Comment réaliser un semis ?

[guicha]

alor sa je ne sais pas lol!

[elio]

Salut,
moi je prends des gobelets en plastiques rempli de tourbe je semes les plantes la-dessu puis je recouvre de paipier plastique. Pour la stratification, je la fait avec de l'eau très chaude pour les graines de sarra.

[dydylamouche baveuse]

le mieux, c'est de planter directement là ou sa doit pousser...
d'après se que j'ai pu lire sur byblis liniflora et d'après se qui m'en reste...
c'est un sol trés drainant et pas forcément de la tourbe, (je viens d'en récupéré in vitro et j'attends avec impatience ces petites fleurs)
http://encyclo.free.fr/pages/byblis.htm#Culture
stratifaction solaire : le déclenchement de germination se fait après un bon coup de soleil, enfin c'est se que je pense...
pour les drosera 60% de tourbe et 40% de sable, mais là fait des recherches...
pour grandiflora http://encyclo.free.fr/pages/ping_01.htm ou http://www.pinguicula.org/ ou http://pinguicula.free.fr/

[limpsplit]

Pour les droseras (je vais apporter encore une autre facon )
je seme les graines dans le sphaigne vivante bien humide, dans un verre transparent (qui permet d'ailleurs de faire pousser la sphaigne en meme temps lolette) que je recouvre d'un plastique alimentaire pour garder l'humidité dans lequel je perce un trou quand même pour aérer !!!
Le tout placer dans une fenetre a l'Est pour le soleil du matin !
J'ai des résultats tout à fait satisfaisant !!

[blur]have fun[/blur]

[le grand lapin]

hello,

stratification par la lumière : les graines ne déclenchent leur germination qu'en présence de facteur favorables, certaines après l'hiver lorsque les températures remontent, d'autres lorsque la luminosité est assez intense (ou plutôt, lorsque la durée d'insolation devient plus longue.
D.anglica fait partie de ces graines qui germent mieux après une bonne période d'insolation.

Seed dormancy-breaking and germination requirements of
Drosera anglica, an insectivorous species of the Northern Hemisphere
Carol C. Baskina,b*, Per Milbergc, Lars Anderssond, Jerry M. Baskina
a School of Biological Sciences, University of Kentucky, Lexington, KY 40506-0225, USA
b Department of Agronomy, University of Kentucky, Lexington, KY 40546-0091, USA
c Department of Biology-IFM, Linköping University, 581 83 Linköping, Sweden
d Department of Ecology and Crop Production Science, Swedish University of Agricultural Sciences,
Box 7043, 750 07 Uppsala, Sweden
Received 6 June 2000; revised 25 October 2000; accepted 20 November 2000
Abstract – Seeds of Drosera anglica collected in Sweden were dormant at maturity in late summer, and dormancy break occurred during cold
stratification. Stratified seeds required light for germination, but light had to be given after temperatures were high enough to be favorable for
germination. Seeds stratified in darkness at 5/1 °C and incubated in light at 12/12 h daily temperature regimes of 15/6, 20/10 and 25/15 °C
germinated slower and to a significantly lower percentage at each temperature regime than those stratified in light and incubated in light. Length
of the stratification period required before seeds would germinate to high percentages depended on (1) whether seeds were in light or in darkness
during stratification and during the subsequent incubation period, and (2) the temperature regime during incubation. Seeds collected in 1999
germinated to 4, 24 and 92 % in light at 15/6, 20/10 and 25/15 °C, respectively, after 2 weeks of stratification in light. Seeds stratified in light
for 18 weeks and incubated in light at 15/6, 20/10 and 25/15 °C germinated to 87, 95 and 100 %, respectively, while those stratified in darkness
for 18 weeks and incubated in light germinated to 6, 82 and 91 %, respectively. Seeds collected from the same site in 1998 and 1999, stratified
in light at 5/1 °C and incubated in light at 15/6 °C germinated to 22 and 87 %, respectively, indicating year-to-year variation in degree of
dormancy. As dormancy break occurred, the minimum temperature for germination decreased. Thus, seed dormancy is broken in nature by cold
stratification during winter, and by spring, seeds are capable of germinating at low habitat temperatures, if they are exposed to light. © 2001
Éditions scientifiques et médicales Elsevier SAS
cold stratification / Drosera / insectivorous species / light requirement / seed dormancy / seed germination
1. INTRODUCTION
The insectivorous plant genus Drosera (commonly
called sundews) is cosmopolitan, but many of its about
110 species grow only in the Southern Hemisphere
[22], with a concentration of species in Australia [27].
However, at least five species are restricted to the
Northern Hemisphere [16], and three of the five are
found in Europe: D. rotundifolia L., D. intermedia
Drev. & Hayne and D. anglica (Huds.) LePage & W.
Bldw. [19]. These three species also occur in North
America [16], D. anglica and D. rotundifolia in Asia
[19, 26] and D. anglica on mountains in Hawaii [13,
17]. Regardless of the continent on which these three
species occur, they grow in wet boggy sites [13], with
D. anglica being more tolerant of calcareous soils than
the other two species [19].
Recently, there has been considerable interest in
germinating seeds of the various taxa of Droseraceae.
Newly-germinated seedlings of Droseraceae differ
with regard to the amount of cotyledonary tissue that
emerges from the seed coats [10], and these morphological
characteristics have been used, along with
molecular data, to construct cladograms of the family
[35]. Conran et al. [10] germinated seeds of about 100
taxa of Drosera and recorded number of days from
time of sowing until the first seeds germinated and
type of seedling morphology. However, from a seed
germination ecology perspective these data are not
very useful, because dormancy state at time of seed
maturation and age of seeds when they were sown are
*Correspondence and reprints: fax +1 859 257 1717.
E-mail address: ccbask0@pop.uky.edu (C.C. Baskin).
Acta Oecologica 22 (2001) 1−8
© 2001 Éditions scientifiques et médicales Elsevier SAS. All rights reserved
S1146609X00010936/FLA
not given. Seeds of some taxa may have been nondormant
at maturity, whereas those of others may have
been dormant. In species with dormant seeds, dormancy
break (afterripening) could have occurred as
seeds were stored prior to sowing.
Relatively little information is available on the seed
dormancy-breaking and germination requirements of
Drosera. Seeds of D. aliciae Rayn-Hamet from South
Africa required a 24-d period of imbibition at 15/10 °C
before any germination occurred, but after 34 d ca. 70
% of the seeds had germinated [14]. These authors
concluded that dormancy break took place if seeds
were subjected to warm, moist conditions but not if
they were stored dry. In contrast, seeds of D. rotundifolia
germinated to 30 % in light at 20/15 °C after 4
months of stratification at 5 °C [18]. Seeds of D.
rotundifolia mostly germinate in May (spring) in
Sweden [29], indicating that dormancy break occurs
during winter. Crowder et al. [12] obtained 90–95 %
germination of D. anglica, D. intermedia and D.
rotundifolia seeds from Saskatchewan, Canada, in
light in a glasshouse at 18–22 °C after they had been
imbibed in darkness at 10 °C for 8, 16 and 8 weeks,
respectively. Seeds of D. anglica, D. intermedia and
D. rotundifolia, sown on wet filter paper in plastic
Petri dishes kept outdoors in Ontario, Canada, all
winter, germinated to 64, 22 and 0 %, respectively, the
following spring [12]. Kinzel [21] reported that seeds
of D. anglica, D. intermedia and D. rotundifolia
required light for germination. Crowder et al. [12] also
found that light was required for germination of D.
rotundifolia and D. anglica, but some seeds (percentages
not given) of D. intermedia germinated in darkness.
The data available from germination studies of
Drosera spp. restricted to the North Hemisphere raise
several questions. (1) How much cold stratification is
required to break seed dormancy? (2) As seeds come
out of dormancy, what are the temperature requirements
for germination? (3) Based on the temperature
requirements for germination of non-dormant seeds,
when would germination be expected to occur in the
habitat? (4) Do stratified seeds require light for germination
at some, but not at other, temperatures? (5) If
light is given during the stratification period, will seeds
subsequently germinate in darkness at simulated
spring habitat temperatures? The purpose of our study
was to answer these questions using seeds of D.
anglica collected in Sweden.
The terms non-dormant, conditionally dormant and
dormant are used in this paper. Non-dormant seeds
germinate over the full range of environmental conditions
possible for the species, while dormant seeds do
not germinate at any condition [7]. Conditional dormancy
(sensu [7, 34]) refers to the series of dormancy
states through which seeds progress between dormancy
and non-dormancy. When seeds first enter
conditional dormancy they germinate over a limited
set of environmental conditions, but the range of
conditions over which seeds will germinate widens as
dormancy break continues. After the seeds gain the
ability to germinate over the full range of conditions
possible for the taxon or ecotype, they are nondormant.
2. METHODS
2.1. Stratification of seeds collected in 1997
Regardless of collection site and year, the alternating
temperature regimes used for germination tests of
D. anglica seeds approximate mean daily maximum
and minimum monthly temperatures during the growing
season in south-central Sweden, based on 30-year
temperature data from Stockholm [25]: May, 14.4
(maximum) and 6.0 (minimum) °C; June, 19.2 and
10.8 °C; July, 21.9 and 14.1 °C; August, 20.2 and
13.3 °C; and September 15.3 and 9.4 °C. Protrusion of
the radicle was the criterion for germination, and at the
end of all germination tests, ungerminated seeds were
pinched with forceps under a dissecting microscope to
determine if seeds contained a firm, white thus viable
embryo or a soft, gray nonviable one.
Seeds of D. anglica were collected on 19 August
1997 in Gästrikland, Sweden (60°55’ N), and on 1
September 1997 in Östergötland, Sweden (58°20’ N),
and dried for 2 and 3 d, respectively, before initiation
of experiments. Seeds were placed in 55-mm diameter
Petri dishes on two sheets of Munktell 1003 filter
paper moistened with de-ionized water; three replications
of fifty seeds each were used for each test
condition. All dishes were sealed with a strip of
parafilm to reduce water loss, and darkness was
maintained by wrapping the dishes with two layers of
aluminum foil. Seeds from both collections were
stratified in darkness at a constant temperature of 1 °C
for 12 weeks. After 12 weeks of stratification treatment,
seeds from each collection were tested for
germination in light (12 h of ca. 40 µmol•m–2•s–1,
400–700 nm cool white fluorescent light each day) and
in continuous darkness at 12/12 h daily alternating
temperature regimes of 15/5, 20/10 and 25/15 °C for 2
weeks. As a control, seeds from each collection were
placed in light and in darkness at 15/5, 20/10 and
25/15 °C on the same day the cold stratification
treatments were initiated. Control seeds incubated in
light were checked for germination at 2-week intervals
2 C.C. Baskin et al. / Acta Oecol. 22 (2001) 1–8
for 14 weeks. On the other hand, control seeds
incubated in darkness were checked after 2 weeks and
discarded, since they had been exposed to light while
germination was being checked.
2.2. Stratification of seeds collected in 1998
and in 1999
Seeds were sown on Whatman No. 1 filter paper
moistened with distilled water in 55-mm Petri dishes;
three replications of fifty seeds each were used for
each test condition. Tests were conducted in incubators
at a 14-h daily photoperiod (ca. 40 µmol•m–2•s–1,
400–700 nm cool white fluorescent light) and in
continuous darkness at alternating (12/12 h) temperature
regimes of 15/6, 20/10 and 25/15 °C. At each
alternating temperature regime, the photoperiod extended
from 1 h before to 1 h after the daily high
temperature period. All dishes of seeds were wrapped
with plastic film to reduce loss of water, and those to
be stratified or tested in darkness were wrapped
additionally with two layers of aluminum foil.
Seeds of D. anglica were collected on 18 September
1998 (same site in Östergötland as in 1997) and dried
at room temperatures until 6 October 1998. On this
date, seeds were sown on moist filter paper in 36 Petri
dishes and placed in light (12 h daily photoperiod,
40 µmol•m–2•s–1) at a 12/12 h daily alternating temperature
regimes of 5(day)/1(night) °C for stratification
treatments of 2, 6, 12 and 18 weeks in duration.
After the various periods of stratification, seeds were
transferred from 5/1 to 15/6, 20/10 and 25/15 °C for a
4-week germination test in light. Germination of seeds
tested in light was checked after 2 and 4 weeks. Also,
on 6 October, nine dishes of seeds were placed in
darkness at 5/1 °C. After 18 weeks of stratification,
seeds were transferred from 5/1 to 15/6, 20/10 and
25/15 °C for a 4-week germination test in darkness. As
a control, fresh seeds were placed in light and in
darkness at 15/6, 20/10 and 25/15 °C on 6 October
1998. Control seeds in light were checked at 2-week
intervals for 22 weeks, while those in darkness were
checked after 4 weeks and discarded, because they had
been exposed to light when germination was checked.
Seeds of D. anglica were collected on 3 September
1999 (same site in Östergötland as in 1997 and 1998)
and dried at room temperatures until 20 September
1999. On this date, seeds were sown on moist filter
paper in 72 Petri dishes and placed in light at 5/1 °C
for stratification treatments of 2, 4, 6, 8, 10, 12, 14 and
16 weeks in duration. After the various periods of
stratification, seeds were transferred from 5/1 to 15/6,
20/10 and 25/15 °C for a 4-week germination test in
light. Germination was checked after 2 and 4 weeks.
Also, on 20 September, eighteen dishes of seeds were
placed in light and 18 in darkness at 5/1 °C. After 18
weeks of stratification, seeds stratified in light and in
darkness were tested in both light and in darkness at
15/6, 20/10 and 25/15 °C for 4 weeks. As a control,
fresh seeds were placed in light and in darkness at
15/6, 20/10 and 25/15 °C on 20 September 1999.
Control seeds in light were checked at 2-week intervals
for 22 weeks, while those in darkness were
checked after 4 weeks and discarded.
2.3. Statistical analyses
A two-way analysis of variance (ANOVA) and
comparison of means by protected least significant
difference tests (PLSDs, P 0.05) were based on the
arcsine-transformed proportion of seeds germinating
in each dish after 4 weeks of incubation in light for
seeds collected on 18 September 1998 and on 3
September 1999. Also, the same analyses were done
on 1999 seeds stratified in darkness and in light for 18
weeks and then incubated in both light and darkness at
the three temperature regimes for 4 weeks.
2.4. Germination phenology
Seeds of D. anglica collected on 18 September 1998
in Östergötland were used in this experiment. Three
replications of 200 seeds each were sown, on 22
September 1998, on the surface of commercial peat
potting soil in pots (90 mm diameter, 70 mm height)
and placed outdoors, 35 km WSW of the collection
site. Pots were placed under a table on the north side of
a greenhouse, i.e. they were exposed to natural temperature
conditions but protected from direct rainfall
and direct sunlight. Temperature was recorded approximately
every second hour in a parallel pot at 10
mm depth with a TINYTALK-TEMP logger (Orion
components Ltd., Chichester, England). The pots were
placed in a tray, and the soil was kept constantly moist
by adding water to this tray when needed. The pots
were inspected for seedlings weekly or biweekly. The
experiment was terminated after 14 months.
3. RESULTS
3.1. Stratification of seeds collected in 1997
None of the fresh (non-stratified) seeds of D. anglica
from Östergötland germinated after 2 weeks of
incubation in either light or darkness, and after 14
weeks in light, one (0.7 %) seed had germinated at
15/5 and one (0.7 %) at 25/15 °C. Seeds given 12
weeks stratification at 1 °C and then incubated in light
for 2 weeks germinated to 0, 0 and 13 % at 15/5, 20/10
and 25/15 °C, respectively, while none of the seeds
stratified and incubated in darkness germinated. No
fresh seeds of D. anglica from Gästrikland germinated
C.C. Baskin et al. / Acta Oecol. 22 (2001) 1–8 3
in darkness or in light after 2 and 14 weeks incubation,
respectively, and seeds stratified in darkness at 1 °C
failed to germinate in light or in darkness at 15/5,
20/10 and 25/15 °C. As verified by data from subsequent
studies on seeds from both sites that had been
stored dry for 7–13 months in a freezer, 95 and 80 %
of the seeds from Gästrikland and Östergötland, respectively,
were viable.
3.2. Stratification of seeds collected in 1998
Fresh (0 weeks of stratification) seeds of D. anglica
did not germinate in light or in darkness after 4 weeks
of incubation at the three alternating temperature
regimes, and after 22 weeks of incubation in light 0, 0
and 8 % of the seeds had germinated at 15/6, 20/10 and
25/15 °C, respectively (table I). Stratification signifi-
cantly increased germination (F4 = 178.86; P 
0.0001). There also was significantly more germination
at higher temperatures (F2 = 397.49; P 0.0001),
as well as a significant stratification temperature
interaction effect (F8 = 36.41; P 0.0001). With an
increase in the length of the stratification period (1)
germination percentages of seeds incubated in light
increased, and (2) the minimum temperature at which
seeds would germinate decreased (table I). No seeds
germinated in darkness.
3.3. Stratification of seeds collected in 1999
Non-stratified seeds of D. anglica germinated to 0,
3 and 6 % in light at 15/6, 20/10 and 25/15 °C,
respectively, after 4 weeks of incubation (figure 1) and
to 2, 7 and 15 %, respectively, after 22 weeks of
imbibition. After 4 weeks of incubation, there was no
germination of non-stratified seeds in darkness at any
temperature regime. Stratification significantly increased
germination only in light (F9 = 99.55;
P 0.0001). There also was significantly more germination
at higher temperatures (F2 = 329.19;
P 0.0001), as well as a significant stratification 
temperature interaction effect (F18 = 9.18; P 0.0001).
As was true for the 1998 seeds, germination percentages
of seeds incubated in light increased and the
minimum temperature at which seeds would germinate
decreased with an increase in length of the stratification
period (figure 1). Light was required for germination
of stratified seeds (table II). Further, seeds
stratified and incubated in light germinated to signifi-
cantly higher percentages than those stratified in darkness
and incubated in light (light-dark treatment,
F3 = 183.89, P 0.0001; temperature regime,
F2 = 10.78, P 0.0001; treatment temperature effect,
F6 = 7.96, P 0.0001).
Table I. Germination percentages (mean SE) of Drosera anglica seeds incubated at three alternating temperature regimes following
stratification at 5/1 °C for 0 to 18 weeksa. Seeds were collected in 1998. ANOVA and PLSDs were calculated only for germination data after 4
weeks of incubation in light.
Stratification time Incubation time Test temperature regimes (°C)
(week) (week) 15/6 20/10 25/15
Incubation in light
0 2 0 0 0
0 4 0bC 0aB 0aA
0 22 0 0 8 2
2 2 0 0 0
2 4 0bA 18 3bB 92 4bC
6 2 0 0 62 6
6 4 0bA 51 12cB 76 4cB
12 2 0 15 ±4 96 1
12 4 0bA 84 3dB 100dC
18 2 0 0 97 3
18 4 22 3aA 100eB 100dB
Incubation in darkness
0 4 0 0 0
18 4 0 0 0
a Numbers in a column followed by the same lower case letter are not significantly different from each other, and those in a row followed by the
same upper case letter are not significantly different from each other.
4 C.C. Baskin et al. / Acta Oecol. 22 (2001) 1–8
3.4. Germination phenology
No seedlings emerged during the autumn or spring
after sowing. In the succeeding summer, however,
seven (1.2 %) seedlings were recorded. The first
seedling was recorded on 24 June 1999 and the last on
12 August, i.e. 9 months after sowing. By 24 June,
daily minimum temperatures exceeded 9 °C, and most
maximum daily temperatures were 20 °C. Mean
daily maximum and minimum temperatures from 20
June to 10 August were 22 and 14 °C, respectively.
Average temperature recorded from 20 June to 10
August was 17 °C, while daily averages were between
13 and 22 °C.
5. DISCUSSION
Although 80 and 95 % of the D. anglica seeds
collected in 1997 in Östergötland and in Gästrikland,
Sweden, respectively, were viable (based on germination
percentages from subsequent studies; see section
3.1), maximum germination of stratified seeds was
only 13 %. There are various possible reasons why
high germination percentages were not obtained. (1)
The 2-week incubation period was not long enough to
allow seeds to germinate. (2) Light was required
during both the stratification and incubation periods to
promote germination. (3) A 12-week period of strati-
fication was not long enough to break dormancy. (4)
The stratification temperature was too low for dormancy
break to occur.
Seeds collected in 1999 and given 4 weeks of
stratification in light germinated to 85 % during 2
weeks of incubation in light at 25/15 °C (figure 1).
Also, 1999 seeds stratified in darkness for 18 weeks
germinated to 72 % after 2 weeks of incubation in light
at 25/15 °C (table II). Thus, of the four explanations
for low germination percentages of the 1997 seeds, the
12-week period of stratification and the 2-week period
of incubation should have been long enough, and light
was not generally needed during stratification. Strati-
fication treatments of 1998 and 1999 seeds were not
conducted at a constant 1 °C, as was the case for 1997
seeds. A light tube (controlled by a time clock) placed
inside a refrigerator increased the temperature from 1
to 5 °C during the period of illumination. Consequently,
we used a 12/12 h daily temperature regime of
5/1 °C for stratification treatments. The effective
temperature range for cold stratification of seeds is
0–10 °C [11, 30], with 5 °C being optimal for seeds of
many species that require a moist low-temperature
Figure 1. Germination percentages (mean, +1 SE if ≥5 %) of
Drosera anglica seeds incubated in light at 15/6 (a), 20/10 (b) and
25/15 °C (c) for 2 (dark) and 4 (open) weeks following 0 to 18 weeks
of stratification in light at 5/1 °C. Seeds were collected in 1999.
ANOVA and PLSDs are based on germination after 4 weeks of
incubation at test temperature regimes. Germination means after a
given period of stratification indicated by the same lower case letter
are not significantly different from each other, and those for a given
temperature followed by the same upper case letter are not signifi-
cantly different from each other.
Table II. Effect of 18 weeks of stratification at 5/1 °C in light and in
darkness on germination percentages (mean SE) of Drosera anglica
seeds incubated in both light and in darkness for 4 weeks at three
alternating temperature regimesa. Seeds were collected in 1999.
ANOVA and PLSDs were calculated only for germination data after
4 weeks of incubation.
Stratification
in
Incubation
time
Test temperature regimes ( °C)
(week) 15/6 20/10 25/15
Incubation in light
Light 2 23 ±5 812 100
Light 4 87 2cA 95 2cAB 100cB
Dark 2 0 1 ±1 728
Dark 4 6 1bA 82 1bB 91 3bB
Incubation in darkness
Light 4 0aA 0aA 0aA
Dark 4 0aA 0aA 0aA
a Numbers in a column followed by the same lower case letter are not
significantly different from each other, and those in a row followed by
the same upper case letter are not significantly different from each
other.
C.C. Baskin et al. / Acta Oecol. 22 (2001) 1–8 5
treatment for dormancy break [30]. Thus, a daily
temperature regime of 5 and 1 °C was well within the
range of temperatures known to be suitable for cold
stratification. As evidenced by 100 % germination in
some of the tests (tables I, II, figure 1), the 5/1 °C
regime was favorable for dormancy break in seeds of
D. anglica. It appears that a constant temperature of
1 °C may have been too low for dormancy break of the
1997 seeds of D. anglica, or that dormancy break may
require an alternating temperature regime rather than a
constant temperature (e.g. [15]). The high germination
percentage (ca. 90) that Crowder et al. [12] obtained
after seeds of D. anglica had been stratified for 8
weeks (presumably in darkness) at a constant temperature
of 10 °C suggests that the daily high temperature
of 5 °C used in our stratification studies rather than the
daily alternating temperature regime of 5 and 1 °C per
se may have promoted dormancy break in the 1998
and 1999 seeds.
As mentioned previously, seeds of D. anglica were
collected from the same site in Östergötland in 1997,
1998 and 1999. None of the freshly-collected 1997 and
1998 seeds germinated after 4 weeks of incubation in
light at 15/5(6), 20/10 or 25/15 °C; however, 0, 3 and
5 % of the fresh 1999 seeds germinated at 15/6, 20/10
and 25/15 °C, respectively (figure 1). Thus, while none
of the freshly-collected 1997 or 1998 seeds germinated
at any condition at which they were tested, some of the
1999 seeds germinated in light at 20/10 and 25/15 °C;
they were conditionally dormant. Another indication
that the 1999 seeds were less dormant than the 1998
seeds is that a shorter period of stratification was
required to obtain high germination percentages in the
1999 than in the 1998 seeds. Whereas the 1998 seeds
germinated to only 22 % in light at 15/6 °C after 18
weeks of stratification in light (table I), the 1999 seeds
germinated to 87 % (figure 1).
Year-to-year variation in germination of seeds produced
at the same site has been attributed to differences
in environmental conditions during the time
seeds were maturing on the mother plant [5, 8]. Data
recorded by the Swedish Meteorological and Hydrological
Institute in Norrköping (58°58’ N, 16°15’ E),
about 10 km south of the Östergötland D. anglica
collection site reveal that mean daily maximum and
minimum temperatures were 18.6 and 10.5 °C, respectively,
for August 1998 and 21.5 and 10.3 °C, respectively,
for August 1999 [31, 32]. Further, the average
temperature in August 1998 and 1999 was 14.3 and
16.0 °C, respectively, and the average August temperature
for 1961–1990 in Norrköping was 15.7 °C [31,
32]. Since seeds of D. anglica were collected in early
September, temperature data for August provide information
on the conditions under which the seeds
developed. Thus, the 1998 D. anglica seeds, which
were more dormant than the 1999 seeds, matured at
lower temperatures than the 1999 seeds. The ecological
implication of these results is that with the same
amount of cold stratification (table I, figure 1) seeds
produced in warm summers gain the ability to germinate
to higher percentages at 15/6 °C than those
produced in cool summers. Thus, seeds produced in
warm summers are more likely to germinate the
following May when daily temperature regimes are
about 15/6 °C, while germination of most seeds
produced in cool summers would be delayed until
June. Seeds used in the germination phenology study
were produced in 1998 (cool summer), and their
period of germination was from 24 June to 12 August
1999. Seeds of Arenaria patula Michx. var. robusta
(Steyerm.) Maguire that matured at relatively low
temperatures (mean daily maximum and minimum
temperatures 30 d prior to seed maturation were 26.4
and 10.4 °C, respectively) were also more dormant
than those matured under relatively high temperatures
(28.9 and 12.1 °C, respectively) [5].
The 1997 seeds were tested 3 d after collection, and
the 1998 and 1999 seeds were tested 18 and 17 d,
respectively, after collection. Thus, some afterripening
(dormancy break) could have occurred in the 1998 and
1999 seeds prior to the time germination studies were
initiated. However, since 1998 and 1999 seeds were
stored at room temperatures for about the same period
of time, the higher germination in the initial germination
test of 1999 than in that of the 1998 seeds can not
be attributed to length of the afterripening period prior
to the time germination studies were started.
The 1998 and 1999 seeds tested in light at the
alternating temperature regimes after various periods
of stratification exhibited a decrease in the minimum
temperature at which seeds would germinate with an
increase in the stratification period (table I, figure 1).
This kind of change in the temperature requirements
for germination of seeds as they come out of dormancy
was described by Vegis [33, 34], and Baskin et al. [4]
called it a Type 2 response pattern. A Type 2 pattern
has been found in many summer annuals and perennials
in various plant families, including the Amaranthaceae,
Asclepiadaceae, Asteraceae, Boraginaceae,
Brassicaceae, Campanulaceae, Caryophyllaceae, Chenopodiaceae,
Cyperaceae, Euphorbiaceae, Lamiaceae,
Poaceae, Polygonaceae, Portulacaceae, Rosaceae,
Scrophulariaceae and Solanaceae [1]. The presence of
a Type 2 pattern in D. anglica seeds is the first report
6 C.C. Baskin et al. / Acta Oecol. 22 (2001) 1–8
of this response pattern in Droseraceae. Seeds of most
species known to have a Type 2 response pattern are
from the northern temperate region and require cold
stratification for dormancy break; nevertheless, those
of a few species in this region have a Type 2 response
and come out of dormancy during summer. Since
Drosera ranges from temperate to tropical regions of
the world, it would be interesting to know if Type 2 is
found in seeds of Drosera from throughout its range or
only in Drosera species from temperate regions, where
winter temperatures are suitable for cold stratification.
Dormancy break in seeds of D. anglica occurs
during winter when environmental conditions in the
habitat are not favorable for seedling establishment.
However, a lowering of the minimum temperature for
germination during cold stratification means germination
can begin when temperatures are quite low in
spring. Consequently, seedlings from springgerminating
seeds would have the maximum period of
time for growth before temperatures drop below freezing
in autumn. None of the D. anglica seeds germinated
during the 18-week period in which they were
being stratified in light at 5/1 °C, and germination of
seeds stratified in light and incubated in light at
15/6 °C was slow (figure 1). Seeds stratified in light for
18 weeks germinated to 23 and 87 % after 2 and 4
weeks, respectively, in light at 15/6 °C. Thus, although
seeds eventually may be able to germinate at simulated
May field temperatures, temperatures in the field could
increase above this level before seeds have enough
time to germinate. In the germination phenology study,
mean daily maximum and minimum temperatures for
April 1999 were 10.8 and 4.5 °C, respectively; for
May, 15.1 and 5.7 °C; and for June, 20.3 and 11.7 °C.
Thus, little or no germination could be expected to
occur until late May or June. In fact, the first seedling
was not recorded until 24 June, by which time daily
maximum and minimum temperatures were about 20
and 9 °C, respectively.
Dry seeds of D. angelica are ca. 1.6 mm in length
and easily fit into Martin’s [23] category of dwarf
seeds, which are 0.3 to 2.0 mm in length. Since many
dwarf seeds require light for germination (e.g. [2, 9]),
it is not surprising that those of D. anglica also have
this requirement. However, seeds of D. anglica not
only required light for germination, but light had to be
given after dormancy break had occurred (table II).
That is, exposure to light during the cold stratification
period did not promote germination in darkness at
15/6, 20/10 or 25/15 °C. In contrast, the light requirement
for germination in some species with seeds
greater than 2 mm in length can be fulfilled during
cold stratification (e.g. [3, 6]). Seeds of D. anglica
stratified in darkness and incubated in light germinated
at a slower rate and to a significantly lower percentage
than those stratified in light and incubated in light
(table II). The light requirement for germination may
explain why so few seeds germinated in the phenology
study. Frost-heaving of the soil in the pots may have
resulted in many of the seeds becoming covered by
soil particles; consequently, darkness would have prevented
them from germinating. It seems reasonable
that the dwarf, light-requiring seeds of D. anglica
would form a soil seed bank, but to our knowledge this
has not been demonstrated. However, persistent soil
seed banks have been reported for D. intermedia [20]
and D. rotundifolia [24, 28].
Drosera anglica is a perennial that reproduces
mostly by seeds, but vegetative reproduction by axillary
and leaf buds has been observed [12]. Sexual
reproduction requires that seed germination be followed
by successful seedling establishment and eventual
seed production by plants. Seeds of D. anglica are
dormant at maturity and require cold stratification for
dormancy break. Length of the stratification period
required for a high percentage of the seeds to germinate
depends on (1) whether seeds are exposed to light
during stratification and during the subsequent incubation
period, and (2) the temperature during incubation
(tables I, II, figure 1). Also, the year in which
seeds mature may influence the amount of stratification
needed to promote germination, especially at early
spring habitat temperatures.
REFERENCES
[1] Baskin C.C., Baskin J.M., Germination ecophysiology of
herbaceous plant species in a temperate region, Am. J. Bot. 75
(1988) 286–305.
[2] Baskin C.C., Baskin J.M., Chester E.W., Effect of seasonal
temperature changes on germination responses of buried seeds
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with 12 other summer annuals native to eastern North
America, Plant Species Biol. 13 (1998) 77–84.
[3] Baskin C.C., Baskin J.M., Hoffman G.R., Seed dormancy in
the prairie forb Echinacea angustifolia var. angustifolia
(Asteraceae): Afterripening pattern during cold stratification,
Int. J. Plant Sci. 153 (1992) 239–243.
[4] Baskin C.C., Baskin J.M., Van Auken O.W., Germination
response patterns during dormancy loss in achenes of six
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(1994) 113–117.
[5] Baskin J.M., Baskin C.C., Year-to-year variation in the germination
of freshly-harvested seeds of Arenaria patula var.
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106–108.
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[6] Baskin J.M., Baskin C.C., Germination of common milkweed
(Asclepias syriaca L.) seeds, Bull. Torrey Bot. Club 104
(1977) 167–170.
[7] Baskin J.M., Baskin C.C., The annual dormancy cycle in
buried weed seeds: A continuum, BioScience 35 (1985)
492–498.
[8] Baskin J.M., Baskin C.C., Variation in the annual dormancy
cycle in buried seeds of the weedy winter annual Viola
arvensis, Weed Res. 35 (1995) 353–362.
[9] Baskin J.M., Baskin C.C., Spooner D.M., Role of temperature,
light and date seeds were exhumed from soil on germination
of four wetland perennials, Aquat. Bot. 35 (1989) 387–394.
[10] Conran J.G., Jaudzems V.G., Hallam N.D., Droseraceae germination
patterns and their taxonomic significance, Bot.
J. Linn. Soc. 123 (1997) 211–223.
[11] Crocker W., Barton L.V., Physiology of Seeds, Chronica
Botanica, Waltham, 1957.
[12] Crowder A.A., Pearson M.C., Grubb P.J., Langlois P.H.,
Biological flora of the British Isles. No. 167. Drosera L.,
J. Ecol. 78 (1990) 233–267.
[13] Fernald M.L., Gray’s Manual of Botany, 8th ed., American
Book Co., New York, 1950.
[14] Ferreira D.P., Small J.G.C., Preliminary studies on seed
germination of Drosera aliciae Hamet, J. S. Afr. Bot. 40
(1974) 65–73.
[15] Flemion F., Physiological and chemical studies of afterripening
of Rhodotypos kerrioides seeds, Contrib. Boyce
Thompson Inst. 5 (1933) 143–159.
[16] Gleason H.A., Cronquist A., Manual of Vascular Plants of
Northeastern United States and Adjacent Canada, 2nd ed., The
New York Botanical Garden, Bronx, 1991.
[17] Good R., The Geography of the Flowering Plants, 4th ed.,
Longman Group Ltd, London, 1974.
[18] Grime J.P., Mason G., Curtis A.V., Rodman J., Band S.R.,
Mowforth M.A.G., Neal A.M., Shaw S., A comparative study
of germination characteristics in a local flora, J. Ecol. 69
(1981) 1017–1059.
[19] Hultén E., Fries M., Atlas of North European Vascular Plants
North of the Tropic of Cancer, Koeltz Scientific Books,
Königstein, 1986.
[20] Keddy P.A., Reznicek A.A., The role of seed banks in the
persistence of Ontario’s coastal plain flora, Am. J. Bot. 69
(1982) 13–22.
[21] Kinzel W., Lichtkeimung. Erläuterungen und Ergänzungen,
Ber. Deutsch. Bot. Ges. 27 (1909) 536–545.
[22] Mabberley D.J., The Plant-Book, 2nd ed., Cambridge University
Press, Cambridge, 1997.
[23] Martin A.C., The comparative internal morphology of seeds,
Am. Midl. Nat. 36 (1946) 513–660.
[24] McGraw J.B., Seed-bank properties of an Appalachian sphagnum
bog and a model of the depth distribution of viable seeds,
Can. J. Bot. 65 (1987) 2028–2035.
[25] Müller M.J., Selected Climatic Data for a Global Set of
Standard Stations for Vegetation Science, DrW. Junk Publishers,
The Hague, 1982.
[26] Ohwi J., Flora of Japan, Smithsonian Institution, Washington,
DC, 1965.
[27] Pietropaola J., Pietropaola P., Carnivorous Plants of theWorld,
Timber Press, Portland, 1986.
[28] Poschlod P., Diaspore rain and diaspore bank in raised bogs
and implications for the restoration of peat-mined sites, in:
Wheeler B.D., Shaw S.C., Fojt W.J., Robertson R.A. (Eds.),
Restoration of Temperate Wetlands, John Wiley and Sons Ltd,
Chichester, 1995, pp. 471–494.
[29] Redbo-Torstensson P., The demographic consequences of
nitrogen fertilization of a population of sundew, Drosera
rotundifolia, Acta Bot. Neerl. 43 (1994) 175–188.
[30] Stokes P., Temperature and seed dormancy, in: Ruhland W.
(Ed.), Encyclopedia of Plant Physiology, vol. 15/2, Springer-
Verlag, Berlin, Heidelberg and New York, 1965, pp. 746–803.
[31] Swedish Meteorological and Hydrological Institute, Väder
och vattern. September. Norrköping, Sweden (1998) (August
data in the September issue).
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och vattern. September. Norrköping, Sweden (1999) (August
data in the September issue).
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dormancy, in: Evans L.T. (Ed.), Environmental Control of
Plant Growth, Academic Press, New York, 1963, pp. 265–287.
[34] Vegis A., Dormancy in higher plants, Annu. Rev. Plant
Physiol. 15 (1964) 185–215.
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8 C.C. Baskin et al. / Acta Oecol. 22 (2001) 1–8

[West]

Byblis liniflora peut être repiquée lorsqu'elle est très jeune (2 - 4 feuilles).

[dydylamouche baveuse]

tu ne fais pas beaucoup d'effort
tu ne traduits jamais tes textes
il faut savoir se mettre à la portée de tous...

[le grand lapin]

hello,

dydylamouche baveuse :
je suppose que tu parles de moi ?

tu ne fais pas beaucoup d'effort

si si....je suis connecté deux heures par jour minimum, tous les jours, depuis l'ouverture du forum pour répondre à vos questions...ça fait bcp d'heures....
le document cité a été récupéré auprès d'un collègue scientifique qui a accès à une base de donnée payante, il est passé du PDF au format Word pour être lisible par tous, et a été transféré sur le forum.....
d'autre part, là il est 1h30 du matin, je suis rentré du boulot ce soir, demain matin je bosse, et pourtant je vous répond....et je me suis quand même occupé de ma p'tite famille....donc si si, je fais bcp d'efforts

tu ne traduits jamais tes textes

j'estime ne pas en avoir besoin....si une personne n'arrive pas à traduire, qu'elle le dise, je le ferais, ou du moins, je lui donnerais les grandes lignes (d'ailleurs, c'est dans la première partie de ma réponse....)
....sinon, il existe des traducteurs automatiques : nous sommes en l'an 2005, vivons avec notre temps !
d'autre part, lorsque je vous lis, je constate que le niveau social et culturel de notre population visiteuse du forum est assez élevée, il me semble donc normal de penser que l'on trouve parmi nous des gens capables de lire l'anglais assez courament (d'autre part, un récent sondage disait que plus de 50% des français déclarent maîtriser au moins une langue étrangère...si on sait que le panel des interrogés inclut des gens incultes, je te laisse pondérer le chiffre et le passer à la moulinette....on devrait donc obtenir un pourcentage assez élevé de gens cultivés maîtrisant très bien une seconde langue....ensuite, comme l'anglais est tout de même la langue la plus utilisée.....on re-mouline.....)

il faut savoir se mettre à la portée de tous...

je fais très bien mon boulot, et j'y pense à chaque message que je rédige.
si tu connais un peu le forum, tu t'appercevra que je suis l'un des rares qui a rédigé des fiches informatives, destinées à tous, justement (par exemple, voir la fiche "comment semer des graines", tout à fait adaptée à la question de TheFab...)
autre notion, j'ai monté une section "débutants" dans ma banque de graines, action qui permet aux débutants de débuter une culture de plantes de façon simple : je met dons à la portée de tous de quoi entrer ds le monde des plantes carnivores.
donc si si, je me met toujours à la portée de tous, c'est une idée sous-jacente à tout mon discours, et à toutes mes actions....

je ne te ferais, pas l'afront de mettre des smillies partout, mais l'idée y est....je ne suis pas rancunier, je renseigne, c'est pas pareil....

[Sweet Tom]

Salut,

j'ai un Byblis Liniflora depuis cet été, et j'ai récolté pas mal de graines (j'en récupère d'ailleurs encore tous les quelques jours).
Par curiosité j'ai posé une graine dans mon pot (18x18) qui contient Adelae et Prolifera, et qui est situé juste sous deux neons 2x55W. Les deux Drosera sont protégés de la lumière par une feuille de papier, sauf dans le coin ou j'ai posé la graine.

Ca a germé en quelques jours !

Ca confirme ce que j'ai pu lire sur la germination de cette espece, température élevée (25-30% dans mon cas) et beaucoup beaucoup de lumière.

[le grand lapin]

hello,

et beaucoup beaucoup de lumière.

voilà un élément intéressant, dans la mesure où je vais détourner cette phrase à mon usage : les allemands parlent de Lichtkeimer, littéralement plante germant à la lumière.....c'est le cas de bcp de plantes.....
le language allemand a celà d'intéressant qu'il permet de facilement faire passer pas mal de notions sans qu'il soit nécessaire d'avoir un dictionnaire, ou plutôt, il est structuré de façon à pouvoir associer des mots tout en restant compréhensible par tlm, à l'opposé des langues latines qui utilisent des mots spécialisés pour chaque notion et ne sont accessibles qu'à ceux qui ont une culture "étendue", ou un dictionnaire.....notion qui manque dans notre cas : il n'y a pas de mot pour désigner un Lichtkeimer en français, or si ce mot existait, cette notion serait bien plus répandue parmi nous.....

ps : 2h30 je suis tjrs là, à 6h00 je suis debout
ENERGY !!!