In diesem Z u s a m m e n h a n g sei kurz auf eine normal
Heteromorphosen
zählen. Die Besonderheit
besteht
ausgebildete männliche Z y g a e n e (Abb. 11) hingewie-
darin, daß die 6-Fleck-Zeichnung des Vorderflügels
sen, die ebenfalls zur ssp. modesta
auf d e m rechten Hinterflügel entsprechend der Hin-
B g f f . gehört und
von mir aus einer R a u p e g e z o g e n wurde. D a beide
terflügel-Aderung
Vorder- und Hinterflügel, nebst der A d e r u n g typisch
teilung w a r also der Aderverlauf
ausgebildet sind, können wir dieses Tier nicht zu den
Aderzeichnung).
ausgeprägt ist. Bei der
Fleckver-
m a ß g e b e n d (typische
NOTIZEN
A critical experiment on B ü n n i n g
of Photoperiodism
s theory
By D. J. C a r r
Max-Planck-Institut für Biologie, Abt.
Tübingen
Melchers,
(Z. Naturforschg. 7 b, 570—571 [1952]; eingeg. am 2. Okt. 1952)
The theory of photoperiodism propounded by B ü n n i n g , which assumes the existence in plants of an endogenous component of diurnal rhythms of activity is the
only one of the many theories which have so far been put
forward which explains the- effects of daylength on both
long-day and short-day plants in a uniform manner.
Although this theory has had notable successes in
predicting and accounting for the various and complex
effects so far discovered in photoperiodic experiments, it
has always been possible to explain these effects without
assuming the existence of an endogenous rhythm in
plants. C 1 a e s and L a n g 1 , however, performed experiments on the long-day plant Hyoscyamus
niger in
which they used 48-hour cycles consisting of a 7-hour
main light period and 41 hours of darkness. At intervals
of 1 hour successive experimental groups of plants
received another period of light lasting two hours, interrupting the long dark period. It was found that the
flower-inducing effect of this light break readied optimal
Such an experiment was carried out this summer at
the Max-Planck-Institut für Biologie, Abt. M e l c h e r s ,
in Tübingen 3 using the short-day plant Kalanchoe
blossfeldiana.
Seeds kindly supplied by Prof. H a r d e r were
sown on 1 7 / 4 / 1 9 5 2 under long-day (c. 18 hours of light
per day) conditions and the plants were kept continuously
under these conditions up to the time of the experiment,
when they had formed 7 pairs of expanded leaves. The
plants were distributed into 21 groups of 9 plants each.
One group (Gr. 21) was maintained under long-day conditions. Beginning on 5 / 8 the other groups were exposed
to day-light in the greenhouse from 7.30 a.m. to 7.0 p.m.
Kalanchoe blossfeldiana
Effect of light break in 72-hr. cycle
No. ofplants
flowering
or av. number
of flowers
per plant
19
9
12
15
18 21 21
27
30 33 36
39
12 15
values at two points, one near the beginning and one
near the end of the dark period. No flower-inducing effect
was found when the light-break occurred near the middle
of the dark period, in striking contrast to the light-break
effect with 24-hour cycles. This result can either be
explained in terms of B ü n n i n g s theory or on an alternative basis suggested by the authors. They assumed that
a light-break may interact with a main light period when
the interval between them is not too great, and that it
is indifferent whether the light break precedes or follows
the main light period. Similar results were obtained by
C a r r 2 with the short-day plants Xanthium
saccharatum
and Perilla ocymoides,
but here the light effect at the two
optima is inhibitory of flowering and light at the middle
of the long dark period stimulates, or at least is not
inhibitory to flowering. Both C 1 a e s and L a n g , and
C a r r concluded that a critical experiment discriminating
between the two possible explanations of this phenomenon
could be made using a 72-hour cycle with a short main
light period as before, but extending the dark period by
another 24 hours. On B ü n n i n g s theory light breaks
during such a very long dark period should show 3 optima
in their promoting effect on flowering in long-day plants
and inhibiting effect in short-day plants. On the alternative explanation of C 1 a e s and L a n g only 2 optima,
situated near the beginning and near the end of the dark
period would be expected.
18 51 51
Hours of the dark period
Hatched columns - Mean No. of flowers per plant
Shaded »
- No. ofplants flowering per group
57 60
—
1 H. C l a e s
u. A. L a n g , Z. Naturforschg. 2 b, 56
[1947],
2 D. J. C a r r ,
Physiol. Plantarum 5, 78—84 [1952].
3 The author wishes to express his gratitude to Prof.
M e l c h e r s for placing the facilities of his Institute at
his disposal and to the M a x - P l a n c k - G e s e l l s c h a f t
for providing financially for his stay in Tübingen. He also
wishes to thank the staff and other workers at the Institute
for their invaluable co-operation in carrying out the experimental treatments.
Unauthenticated
Download Date | 7/31/17 4:25 PM
and then removed to dark cabinets kept at 21° C and a
relative humidity of 90%. Every 3 hours thereafter a
group of plants was removed from the dark cabinet and
exposed for 1 hour to light of 1000 Lux intensity (at plant
height) from warm-type fluorescent lamps (Osram HNG) 4 ,
at a controlled temperature of 21° C and atmospheric
humidity of 90%. The plants were then returned to the
dark cabinet for the rest of the 60,5-hour-long dark period.
It was thus possible to test the effectiveness of the lightbreak in inhibiting or promoting flowering at successive
intervals of 3 hours during the prolonged dark period.
After 9 cycles of this treatment the plants were returned
on 1/9 to longday conditions in the greenhouse. About
two weeks after the end of the experimental treatment
certain groups of plants were seen to be developing inflorescences. The plants are still under observation but the
results are such that in view of the importance of this
experiment it has been decided to publish an interim
report.
On 27/9 the macroscopic flower buds on each plant
were counted and the heights of the plants measured.
The data for the number of plants flowering, the mean
number of flowers per plant and the mean plant height
in each group are presented in the diagram.
The results show clearly that flowering was induced
only in groups 5—8 and in groups 14 and 15; that the
degree of flowering as measured by the mean number of
flowers per plant reaches an optimal value in groups 6
and 7 and in group 14; and that the mean heights of the
plants show 3 clear optima, in groups 2, groups 11—13
and group 18. Thus whether we regard the effect of the
light break on flowering or on vegetative growth the
results agree closely with expectations from B i i n n i n g s
theory and not with those from C 1 a e s and L a n g ' s
suggestions. This experiment constitutes a critical test of
the theory of B ü n n i n g which must therefore be
regarded as finally and decisively proved. It is desirable
however that the experiment should be repeated with
other short-day plants and with long-day plants and it
is hoped that this will be done in the near future.
4 The author and the Max-Plandc-Institut f. Biologie
thank O s r a m G. m. b. H., K. G., for supplying the
fluorescence lamps.
Berichtigung
Von O. R e n n e r und M. B r a u n
Botanisches Institut der Universität München
(Z. Naturforschg. 7 b, 571 [1952]; eingeg. am 11. Okt. 1952)
In der Notiz „Das Scheitelwachstum des Sprosses von
Epilobium" 1 sollte hinter der Überschrift „Induktion der
Blattstellung durch die Keimblätter" ein Fragezeichen
stehen.
Weitere Beobachtung von Epilobium
trigonum hat
wahrscheinlich gemacht, daß der Übergang von dekussierter zu mehrzählig-wirteliger Blattstellung hier wie in anderen Fällen ein Erstarkungsphänomen darstellt, bei dem
primär der Vegetationspunkt in seiner Masse und in seiner
Symmetrie verändert wird.
i O. R e n n e r u. M. B r a u n ,
422 [1952],
Z. Naturforschg. 7b,
Die Erzeugung von Verklebungen an Blastulae
von Seeigeln durch Benzodiinon *
Von H e r m a n n D r u c k r e y
(Z. Naturforschg. 7 b, 571—572 [1952]; eingeg. am 10. Aug. 1952)
Bi- oder polyfunktionelle Substanzen, die also zwei oder
mehrere reaktive Gruppen aufweisen, wie z. B. das Bis[/?-chloraethyl] -methyl-amin, können an Chromosomen
lebender Zellen nicht nur zu Fragmentationen, sondern
auch zu Verklebungen führen („cross linkage")
ähnlich
wie das von Strahlenwirkungen bekannt ist („radiomimetischer Effekt")
Wahrscheinlich beruht die mutagene und
cancerogene Wirkung dieser Agentien auf der Erzeugung
derartiger Veränderungen an Chromosomen 3 oder anderen „Duplikanten". Wirksam sind vornehmlich solche Substanzen, die Ionen oder Radikale bilden. Soweit sie bioder polyfunktionell sind, sind sie polymerisationsfähig.
Auch bei Folien aus polymeren Kunststoffen wurden
kresbserzeugende Wirkungen festgestellt 4 ' 5 , die wir darauf beziehen, daß an der Oberfläche der Folien in einem
bestimmten Ladungsmuster freie Restvalenzkräfte vorliegen. Solche Polymere würden demnach als polyfunktionelle Substanzen anzusehen sein, so daß für ihre krebserzeugende Wirkung ein prinzipiell ähnlicher Mechanismus in Frage kommt wie für bifunktionelle Substanzen
bzw. die aus ihnen entstehenden Polymere 5 .
Es erschien notwendig, die damit aufgeworfenen
schwierigen Probleme experimentell weiter zu verfolgen,
weil der diskutierte Wirkungsmechanismus pharmakologisch von Interesse ist und weil polymere Kunststoffe und
ihre monomeren Grundsubstanzen eine zunehmende Bedeutung auf vielen Gebieten erlangen. Hier sei kurz über
Untersuchungen berichtet, die die Frage prüfen, ob bifunktionelle Substanzen auch Proteine lebender Zellen zur
Verklebung bringen können.
Versuchsobjekt waren Keime von Seeigeln (Paracentrotus lividus) im Blastula-Stadium, in dem sie nach Ausschlüpfen aus der Befruchtungsmembran „nackt" vorliegen und sich durch Wimpern bewegen. Als Modell einer
„bifunktionellen" Substanz benutzten wir das Benzodiinon. Diese Substanz ist ein wirksames Zellgift, das
die Zellteilung z. B. von Seeigeleiern stark hemmt 6 ,
ähnlich wie 2-wertige pöro-Phenole 7 .
Wurde dem Meerwasser, in dem die Keime suspen* Die Untersuchungen wurden mit Unterstützung der
Deutschen
Forschungsgemeinschaft
an
der zoologischen Station in Neapel durchgeführt. Adresse
des Verf.: Freiburg i. Br., Laboratorium der Chirurgischen
Universitätsklinik.
1 R. J. G o l d a c r e ,
A. L o v e l e s s u. W. C. R o s s ,
Nature [London] 163, 667 [1949].
2 P. D u s t i n , Nature [London] 159, 794 [1947],
3 E. B o y l a n d , Endeavour 11, Nr. 42 [1952],
4 B. S. O p p e n h e i m e r ,
T. E. O p p e n h e i m e r
u. A. P. S t o u t , Proc. Soc. exp. Biol. Med. 67, 33 [1948];
79, 366 [1952],
5 H . D r u c k r e y , P . D a n n e b e r g u. D . S c h m ä h l ,
Z. Naturforschg. 7b, 353 [1952],
6 F. E. L e h m a n n , Experientia [Basel] 3, 223 [1947];
E. F r i e d m a n n , Brit. J. Pharmacol. Chemotherapv
3, 263 [1948]; H. S. R e e d , Experientia [Basel] 5, 237
[1948].
7 H. D r u c k r e y , P. D a n n e b e r g
u. D . S c h m ä h l ,
Naturwiss. 39, 381 [1952],
Unauthenticated
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