbos and van ’t Leven, 1996). It is assumed that the
whole respiratory chain can be described by one enzymemediated reaction, with the substrate glucose considered as
non-limiting and the substrate O as limiting. Three types of
2
inhibition of enzyme functioning can be distinguished (Chang,
1981), but often the non-competitive type was used (Lee et al.,
1991; Peppelenbos and van ’t Leven, 1996):
V ×O
mO2
2
V =
(1)
O2 (K +O )×(1+CO
/K
)
mO2
2
2 mCO2
where V is the O consumption rate (nmol kg−1 s−1), V
is
O2
2
mO
the maximum
reaction rate (nmol kg−1 s−1), O is the 2O
2
2
partial pressure (kPa), K
is the Michaelis–Menten constant
mO2
for O inhibition of O consumption (kPa O ), CO is the CO
2
2
2
2
2
partial pressure (kPa) and K
is the Michaelis–Menten
mCO2
constant for CO inhibition of O consumption (kPa CO ).
2
2
2
When it is assumed that ethylene biosynthesis can also be
described by one enzyme-mediated reaction, with the substrate
O as limiting, the non-competitive inhibition of ethylene
2
production can be described by equation (1) with a small
modification:
V
×O
mC2H4
2
(2)
(K
+O )×(1+CO /K
)
meO2
2
2 meCO2
where V
is the ethylene production rate (pmol kg−1 s−1),
C H4
V
is 2the
maximum reaction rate (pmol kg−1 s−1), K
is
mC H4
meO2
the 2Michaelis–Menten
constant for O inhibition of ethylene
2
is the Michaelis–Menten
production (kPa O ) and K
2
meCO2
constant for CO inhibition of ethylene
production (kPa CO ).
2
2
Also models with competitive and uncompetitive types of
V
C2H4
=
Gas exchange in pear 839
inhibition as described by Peppelenbos and van ’t Leven (1996)
were used for modelling O uptake and ethylene production
2
rates.
Lineweaver-Burk plots
In enzyme kinetics a Lineweaver-Burk plot reflects the type of
enzyme inhibition (Chang, 1981). Lineweaver-Burk plots as
used in the study of enzyme kinetics are applied in the present
experiment to ethylene production and respiration rates at
whole fruit level.
Statistical analysis
The data were compared with the gas exchange models using
the facilities for non-linear regression in the statistical package
Genstat (release 5). The non-linear equation was fitted directly
without any transformation, using an iterative method to
maximize the likelihood, rather than first linearizing the
equations as is often done. Linearizing the equation is equivalent
to changing the weight given to the data in the estimation
procedure.
The ethylene production and O uptake rates were analysed
2
for significant differences by analysis of variance (ANOVA)
with the statistical package Genstat. When significant differences
were found, comparisons between pairs of data were made
using the least significant differences between means (LSD) at
a significance level of 95%.
Results
Effects of O and CO on ethylene production and
2
2
respiration
The mean ethylene production rate at 0 kPa CO was
2
73 pmol kg−1 s−1 at 6–21 kPa O . At lower O partial
2
2
pressures ethylene production rate was reduced (Fig. 1).
At 0 kPa O no ethylene production was detected.
2
Exposure to 5 kPa CO inhibited ethylene production by
2
30% at 21 kPa O . The percentage inhibition was similar
2
at lower O partial pressures.
2
Without additional CO , O uptake rate was reduced
2 2
from 20.8 nmol kg−1 s−1 at 21 kPa O to zero at 0 kPa
2
O (Fig. 2). Exposure to CO inhibited O uptake rate
2
2
2
by 34% at 21 kPa O . At lower O partial pressures, the
2
2
percentage inhibition by CO was similar.
2
Gas exchange models
The relationship between ethylene production and O
2
partial pressure conformed to Michaelis–Menten kinetics.
The ethylene production rate was best described with the
ethylene production model with non-competitive inhibition by CO (equation 2), as was shown by the high
2
percentage of explained variance (R2) ( Table 1). The fitted
curves of this model are given in Fig. 1. According to the
model, an external level of 5 kPa CO reduced maximum
2
ethylene production rate by 39% from 83.8 to
50.8 pmol kg−1 s−1 while the K
value was unaffected.
meO2
The Lineweaver-Burk plot for ethylene
production rate
with K
and V
values derived from the model
meO
mC H4
correlates 2well with 2the
measured values (inset Fig. 1).
The Lineweaver-Burk plot confirms the non-competitive
type of inhibition by CO .
2
Similarly, for O uptake, the model with non2
competitive inhibition of CO (equation 1) gave the best
2
results ( Table 1; Fig. 2). The model indicates that an
additional 5 kPa CO reduced maximum O uptake rate
2
2
by 36% from 21.7 to 13.9 nmol kg−1 s−1. The noncompetitive inhibition by CO was confirmed by the
2
Lineweaver-Burk plot for O uptake rate (inset Fig. 2).
2
Fig. 1. The ethylene production rate (pmol kg−1 s−1) at several O partial pressures combined with 0 kPa CO (&) and 5 kPa CO (%). The
2
2
2
symbols represent the actual values. The curves are fitted using the parameters of the gas exchange model with non-competitive type of inhibition
by CO . Inset is the double reciprocal plot of the same data and the same models.
2
840 de Wild et al.
Fig. 2. The O uptake rate (nmol kg−1 s−1) at several O partial pressures combined with 0 kPa CO (&) and 5 kPa CO (%). The symbols
2
2
2
2
represent the actual values. The curves are fitted using the parameters of the gas exchange model with non-competitive type of inhibition by CO .
2
Inset is the double reciprocal plot of the same data and the same models.
Table 1. Results of the regression analysis for ethylene production
and O uptake with three types of inhibition by CO
2
2
R2=percentage variance accounted for (indication for goodness of fit),
V
=the maximum ethylene production rate (pmol kg−1 s−1), K =
mC2H4
me
Michaelis–Menten
constant for ethylene production, V =the maxmO2
imum O uptake rate (nmol kg−1 s−1), K =Michaelis–Menten constant
2
m
for O uptake, est=estimated values, se=standard error.
2
Ethylene production
R2
V
(est se)
mC H
K 2 4(est se)
meO
K 2 (est se)
meCO2
O uptake
2
R2
V
(est se)
mO
K 2 (est se)
mO2
K
(est se)
mCO2
Competitive
inhibition
Uncompetitive Noninhibition
competitive
inhibition
91.9
74.0
0.83
1.26
4.0
0.18
0.38
93.0
85.1
1.41
6.26
4.9
0.24
1.23
95.0
83.8
1.25
7.70
3.7
0.17
1.18
87.3
18.8
0.39
1.22
1.0
0.11
0.47
89.6
21.9
0.75
7.62
1.3
0.15
1.64
91.6
21.7
0.68
8.95
1.0
0.12
1.63
Effects of 1-MCP and CO on ethylene production and
2
respiration
Fruits from the experiment that included treatment with
280 ppb 1-MCP were measured at day 3 and day 5.
Because no interaction was found between treatment and
day, measured rates were averaged over both days
( Table 2). Application of 1-MCP inhibited ethylene production significantly. Exposure to 5 kPa CO inhibited
2
ethylene production significantly, irrespective of 1-MCP
treatment. The O uptake rate was not affected by 1-MCP
2
at 6 kPa O , but was inhibited at 21 kPa O .
2
2
Treatment with 1750 ppb 1-MCP inhibited ethylene
production rate significantly ( Table 3). Again, exposure
of 1-MCP-treated pears to 5 kPa CO further inhibited
2
ethylene production. Exposure to 20 kPa CO initially
2
stimulated but later strongly inhibited ethylene production rate. Exposure to 20 kPa CO affected ethylene
2
production irrespective of 1-MCP treatment. The O
2
uptake rate was significantly inhibited by elevated CO
2
at day 7, but was not affected by 1-MCP ( Table 3).
Comparison of ethylene production and respiration
The K
value for O uptake was approximately half
mO
2
the K 2 value for ethylene production. The difference
mO2
in K
values results in a non-linear relationship between
mO2
ethylene
production and O uptake at 0 kPa CO as
2
2
shown in Fig. 3. Inhibition of gas exchange rates by 5 kPa
CO was rather similar for both processes as reflected in
2
the K
values. This resulted in a non-linear relationship
mCO
between 2both processes, which is slightly different from
the relationship at 0 kPa CO (Fig. 3).
2
Discussion
Effects of O , CO and 1-MCP on ethylene production
2
2
The observed reduction of ethylene production by 1-MCP
indicates that ethylene production was autocatalytic. The
experiments with 1-MCP treated pears showed an additive
inhibitory effect of CO on ethylene production. The
2
reduction in ethylene production by CO was similar for
2
1-MCP treated and untreated pears. 1-MCP was added
Gas exchange in pear 841
Fig. 3. Comparison between ethylene production rate (pmol kg−1 s−1) and O uptake rate (nmol kg−1 s−1) at 0 kPa CO (&) and 5 kPa CO (%),
2
2
2
fitted with the non-competitive type of inhibition.
Table 2. Ethylene production rate (pmol kg−1 s−1) and O uptake
2
rate (nmol kg−1 s−1) of pears, averaged over day 3 and 5
Means within each row followed by different letters are significantly
different (P<0.05)
O
2
(kPa)
Control
1-MCP
(280 ppb)
CO
2
(5 kPa)
Combined
treatment
Ethylene production
6
21
84.3 a
73.5 a
65.7 b
57.8 b
52.7 b
50.1 c
29.8 c
29.2 d
O uptake
2
6
21
15.3 ab
20.1 a
18.0 a
15.3 b
12.4 bc
13.7 bc
10.3 c
11.0 c
in such an amount and duration that it can be assumed
that all the ethylene receptors were blocked especially
when 1750 ppb 1-MCP was used. To cause an inhibition
of ethylene production under these circumstances, CO
2
must have had an influence other than at the level of
ethylene perception. Often reference is made to the hypothesis of Burg and Burg (1967) that autocatalytic ethylene
production is inhibited by CO at the receptor level
2
(Cheverry et al., 1988; Lelièvre et al., 1997). The present
experiments show the importance of taking into account
the inhibition by CO through another mechanism at the
2
applied low temperature. The relevance of this type of
inhibition at higher temperatures has to be elucidated.
Data on ethylene production rate in relation to external
O partial pressures conformed to a Michaelis–Menten
2
equation. This strongly suggests enzyme kinetics, probably the conversion from ACC to ethylene by ACC
oxidase which requires O . Michaelian kinetics for ethy2
lene production with the substrate O have been shown
2
before in vivo ( Yip et al., 1988) and in vitro (McGarvey
and Christoffersen, 1992). Yip et al. (1988) found that
the K value for O varied greatly depending on the ACC
m
2
content. They suggested an ordered binding mechanism
in which ACC oxidase binds first to O and then to ACC.
2
When this mechanism is supposed to be valid for the
present experiments, the unchanged K value for O
m
2
indicates that ACC content was not influenced by CO
2
treatment and inhibition must have been at the level of
conversion of ACC to ethylene. Rothan and Nicolas
(1994) found that when ACC content is low, high CO
2
Table 3. Ethylene production rate (pmol kg−1 s−1) and O uptake rate (nmol kg−1 s−1) of pears at 21 kPa O
2
2
Means within each row followed by different letters are significantly different (P<0.05)
Day
Control
1-MCP
(1750 ppb)
CO
2
(20 kPa)
1-MCP+
20 kPa CO
2
1-MCP+
5 kPa CO
Ethylene production
3
7
9
35.8 b
44.8 a
42.0 a
20.6 c
27.8 b
27.1 b
55.3 a
11.2 c
5.7 cd
21.1 c
6.1 c
3.4 d
14.1 c
9.0 c
10.4 c
O uptake
2
3
7
14.3 a
17.6 a
11.9 a
17.5 a
10.5 a
12.5 b
10.9 a
14.3 ab
9.8 a
14.0 ab
2
842 de Wild et al.
may inhibit ethylene production by reducing the efficiency
of the conversion of ACC to ethylene. When another
mechanism than the ordered binding mechanism is
involved, the observed CO inhibition may also be attrib2
uted to reduced ACC content. A reduction of ACC
content by CO in the present experiments may be
2
explained by depletion of ACC synthase protein due to
degradation and/or inhibition of synthesis or by inactivation of ACC synthase activity (Mathooko et al., 1995)
which is, however, apparently not directed via the ethylene
receptor.
The effect of CO on the Michaelian kinetics of ethylene
2
production in relation to O partial pressure in vivo has
2
not been reported before. Whether conditions in vitro are
relevant to the operation of the enzyme ACC oxidase in
vivo is not clear (John, 1997). Also little information is
available on ethylene production kinetics of whole plant
organs. Dadzie et al. (1996) found for whole apple fruit
a relationship between ethylene production rate and
internal O partial pressure that was reasonably described
2
by a Michaelis–Menten type hyperbolic curve. However,
physiological changes (in potential maximum rates of
ethylene production) over the duration of the experiment
had made it difficult to resemble a good relationship. In
the present experiment pears were exposed to various O
2
partial pressures for 6 d at 2 °C. At this duration and
temperature, a change in ethylene production capacity is
negligible. This was verified in a separate experiment
(data not shown). Under conditions with minimal physiological change of the product during the experimental
period, the used experimental set-up proved to be
adequate for ethylene research of whole plant organs.
The high percentages of explained variance obtained with
all used models, supports the use of Michaelis–Menten
kinetics for modelling ethylene production at the level of
whole plant organs.
Effects of O and CO on respiration
2
2
Data on O uptake rate in relation to O partial pressures
2
2
at different CO levels conformed well to a Michaelis–
2
Menten equation. The K
value was low relative to
mCO
other harvested plant organs2 (Peppelenbos and van ’t
Leven, 1996) indicating a pronounced inhibitory effect of
CO on pear respiration. Enzymes that may be affected
2
by elevated CO are ATP5phosphofructokinase and
2
PPi5phosphofructokinase ( Kerbel et al., 1988, 1990).
Comparison ethylene production and respiration
Inhibition of ethylene production rate by CO occurred
2
simultaneously with an inhibition of O uptake rate. A
2
similar decrease in ethylene production rate by 1-MCP
was in most cases not accompanied by a reduction in O
2
uptake. Also, the observed initial stimulation of ethylene
production by 20 kPa CO was not accompanied by a
2
rise in O uptake. These results indicate that there was
2
no direct effect of ethylene on O uptake rate. The
2
question arises whether there is an inverse causal relationship between ethylene production and O uptake rate.
2
The inhibitory effect of CO on ethylene production could
2
be mediated by the effect of CO on respiration. This
2
could be explained as follows: an inhibition of respiration
results in reduced ATP production. ATP is involved in
the conversion of ACC to ethylene. Inhibitors of electron
transfer and oxidative phosphorylation reduced ATP
levels and inhibited the conversion of ACC to ethylene
(Apelbaum et al., 1981). Gorny and Kader (1996) mentioned the possibility that reduced ATP pools affects the
Fig. 4. Possible sites of inhibition of ethylene production by CO . Arrow ‘a’ represents inhibition of the conversion of SAM to ACC by depletion
2
of ACC synthase protein or inactivation of ACC synthase activity (Mathooko, 1995); however, not via the ethylene receptor. Arrow ‘b’ represents
the reduction of the efficiency of the conversion of ACC to ethylene which can lead to inhibition of ethylene production when ACC content is low
(Rothan and Nicolas, 1994). Arrow ‘c’ represents inhibition of the conversion of ACC to ethylene by reduced ATP production due to inhibition
of respiration (present report).
Gas exchange in pear 843
protein phosphorylation that might be necessary for
activation of ACC oxidase.
In summary, possible explanations for the observed
inhibition of ethylene production by CO are (1) depletion
2
of ACC synthase protein due to degradation and/or
inhibition of synthesis, or inactivation of ACC synthase
activity (Mathooko et al., 1995), but without interference
with the ethylene receptor (Fig. 4, ‘a’); (2) reduction of
the efficiency of conversion of ACC to ethylene. This can
lead to inhibition of ethylene production when ACC
content is low (Rothan and Nicolas, 1994) ( Fig. 4, ‘b’);
and (3) reduced ATP level by inhibition of respiration as
shown in the present experiment (Fig. 4, ‘c’).
Conclusions
Both O uptake rate and ethylene production rate in
2
relation to O partial pressures conformed to a Michaelis–
2
Menten equation. Elevated CO inhibited ethylene pro2
duction rate and respiration rate at similar levels. For
both processes, this was best described by the noncompetitive type of inhibition by CO . Present results
2
showed that CO did not exert its effect on respiration
2
through its influence on ethylene production or action as
suggested by Kubo et al. (1990). Ethylene production
can be inhibited at the level of ethylene perception (Burg
and Burg, 1967; Gorny and Kader, 1996) (Fig. 4).
Inhibition of ethylene production by 1-MCP showed that
this was true in the present experiments. However, CO
2
must have had an influence other than on ethylene
perception.
References
Apelbaum A, Wang SY, Burgoon AC, Baker JE, Lieberman M.
1981. Inhibition of the conversion of 1-aminocyclopropane1-carboxylic acid to ethylene by structural analogs, inhibitors
of electron transfer, uncouplers of oxidative phosphorylation,
and free radical scavengers. Plant Physiology 67, 74–79.
Banks NH, Hewett EW, Rajapakse NC, Cleland DJ, Austin PC,
Stewart TM. 1989. Modelling fruit response to modified
atmospheres. In: Fellman JK, ed. Proceedings of the Fifth
International Controlled Atmosphere Research Conference,
Wenatchee, Washington USA, 359–366.
Baumann H, Henze J. 1983. Intercellular space volume of fruit.
Acta Horticulturae 138, 107–111.
Bown AW. 1985. CO and intracellular pH. Plant, Cell and
2
Environment 8, 459–465.
Burg SP, Burg EA. 1967. Molecular requirements for the
biological activity of ethylene. Plant Physiology 42, 144–152.
Cameron AC, Talasila PC, Joles DW. 1995. Predicting film
permeability needs for modified atmosphere packaging of
lightly processed fruits and vegetables. HortScience 30, 25–34.
Chang R. 1981. Enzyme kinetics. In: Chang R, ed. Physical
chemistry with applications to biological systems, 2nd edn.
New York: Macmillan Publishing Co, Inc, 390–405.
Chavez-Franco SH, Kader AA. 1993. Effects of CO on ethylene
2
biosynthesis in ‘Bartlett’ pears. Postharvest Biology and
Technology 3, 183–190.
Cheverry JL, Sy MO, Pouliqueen J, Marcellin P. 1988.
Regulation by CO of 1-aminocyclopropane-1-carboxylic acid
2
conversion to ethylene in climacteric fruits. Physiologia
Plantarum 72, 535–540.
Chevillotte P. 1973. Relation between the reaction cytochrome
oxidase-oxygen and oxygen uptake in cells in vivo. The role
of diffusion. Journal of Theoretical Biology 39, 277–295.
Dadzie BK, Banks NH, Cleland DJ, Hewett EW. 1996. Changes
in respiration and ethylene production of apples in response
to internal and external oxygen partial pressures. Postharvest
Biology and Technology 9, 297–309.
Dong JG, Fernández-Maculet JC, Yang SF. 1992. Purification
and characterization of 1-aminocyclopropane-1-carboxylate
oxidase from apple fruit. Proceedings of the National Academy
of Sciences, USA 89, 9789–9793.
Gorny JR, Kader AA. 1996. Controlled-atmosphere suppression
of ACC synthase and ACC oxidase in ‘Golden Delicious’
apples during long-term cold storage. Journal of the American
Society for Horticultural Science 121, 751–755.
John P. 1997. Ethylene biosynthesis: the role of
1-aminocyclopropane-1-carboxylate (ACC ) oxidase, and its
possible evolutionary origin. Physiologia Plantarum 100,
583–592.
Kader AA, Zagory D., Kerbel EL. 1989. Modified atmosphere
packaging of fruits and vegetables. Critical Reviews in Food
Science and Nutrition 28, 1–30.
Kerbel EL, Kader AA, Romani RJ. 1988. Effects of elevated
CO concentrations on glycolysis in intact ‘Bartlet’ pear fruit.
2
Plant Physiology 86, 1205–1209.
Kerbel EL, Kader AA, Romani RJ. 1990. Respiratory and
glycolytic response of suspension-cultured ‘Passe Crassane’
pear fruit cells to elevated CO concentrations. Journal of the
2
American Society for Horticultural Science 115, 111–114.
Kubo Y, Inaba A, Nakamura R. 1990. Respiration and C H
2 4
production in various harvested crops held in CO -enriched
2
atmospheres. Journal of the American Society for Horticultural
Science 115, 975–978.
Lange DL, Kader AA. 1997a. Effects of elevated carbon dioxide
on key mitochondrial respiratory enzymes in ‘Hass’ avocado
fruit and fruit disks. Journal of the American Society for
Horticultural Science 122, 238–244.
Lange DL, Kader AA. 1997b. Elevated carbon dioxide exposure
alters intracellular pH and energy charge in avocado fruit
tissue. Journal of the American Society for Horticultural
Science 122, 253–257.
Lee DS, Haggar PE, Lee J, Yam KL. 1991. Model for fresh
produce respiration in modified atmospheres based on
principles of enzyme kinetics. Journal of Food Science 56,
1580–1585.
Lelièvre JM, Latché A, Jones B, Bouzayen M, Pech JC. 1997.
Ethylene and fruit ripening. Physiologia Plantarum 101,
727–739.
Mathooko FM. 1996. Regulation of respiratory metabolism in
fruits and vegetables by carbon dioxide. Postharvest Biology
and Technology 9, 247–264.
Mathooko FM, Kubo Y, Inaba A, Nakamura R. 1995.
Characterization of the regulation of ethylene biosynthesis in
tomato fruit by carbon dioxide and diazocyclopentadiene.
Postharvest Biology and Technology 5, 221–233.
McGarvey DJ, Christoffersen RE. 1992. Characterization and
kinetic parameters of ethylene-forming enzyme from avocado
fruit. The Journal of Biological Chemistry 267, 5964–5967.
Peppelenbos HW, van ’t Leven J. 1996. Evaluation of four types
of inhibition for modelling the influence of carbon dioxide
on oxygen consumption of fruits and vegetables. Postharvest
Biology and Technology 7, 27–40.
844 de Wild et al.
Rothan C, Nicolas J. 1994. High CO levels reduce ethylene
2
production in kiwifruit. Physiologia Plantarum 92, 1–8.
Shipway MR, Bramlage WJ. 1973. Effects of carbon dioxide on
activity of apple mitochondria. Plant Physiology 51,
1095–1098.
Siriphanich J, Kader AA. 1986. Changes in cytoplasmic and
vacuolar pH in harvested lettuce tissue as influenced by CO .
2
Journal of the American Society for Horticultural Science
111, 73–77.
Sisler EC. 1979. Measurement of ethylene binding in plant
tissue. Plant Physiology 64, 538–542.
Sisler EC, Serek M. 1997. Inhibitors of ethylene responses in
plants at the receptor level: recent developments. Physiologia
Plantarum 100, 577–582.
Sisler EC, Wood C. 1988. Interaction of ethylene and CO .
2
Physiologia Plantarum 73, 440–444.
Yip WK, Jiao XZ, Yang SF. 1988. Dependence of in vivo
ethylene production rate on 1-aminocyclopropane1-carboxylic acid content and oxygen concentrations. Plant
Physiology 88, 553–558.