Annals of Botany 78 : 619–623, 1996
Petal Abscission in Rose Flowers : Effects of Water Potential, Light Intensity and
Light Quality
W. G. V A N D O O RN* and A. V O J I N O V I C
Agrotechnological Research Institute (ATO-DLO), P.O. Box 17, 6700 AA Wageningen, The Netherlands
Received : 27 February 1996
Accepted : 16 May 1996
Petal abscission was studied in roses (Rosa hybrida L.), cvs. Korflapei (trade name Frisco), Sweet Promise (Sonia) and
Cara Mia (trade name as officially registered cultivar name). Unlike flowers on plants in greenhouses, cut flowers
placed in water in the greenhouse produced visible symptoms of water stress, depending on the weather during the
experiment and on the cultivar. Cut Frisco roses showed no visible signs of water stress and the time to petal
abscission was as in uncut flowers. In Sonia roses the symptoms of water stress varied from mild to severe, and the
number of flowers in which the petals abscised varied from 100 % (mild stress) to 0 % (severe stress). An antimicrobial
compound in the vase water of Sonia roses, or removal of the leaves, alleviated the symptoms of water stress and
increased the number of stems in which the petals abscised. Cut Cara Mia roses showed severe symptoms of water
stress in all experiments and petal abscission was found in only a few flowers, even when the stems were placed at
20 °C and low photon flux (15 µmol m−# s−"). Abscission in Sonia and Cara Mia roses was low or absent when the
water potential of the leaves reached values below ®2±0 MPa within the first 5 d of the experiment ; such low values
were not reached in Frisco roses.
Addition of sucrose to the vase solution, together with an effective antimicrobial compound, had no effect on the
time to petal abscission, at any light intensity. Placing flowers in far-red light also had no effect on abscission,
compared with flowers placed in red light or white light of the same photon fluence.
It is concluded that petal abscission in the rose cultivars studied is not affected by their water status unless the plants
reach a low water potential (about ®2 MPa) early on during vase life. Petal abscission is not inhibited by low light
intensity nor affected by the Pr}Pfr ratio.
# 1996 Annals of Botany Company
Key words : Abscission, light intensity, petals, phytochrome, Rosa hybrida L., rose, sugars, water potential.
INTRODUCTION
In previous research it was found that the time to petal
shedding in cut roses placed in water, in a climate-controlled
room or in a greenhouse, was the same as in intact plants,
provided that the temperatures were similar. These experiments were in winter, when the incident radiation was low.
Cutting of the flowers and placing them in water resulted in
visible symptoms of water stress, depending on the cultivar.
Endogenous carbohydrate levels were reduced in plants
placed in the climate-controlled room, owing to the low
light levels. These results suggested that petal abscission in
roses was remarkably insensitive to a decrease in both water
potential and carbohydrate level, at least when these two
factors concurred (van Doorn and Schro$ der, 1995). Other
(preliminary) experiments on cut rose flowers showed,
however, that severe wilting may occur within a few days of
vase life, and that the petals of such flowers do not abscise.
Petal abscission in roses is hastened by exogenous ethylene
(Woltering and van Doorn, 1988), and as water stress may
increase the rate of ethylene production in various plant
parts (Apelbaum and Yang, 1981), including flowers (van
Doorn and Reid, 1991), it may stimulate abscission. A low
water potential can also directly affect abscission, as low
water availability may inhibit metabolic processes such as
* For correspondence.
0305-7364}96}110619­05 $25.00}0
the production and action of enzymes involved in the cell
separation process.
Placing roses under low light intensity (15 µmol m−# s−")
in a climate-controlled chamber reduced the endogenous
content of sucrose, glucose and fructose in the petal cells
(van Doorn et al., 1991). In other experimental systems,
external application of sucrose reduced flower abscission in
Lathyrus odoratus (Mor, Reid and Kofranek, 1984), delayed
leaf abscission in Phaseolus Šulgaris (Martin, 1954), and had
no effect on leaf abscission in Vigna radiata (Mao and
Craker, 1990), hence the effect of carbohydrates on stem
and leaf abscission is as yet unclear, and little is apparently
known about its effect on petal abscission.
Placing the flowers at low photon flux density can alter
their Pr}Pfr ratio. Leaf abscission in Vigna radiata was
hastened by far-red light and delayed by red light (Decoteau
and Craker, 1987 ; Mao and Craker, 1990). Petal abscission
may similarly be increased under low photon flux density,
through phytochrome control.
In the present paper an attempt is made to separate the
effects of water stress, photon flux density and light quality
on rose petal abscission. We hypothesized that abscission
would be hastened when the water stress is moderate and
delayed or prevented after severe water stress. A series of
flowers was placed in darkness which prevented water stress
but resulted in low endogenous carbohydrate levels and in
a change in the Pr}Pfr ratio. Placing flowers in red and far# 1996 Annals of Botany Company
Šan Doorn and VojinoŠic—EnŠironmental Effects on Rose Petal Abscission
620
red light further separated these effects. Tests included
Frisco, Sonia and Cara Mia roses, cultivars which show
little, intermediate and severe symptoms of water stress
when cut and placed in water, respectively.
(Sigma, St. Louis, MO, USA) at 20 mg l−". Sucrose (Merck)
was added at 20 g l−". Aluminium sulphate and silver
nitrate, at the concentrations used, have previously been
found to adequately control bacterial growth in the vase
water of rose stems (van Doorn, de Witte and Perik, 1990).
MATERIALS AND METHODS
Plant material
Flower diameter
Rose flowers (Rosa hybrida L.) of the cultivars Korflapei
(trade name Frisco), Sweet Promise (trade name Sonia), and
Cara Mia (trade name as officially registered cultivar name)
were investigated. The cultivars are indicated by their trade
names in this paper.
Flowers were left on the plant in the glasshouses of the
Department of Horticulture, Agricultural University at
Wageningen, The Netherlands. The experiments occurred
between Apr. and Oct. 1993. Temperatures and relative
humidity (RH) were recorded constantly, on an hourly
basis, and averaged 20–24 °C and 55–71 % in the various
experiments, respectively. Other flowers were cut at the
commercial cutting stage, at a stem length of 40 cm. Stems
were placed in water within minutes of cutting, after
recutting the basal 5 cm in air. Leaves on the basal 10 cm
segment of the stem, when present, were removed. Individual
stems were then placed in about 300 ml of vase solutions
made from deionized water, at 20 °C, 60 % RH and a
photon flux of 15 µmol m−# s−" (cool white fluorescent light ;
Philips 36W}84 lamps) for 12 h each day (0700 to 1900 h).
The maximum diameter of the flowers was measured at
intervals using a digital micrometer (type 500-301, Mitutoyo,
Veenendaal, The Netherlands).
Effects of darkness and light quality
In order to investigate effects of light and RH, some cut
flowers were placed under a polyethylene bag and compared
with flowers outside the bag. The RH inside the bag was
more than 90 %, but some ventilation was allowed in order
to prevent condensation. Other series were placed at 20 °C,
60 % RH in darkness, red or far-red light, and in a regime
where red and far-red light were alternated (30 s red and
45 s far-red) or red and darkness were alternated (30 s red
and 45 s darkness), as previously described (van Doorn and
van Lieburg, 1993). Photosynthetically active photon fluence
(400–700 nm) at the level of the uppermost leaves was
120 µmol m−# s−" averaged over 75 s, both in the cyclic
red}darkness and the red}far-red treatments, determined
with a Li-Cor 1800 spectroradiometer (Li-cor, Lincoln, NE,
USA).
Water potential
The water potential was determined in leaf 3 below the
flower head, using a Scholander pressure chamber. Leaves
were wrapped in plastic bags prior to determination of the
potential, with only the petiole extruding, and the bag was
left around the leaf during the measurement. Five replicate
stems were used.
Chemicals
Aluminium sulphate (Merck, Darmstadt, Germany) was
included in the vase water at 0±8 g l−", and silver nitrate
Abscission, wilting
The time between the commercial cutting stage and
abscission (more than 50 % of petals lost) was measured by
daily observation of individual flowers, using ten replications. The percentage petal abscission refers to the number
of flowers showing " 50 % abscission of their petals.
Similarly, the time between cutting and visible symptoms of
petal wilting was measured in ten replications, and recorded
daily. Wilting was considered mild when the petals and the
leaves were somewhat flaccid, and severe when the leaves
and the petals had clearly lost turgor and the pedicel showed
bending.
Statistics
Results were compared by analysis of variance and F test
at P " 0±05, using the GENSTAT V Statistical Package
(Rothamsted, UK). All experiments were repeated at least
once.
RESULTS
Effect of cutting and placement in water in the greenhouse
Frisco roses placed in water in the greenhouse opened and
grew as non-cut flowers, did not show visible signs of
wilting, and the petals of all cut flowers abscised as in the
non-cut ones (Fig. 1 A). Abscission occurred even in
experiments in which the temperature in the greenhouse and
the incident radiation was high. In cut Sonia roses placed in
water in the greenhouse, flower growth and symptoms of
water stress were largely dependent on the climate. During a
cool and overcast period, growth and opening was similar
to non-cut flowers, the flowers showed slight wilting, and
the petals of all flowers abscised, with a time to abscission
similar to that of non-cut flowers. During warm and sunny
weather, petal growth was inhibited with respect to the
uncut controls, the leaves and petals showed severe wilting,
and only approx. 20 % of the flowers showed petal abscission
(Fig. 1 B). In cut Cara Mia roses placed in water in the
greenhouse symptoms of severe water stress were even
found during a period of cool weather, and abscission in this
cultivar was always low (Fig. 1 C). Even when placed in
water in the climate-controlled room (in the light) the
number of stems showing abscission was very low (Table 1).
Removal of the leaves of Sonia roses, prior to placement
in water, decreased the symptoms of water stress in the
flower heads, and increased the number of flowers with
Šan Doorn and VojinoŠic—EnŠironmental Effects on Rose Petal Abscission
80
50
40
25
0
0
10
120
75
80
50
40
25
0
0
30
20
100
0
10
20
Time (d)
30
Time (d)
C
100
120
75
80
50
40
25
0
0
0
10
Petal abscission (%)
Flower diameter (mm)
Petal abscission (%)
75
Flower diameter (mm)
120
0
B
100
Petal abscission (%)
Flower diameter (mm)
A
621
30
20
Time (d)
F. 1. Flower diameter (+, _) and petal abscission (percentage of flowers showing " 50 % abscission ; *, ^) in Frisco (A), Sonia (B) and Cara
Mia (C) rose flowers, left attached to the plant (+, *) or cut and placed in water in the greenhouse (_, ^). Experiments in summer, during sunny
and warm weather.
T     1. Effects of fluorescent light (15 µmol m−# s−"), of darkness at Šarious relatiŠe humidities, and of red and far-red light
at low photon fluence flux, on petal abscission in cut rose flowers of three cultiŠars placed in water in a climate-controlled room
at about 20 °C. The number in parenthesis refers to the percentage of flowers showing petal abscission
Time to petal abscission (d)
Treatment
Fluorescent light (60 % RH)
Darkness (high humidity
due to plastic bag)
Darkness (60 % RH)
Red (60 % RH)
Far-red (60 % RH)
Red}Far-red (60 % RH)
Red}Darkness (60 % RH)
Frisco
Sonia
Cara Mia
26±8³1±9 (100 %)
27±4³2±3 (100 %)
14±5³2±3 (100 %)
13±6³2±1 (100 %)
— (20–30 %)
17±8³3±1 (100 %)
27±8³2±9
26±9³2±2
27±1³2±7
26±5³2±3
27±0³2±6
14±1³2±0
13±2³1±8
14±4³2±2
14±7³2±0
13±9³2±0
(100 %)
(100 %)
(100 %)
(100 %)
(100 %)
abscission (Fig. 2 A). The inclusion of antibacterial compounds, such as aluminium sulphate (Fig. 2 B) or silver
nitrate (not shown), in the vase solution also alleviated the
symptoms of water stress and increased the number of
flowers of which the petals abscised. The inclusion of
sucrose (together with aluminium sulphate at 0±8 g l−") in the
vase solution had no effect on abscission (Fig. 2 B).
(100 %)
(100 %)
(100 %)
(100 %)
(100 %)
—
—
—
—
—
(30 %)
(20 %)
(30 %)
(20 %)
(20 %)
Effects of placement in darkness or in red and far-red light
Placement of cut Frisco or Sonia roses in darkness at
60 % RH or at high humidity (more than 90 %, due to
placement under a polyethylene bag) did not change the
time to petal abscission nor the number of stems showing
petal fall (Table 1). When cut Cara Mia flowers were placed
Šan Doorn and VojinoŠic—EnŠironmental Effects on Rose Petal Abscission
622
100
A
100
Petal abscission (%)
Petal abscission (%)
75
50
25
50
25
0
0
0
10
20
30
Time (d)
100
0.0
– 1.0
– 2.0
Water potential (MPa)
–3.0
F. 3. Relationship between the lowest leaf water potential during the
first 5 d of vase life and petal abscission in cut rose flowers of cultivars
Frisco (D, E), Sonia (^, _) and Cara Mia (x, s, t, y). (D, ^, x)
Control flowers, left uncut. (E, _, y) Flowers cut and placed in water
next to the intact plants, in a greenhouse. The tests represent a range of
weather conditions, from overcast and cool to sunny and warm. Also
shown are Cara Mia flowers placed in water in a climate-controlled
room at 20 °C, in the light (t) or in darkness at high RH (s).
B
Petal abscission (%)
75
75
50
25
0
0
10
20
30
Time (d)
F. 2. Petal abscission in Sonia roses, cut and placed in water in the
greenhouse, during warm weather. A, Effect of leaf removal (*, leaves
removed ; +, leaves attached) ; B, Effect of aluminium sulphate
(0±8 g l−", *) or sucrose (20 g l−") and aluminium sulphate (0±8 g l−",
^) in the vase solution. +, Leafy control flowers.
in darkness at high RH no symptoms of water stress were
observed and all flowers shed their petals, but in darkness at
60 % RH petal abscission occurred in a few stems only
(Table 1). Red and far-red light, at low photon fluence,
given at 60 % RH, had no effect on the time to abscission in
Frisco and Sonia roses, nor did it change the number of
flowers exhibiting petal abscission (Table 1). Such treatments
also did not change the number of Cara Mia flowers
showing abscission, but as the number of abscising flowers
was low the time to abscission could not be adequately
determined (Table 1).
Water potential
The water potential of the leaves of well watered plants in
the greenhouse was about ®0±6 MPa, in all cultivars
investigated. In cut flowers placed in water in the greenhouse
the water potential always dropped and the onset of this
drop and its rate depended on the cultivar and the weather
conditions. A low water potential reached during the last
5 d prior to petal fall showed no correlation with abscission.
In contrast, when a low water potential occurred within the
first 5 d of vase life it was correlated with a low number of
stems showing abscission.
During the first 5 d of the experiment, the water potential
of the leaves of cut Frisco flowers placed in the greenhouse
fell to ®1±1 MPa in experiments in which the number of
sunshine hours per day was high. Under such conditions the
water potential of Sonia roses fell to ®2±4 MPa. The water
potential of the leaves of Cara Mia roses was as low as
®1±9 MPa even in experiments during cool weather. The
relationship between the lowest leaf water potential during
the first 5 d of vase life and petal abscission is shown in Fig.
3. Cut Frisco and Sonia roses placed in water in the climatecontrolled room reached a water potential usually not lower
than ®1±5 MPa (results not shown). In cut Cara Mia roses
placed in water in the climate-controlled room, the water
potential fell to ®2±0}®2±5 MPa in flowers placed in the
light, but remained below ®2±0 MPa when placed in
darkness at high RH (Fig. 3).
DISCUSSION
The present results indicate that petal senescence, although
insensitive to moderate water stress, is inhibited by severe
water stress. In previous experiments, carried out in Jan. and
Feb., during a period with little sunshine, no inhibition of
petal abscission was observed in cut Sonia roses placed in
water in the greenhouse (van Doorn and Schro$ der, 1995).
This is now corroborated, but when the weather during the
experiment was sunny and warm, Sonia roses placed in
water in the greenhouse, next to the uncut flowers, exhibited
little or no petal abscission. Whenever the water potential of
the leaves in these experiments decreased to approx.
®2±0 MPa during the first 5 d of the experiments, petal
Šan Doorn and VojinoŠic—EnŠironmental Effects on Rose Petal Abscission
abscission was strongly inhibited or absent. The inhibition
was alleviated by removal of the leaves or the inclusion of an
antibacterial compound in the water, which prevented the
water potential falling to below ®2±0 MPa.
Rose cultivars differ greatly in the degree of water stress
during vase life. Frisco roses usually show no symptoms of
water stress, Sonia intermediate symptoms, such as lack of
opening and slight wilting, and Cara Mia roses strong
symptoms, including wilting and desiccation. The water
potential of Frisco roses placed in water in the climatecontrolled room did not reach ®1±5 MPa, but in Cara Mia
roses it dropped to below ®2±0 MPa in most experiments.
Only when cut Cara Mia roses were placed in darkness at a
high RH, abscission occurred in all stems and the water
potential of the leaves did not drop below ®2±0 MPa. In all
three cultivars studied, therefore, petal abscission of cut
flowers was as in uncut ones, provided that the water
potential did not reach values below about ®2±0 MPa.
In flowers placed in the climate-controlled room for a few
days the levels of sucrose, glucose and fructose in the petals
is much lower than in flowers left uncut (van Doorn et al.,
1991). Excised flowers placed in a climate-controlled room
showed the same time to petal abscission as uncut flowers,
which could relate to a combined effect of slight water stress
and carbohydrate stress. When water stress was excluded, as
in the experiments where cut flowers were placed under a
polyethylene bag in the climate-controlled room, abscission
was still not affected. Similarly, abscission was not changed
when sucrose was fed via the vase solution, in cut flowers
placed in the climate-controlled room. (It should be noted
that the data of Fig. 2 show an increase of abscission in
sucrose-treated flowers over controls, an effect due to the
aluminium sulphate given with the sucrose. A sucrose
treatment by itself is not relevant as it stimulates bacterial
growth, which results in early water stress.) These results,
therefore, indicate that the carbohydrate status of the petals
has little effect on the abscission process.
Placing plants in darkness often changes their phytochrome status. Far-red light has been reported to increase
the rate of flower abscission, for example in Hibiscus
(Heindl and Brun, 1983 ; van Lieburg, van Doorn and van
Gelder, 1990). Experiments in which cut roses were placed
in red light, far-red light, and in alternating red and far-red,
however, showed no effect of the treatments on petal
abscission. A change in the Pr}Pfr ratio, therefore,
apparently has little effect on the process of cell separation
in petals of cut roses.
Petal abscission of roses is sensitive to ethylene (Woltering
and van Doorn, 1988) and ethylene production is often
stimulated by water stress (Apelbaum and Yang, 1981), by
sucrose feeding (Mayak and Dilley, 1976) and by far-red
light (Goeschl, Pratt and Bonner, 1967 ; Samimy, 1968). In
carnation flowers, a sucrose treatment increased the rate of
ethylene synthesis, but simultaneously reduced the sensitivity to ethylene (Mayak and Dilley, 1976). We did not
determine the effects of the present treatments on ethylene
synthesis and ethylene sensitivity, but if increased ethylene
production occurred, it did not stimulate abscission.
623
It is concluded that severe water stress inhibits petal fall
in roses. Petal abscission was not affected by a reduction in
the level of metabolically active carbohydrates, nor by its
reversal by sucrose feeding. A change in the phytochrome
status of the plants had no effect either. In roses, cutting and
placement in water often inhibits petal abscission, depending
on the cultivar, an effect which is apparently mainly due to
early water stress.
A C K N O W L E D G E M E N TS
We thank Prof. Daniel Co# me (Universite! Pierre et Marie
Curie, Paris, France), for facilitating the visit of A. V. to
ATO-DLO, and Dr. Peter van de Pol (Department of
Horticulture, Agricultural University, Wageningen, The
Netherlands) for allowing us to work in the Departments’
greenhouses.
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