Download Changes of Carbohydrates in Pepper (Capsicum annuum L

Annals of Botany 78 : 163–168, 1996
Changes of Carbohydrates in Pepper (Capsicum annuum L.) Flowers in Relation
to Their Abscission Under Different Shading Regimes
B. ALONI*, L. K A R N I, Z. Z A I D M AN and A. A. S C H A F F E R
Department of Vegetable Crops, Institute of Field and Garden Crops, Agricultural Research Organization,
The Volcani Center, P.O.B. 6, Bet Dagan 50250, Israel
Received : 24 July 1995
Accepted : 25 January 1996
Abscission of pepper flowers is enhanced under conditions of low light and high temperature. Our study shows that
pepper flowers accumulate assimilates, particularly in the ovary, during the day time, and accumulate starch, which
is then metabolized in the subsequent dark period. With the exception of the petals, the ovary contains the highest
total amounts of sugars and starch, compared with other flower parts and contains the highest total activity, as well
as activity calculated on fresh mass basis, of sucrose synthase, in accordance with the role of this enzyme in starch
biosynthesis. Low light intensity or leaf removal decreased sugar accumulation in the flower and subsequently caused
flower abscission. The threshold of light intensity for daily sugar accumulation in the sink leaves was much lower than
in flowers, resulting in higher daytime accumulation of sugars in the sink leaves than in the adjacent flower buds under
any light intensity, suggesting a competition for assimilates between these organs. Flowers of bell pepper cv. ‘ Maor ’
and ‘ 899 ’ (sensitive to abscission) accumulated less soluble sugars and starch under shade than the flowers of bell
pepper cv. ‘ Mazurka ’ and of paprika cv. ‘ Lehava ’ (less sensitive). The results suggest that the flower capacity to
accumulate sugars and starch during the day is an important factor in determining flower retention and fruit set.
# 1996 Annals of Botany Company
Key words : Pepper, Capsicum annuum L., abscission, shading, pepper flowers, ovary, leaves, sugars, starch, acid
invertase, sucrose synthase.
INTRODUCTION
In most agricultural crops, flower retention and fruit set are
highly sensitive to environmental stresses. High temperature
and low light conditions are known to enhance flower
abscission and to affect photosynthetic rates (Gent, 1986 ;
Shishido, Chala and Krupa, 1987 ; Kitroongruang et al.,
1992 ; Havaux, 1993), assimilate partitioning (Dinar and
Rudich, 1985 b ; Aloni, Pashkar and Karni, 1991 a) and
sugar metabolism in source and sink tissues (Hawker, 1982 ;
Dinar and Rudich, 1985 a; Bhuller and Jenner, 1986 ;
Macleod and Duffus, 1988). In addition, hormonal balance,
particularly of ethylene and auxin, is important in controlling abscission (Beyer and Morgan, 1971 ; Wien, Turner
and Yang, 1989 ; Ofir et al., 1993). Low light intensity
enhances pepper flower abortion and thus reduces fruit
yield. While fertilization is sensitive to high temperature (ElAhmadi and Stevens, 1979 ; Kao, Chen and Ma, 1986 ;
Mutters and Hall, 1992), this process may not be important
in the abortion of flower buds (pre-anthesis) and fruitlets
(post-fertilization).
Both flower retention and fruit set depend on assimilate
supply to the developing reproductive organ, as shown in
many studies in which leaf area, CO enrichment, leaf
#
removal and alterations of competing sinks were found to
* For correspondence.
Contribution from the Agricultural Research Organization, The
Volcani Center, Bet Dagan, Israel. No. 1655–E, 1995 series.
0305-7364}96}080163­06 $18.00}0
affect flower development, flower abortion and fruit set (see
review by Kinet, Sachs and Bernier, 1985 and references
therein). More recently it was shown that flower retention in
pepper decreases under shading stress (Wien, Turner and
Yang, 1989) and flower abscission was higher if shading was
applied in combination with high temperature. It has been
suggested (Aloni, Pashkar and Karni, 1991 b) that competition for assimilates between the flowers and the adjacent
young leaves may be important in determining flower
retention. Only recently Turner and Wien (1994) have
shown that susceptibility of pepper cultivars may be related
to assimilate partitioning to the flower buds. In order to
investigate the relationships between assimilate concentration and metabolism in peppers further we investigated
the daily changes in carbohydrate concentration of the
flowers in relation to their abscission when assimilate supply
was limited by removal of source leaves or by low light
intensity in pepper cultivars with different sensitivity to
flower abortion.
MATERIALS AND METHODS
Plant material, growth conditions and shading treatments
Seedlings of pepper plants of several different cultivars (Bell
pepper cvs. ‘ Maor ’, ‘ 899 ’, from Hazera, Israel, ‘ 11480’
from Zeraim Gedera, Israel, Mazurka’ from Rijk Zvaan,
Holland, Paprika ‘ Lehava ’, from The Volcani Center,
Israel) were transplanted on 1 Jul. 1993 into 10 l pots filled
# 1996 Annals of Botany Company
164
Aloni et al.—Carbohydrate Content of Pepper Flowers
1
2
3
4
Each treatment was applied to 24 plants, divided among
three replicates. After the trimming treatments the rate of
abscission of the primary and secondary flower buds of
internode 8 was recorded.
Abscission of reproductive organs was determined by
counting vacant internodes on the whole plant and
calculating the percentage of aborted organs.
Photosynthesis measurements
F. 1. Schematic drawing of leaf pruning. The arrow points to
internode 8 at which the main stem flower bud (E) was maintained.
The (*) symbolize the attached leaves. The broken line symbolizes the
stem continuation. Nos 1–4 are the treatments as explained in the
Materials and Methods.
with a peat : perlite mixture (60 : 40, v}v) and irrigated with
commercial nutrient solution (‘ Shefer ’, Deshanim Co.
Israel, N : P : K, 7 : 3 : 7 and microelements). The plants were
grown in a greenhouse with minimum and maximum
temperatures of 22 and 28 °C, respectively. After 30 d each
plant was allowed to develop two main stems, which were
supported by training threads. The flowers of each internode,
on both stems, were maintained with two adjacent source
leaves. All the side shoots were removed. Sixty days after
transplantation, pepper plants of different cultivars developed flowers, fruitlets and fruits, at different developmental stages. The mature fruits were removed in order
to avoid any effects of fruit load. At that stage the plants
were placed under nets of several different meshes in order
to reduce the maximum photosynthetically active radiation
(PAR) intensity (range 200–920 µmol m−# s−") and different
daily integrated total radiation, 2–8 MJ d−". PAR was
measured continuously by LI-COR (Lincoln, Nebraska,
USA), LI-185B, radiometer. Each shading treatment was
applied to 20 plants (5 plants¬4 replicates) of each cultivar
for a period of 15 d. Control plants were unshaded and
received an average maximum PAR of 920 µmol m−# s−".
Photosynthesis, as net carbon exchange rate (CER), was
determined by infra red gas analysis (IRGA) measurements
(ADC—The Analytical Development Co, Hoddesdon,
Herts, UK). The measurements were made between 1100
and 1200 h on fully expanded leaves, 24 h from the onset of
the shading treatments. Samples of sink leaves (approximately 5 cm long) were taken for sugar and starch
determinations at dawn (0600 h) and dusk (1800 h) of that
day.
Determinations of soluble sugars and starch
Five samples of leaf discs (each of 1 cm in diameter) from
sink leaves 5 cm long, or of flowers or flower parts of
approximately 200 mg fresh mass each, were extracted three
times with 80 % ethanol at 80 °C. The combined extracts
were evaporated to dryness and redissolved in 2 ml distilled
water, from which aliquots of 50–200 µl were taken for
sugar determination. Reducing sugars were determined
colorimetrically using dinitrosalicylic acid (Miller, 1959) ;
sucrose was determined by using the anthrone reagent
method as modified for determination of non-reducing
sugars (Van Handel, 1968). Starch was determined by
measuring glucose following digestion of the ethanolinsoluble residue with amyloglucosidase (Dinar, Rudich
and Zamski, 1983). Total non-structural carbohydates
(NSC) is the sum of soluble sugars and starch and daily
accumulation of them was calculated as the difference
between sugar concentrations at dawn and dusk.
Calculations of significant differences at the 5 % level
were carried out by analysis of variance and least significant
differences.
Manipulations of source}sink ratio
Plants of cv. ‘ Mazurka ’ were grown in an unshaded
greenhouse and trimmed as described above. Leaves and
flowers were trimmed at the eighth internode of each stem,
as follows (see Fig. 1) : (1) The primary (main stem) flower
bud (3 d before anthesis) was retained but the source leaf
and the side shoots at this internode were cut off. This
treatment was designated as : Flower (®). (2) The primary
flower bud retained with one adjacent source leaf attached ;
Flower (­1). (3) The primary flower bud retained with two
adjacent source leaves attached ; Flower (­2). (4) The
primary flower bud retained with two source leaves and
secondary flower bud (present on the side shoot of the same
internode) with its adjacent leaf attached ; Flower (­2­SF).
Enzyme assays
Determination of soluble acid invertase activity in pepper
flowers was as described by Aloni et al. (1991 a, b). In short,
tissue samples of approximately 300 mg were ground with a
Polytron homogenizer in 5 ml ice-cold grinding medium
containing : 25 m HEPES buffer (N-2-hydroxyethylpiperazine-N2-2-ethanesulphonic acid) pH 7±2, 5 m
MgCl , 2 m DDT (- Dithiothreitol) and 3 m DIDCA
#
(diethyldithiocarbamic acid) as antioxidant. The mixture
was centrifuged at 20 000 g for 20 min at 4 °C. Aliquots of
100 µl of the supernatant were incubated in 1±0 ml 0±1 N
phosphate citrate buffer, pH 5±0 and 20 m sucrose (Km of
the enzyme found to be 5 m sucrose). The incubation was
Aloni et al.—Carbohydrate Content of Pepper Flowers
carried out for 30 min at 37 °C and was terminated by
addition of 1 ml dinitrosalicylic acid reagent. After boiling
for 5 min, the resulting sugars were determined colorimetrically as described above.
Sucrose synthase activity was determined according to
Schaffer, Aloni and Fogelman (1987). Following extraction
as described for acid invertase the mixture was dialysed
overnight in order to remove the internal sugars. The
enzymatic activity was determined as sucrose breakdown on
aliquots of 200 µl incubated in incubation medium containing 0±1  phosphate-citrate buffer pH 7±0, 200 m
sucrose (with Km being 125 m) and 5 m UDP. After
incubation at 37 °C for 30 min the resulting fructose was
determined by the dinitrosalicylic acid reaction. The data
were expressed on fresh mass basis.
RESULTS
Effect of light intensity on flower abscission
Table 1 shows that reduction of maximum light intensity
from 920 to 200 µmol m−# s−" by shading, enhanced pepper
flower abscission in several cultivars, but there were
differences in their susceptibility. Paprika, cv. ‘ Lehava ’ and
bell pepper ‘ Mazurka ’ appeared to be the least sensitive
while bell pepper cvs. ‘ 899 ’, ‘ Maor ’ and ‘ 11480 ’ were
highly susceptible. Shading reduced CER in all the tested
cultivars but it was not related to the flower abscission in
these cultivars under the shading treatments.
Effect of source size
The effect of source reduction was studied by removing
different numbers of source leaves from the internode of
given primary flower buds and by monitoring daily sugar
accumulation in these flowers on the day which followed the
treatment. Subsequently, the abscission rate was monitored.
Table 2 shows that when a single source leaf was present, the
flower at the same internode [Flower (­1)] accumulated
T     1. The effect of maximum daily light intensity on
photosynthesis, measured 24 h after the onset of the shading
treatments, and on flower abscission (in the whole plant),
determined 15 d later
Light
( µmol m−# s−")
200
Cultivar
500
920
Flower abscission
(%)
‘ Maor ’
86
‘ 899 ’
100
‘ 11480 ’
93
‘ Mazurka ’
26
‘ Lehava ’
21
l.s.d. (P ¯ 0±05)
40
71
32
10
12
8
12
15
8
0
0
200
500
920
Photosynthesis
( µmol CO m−# s−")
#
2±5
2±3
2±8
3±0
1±7
4±2
4±0
4±5
5±7
4±2
2±2
12±0
11±8
8±2
9±2
7±0
165
T     2. The effect of pruning treatments on flower
abscission, 21 d from leaf remoŠal and on daytime gain or
loss of soluble sugars, starch and non-structural sugars (NSC,
soluble sugars­starch) in flowers of pepper plants cŠ.
‘ Mazurka ’
Change in carbohydrates during the
light period
(mg per flower)
Pruning
Treatment
Flower (®)
Flower (­1)
Flower (­2)
Flower (­2­SF)
SF
l.s.d. (P ¯ 0±05)
Flower
abscission
reducing
(%)
sucrose sugars
65
10
10
40
100
35
®0±1
­0±2
­0±4
—
®0±1
0±05
®0±3
0±0
­1±3
—
®0±2
0±08
starch
total
NSC
®0±8
­1±1
­1±2
—
®0±2
0±09
®1±2
­1±3
­2±9
—
®0±5
0±55
Sugar was determined 24 h after the pruning treatments. ­ and ®
signs indicate gain and loss of sugars, respectively. Explanation for the
lettering of the pruning treatments is given in the Materials and
Methods section.
T     3. The distribution of carbohydrates (NSC is non
reduced carbohydrate­sucrose­starch) between Šarious
pepper flower parts (cŠ. ‘ Mazurka ’). Data are means (n ¯ 5)
Flower
part
Petals
Ovary
Sepals
Style­stamen
l.s.d. (P ¯ 0±05)
Reducing
sugars
Sucrose
(mg per
organ)
Starch
Total
NSC
2±4
0±8
0±3
0±5
0±4
0±3
0±6
0±1
0±2
0±3
0±4
1±7
0±2
0±5
0±4
3±1
3±1
0±6
1±2
0±6
1±3 mg sugars d−". Detaching this leaf [Flower (®)] caused
a loss of 1±2 mg d−" of sugars from this flower. When two
leaves were attached [Flower (­2)], the adjacent primary
flower gained 2±9 mg sugars d−" on the following day. The
secondary flower (SF) lost 0±5 mg in the same period. Table
2 shows that 21 d after the onset of the pruning, abscission
of flowers without adjacent source leaf [Flower (®)] was
65 %. In Flower (­1) and (­2), abscission had diminished
to only 10 % during that time. When a flower bud was
present on the side shoot [Flower (­2­SF)], abscission of
the primary flower was increased to 40 %. All the secondary
flower buds were aborted 21 d after leaf pruning.
Distribution of sugars in pepper flowers
Flower parts differ in the amount of carbohydrates (Table
3). The petals and the ovary had the largest amounts of
reducing sugars and starch. Sucrose appeared only in
minute amounts in all flower parts, indicating that if
translocated it was rapidly metabolized. There were differences in sugar accumulation between sink leaves and
166
Aloni et al.—Carbohydrate Content of Pepper Flowers
T     4. The effect of accumulatiŠe daily PAR, measured
inside the greenhouse on the concentration and increase in
concentration between dusk and dawn of total NSC
(soluble­starch) in sink leaŠes (5 cm long) and flower buds of
pepper cŠ. ‘ Mazurka ’
T     6. The actiŠities of acid inŠertase and sucrose synthase
per gram fresh mass or per organ in Šarious parts of pepper,
cŠ. ‘ Mazurka ’, flowers at anthesis. Data are means (n ¯ 5)
Enzymatic activity,
sucrose hydrolysed
Total NSC (mg g f. wt−")
Light
(MJ d−")
Dawn
Dusk
7±2
7±1
12±3
15±0
9±6
18±2
23±8
40±4
­2±4
­11±1
­11±5
­25±4
3±5
16±0
17±8
19±7
25±1
27±3
®2±3
®2±4
®1±5
­0±7
­6±1
1±4
Leaves
1±6
2±66
5±15
8±31
l.s.d. (P ¯ 0±05)
Flower buds
1±6
2±66
3±11
5±15
8±31
l.s.d. (P ¯ 0±05)
3±9
18±3
20±2
21±2
24±4
21±2
0±8
Acid
invertase
Flower part
Dusk®Dawn
(difference)
( µmol g f. wt min−")
Activity per unit
fresh mass
Petals
Ovary
Sepals
Stamen­style
l.s.d. (P ¯ 0±05)
Total activity
per gram
Petals
Ovary
Sepals
Stamen
l.s.d. (P ¯ 0±05)
flowers under different daily integrated PAR (Table 4).
Sugar concentration at the end of the day was increased in
5 cm long sink leaves as light in the greenhouse increased
from 1±6 to 8±31 MJ d−". These values were typical of cloudy
and sunny days, respectively, during the experiment. At a
total PAR of 1±6 MJ d−", sugar accumulated in sink leaves
during the day. On the other hand, in flowers, positive sugar
balance was observed only when the daily integrated PAR
was approximately 5±0 MJ d−".
CultiŠar differences
The ‘ Lehava ’ and ‘ Mazurka ’ cultivars, which were the
Sucrose
synthase
0±46
0±09
0±47
0±87
0±24
0±14
0±58
0±72
0±12
0±24
( µmol per organ min−")
52
32
7
15
15
10
60
4
18
21
least sensitive to abscission (as shown in Table 1) gained
sugars and starch in their flowers during the day even under
shade, while the more susceptible cultivars (‘ Maor ’ and
‘ 899 ’) had negative daily sugar balance in their flowers
under shade (Table 5).
Enzymatic actiŠity
Acid invertase and sucrose synthase (the sucrose cleaving
enzymes) are both present in the pepper flower bud. There
were no significant differences in acid invertase activity
between different flower parts except for the low enzymatic
activity in the sepals (Table 6). On the other hand, the
T     5. The concentration and daily accumulation of starch and total NSC in flower buds of Šarious pepper cultiŠars in
control (maximum irradiation of 920 µmol m−# s−") and shading (500 µmol m−# s−") treatments. Diff. indicates the difference
between dusk and dawn Šalues
Carbohydrate concentration (mg g f. wt−")
Starch
Cultivar
Total NSC
dawn
dusk
Diff.
dawn
dusk
Diff.
control
shade
l.s.d. (P ¯ 0±05)
4±2
3±2
7±8
2±8
­3±6
®0±4
18±6
18±3
27±5
13±4
­8±9
®4±9
control
shade
l.s.d. (P ¯ 0±05)
4±1
2±2
14±6
5±1
­6±7
®1±1
control
shade
l.s.d. (P ¯ 0±05)
3±5
2±9
33±6
30±4
­12±8
­8±0
control
shade
l.s.d. (P ¯ 0±05)
5±1
3±3
17±0
11±5
­8±9
­4±5
‘ Maor ’
1±2
3±8
‘ 899 ’
6±1
1±6
­2±0
®0±6
7±9
6±2
1±1
3±8
‘ Lehava ’
12±4
8±5
­8±9
­5±6
20±8
22±4
2±8
5±2
‘ Mazurka ’
10±3
7±2
3±1
­5±2
­2±9
8±1
7±0
2±4
Aloni et al.—Carbohydrate Content of Pepper Flowers
sucrose synthase concentration was greatest in the ovary,
followed by stamen­style and sepals with the least being in
the petals.
DISCUSSION
Photosynthesis is an important factor in determining pepper
flower abortion, since its reduction by shading enhanced
flower abortion in several pepper cultivars (Table 1).
However, differences in photosynthetic rates do not explain
the differences in cultivar susceptibility. For example, the
photosynthesis measured in cvs. ‘ Maor ’ and ‘ 899 ’, which
are highly susceptible to shading-induced flower abscission,
was greater than that measured in the less sensitive cultivars
‘ Mazurka ’ and ‘ Lehava ’. This agrees with the results of
Turner and Wien (1994) who found no differences in
photosynthetic rates between pepper cultivars with different
sensitivities to shading, and with a report by Aloni et al.
(1991 b) that flower abortion in pepper, caused by high
temperatures, was not accompanied by changes in photosynthesis. It is suggested that assimilate allocation to the
flower and its metabolism within the flower is a more
important factor for its retention than photosynthesis.
Nevertheless, when the availability of assimilates to the
developing flower is reduced (e.g. by leaf pruning or
shading) abscission is greatly enhanced.
Based on leaf pruning and shading experiments, it is
calculated that to set properly, a ‘ Mazurka ’ flower has to
accumulate about 1±2 mg sugars d−" until pollination takes
place. This amount can be provided if a given flower has at
least one source leaf attached at its internode and the plant
is exposed to light of approximately 5 MJ d−" (Table 4). If
irradiation is less, the daily balance of sugar accumulation
in the flower becomes negative, resulting in abscission. The
sink leaves, on the other hand, start to accumulate sugars at
a daily light imput of only 1±6 MJ d−", indicating a stronger
sink capacity than that of the flower bud. These results
reinforce our previous suggestion that the sink leaves and
the adjacent flower buds may compete for translocated
assimilates (Aloni et al., 1991 b) and that the sink leaves are
stronger sinks than the adjacent flowers. In contradiction,
Turner and Wien (1994) showed that removal of sink leaves
did not affect the abscission of pepper flower buds under
low light conditions. They also showed that pepper cultivars
of differing susceptibility of flower abscission to low light
did not differ in dry-matter partitioning between flower
buds and sink leaves. However, since these studies were
carried out on small numbers of cultivars and in plants
subjected to a single low light treatment (30–35 µmol
m−# s−") this hypothesis requires more tests.
Within the flower, the ovary and the petals accumulate
most of the incoming sugars. However, while petals
accumulate reducing sugars, the ovary metabolizes a large
proportion of the sugars into starch (Table 3). Walker and
Hawker (1976) suggested that the sink capacity of pepper
fruit is initiated only after pollination takes place and that
acid invertase and sucrose synthase activities are associated
with sink activity. Sun et al. (1992) suggested that sucrose
synthase may serve as an indicator for sink strength in
growing tomato fruits. Robinson, Hewitt and Bennett
(1988) have shown that both sucrose synthase and ADP-
167
glucose pyrophosphorylase activities correlate with a transient starch accumulation found in developing tomato
fruits. Our work shows that sucrose synthase activity is
present predominantly in the flower ovary while acid
invertase activity is similar (with the exception of the sepals)
in all flower parts (Table 6), suggesting that the ovary serves
as the main active sink for assimilates, possibly due to its
high capacity for starch biosynthesis. The differences in
cultivar susceptibility to flower abscission caused by shade
(Table 1), and the differences between cultivars in daily
capacity to accumulate sugar­starch under shade (Table 5)
indicate that pepper cultivars with differing susceptibilities
to flower abscission may also differ in their capacity to
metabolize sucrose and accumulate starch during the light
periods until pollination takes place. The daily accumulation
of starch may increase the sucrose gradient between the
source leaf and the developing flower, therefore driving
sucrose transport toward the flower. Sucrose synthase,
located in the ovary, is a sucrose cleaving enzyme producing
ADP glucose which is subsequently metabolised to starch.
This enzyme may be regulatory in the pathway to starch
biosynthesis, as has been previously suggested (Claussen,
1983 ; Claussen, Hawker and Loveys, 1985 ; Sung, Xu and
Black, 1988). Possibly, pepper cultivars of different susceptibility to flower abscission may differ in the concentration
and activity of this enzyme in the developing flower. This
possibility is presently being investigated.
A C K N O W L E D G E M E N TS
This research was supported by Grant No. US-1706-89
from BARD, the United States-Israel Binational Agricultural Research and Development Fund and by The
Cooperative Arid Land Agricultural Research Program
(CALAR II), an AID Fund, contract no : GNE-0158-G0017-00.
LITERATURE CITED
Aloni B, Pashkar T, Karni L. 1991 a. Nitrogen supply influences
carbohydrate partitioning in pepper seedlings and transplant
development. Journal of the American Society of Horticultural
Science 116 : 995–999.
Aloni B, Pashkar T, Karni L. 1991 b. Partitioning of [14]-C sucrose and
acid invertase activity in reproductive organs of pepper plants in
relation to their abscission under heat stress. Annals of Botany 67 :
371–377.
Beyer EM, Morgan PW. 1971. Abscission : the role of ethylene
modification of auxin transport. Plant Physiology 48 : 208–212.
Bhullar SS, Jenner CF. 1986. Effects of temperature on the conversion
of sucrose to starch in the developing wheat endosperm. Australian
Journal of Plant Physiology 13 : 605–615.
Claussen W. 1983. Investigation on the relationship between the
distribution of assimilates and sucrose synthase activity in Solanum
melongena L. 2. Distribution of assimilates and sucrose synthase
activity. Zeitschrift fuX r Pflanzenphysiologie 110 : 175–182.
Claussen W, Hawker JS, Loveys BR. 1985. Comparative investigation
of the distribution of sucrose synthase activity and invertase
activity within growing mature and old leaves of some 3-carbon
photosynthetic pathway plant species. Physiologia Plantarum 65 :
275–280.
Dinar M, Rudich J. 1985 a. Effect of heat stress on assimilate metabolism
in tomato flower buds. Annals of Botany 56 : 249–257.
168
Aloni et al.—Carbohydrate Content of Pepper Flowers
Dinar M, Rudich J. 1985 b. Effect of heat stress on assimilate partitioning
in tomato. Annals of Botany 56 : 239–248.
Dinar M, Rudich J, Zamski E. 1983. Effect of heat stress on carbon
transport from tomato leaves. Annals of Botany 51 : 97–103.
El-Ahmadi AB, Stevens MA. 1979. Reproductive responses of heat
tolerant tomatoes to high temperatures. Journal of the American
Society of Horticultural Science 104 : 686–691.
Gent MPN. 1986. Carbohydrate level and growth of tomato plants : the
effect of irradiance and temperature. Plant Physiology 81 :
1075–1079.
Havaux M. 1993. Rapid photosynthetic adaptation to heat stress
triggered in potato leaves by moderately elevated temperatures.
Plant Cell and EnŠironment 16 : 461–467.
Hawker JS. 1982. Effect of temperature on lipids, starch and enzymes
of starch metabolism in grape, tomato and broad bean leaves.
Phytochemistry 21 : 33–36.
Kao CG, Chen HM, Ma LH. 1986. Effect of high temperature on
proline content in tomato floral buds and leaves. Journal of the
American Society of Horticultural Science 111 : 734–750.
Kinet JM, Sachs RM, Bernier G. 1985. Photosynthesis, assimilate
supply and utilization. In : Kinet JM, Sachs RM, Bernier G, eds.
The physiology of flowering, Vol III. Boca Raton, Florida : CRC
Press Inc.
Kitroongruang N, Jodo S, Hisai J, Kato M. 1992. Photosynthesis
characteristics of melons grown under high temperatures. Journal
of the Japanese Society of Horticultural Science 61 : 107–114.
Macleod LC, Duffus CM. 1988. Reduced starch content and sucrose
synthase activity in developing endosperm of barley plants grown
at elevated temperatures. Australian Journal of Plant Physiology
15 : 367–375.
Miller GL. 1959. Use of dinitrosalicylic acid reagent for determination
of reducing sugars. Analytical Chemistry 3 : 426–428.
Mutters RG, Hall AE. 1992. Reproductive responses of cowpea to high
temperature during different night periods. Crop Science 32 :
202–206.
Ofir M, Gross Y, Bangeth F, Kigel J. 1993. High temperature effects on
pod and seed production as related to hormone levels and
abscission of reproductive structure in common beans (Phaseolus
Šulgaris L.). Scientia Horticulturae 55 : 201–211.
Robinson NL, Hewitt JD, Bennett AB. 1988. Sink metabolism in
tomato fruit. Developmental changes in carbohydrate metabolizing enzymes. Plant Physiology 87 : 727–730.
Schaffer AA, Aloni B, Fogelman E. 1987. Sucrose metabolism and
accumulation in developing fruit of sweet and non-sweet genotypes
of Cucumis. Phytochemistry 26 : 1883–1887.
Shishido Y, Challa H, Krupa J. 1987. Effects of temperature and light
on the carbon budget of young cucumber plants studied by steady
state feeding with "%CO . Journal of Experimental Botany 38 :
#
1044–1054.
Sun J, Loboda T, Sung SS, Black CC Jr. 1992. Sucrose synthase in wild
tomato, Lycopersicon chmielewskii, and tomato fruit strength.
Plant Physiology 98 : 1163–1169.
Sung SJ, Xu DP, Black CC. 1988. Purification and properties of
actively filling sucrose sinks. Plant Physiology 89 : 1117–1121.
Turner AD, Wien HC. 1994. Dry matter assimilation and partitioning
in pepper cultivars differing in susceptibility to stress-induced bud
and flower abscission. Annals of Botany 73 : 617–622.
Van Handel E. 1968. Direct microdetermination of sucrose. Analytical
Chemistry 22 : 280–283.
Wien HC, Turner AD, Yang SF. 1989. Hormonal basis for low light
intensity induced flower bud abscission of pepper. Journal of the
American Society for Horticultural Science 114 : 981–985.
Walker RR, Hawker JS. 1976. Effect of pollination on carbohydrate
metabolism in young fruits of Citrullus lanatus and Capsicum
annuum. Phytochemistry 15 : 1881–1884.