Directory UMM :Data Elmu:jurnal:S:Scientia Horticulturae:Vol85.Issue4.Agust2000:
Scientia Horticulturae 85 (2000) 295±306
Effects of duration of bulb chilling on dry matter
distribution in hydroponically forced tulips
Katsuhiko Inamoto*, Takanori Hase, Motoaki Doi,
Hideo Imanishi
College of Agriculture, Osaka Prefecture University, Sakai, Osaka 599-8531, Japan
Accepted 10 December 1999
Abstract
Bulbs of tulip (Tulipa gesneriana L. `Gander'), in which the formation of ¯oral organs had been
completed, were chilled at 28C for 3±30 weeks and then forced hydroponically at 208C under a 12 h
photoperiod with the light at 100 mmol mÿ2 sÿ1. The fresh weight and the perianth length of the cut
¯ower highly correlated with the dry weights of shoots and ¯oral organs at anthesis, respectively.
The dry weights at planting (DWp) of shoots, ¯oral organs and daughter bulbs increased with
increasing the duration of bulb chilling at 28C (tc). After a 30-week tc, enlargement of daughter
bulbs had already started and their DWp was high. The days from planting to anthesis (tpa)
decreased hyperbolically with increasing tc. The dry weight at anthesis (DWa) of shoots increased
with increasing tc up to 12 weeks and then decreased. DWa of ¯oral organs decreased and that of
daughter bulbs increased with increasing tc. After a 30-week tc, the DWa values of shoots and ¯oral
organs were markedly small and that of daughter bulbs was very large. The dry weights of shoots,
¯oral organs and daughter bulbs increased exponentially after planting, and the relative growth rate
during the period from planting to anthesis (Rpa) in each plant part was calculated. The changes of
DWa of each plant part after various tc could be explained by their changes in the growth
parameters, i.e., DWp, tpa, and Rpa which were shown as functions of tc. # 2000 Elsevier Science
B.V. All rights reserved.
Keywords: Bulb chilling; Daughter bulbs; Dry matter distribution; Growth analysis; Regression;
Tulipa gesneriana L.
*
Corresponding author. Tel.: 81-722-54-9424; fax: 81-722-54-9423.
E-mail address: [email protected] (K. Inamoto)
0304-4238/00/$ ± see front matter # 2000 Elsevier Science B.V. All rights reserved.
PII: S 0 3 0 4 - 4 2 3 8 ( 0 0 ) 0 0 1 2 8 - X
296
K. Inamoto et al. / Scientia Horticulturae 85 (2000) 295±306
1. Introduction
Bulbs of tulip (Tulipa gesneriana L.) require chilling for shoot elongation
following the completion of the ¯oral organ formation (Rees and CharlesEdwards, 1975; Le Nard and De Hertogh, 1993). The duration of bulb chilling
greatly in¯uences forcing duration and cut ¯ower quality (Moe and Wickstùrm,
1973; Charles-Edwards and Rees, 1975; Aoba, 1976; Hobson and Davies, 1978).
We assumed that the quality of cut tulips is determined by the dry matter
allocated to the shoots including ¯oral organs. This experiment was conducted to
examine: (1) how the duration of bulb chilling at 28C in¯uences the dry matter
distribution at planting and anthesis, (2) whether the growth analysis method is
useful to estimate dry matter accumulation in plant parts, and (3) whether
individual parameter in growth analysis can be expressed as a function of the
duration of bulb chilling.
2. Materials and methods
2.1. Plant materials
Bulbs of `Gander' (11±12 cm in circumference) produced in sandy ®eld in
Toyama Prefecture in Japan were purchased. The bulbs were divided into each
treatment lot uniformly in weight and stored under dry conditions. To promote the
development of the shoots and the ¯oral organs, the bulbs were stored at 308C for
1 week starting on 15 June 1993, and then transferred to 208C. This storage
method was similar to that previously described by Imanishi et al. (1993) and Le
Nard (1980). Following the storage at 208C for 8 weeks, when trilobed
gynoecium had been formed in the ¯ower buds, chilling at 28C for 0, 3, 6, 9, 12,
15, 18 and 30 weeks started. The rooms for bulb storage were well ventilated.
Following the chilling, the bulbs were forced hydroponically.
2.2. Forcing methods
Forty bulbs with tunica and external offsets removed per each treatment lot
were inserted into holes (85) on a foamed polystyrene plate (620 mm
L278 mm W15 mm T). A plastic container (620 mm L278 mm W153 mm
H) was ®lled with nutrient solution containing 1000 mg lÿ1 CaNO3, and the
foamed polystyrene plates with bulbs were ¯oated on the solution. The forcing
condition was 208C and 12 h photoperiod with the light at 100 mmol mÿ2 sÿ1
PPFD at bulb level supplied from the combination of three-band ¯uorescent tubes
(FL20SS EEXN/18-H; Toshiba Company, Tokyo, Japan) and incandescent lamps
(LW110V100W; Matsushita Electric Company, Osaka, Japan).
K. Inamoto et al. / Scientia Horticulturae 85 (2000) 295±306
297
2.3. Fresh and dry weight
In all experimental plots, 10 bulbs or plants were sampled at the time of
planting and at weekly intervals after planting, and 20 plants were sampled at
anthesis when the tip of the perianths dehisced. The length of stem and perianth
and the fresh weights of whole plants and their component parts, i.e., mother bulb
scales and basal plates, ¯oral organs, leaves, stems, roots and inner daughter
bulbs, were measured. Each part was dried in an oven at 808C for 72 h and weighed.
The dry weights of whole plants and their parts measured weekly were plotted
against the days after planting and the relations were shown by ®tting them on
exponential curves:
when the part was growing,
DW b eat
and when the part was senescing,
DW c ÿ b eat
(1)
(2)
where DW is the dry weight, t the days after planting, a, b and c are constants and
e the base of natural logarithms.
2.4. Relative growth rate
When the regression to Eq. (1) was signi®cant, relative growth rates during the
period from planting to anthesis (Rpa) of the whole plant and each part were
calculated as follows:
Rpa ln DWa ÿ ln DWp =tpa
(3)
where Rpa is the relative growth rate from planting to anthesis, tpa the days from
planting to anthesis, DWa the dry weight at anthesis and DWp the dry weight at
planting.
2.5. Regression of growth parameters
The relations between the growth parameters (Table 1), i.e., tpa, DWp, DWa and
Rpa, and the duration of bulb chilling at 28C (tc) were formulated by regression
analysis. We applied linear, quadratic, hyperbolic and logistic curves to them, and
chose the best ®tting model which had the smallest p value.
3. Results
3.1. Flowering and quality of cut ¯owers
The bulbs which had not been chilled completely failed to ¯ower, and only half
of those chilled for 3 weeks ¯owered (Table 2). The length of stems and the fresh
298
K. Inamoto et al. / Scientia Horticulturae 85 (2000) 295±306
Table 1
List of abbreviations of parameters
Abbreviation
Description
Unit
tc
tpa
DWp
Dwa
Rpa
Duration of bulb chilling at 28C
Time from planting to anthesis
Dry weight at planting
Dry weight at anthesis
Relative growth rate from planting to anthesis
week
day
g
g
dayÿ1
weight of shoots including a stem, leaves, and ¯oral organs at anthesis, increased
with the increase in duration of bulb chilling at 28C (tc) up to 12 weeks, but
decreased when tc was longer than 18 weeks (Table 2). The perianth length at
anthesis decreased with the increase in duration of bulb chilling (Table 2). The
correlation coef®cient between the fresh weight and the dry weight of shoots at
anthesis was 0.972 (p
Effects of duration of bulb chilling on dry matter
distribution in hydroponically forced tulips
Katsuhiko Inamoto*, Takanori Hase, Motoaki Doi,
Hideo Imanishi
College of Agriculture, Osaka Prefecture University, Sakai, Osaka 599-8531, Japan
Accepted 10 December 1999
Abstract
Bulbs of tulip (Tulipa gesneriana L. `Gander'), in which the formation of ¯oral organs had been
completed, were chilled at 28C for 3±30 weeks and then forced hydroponically at 208C under a 12 h
photoperiod with the light at 100 mmol mÿ2 sÿ1. The fresh weight and the perianth length of the cut
¯ower highly correlated with the dry weights of shoots and ¯oral organs at anthesis, respectively.
The dry weights at planting (DWp) of shoots, ¯oral organs and daughter bulbs increased with
increasing the duration of bulb chilling at 28C (tc). After a 30-week tc, enlargement of daughter
bulbs had already started and their DWp was high. The days from planting to anthesis (tpa)
decreased hyperbolically with increasing tc. The dry weight at anthesis (DWa) of shoots increased
with increasing tc up to 12 weeks and then decreased. DWa of ¯oral organs decreased and that of
daughter bulbs increased with increasing tc. After a 30-week tc, the DWa values of shoots and ¯oral
organs were markedly small and that of daughter bulbs was very large. The dry weights of shoots,
¯oral organs and daughter bulbs increased exponentially after planting, and the relative growth rate
during the period from planting to anthesis (Rpa) in each plant part was calculated. The changes of
DWa of each plant part after various tc could be explained by their changes in the growth
parameters, i.e., DWp, tpa, and Rpa which were shown as functions of tc. # 2000 Elsevier Science
B.V. All rights reserved.
Keywords: Bulb chilling; Daughter bulbs; Dry matter distribution; Growth analysis; Regression;
Tulipa gesneriana L.
*
Corresponding author. Tel.: 81-722-54-9424; fax: 81-722-54-9423.
E-mail address: [email protected] (K. Inamoto)
0304-4238/00/$ ± see front matter # 2000 Elsevier Science B.V. All rights reserved.
PII: S 0 3 0 4 - 4 2 3 8 ( 0 0 ) 0 0 1 2 8 - X
296
K. Inamoto et al. / Scientia Horticulturae 85 (2000) 295±306
1. Introduction
Bulbs of tulip (Tulipa gesneriana L.) require chilling for shoot elongation
following the completion of the ¯oral organ formation (Rees and CharlesEdwards, 1975; Le Nard and De Hertogh, 1993). The duration of bulb chilling
greatly in¯uences forcing duration and cut ¯ower quality (Moe and Wickstùrm,
1973; Charles-Edwards and Rees, 1975; Aoba, 1976; Hobson and Davies, 1978).
We assumed that the quality of cut tulips is determined by the dry matter
allocated to the shoots including ¯oral organs. This experiment was conducted to
examine: (1) how the duration of bulb chilling at 28C in¯uences the dry matter
distribution at planting and anthesis, (2) whether the growth analysis method is
useful to estimate dry matter accumulation in plant parts, and (3) whether
individual parameter in growth analysis can be expressed as a function of the
duration of bulb chilling.
2. Materials and methods
2.1. Plant materials
Bulbs of `Gander' (11±12 cm in circumference) produced in sandy ®eld in
Toyama Prefecture in Japan were purchased. The bulbs were divided into each
treatment lot uniformly in weight and stored under dry conditions. To promote the
development of the shoots and the ¯oral organs, the bulbs were stored at 308C for
1 week starting on 15 June 1993, and then transferred to 208C. This storage
method was similar to that previously described by Imanishi et al. (1993) and Le
Nard (1980). Following the storage at 208C for 8 weeks, when trilobed
gynoecium had been formed in the ¯ower buds, chilling at 28C for 0, 3, 6, 9, 12,
15, 18 and 30 weeks started. The rooms for bulb storage were well ventilated.
Following the chilling, the bulbs were forced hydroponically.
2.2. Forcing methods
Forty bulbs with tunica and external offsets removed per each treatment lot
were inserted into holes (85) on a foamed polystyrene plate (620 mm
L278 mm W15 mm T). A plastic container (620 mm L278 mm W153 mm
H) was ®lled with nutrient solution containing 1000 mg lÿ1 CaNO3, and the
foamed polystyrene plates with bulbs were ¯oated on the solution. The forcing
condition was 208C and 12 h photoperiod with the light at 100 mmol mÿ2 sÿ1
PPFD at bulb level supplied from the combination of three-band ¯uorescent tubes
(FL20SS EEXN/18-H; Toshiba Company, Tokyo, Japan) and incandescent lamps
(LW110V100W; Matsushita Electric Company, Osaka, Japan).
K. Inamoto et al. / Scientia Horticulturae 85 (2000) 295±306
297
2.3. Fresh and dry weight
In all experimental plots, 10 bulbs or plants were sampled at the time of
planting and at weekly intervals after planting, and 20 plants were sampled at
anthesis when the tip of the perianths dehisced. The length of stem and perianth
and the fresh weights of whole plants and their component parts, i.e., mother bulb
scales and basal plates, ¯oral organs, leaves, stems, roots and inner daughter
bulbs, were measured. Each part was dried in an oven at 808C for 72 h and weighed.
The dry weights of whole plants and their parts measured weekly were plotted
against the days after planting and the relations were shown by ®tting them on
exponential curves:
when the part was growing,
DW b eat
and when the part was senescing,
DW c ÿ b eat
(1)
(2)
where DW is the dry weight, t the days after planting, a, b and c are constants and
e the base of natural logarithms.
2.4. Relative growth rate
When the regression to Eq. (1) was signi®cant, relative growth rates during the
period from planting to anthesis (Rpa) of the whole plant and each part were
calculated as follows:
Rpa ln DWa ÿ ln DWp =tpa
(3)
where Rpa is the relative growth rate from planting to anthesis, tpa the days from
planting to anthesis, DWa the dry weight at anthesis and DWp the dry weight at
planting.
2.5. Regression of growth parameters
The relations between the growth parameters (Table 1), i.e., tpa, DWp, DWa and
Rpa, and the duration of bulb chilling at 28C (tc) were formulated by regression
analysis. We applied linear, quadratic, hyperbolic and logistic curves to them, and
chose the best ®tting model which had the smallest p value.
3. Results
3.1. Flowering and quality of cut ¯owers
The bulbs which had not been chilled completely failed to ¯ower, and only half
of those chilled for 3 weeks ¯owered (Table 2). The length of stems and the fresh
298
K. Inamoto et al. / Scientia Horticulturae 85 (2000) 295±306
Table 1
List of abbreviations of parameters
Abbreviation
Description
Unit
tc
tpa
DWp
Dwa
Rpa
Duration of bulb chilling at 28C
Time from planting to anthesis
Dry weight at planting
Dry weight at anthesis
Relative growth rate from planting to anthesis
week
day
g
g
dayÿ1
weight of shoots including a stem, leaves, and ¯oral organs at anthesis, increased
with the increase in duration of bulb chilling at 28C (tc) up to 12 weeks, but
decreased when tc was longer than 18 weeks (Table 2). The perianth length at
anthesis decreased with the increase in duration of bulb chilling (Table 2). The
correlation coef®cient between the fresh weight and the dry weight of shoots at
anthesis was 0.972 (p