disclaimer - seoul national university · 2019. 11. 14. · nam hyun lim . depart of plant science...
TRANSCRIPT
저 시-비 리- 경 지 2.0 한민
는 아래 조건 르는 경 에 한하여 게
l 저 물 복제, 포, 전송, 전시, 공연 송할 수 습니다.
다 과 같 조건 라야 합니다:
l 하는, 저 물 나 포 경 , 저 물에 적 된 허락조건 명확하게 나타내어야 합니다.
l 저 터 허가를 면 러한 조건들 적 되지 않습니다.
저 에 른 리는 내 에 하여 향 지 않습니다.
것 허락규약(Legal Code) 해하 쉽게 약한 것 니다.
Disclaimer
저 시. 하는 원저 를 시하여야 합니다.
비 리. 하는 저 물 리 목적 할 수 없습니다.
경 지. 하는 저 물 개 , 형 또는 가공할 수 없습니다.
A THESIS FOR THE DEGREE OF MASTER OF SCIENCE
Growth and Flowering Responses of
Lysimachia mauritiana Lam. to
Cold Temperature, Photoperiod, and Juvenility
저온과 일장 및 유년성에 대한
갯까치수염의 생장 및 개화 반응
BY
NAM HYUN LIM
FEBRUARY, 2019
MAJOR IN HORTICULTURAL SCIENCE AND BIOTECHNOLOGY
DEPARTMENT OF PLANT SCIENCE
THE GRADUATE SCHOOL OF SEOUL NATIONAL UNIVERSITY
i
Growth and Flowering Responses of
Lysimachia mauritiana Lam. to
Cold Temperature, Photoperiod, and Juvenility
NAM HYUN LIM
DEPART OF PLANT SCIENCE
THE GRADUATE SCHOOL OF SEOUL NATIONAL
UNIVERSITY
ABSTRACT
These studies were conducted to investigate the growth and flowering responses
of Lysimachia mauritiana Lam. (갯까치수염, spoonleaf yellow loosestrife) to
photoperiod and cold treatment (Expt. 1), and juvenility (Expt. 2). In Exp. 1, seed
propagated 8-week-old seedlings with 4–6 leaves were delivered to cold treatment
at 5oC and 9/15 h photoperiod for 0, 3, 6, 9, and 12 weeks (wk). After cold treatments,
plants were forced under five photoperiod treatments (9/15, 12/12, 14/10, 16/8, and
ii
24/0 h) in a greenhouse. Vegetative growth such as the number of leaves, plant width
and height, and biomass increased with increasing photoperiod, regardless of cold
treatments. In the non-cold treatment group, flowering did not occur during the
experimental period, even under ≥ 16/8 h. Under 16/8 and 24/0 h, flowering
percentages were 83% and 82% at 6-wk, and 100% at both 9- and 12-wk cold
treatments, respectively. However, flowering was also induced under 14/10 h with ≥
6 wk cold treatments with flowering percentages of ≤ 20%. In Expt. 2, growth stages
were divided into two groups according to the number of leaves: growth stage 1 (4–
6 leaves) and 2 (10–12 leaves). The seedling period were 6 and 10 weeks in the
growth stage 1 and 2, respectively. Cold treatments were forced for 0, 5, and 10 wks
and photoperiod treatments were the same as Exp. 1, but the experimental location
was changed to a closed system to examine accurate responses under controlled
temperature conditions. Similar to the former results, vegetative growth was
significantly promoted under longer photoperiod, while decreased with increasing
duration of cold treatment. Furthermore, although the plants were exposed to a cold
temperature at 5oC, flowering was not induced in the growth stage 1. Only in the
growth stage 2, flowering was observed with flowering percentages of 40% and 47%
at 5-wk, and 71% and 91% at 10-wk cold treatments under 16/8 and 24/0 h,
respectively. Therefore, both cold temperature at 5oC and long-day photoperiod were
absolutely required for the flowering, implying that these plants require vernalization
and long-day. In addition, L. mauritiana requires an appropriate level of vegetative
iii
growth to respond to cold temperature, but more detailed studies are needed for
juvenility.
Additional key words: daylength, floral induction, photoperiodism, qualitative long-
day plant, vernalization
Student number: 2017-22672
iv
CONTENTS
ABSTRACT ·················································································· i
CONTENTS ················································································ iv
LIST OF TABLES ·········································································· v
LIST OF FIGURES ········································································ vi
INTRODUCTION ·········································································· 1
LITERATURE REVIEW··································································· 4
Flowering Responses to Photoperiod ·················································· 4
Flowering Responses to Cold Temperature ··········································· 4
Flowering Responses to Juvenility ····················································· 5
MATERIALS AND METHODS ·························································· 7
RESULTS ··················································································· 11
Flowering Responses to Cold Temperature and Photoperiod (Expt. 1) ··········· 11
Flowering Responses to Juvenility (Expt. 2) ········································ 17
DISCUSSION ············································································· 22
LITERATURE CITED ··································································· 27
ABSTRACT IN KOREAN ······························································ 33
v
LIST OF TABLES
Table 1. Effects of cold temperature and photoperiod on vegetative growth of
Lysimachia mauritiama after 15 weeks of photoperiod treatment in Expt. 1.
······················································································ 13
Table 2. Effects of cold temperature and photoperiod on reproductive growth
of Lysimachia mauritiana in Expt. 1. ········································· 16
Table 3. Effects of growth stage, cold temperature and photoperiod on
vegetative growth of Lysimachia mauritiama after 15 weeks of
photoperiod treatment in Expt. 2. ············································· 18
Table 4. Effects of growth stage, cold temperature and photoperiod on
reproductive growth of Lysimachia mauritiana in Expt. 2. ················· 21
vi
LIST OF FIGURES
Fig. 1. Schematic diagram of experimental schedule and treatment timing in
this study. ··········································································· 9
Fig. 2. Effects of cold temperature and photoperiod on vegetative and
reproductive growth of Lysimachia mauritiana in Expt. 1. ··············· 14
Fig. 3. Changes in indoor temperature of a greenhouse during Expt. 1. ···· 15
Fig. 4. Effects of cold temperature and photoperiod treatments during the
growth stage 1 on growth of Lysimachia mauritiana in Expt. 2. ········· 19
Fig. 5. Effects of cold temperature and photoperiod treatments during the
growth stage 2 on growth of Lysimachia mauritiana in Expt. 2. ········· 20
1
INTRODUCTION
Interest in Korean native plants continues to increase and make a new demand in
the flower market, and the scale of wild flower markets is consistently increasing
(Korean Forest Service, 2018). However, the flowering responses are still unknown
in many wild species and many greenhouse growers have difficulties in scheduling
native plants and developing new flowering crops from wild flower (Davis and
Andersen, 1989; Fausey and Cameron, 2005).
Lysimachia mauritiana Lam. (갯까치수염, spoonleaf yellow loosestrife; family
Primulaceae) is regarded as a potential pot plant for succulent leaves and attractive
white flowers. This species is a monocarpic herbaceous plant, biennial, and
flowering season is from July to August in Korea. Many of these plants grow
naturally in exposed rock crevices and seepages on the seacoast and are distributed
in southern coastal region and island, Jeju-do and Ullung-do in Korea (Korea
Biodiversity Information System). Most of the coastal species have high tolerances
to environmental stresses, so their hardiness can be one of the advantages in
introduction and development for new ornamental flowering plants (Kodela et al.,
2014).
In many herbaceous perennials, growers control flowering by temperature,
photoperiod, or both. Ornamental herbaceous species in a temperate climates require
optimum photoperiod and exposure to cold temperature for flowering (Mattson and
2
Erwin, 2005). Photoperiodic flowering responses are generally divided into five
groups: short-day plants (SDP), long-day plants (LDP), day-neutral plants (DNP),
intermediate day plants, and ambiphotoperiodic-day plants. SDP and LDP groups are
further classified into two categories, obligate (qualitative) and facultative
(quantitative) (Tomas and Vince-Prue, 1997). Many herbaceous perennials in
temperate climate are commonly LDPs, so flowering can be promoted by artificial
long-day (LD) lighting (Heins et al., 1997). Furthermore, many species classified as
LDPs need several weeks of cold temperature (1 to 7 oC) that is exposed to seeds or
young plants and promotes flowering. This exposure to cold temperature for floral
induction is defined as vernalization and the duration of exposure usually ranged
from several days to months (Lang, 1965; Thomas and Vince-Prue, 1997).
Many researchers reported that the effects of photoperiod and cold treatment on
flowering of herbaceous ornamental crops. For example, Lobelia ×speciosa Sweet
‘Compliment Scarlet’ is obligate LDP and cold treatment promoted the flowering
even under SD photoperiod (Runkle et al., 1999). In Leucanthemum ×superbum
‘Snowcap’, ≥ 6 weeks at 5oC and ≥ 16/8 h photoperiod were recommended for
complete and rapid flowering. In Phlox paniculata, LD photoperiod and cold
treatment considerably decreased the time to flower and enabled to have at least three
times more flowers than at SD photoperiod and non-cooled treatment (Runkle et al.,
1998).
However, although plants are forced at cold temperature and LD condition, there
3
may not be flowering if plants are not mature enough to respond to environmental
signals. This is defined as juvenility that is insensitive to environmental signal for
flowering. The juvenile phase of plants is usually related to plant longevity and long-
lived species such as trees require long-term vegetative growth for flowering (Erwin,
2006). The research of juvenile phase must be accompanied with researches of
photoperiod and cold treatment for floral induction.
Thus, the objectives of this study were to investigate the flowering responses of L.
mauritiana to photoperiod and cold treatment (Expt. 1) and to examine the effect of
juvenility on sensing environmental stimuli for floral induction (Expt. 2). The results
of this study will provide a foundation for flowering manipulation of floricultural
researches and ornamental crop production.
4
LITERATURE REVIEW
Flowering Responses to Photoperiod
Photoperiod, which is decided by night length, are closely related to flowering,
floral induction and initiation, and development of many plant species. At a given
latitude, plants detect the seasonal information from changing photoperiod, and
flowering is induced under optimum season that is the proper environment for
reproduction of the next generation (Mattson and Erwin, 2005). Thomas and Vince-
Prue (1997) divided photoperiodic responses into five groups: SDPs, LDPs, DNPs,
intermediate day plants, and ambiphotoperiodic-day plants, and this classification
have been generalized in flowering plants. Most photoperiodic ornamental
floricultural crops that flower in spring and summer usually require long-days
(facultative LDP), thus growers have applied artificial LD condition or night
interruption (NI) to facilitate growth and control crop production (Heins et al., 1997;
Runkle et al. 1998). However, because photoperiodic responses about all plant
species are not identified, it is important to investigate how photoperiod affects
flowering of herbaceous ornamentals (Runkle et al., 1999).
Flowering Responses to Cold Temperature
In addition to photoperiod, cold temperature is required for flowering of many
herbaceous plants and one of the important signals to notice seasonal changes. The
5
cold temperature treatment for flowering is defined as vernalization and cold
temperature requiring plants in temperate climate experience cold at 1 to 7oC for
several weeks in winter. The duration and effective temperature range are very
different and diverse depending on species (Lang, 1965). While warm temperature
and LD condition generally hasten flowering, flowering time or floral induction may
be delayed in non-cooled plants. Thus, vernalization is often considered as a
prerequisite before optimum photoperiod (Roberts and Summerfield, 1987). Merit et
al. (1997) reported that vernalization of dry seed promoted earlier flowering, and
Weiler and Shedron (1986) also showed that flowering of vernalized plants was
hastened in LD. In Calandrinia and Brunonia, vernalization for 6 weeks at 4.8oC
was effective for promoting flowering and qualities such as the number of
inflorescences or flowers. The combination of vernalization and LD condition
commonly have a positive effect on the floral induction of ornamental species that
flower in the spring and summer season (Cave and Johnston, 2010).
Flowering Responses to Juvenility
Plants are insensitive to environmental stimuli during the juvenile stage and need
a certain period for enough growth or adult stage to initiate flowering (Bernier et al.,
1981). Generally, long-lived species such as trees have a long juvenile period and
juvenile phases of Citrus sinensis and Fagus sylvatica are 5–8 and 30–40 years,
respectively. On the other hand, most floriculture crops have relatively short juvenile
6
phase and Athirrhinum majus needs about one month (Cockshull, 1985; Dole and
Wilkins, 2004; McMahon et al., 2001). In Cinenaria cultivars, when the number of
leaves was 6–8, plants were sensitive to floral stimuli such as cold temperature and
photoperiod (Yeh and Atherton, 1997).
7
MATERIALS AND METHODS
Plant Materials and Growth Conditions
Seeds of Lysimachia mauritiana were sown in 105-cell plug trays filled with a
commercial soil (Baroker, Seoul Bio Co., Ltd., Eumseong, Korea) on May 19, 2017,
in Expt. 1 and on March 23, 2018, in Expt. 2 (Fig. 1). Seedlings were proceeded in
a closed plant production system of experimental farm (Seoul National University,
Suwon, Korea). The temperature and relative humidity (RH) were controlled at 22oC
and 60%, and light intensity and photoperiod were 110 μmol·m-2·s-1 and 9/15 h,
respectively.
In Expt. 2, growth stages were divided into two groups: stage 1 (4–6 leaves) and
stage 2 (10–12 leaves). Growth stage 2 required four more weeks than stage 1.
Transplanted plants in photoperiod treatments were irrigated at least twice a week.
The plants of Exp. 1 were only irrigated with water, whereas plants in Exp. 2 were
additionally fertigated once every two weeks with water soluble fertilizer (EC 0.8
mS·cm-1; HYPONeX professional 20N-20P-20K, HYPONeX Japan Co., Ltd.,
Osaka, Japan).
Cold Treatments
When the number of leaves of seedlings was 4–6 (Expt. 1 and 2) or 10–12 (Expt.
2), seedlings were moved to the cold storage room (Seoul National University Farm,
8
Suwon, Korea) for vernalization. The temperature of the cold storage room was 5oC,
which lasted for 0, 3, 6, 9, or 12 weeks (wk) in Expt. 1 and 0, 5, or 10 wk in Expt. 2
(Fig. 1). During the cold treatment, light intensity and photoperiod were 5 μmol·m-
2·s-1 and 9/15 h, respectively. After cold treatments, seedlings were transplanted in
7-cm (Expt. 1) and 10-cm (Expt. 2) plastic pots filled with commercial soil (Baroker,
Seoul Bio Co., Ltd., Eumseong, Korea) for photoperiod treatments.
Photoperiod Treatments
In Expt. 1, plants were placed in a greenhouse (Seoul National University Farm,
Suwon, Korea) after cold treatments, and then were grown under various
photoperiods. The photoperiods were controlled by supplemental lighting with white
LED (12V SMD 5050 LED, CamFree Co., Ltd., Seoul, Korea) at 9 h short-day to
make 9/15, 12/12, 14/10, 16/8, or 24/0 h photoperiods. The light intensity of white
LED for day extension was only 3 μmol·m-2·s-1 to avoid effects of daily light integral
(DLI) Expt. 2 was proceeded in a closed plant production system for accurate
environmental control. The temperature, RH, and light intensity was maintained at
22oC, 60%, and 300 μmol·m-2·s-1 [110 μmol·m-2·s-1 fluorescent lamp (TL-D 32W RS
865, Philips Lighting Co., Ltd., Eindhoven, Netherlands) + 190 μmol·m-2·s-1 white
LED (LEDT5-9015-DHE, FOCUS lighting Co., Ltd., Bucheon, Korea)],
respectively. Photoperiod treatments were the same as in Expt. 1 and the light
intensity for day extension was only 4 μmol·m-2·s-1.
9
Fig. 1. Schematic diagram of experimental schedule and treatment timing in this study.
10
Data Collection and Statistical Analysis
All vegetative growth parameters, such as the number of leaves, plant width, plant
height, and dry weight, were recorded after 15 weeks of photoperiod treatment. Plant
height was measured from the base of the stem to the shoot apex or the top of the
inflorescence. Dry weight was measured after drying at 80oC for 72 hours. Days to
visible bud and the first open flower, height at floral induction and the first open
flower, and the number of inflorescences were recorded as reproductive growth
parameters. Days to visible bud and the first open flower was counted from the start
date of photoperiod treatment. Plants not having an inflorescence after 15 weeks of
photoperiod treatment were considered as vegetative or non-flowering. All photos
were taken after 15 weeks of photoperiod treatment. In Expt. 1, the greenhouse air
temperature was recorded using a data logger (WatchDog 1000 series, Spectrum
Technologies, Inc., Plainfield, IL, USA). Statistical and graph module analyses were
performed using the SAS version 9.4 (SAS Institute, Inc., Cary, NC, USA) and
SigmaPlot version 10.0 (Systat Software, Inc., Chicago, IL, USA).
11
Results
Flowering Responses to Cold Temperature and Photoperiod (Expt. 1)
In all treatments, vegetative growth such as the number of leaves, plant width and
height, and shoot dry weight was significantly enhanced under longer photoperiod,
whereas plant width and height in non-flowering plants decreased with increasing
duration of cold treatment. Root dry weight of flowering plants was lower than those
of non-flowering plants (Table 1, Fig. 2). Plant height of flowering plants was
promoted as increasing duration of cold treatment by bolting. However, this response
assumed to be overgrowth that was caused by the difference from the starting time
of photoperiod treatments and the low light intensity by a thermal screen in the
winter season (Figs. 1, 3).
Without cold treatment, plants could not induce flowering in all photoperiod
treatments. Flowering occurred when the plants were grown under 14/10, 16/8 and
24/0 h LD photoperiod after cold treatment (Fig. 2). The flowering plants treated
under 14/10 h photoperiod showed very low flowering percentages, 18, 10, and 15%
under 6, 9, and 12 wk cold treatment, respectively, and floral organ degeneration and
abnormal late flowering were observed. The 3 wk cold treatment was not sufficient
for flowering because of low percent flowering, 38 and 33% at 16/8 and 24/0 h,
respectively (Table 2).
However, 16/8 and 24/0 h significantly promoted flowering. The flowering
12
percentages were 83 and 82% after 6 wk, 100% after both 9 and 12 wk cold
treatments, respectively. Days to visible bud and the first open flower did not always
show significant differences among all treatments, but slightly decreased as
photoperiod increased. Likewise, the number of inflorescences had a little increasing
tendency from 16/8 to 24/0 h (Table 2).
13
Table 1. Effects of cold temperature and photoperiod on vegetative growth of
Lysimachia mauritiama after 15 weeks of photoperiod treatment in Expt. 1.
Cold treatment (weeks)
Photoperiod (h)
Number of leaves
Plant width (cm)
Plant height (cm)
Dry weight (g)
Shoot Root 0 9/15 25.9 cz 12.8 d 3.4 e 1.01 c 0.66 b 12/12 32.3 b 15.0 d 5.3 d 1.46 b 0.96 a 14/10 29.3 bc 17.7 c 7.9 c 1.44 b 0.91 a 16/8 26.6 bc 20.6 b 11.1 b 1.63 b 0.87 a 24/0 39.8 a 24.5 a 13.0 a 2.21 a 0.97 a Significance ∗∗∗ ∗∗∗ ∗∗∗ ∗∗∗ ∗∗∗ 3 9/15 26.3 bc 15.2 c 4.1 c 1.08 c 0.90 b 12/12 28.6 b 15.0 c 5.2 c 1.24 c 0.85 b 14/10 21.9 c 19.9 ab 11.3 ab 1.57 b 1.08 a 16/8 29.7 ab 17.7 bc 22.5 bc 1.84 b 0.93 ab 24/0 35.3 a 21.8 a 29.0 a 2.42 a 1.00 ab Significance ∗∗ ∗∗∗ ∗∗∗ ∗∗∗ ∗ 6 9/15 25.8 b 12.1 c 4.2 c 0.83 d 0.54 c 12/12 25.5 b 15.2 b 7.1 b 1.06 c 0.69 b 14/10 21.7 b 17.3 a 13.4 a 1.32 b 0.84 a 16/8 33.9 a 13.7 bc 45.3 bc 1.51 a 0.49 c 24/0 35.4 a 14.6 b 41.3 b 1.59 a 0.59 bc Significance ∗∗∗ ∗∗∗ ∗∗∗ ∗∗∗ ∗∗∗ 9 9/15 21.9 b 9.9 c 4.4 c 0.67 c 0.51 d 12/12 22.4 b 16.6 ab 8.8 ab 0.93 b 0.67 b 14/10 23.1 b 17.2 a 15.2 a 1.15 b 0.82 a 16/8 34.4 a 14.8 b 48.8 b 1.70 a 0.63 bc 24/0 36.7 a 17.0 a 49.0 a 1.67 a 0.53 cd Significance ∗∗∗ ∗∗∗ ∗∗∗ ∗∗∗ ∗∗∗ 12 9/15 29.1 c 11.2 c 5.3 c 0.75 e 0.58 b 12/12 26.8 c 19.2 a 11.1 a 1.11 d 0.75 a 14/10 28.0 c 19.4 a 19.5 a 1.41 c 0.76 a 16/8 35.9 b 15.1 b 47.3 b 1.63 b 0.51 b 24/0 41.4 a 18.0 a 56.9 a 1.88 a 0.53 b Significance ∗∗∗ ∗∗∗ ∗∗∗ ∗∗∗ ∗∗∗ zMeans within columns followed by different letters are significantly different by Duncan’s multiple range test at p ≤ 0.05. ∗, ∗∗, ∗∗∗ Significant at p ≤ 0.05, 0.01, 0.001, respectively.
14
Fig. 2. Effects of cold temperature and photoperiod on vegetative and reproductive
growth of Lysimachia mauritiana in Expt. 1.
15
Date (mm/dd/yy)
08/01/17 09/01/17 10/01/17 11/01/17 12/01/17 01/01/18
Tem
pera
ture
(o C)
0
10
20
30
40 AvgMaxMin
Fig. 3. Changes in indoor temperature of a greenhouse during Expt. 1.
16
Table 2. Effects of cold temperature and photoperiod on reproductive growth of
Lysimachia mauritiana in Expt. 1.
Cold treatment (weeks)
Photoperiod (h)
Flowering percentage
Days to visible bud
Days to first open
flower
Height at floral
induction
Height at first open
flower
Number of inflorescences
0 9/15 0 – – – – – 12/12 0 – – – – – 14/10 0 – – – – – 16/8 0 – – – – – 24/0 0 – – – – – Significance – – – – – – 3 9/15 0 – – – – – 12/12 0 – – – – – 14/10 0 – – – – – 16/8 38 57.7 70.3 18.2 az 26.3 1.0 24/0 33 50.7 64.0 12.9 b 23.6 1.3 Significance – NS NS ∗ NS NS 6 9/15 0 – – – – – 12/12 0 – – – – – 14/10 18 83.5 a 99.0 a 15.9 21.7 1.0 16/8 83 46.2 b 70.1 b 13.0 26.0 2.0 24/0 82 51.2 b 69.3 b 15.0 24.0 2.6 Significance – ∗∗∗ ∗∗∗ NS NS NS 9 9/15 0 – – – – – 12/12 0 – – – – – 14/10 10 56.0 77.0 10.5 17.9 b 1.0 16/8 100 54.4 79.5 11.8 31.6 a 1.5 24/0 100 51.3 76.2 12.0 30.0 a 1.9 Significance – NS NS NS ∗∗∗ NS 12 9/15 0 – – – – – 12/12 0 – – – – – 14/10 15 73.5 a 96.0 15.4 27.7 b 2.0 16/8 100 58.1 b 82.9 15.7 36.8 a 1.9 24/0 100 51.9 b 81.4 15.3 39.1 a 3.3 Significance – ∗ NS NS ∗ NS zMeans within columns followed by different letters are significantly different by Duncan’s multiple range test at p ≤ 0.05. NS, ∗, ∗∗∗ Non-significant or significant at p ≤ 0.05, 0.001, respectively.
17
Flowering Responses to Juvenility (Expt. 2)
Similar to Expt. 1, vegetative growth remarkably increased under longer
photoperiod. By contrast, plant width and height generally showed declining
tendencies as the duration of cold treatment and growth stage increased (Table 3).
The overgrowth of plant height, which was observed in Exp. 1, did not occur because
plants received the high light intensity (300 μmol·m-2·s-1) in a closed system. In
addition, the vegetative growth was improved and the plant shape in Exp.2 was more
compact than those in Exp. 1 (Fig. 3, 4, 5)
In flowering response, flowering was not induced in growth stage 1 despite
receiving cold treatment (Fig. 4, Table 4). Flowering was only induced in growth
stage 2 and flowering percentages were 40 and 47% at 5 wk, 71 and 91% at 10 wk
cold treatments under 16 and 24 h of photoperiods, respectively. Days to visible bud
and the first open flower significantly decreased with increasing duration of cold and
photoperiod. Height at floral induction also showed the same trend with days to
visible bud. The number of inflorescences under 10 wk of cold and 24/0 h was at
least three times higher than that under other treatments (Fig. 5, Table 4).
18
Table 3. Effects of growth stage, cold temperature and photoperiod on vegetative growth
of Lysimachia mauritiama after 15 weeks of photoperiod treatment in Expt. 2.
Growth stage Cold treatment (weeks)
Photoperiod (h)
Plant width (cm)
Plant height (cm)
4–6 leaves 0 9/15 24.8 e–jz 10.3 h–l 12/12 27.2 b–f 11.2 e–i 14/10 27.5 b–e 11.9 d–h 16/8 28.9 bc 12.6 def 24/0 32.2 a 15.0 b 5 9/15 20.6 lmn 9.1 klm 12/12 21.2 klm 9.7 i–m 14/10 25.9 d–h 10.2 h–l 16/8 27.5 b–e 11.1 f–j 24/0 27.7 bcd 11.2 e–I 10 9/15 18.4 no 8.6 m 12/12 19.6 mn 9.3 klm 14/10 20.5 lmn 8.3 mn 16/8 22.9 i–l 9.7 i–m 24/0 24.4 g–j 11.2 f–j 10–12 leaves 0 9/15 24.9 e–j 11.9 d–h 12/12 24.9 e–j 11.4 e–i 14/10 26.4 c–g 12.3 d–g 16/8 25.5 d–I 12.6 def 24/0 29.2 b 15.5 b 5 9/15 16.5 o 6.9 n 12/12 20.4 lmn 9.5 j–m 14/10 24.7 f–j 10.7 g–k 16/8 26.2 d–g 13.2 cd 24/0 22.4 jkl 12.9 de 10 9/15 18.9 mno 8.8 lm 12/12 21.0 k–n 9.0 lm 14/10 23.3 h–k 10.8 g–k 16/8 25.1 d–I 14.5 bc 24/0 26.8 b–g 19.2 a Significance
Growth stage (G) ∗∗ ∗∗∗ Cold treatment (C) ∗∗∗ ∗∗∗ Photoperiod (P) ∗∗∗ ∗∗∗ G×C ∗∗∗ ∗∗∗ G×P NS ∗∗∗ C×P ∗∗∗ ∗∗∗
zMeans within columns followed by different letters are significantly different by Duncan’s multiple range test at p ≤ 0.05. NS, ∗∗, ∗∗∗ Non-significant or significant at p ≤ 0.01, 0.001, respectively.
19
Fig. 4. Effects of cold temperature and photoperiod treatments during the growth
stage 1 on growth of Lysimachia mauritiana in Expt. 2. No flowering was
observed.
20
Fig. 5. Effects of cold temperature and photoperiod treatments during the growth
stage 2 on growth of Lysimachia mauritiana in Expt. 2.
21
Table 4. Effects of growth stage, cold temperature and photoperiod on reproductive
growth of Lysimachia mauritiana in Expt. 2.
Growth stage
Cold treatment (weeks)
Photoperiod (h)
Flowering percentage
Days to visible
bud
Days to first open
flower
Height at floral
induction
Height at first open
flower
Number of inflorescences
4–6 0 9/15 0 – – – – – leaves 12/12 0 – – – – – 14/10 0 – – – – – 16/8 0 – – – – – 24/0 0 – – – – – 5 9/15 0 – – – – – 12/12 0 – – – – – 14/10 0 – – – – – 16/8 0 – – – – – 24/0 0 – – – – – 10 9/15 0 – – – – – 12/12 0 – – – – – 14/10 0 – – – – – 16/8 0 – – – – – 24/0 0 – – – – – 10–12 0 9/15 0 – – – – – leaves 12/12 0 – – – – – 14/10 0 – – – – – 16/8 0 – – – – – 24/0 0 – – – – – 5 9/15 0 – – – – – 12/12 0 – – – – – 14/10 0 – – – – – 16/8 40 62.7 az 73.7 a 9.0 a 11.8 1.3 b 24/0 47 59.0 a 74.8 a 7.1 b 11.6 3.2 b 10 9/15 0 – – – – – 12/12 0 – – – – – 14/10 0 – – – – – 16/8 71 50.4 b 67.6 a 6.0 b 11.2 3.4 b 24/0 89 34.9 c 51.4 b 5.8 b 11.4 10.7 a Significance
Cold treatment (C) – ∗∗∗ ∗∗∗ ∗∗∗ NS ∗∗ Photoperiod (P) – ∗∗ ∗ ∗ NS ∗∗ C×P – NS NS NS NS NS
zMeans within columns followed by different letters are significantly different by Duncan’s multiple range test at p ≤ 0.05. NS, ∗, ∗∗, ∗∗∗ Non-significant or significant at p ≤ 0.05, 0.01, 0.001, respectively.
22
DISCUSSION
Previous researches have reported that cold treatment and supplemental lighting
for LD condition could enhance vegetative growth and flowering in many
herbaceous ornamental plants (Garner and Armitage, 1998). In general, day
extension by supplementary lighting enhanced vegetative growth and flowering
quality. LD photoperiod significantly improved vegetative growth, such as stem
elongation, the number of branches, internode length, shoot dry weight in Tecoma
stans (Torres and Lopez, 2011).
In most cases, these positive effects of LD condition could be attributed to
increased daily light integral (DLI) from supplemental lighting. Adams et al. (1999)
reported that increasing DLI reduced the period of juvenile phase and promoted the
plant quality. However, in this experiment, the supplemental lighting of very low
light intensity ranging from 1 to 5 μmol·m-2·s-1 was applied for day extension in
order to minimize the effect of DLI. Actually, DLIs were similar under all treatments.
Many studies also showed that the day extension by low light intensity could
improve the crop quality (Kim et al., 2015; Padhye and Cameron, 2008; Runkle et
al., 1998; Torres and Lopez, 2011). From these result, it can be suggested that the
promoting effect by LD could be attributed not solely to DLI but LD itself.
Phlox paniculata Lyon ex Pursh ‘Eva Cullum’ plants remained vegetative under
SD photoperiod and the flowering percentage increased as increasing photoperiod.
23
Cold-treated plants had over three times more flowers than non-cold treated plants
(Runkle et al., 1998). The growth and flowering of Miltonia cultivars were hastened
by artificial chilling temperature under 16/8 h photoperiod (Matsui and Yoneda,
1997).
Besides the inductive photoperiod, many winter annuals, biennials, and perennials
require cold temperature for flowering. The exposure to cold temperature for a
certain period was called vernalization that promotes phase transition from
vegetative to reproductive state. Generally, the range of cold temperature is between
-5 and 15oC and the optimum temperature for plants in a temperate climate are 1 to
7oC. Insufficient cold treatment can cause incomplete or delayed flowering, so
vernalization has been extensively studied in many ornamental crops (Chouard, 1960;
Lang, 1965; Thomas and Vince-Prue, 1997).
In Aquilegia cultivars, which are generally considered to require vernalization,
cooling and LD photoperiod promoted growth and flowering. In addition, Aquilegia
plants without cooling at 4oC showed substantially late flowering responses
(Shedron and Weiler, 1982; White et al., 1989). Phlox paniculata ‘Fairy’s Petticoat’
did not require cold temperature for flowering, but more uniform, robust, and early
flowering was observed in plants treated for 12 weeks at 4.5oC (Iversen and Weiler,
1994).
Winter annuals and perennials show facultative vernalization response and cold
temperature is required for rapid or early flowering, but is not indispensable. By
24
contrast, biennials have an obligate vernalization requirement, so cold treatment is
essentially required for flowering (Michaels and Amasino, 2000). Lysimachia
mauritiana also showed typical biennial responses and obligatory cold temperature
requirement before LD photoperiod for flowering and the time to flower and the
flowering quality, such as the number of inflorescences, were promoted with
increasing duration of cold and photoperiod (Tables 2, 4). These results were in
agreements with Ha (2014) who stated that species that demand vernalization for
flowering are usually LD plants and the shorter time to flowering and the higher
number of flowers and/or inflorescences could be observed with increasing duration
of vernalization.
The cold requirement can also vary among species and the response is usually
quantitative. As the duration of cold increased, flowering was promoted until the
response was saturated in facultative vernalization requiring plants (Lang, 1965). For
example, for the saturated vernalization responses (100% of flowering), Campanula
‘Birch Hybrid’ needed at least 5 weeks at 0 to 12.5oC (Padhye, 2009). 100%
flowering of Dianthus grantianoplitanus ‘Bath’s Pink’ was achieved after cold
treatment at 0oC for more than 4 wk, 5oC for more than 3 wk, and 10oC for 8 wk
(Padhye and Cameron, 2008). In this study, it is suggested that, for high percent and
uniform flowering of Lysimachia mauritiana, ≥ 9 wk of cold treatment at 5oC was
required prior to ≥ 16/8 h photoperiod treatment (Tables 2, 4).
25
In addition, an optimum temperature is important for flowering and the
temperature above the optimum temperatures can inhibit development. The
temperature conditions for vernalization were 14–16oC for cauliflower and 11–17oC
for Miltoniopsis ‘Trinity’ (Lopez and Runkle, 2006; Pearson et al., 1994). In
herbaceous ornamental crops, Veronica spicata ‘Red Fox’ (Fausey and Cameron,
2007) and Dianthus grantianoplitanus ‘Bath’s Pink’ (Padhye and Cameron, 2008)
needed -2.5–0oC and 5oC, respectively, for uniform flowering. Thus, detailed
investigation for the optimum cold temperature treatment for the flowering of
Lysimachia mauritiana is needed.
Plants also required a certain age or stage to perceive cold temperature for
flowering. A juvenile stage is generally short in herbaceous plants and the short
juvenility is commercially desirable to decrease production time (Ramin and
Atherton, 1991). In some species, the meristems are able to perceive cold
temperature when seedling reach a particular stage. The number of leaves and nodes
are commonly used to estimate the juvenility in herbaceous plants (McDonald and
Kwong, 2005; Yuan et al., 1998). The length of juvenile phase was also measured
with a seedling period to inducible phase for flowering. Coreopsis lanceolate ‘Early
Sunrise’ and Anthirrhinum majus initiated flowering when they had 16 and 18–22
leaves, respectively. (Cockshull, 1985; Damann and Lyons, 1993; Yeh and Atherton,
1997). If plants are prematurely forced to inductive cold temperature in juvenile
phase, the plants cannot flower or support quality flowers. Inappropriate timing of
26
cold treatment can decrease the uniformity of flowering and lower the plants quality
(Cavins and Dole, 2001).
In Exp. 2, the floral transition did not occur when cold and photoperiod treatments
were applied during growth stage 1 with 4–6 leaves, whereas flowering was induced
when they were applied during growth stage 2 with 10–12 leaves (Table 4, Figs. 4,
5). These results indicated that this plant has a juvenility and require sufficient
vegetative growth for perceiving cold temperature. But, cold treated plants that had
4–6 leaves could flower in Exp. 1 (Fig. 2). These contrasting results might have been
brought about from the difference between seedling periods. The 4–6 leaves seedling
periods in Exp. 1 and 2 were 8 and 6 weeks, respectively (Fig. 1). This difference
might affect the juvenility and the contrasting results. Thus, additional studies about
the growth stage in this plant are required to judge seedling by adult phase.
In conclusion, Lysimachia mauritiana requires LD condition following cold
temperature for floral induction, indicating that this species is obligate vernalization
requiring LD plants. Additionally, this species needs a sufficient vegetative growth
to be sensitive to vernalizing temperature for flowering. These results can provide a
foundation for manipulating flowering in Korean native wild plants and help
commercial growers to cultivate wild flowers.
27
LITERATURE CITED
Adams SR, Pearson S, Hadley P, Patefield W M (1999) The effects of temperature
and light integral on the phases of photoperiod sensitivity in Petunia ×hybrida.
Ann Bot 83: 263–269
Bernier G, Kinet J, Sachs RM (1981) The Physiology of Flowering, Vol. 1. CRC
Press, Boca Raton, FL, USA
Cave RL, Johnston ME (2010) Vernalization promotes flowering of a heat tolerant
Calandrinia while long days replace vernalization for early flowering of
Brunonia. Sci Hortic 123: 379–384
Cave RL, Birch CJ, Hammer GL, Erwin JE, Johnston ME (2011) Juvenility and
flowering of Brunonia australis (Goodeniaceae) and Calandrinia sp.
(Portulacaceae) in relation to vernalization and daylength. Ann Bot 108: 215–220
Cavins TJ, Dole JM (2001) Photoperiod, juvenility, and high intensity lighting affect
flowering and cut stem qualities of Campanula and Lupinus. HortScience 36:
1192–1196.
Chouard P (1960) Vernalization and its relations to dormancy. Ann Rev Plant Physiol
11: 191–238
Cockshull KE, Halevy AH (1985) Antirrhinum majus. In Halevy AH, ed, Handbook
of Flowering, Vol. I. CRC Press, Boca Raton, FL, USA, pp 476–481
28
Damann MP, Lyons RE (1993) Juvenility, flowering, and the effects of a limited
inductive photoperiod in Coreopsis grandiflora and C. lanceolata. J Am Soc
Hortic Sci 118: 513–518
Davis TD, Andersen A (1988) Growth retardants as aids in adapting new floricultural
crops to pot culture. Acta Hortic 252: 77–86
Dole JM, Wilkins HF (2005) Floriculture: Principles and Species, 2nd ed. Pearson
Prentice Hall, Upper Saddle River, NJ, USA, p 558
Erwin J (2006) Factors affecting flowering in ornamental plants. In Anderson NO,
ed, Flower Breeding and Genetics. Springer, Dordrecht, Netherlands, pp 7–48
Fausey BA, Cameron AC (2005) Evaluating herbaceous perennial species as new
flowering potted crops. Acta Hortic 683: 207–213
Fausey BA, Cameron AC (2007) Differing vernalization responses of Veronica
spicata ‘Red Fox’ and Laurentia axillaris. J Am Soc Hortic Sci 132: 751-757.
Garner JM, Armitage AM (1998) Influence of cooling and photoperiod on growth
and flowering of Aquilegia L. cultivars. Sci Hortic 75: 83–90
Ha TM (2014) A review of plants’ flowering physiology: The control of floral
induction by juvenility, temperature and photoperiod in annual and ornamental
crops. Asian J Agric Food Sci 2: 186–195
Heins RD, Cameron AC, Carlson WH, Runkle ES, Whitman C, Yuan M, Koreman
P (1997) Controlled flowering of herbaceous perennial plants. In Goto E, Kurata
29
K, Hayashi M, Sase S, eds, Plant Production in Closed Ecosystems. Kuluwer
Academin Publishers, Norwell, MA, USA, pp 15–31
Iversen RR, Weiler TC (1994) Strategies to force flowering of six herbaceous garden
perennials. HortTechnology 4: 61–65
Kim YJ, Yu DJ, Roh H, Runkle ES, Lee HJ, Kim KS (2015) Photosynthetic changes
in Cymbidium orchids grown under different intensities of night interruption
lighting. Sci Hortic 186: 124–128
Kodela PG, Adam P, Wiecek BM (2014) Lysimachia mauritiana (Primulaceae) on
seacliffs in the eastern suburbs of Sydney: a new naturalized record for Australia.
Cunninghamia 14: 89–95
Korea Biodiversity Information System
Korea Forest Service (2018) The Statistical Yearbook of Forestry
Lang A. (1965) Physiology of flower initiation. In Ruhland W, ed, Encyclopedia of
Plant Physiology, Vol. 15. Springer, Berlin, Germany, pp 1371–1536
Lopez RG, Runkle ES (2006) Temperature and photoperiod regulate flowering of
potted Miltoniopsis orchids. HortScience 41: 593–597
McDonald MB, Kwong FY (2005) Flower Seeds: Biology and Technology. CABI
publishing, Wallingford, Oxfordshire, UK
McMahon M, Kofranek AM, Rubatzky VE (2002) Hartmann's plant science.
Pearson Prentice Hall, Upper Saddle River, NJ, USA
30
Mattson NS, Erwin JE (2005) The impact of photoperiod and irradiance on flowering
of several herbaceous ornamentals. Sci Hortic 104: 275–292
Matsui N, Yoneda K (1997) Effect of summer temperatures on growth and flowering
of Miltonia. J Jpn Soc Hortic Sci 66: 597–605
Merritt RH, Gianfagna T, Perkins III RT, Trout JR (1997) Growth and development
of aquilegia in relation to temperature, photoperiod and dry seed vernalization.
Sci Hortic 69: 99–106
Michaels SD, Amasino RM (2000) Memories of winter: vernalization and the
competence to flower. Plant Cell Environ 23: 1145–1153
Padhye SR, Cameron AC (2008). Dianthus gratianopolitanus Vill.‘Bath's Pink’ has
a near-obligate vernalization requirement. HortScience 43: 346–349
Padhye SR, Cameron AC (2009) Vernalization responses of Campanula ‘Birch
Hybrid’. J Am Soc Hortic Sci 134: 497–504
Pearson S, Hadley P, Wheldon AE (1994) A model of the effects of temperature on
the growth and development of cauliflower (Brassica oleracea L. botrytis). Sci
Hortic 59: 91–106
Ramin AA, Atherton JG (1991) Manipulation of bolting and flowering in celery
(Apium graveolens L. var. dulce). II. Juvenility. J Hortic Sci 66: 709–717
Roberts EH, Summerfield RJ (1987) Measurement and prediction of flowering in
annual crops. In Atherton JG, ed, Manipulation of Flowering. Butterworths, Kent,
UK, pp 17–51
31
Runkle, ES, Heins RD, Cameron AC, Carlson WH (1998) Flowering of
Leucanthemum ×superbum ‘Snowcap’ in response to photoperiod and cold
treatment. HortScience 33: 1003–1006
Runkle, ES, Heins RD, Cameron AC, Carlson WH (1998) Flowering of Phlox
paniculata is influenced by photoperiod and cold treatment. HortScience 33:
1172–1174
Runkle, ES, Heins RD, Cameron AC, Carlson WH (1999) Cold treatment modifies
the photoperiodic flowering response of Lobelia ×speciosa. Sci Hortic 80: 247–
258
Sheldron KG, Weiler TC (1982) Regulation of growth and flowering in Aquilegia
×hybrid Sims. J Amer Soc Hortic Sci 107: 878–882
Thomas B, Vince-Prue D (1997) Photoperiodism in Plants, 2nd ed. Academic Press.
London, UK, pp 1–26
Torres AP, Lopez RG (2011) Photoperiod and temperature influence flowering
responses and morphology of Tecoma stans. HortScience 46: 416–419
Warner RM (2010) Temperature and photoperiod influence flowering and
morphology of four Petunia spp. HortScience 45: 365–368
Weiler TC, Shedron KG (1986) Aquilegia ×hybrid. In Halevy AH, ed, Handbook of
Flowering, Vol. V. CRC Press, Boca Raton, FL, USA, pp 18–21
White JW, Beattie DJ, Holcomb EJ (1989) Flowering studies with Aquilegia
cultivars. Acta Hortic 252: 219–226
32
Yeh DM, Atherton JG (1997) Manipulation of flowering in cineraria. II. Juvenility.
J Hortic Sci 72: 55–66
Yuan M, Carlson WH, Heins RD, Cameron AC (1998) Determining the duration of
the juvenile phase of Coreopsis grandiflora (Hogg ex Sweet.), Gaillardia
×grandiflora (Van Houtte), Heuchera sanguinea (Engelm.) and Rudbeckia
fulgida (Ait.). Sci hortic 72: 135–150
33
ABSTRACT IN KOREA
본 연구는 갯까치수염(Lysimachia mauritiana Lam.)의 일장과 저온
처리(실험 1) 및 유년성(실험 2)에 대한 생장과 개화 반응을 알아보기
위해서 진행되었다. 실험 1 에서 파종 8 주 후 본엽이 4~6 매일 때,
9/15 시간 일장 조건에서 각각 0, 3, 6, 9, 12 주 동안 5oC 저온 처리가
진행되었다. 저온 처리 이후에는 온실로 옮겨져 총 5 가지의 일장
처리(9/15, 12/12, 14/10, 16/8, 24/0 시간)가 진행되었다. 영양 생장
지표에서는 저온 처리와 관계없이 일장이 증가함에 따라 엽수, 초폭,
초고 및 바이오매스가 모두 증가하는 것으로 나타났다. 저온 처리를
받지 않은 식물들은 16/8 시간 이상의 장일 조건에도 불구하고 개화가
유도되지 않았다. 9 주 저온처리구에서 16/8 시간과 24/0 시간의
일장에서 개화율은 각각 83%와 82%였으며, 9 주와 10 주
저온처리에서는 16/8 시간의 이상의 일장 조건에서 100%의 개화율이
관찰되었다. 6 주 이상의 저온 처리 후, 14/10 시간의 일장 조건에서도
개화가 진행되었으나 개화율은 20%에 미치지 못했다. 실험 2 는 본엽
수에 따라 생육 단계가 2 개의 처리로 구분되었고, 생육 단계 1 과 2 의
본엽 수는 각각 4~6 매, 10~12 매였으며 육묘 기간은 각각 6 주,
34
10 주였다. 실험 2 의 저온 처리는 기간을 0, 5, 10 주, 총 3 개로
구분하였고, 나머지 환경 조건 및 일장 처리는 실험 1 과 동일하게 진행
되었다. 다만 통제된 온도 환경에서 정확한 반응을 확인하기 위해서
실험 2 는 밀폐형 시스템에서 이루어졌다. 이전의 결과와 비슷하게 영양
생장은 일장이 길어질수록 유의하게 증가하였고, 반면에 저온 처리
기간이 길어질수록 감소하는 양상을 나타냈다. 게다가 5oC 저온에
노출이 되었음에도 불구하고 생육 단계 1 에서는 어떠한 개화 반응도
관찰되지 않았다. 개화는 생육 단계 2 에서만 관찰되었으며 개화율은
16/8, 24/0 시간 일장 조건에서 5 주 저온 처리시 각각 40%, 47%, 10 주
저온 처리 시 각각 71%, 91%였다. 결과적으로 개화에 5oC 저온과 장일
조건을 둘 다 필수적으로 요구하므로, 이 식물은 절대적 춘화 요구도가
있는 질적 장일 식물이라 할 수 있다. 또한 갯까치수염에서 개화 유도를
위한 저온에 감응하기 위해서는 일정 수준 이상의 영양 생장을
요구한다고 할 수 있지만, 유년성과 관련된 보다 구체적인 추가 실험이
필요하다.