Development of the Incubated Tyloses in Quercus serrata THUMB.

KURENAI : Kyoto University Research Information Repository
Development of the Incubated Tyloses in Quercus serrata
Shibata, Naoaki; Fujita, Minoru; Saiki, Hiroshi; Harada,
Issue Date
京都大学農学部演習林報告 = BULLETIN OF THE KYOTO
UNIVERSITY FORESTS (1978), 50: 174-182
Departmental Bulletin Paper
Kyoto University
of the
FUJITA, Hiroshi
コナ ラに お け る培 養 チ ロ ー ス の 発 達*
柴 田 直 明 ・藤 田
稔 ・佐 伯
浩 ・原 田
In small blocks numerous and ellipsoidal incubated tyloses developed simaltaneously.
In higher temperature (25-35°C) incubated tyloses developed rapidly, while they deflated
before lignified. In lower temperature (10-25°C) incubated tyloses developed slowly,
but their walls were well lignified. Hence, experiments were done at 20° C in order
to observe the whole process of incubated tylosis formation. During the enlargement
stage, incubated tylosis wall appeared to consist of one layer and was joined with unlignified
"protective layer" . Incubated tylosis wall was 0.3-0.5 pm thick, which did not thicken
afterwards and no pit-like structure was observed. Using TEM the tylosis wall was
beginning to be lignified gradually soon after the enlargement. Golgi apparatus, ER,
and mitochondria increased in number at the enlargement stage. They were observed
until the last stage of development.
小 さ な 培 養 ブ ロ ッ ク を 用 い る と,多
培 養 す る と,培
数 の 培 養 チ ロ ー ス が 一 斉 に 発 生 し楕 円 体 状 に 発 達 し た 。 高
養 チ ロ ー ス は 急 速 に 発 達 し た が,木
化 す る前 に し ぼ ん で し ま っ
た 。 低 温(10-25℃)で
は 発 達 に 時 間 を 要 した が,壁
で チ ロ ー ス を 培 養 し,チ
ロー スの 発 達 の全 段 階 を観 察 した。 伸 張 中 の培 養 チ ロ ー ス壁 は一 層 か ら
な っ て お り,未
木 化 のprotective
連 続 して い た 。 培 養 チ ロ ー ス の 壁 厚 は0.3-0.Sum
張 後 の 肥 厚 は 認 め られ な か っ た 。 ま た,壁
化 は,電
顕 観 察 に よ る と,壁
の 木 化 段 階 ま で 観 察 で き た 。 そ こ で,20℃
孔 様 構 造 も観 察 さ れ な か っ た 。 チmス
壁 の木
の 伸 張 終 了 後 間 もな い 時 点 か ら段 階 的 に 始 ま っ て い た 。 ゴ ル ジ体,
トコ ン ド リ ア は チmス
の 伸 張 段 階 に 数 を 増 し た が,こ
れ らは発 達 の 最 終 段 階 ま で 観 察
され た 。
* This paper was presented at the 25th and 26th Annual
of the Japan Wood Research Society (April,
and April, 1976, in Shizuoka, Japan)
1975, in Fukuoka,
of interest
to researchers
in wood
development process have been observed by many investigators. KORAN and COTE
and FOSTER studied the wall structure of "natural tyloses", which are formed in the
natural circumstances.
"Incubated tyloses"
, which are induced in3)small wood blocks under artificial conditions,
6) have
by JUR
and FujiTA et al. The so-called "protective layer" in Quercusserrata THUNB. was obs)
served by SUGIOKA
et al.
In this paper, the following observations are described.
(1) As a preliminary examination, natural and incubated tyloses were observed with
special emphasis on their shape and structure.
(2) The difference in tylosis development at different incubation temperature was observed,
at proper time interval, in the pore zone of the current year during the dormant season.
(3) The development of tylosis wall and the difference of cell organelles in the whole
process of incubated tylosis formation (from budding to lignification, at 20° C) were
observed by electron microscopy.
Several sample trees, 10-30 year-old Quercus serrata THUNB. growing in Kamigamo
Experimental Forest Station of Kyoto University Forest, were cut down and only pore
zones were examined.
(1) The preliminary observation on shape and structure of natural and incubated tyloses :
The tyloses that had been formed
before cutting are regarded as natural
tyloses in this paper. For the observation of incubated tylosis formation,
3 cm-thick discs were taken from the
stem immediately after it was cut,
and some of them were cut to semicircular pieces (3 cm width) containing both bark and several outer
growth rings.
These discs and
semicircular pieces were placed in a
growth chamber as shown in Fig.l.
The growt hchamber was kept in
the laboratory maintained mainly at
20°C or 25°C.
(2) The
on incubated
tylosis formation at various temperature
: Incubated tyloses formed in the current
year were observed twice during dormant season (from Nov. to Jan.). The incubation
temperature was varied to six gradations, namely 10, 15, 20, 25, 30, and 35°C. The
specimen blocks (semicircular pieces) were incubated at the same time in each
temperature within the growth chamber. They were observed every six or eight
hours for first three days, every twelve hours for subsequent two days, and once per
every one or two days, and then every three or four days after that. For each time,
one block was taken out from each growth chamber and checked for tylosis development. From the result of these experiments, it became clear that the incubation blocks
were dried gradually. For the incubations hereafter, the growth chamber was sealed
up in a polyethylene bag which contained a small amount of water at the bottom, and
the incubation blocks themselves were also moistened suitably once in a while.
(3) More detailed observation on the development of incubated tyloses at 20° C :
Specimen blocks (semicircular pieces) were incubated in the growth chamber at 20°C
in June and December. The incubated tyloses formed at pore zone in the current year
were observed.
For all observations described above, the materials were prepared as follows. The
materials collected were observed with a binocular to check the developmental stages
of tyloses. Some of them were fixed with 3% glutaraldehyde or preserved in 0.8M Dmannitol solution. For transmission electron microscopy (JEM-7), fixation and embedding were made by the ordinary method. Ultra-thin sections were stained with 4%
uranyl acetate. All observations with TEM were on cross sections. For scanning
electron microscopy (JSM-U3), preserved materials were rinsed well with distilled water
and dehydrated. They were dried with a critical point dryer and coated with C-Au or
Au only. For the observation on inner surface of tylosis wall, materials were treated
with 1N KOH to dissolve the protoplasm after rinse.
(1) The preliminary observation on the shape and structure of natural and incubated
Natural tyloses formed in Quercusserrata THUNB.were found in heartwood and intermediate wood, and moreover in sapwood sporadically. In the current year, only a
few tyloses were found. Individual natural tylosis was generally large in size and more
or less spherical (Fig. 3a). The wall was thick (about 2 gm), and a pit-like structure
was observed on the inner surface of the wall. It was found not only where the tylosis
touched the adjacent tylosis but also where tylosis touched the vessel wall (Fig. 3b).
Incubated tyloses, in 3 cm thick discs during the enlargement stages, were biggest
in the current year and became smaller in the older annual rings. Moreover, they
decreased in number to some extent in older vessels. On the other hand, incubated
tyloses were not formed when water was present in the vessel lumina. In the small
blocks incubated tyloses were formed numerously. They were ellipsoidal shape and
the walls were thin. This shape difference between natural and incubated tyloses seems
to be resulted from whether numerous tyloses develop at once or develop one by one,
as being pointed out by MEYER.
(2) The observation on incubated tylosis formation at various temperature (at pore
zone in the current year)
The results of two individual experiments (in dormant season) were in good agreement,
which were summarized in Fig. 2. In this diagram each developmental stage of incubated
tyloses is interpreted as follows.
1: Smaller incubated tylosis buds were formed in some vessels.
2: Incubated tylosis buds were formed in every vessel (Fig. 4a).
3: Most of incubated tyloses were elongated to the length of a quarter of vessel diameter.
4: Most of incubated tyloses were elongated to the length of a half of vessel diameter
and began to block the vessel lumina (Fig. 4b).
5: Lignification of incubated tylosis walls could be confirmed barely with phloroglucinhydrochloric acid.
In high incubation temperature incubated tyloses became deflated after some elongation. Stage 6 showed the time when this phenomenon was observed first in some vessels.
As is evident from Fig. 2, incubated tyloses were formed at every incubation temperature
(10-35°C), of which development was dependent significantly on the temperature. In
higher temperature (above 25°C) they developed rapidly and the effect of incubation
temperature was less remarkable. However, they became deflated before lignified.
In lower temperature (under 25°C) the effect of temperature was remarkable. The
lower the incubation temperature was, the more hours were needed to develop. On
the other hand, numerous incubated tyloses developed simultaneously at higher temperature, while their extent of development more or less varied at lower temperature. From
these experiments, it was revealed that the whole process of incubated tylosis formation
(from the budding to the lignification) could be observed at lower temperature.
Deflatting of incubated tyloses is mainly due to the drying of the incubation wood
blocks. From a more cautious subsequent experiment not to dry incubation blocks,
it became clear that incubated tyloses could be developed to the stage of lignification
(though not perfectly) even at 25°C or 35°C. In this incubation method, some incubated
tylosis buds were observed at 40°C, but they did not develop any further. No tylosis
formation was observed at 50°C. These temperature values agree with the result by
JURASEK. The lack of tylosis development at such a high temperature seems to be
resulted from the decrease of various physiological activities in a parenchyma cell. On
the other hand, tylosis formation was also observed in the case of incubation in a refrigerator
(at about 5° C) in Quercusserrata THUNB. The lowest allowable formation temperature
probably depends on the difference in species.
Incubated tylosis development is more or less different depending on the season (growth
or dormant) in which they are incubated. For example, the tyloses that were incubated
in June needed about 24 hours at 25°C, 34 hours at 20°C, and 70 hours at 10°C to bud
to the developmental stage 2. The time needed for incubation is always shorter than
that in dormant season. However, no remarkable difference was found in the subsequent
developments. The development of incubated tyloses seemed to be less variable in
dormant season.
(3) More detailed observation on the development of incubated tyloses at 20°C in the
current year
(a) The development of incubated tylosis wall
In Quercusserrata THUNB.tylosis wall was formed from the "protective layer" as well.
In June, the tylosis wall was connected with unlignified "protective layer" that had
formed in the neighbouring ray parenchyma cell (Fig. 5a). In December, the tylosis
wall was joined similarly with "protective layer" but only with the unlignified inner
layer. The outer layer touching to the secondary wall of the ray parenchyma cell had
been lignified in this season (Fig. 5b). These "protective layers" with which the tylosis
walls were joined stained darker with GA and 0s04 than the outer "protective layers"
and the secondary walls of other cells. During the enlargement stage of the incubated
tylosis, the wall appeared to consist of one layer in terms of the stainability. This does
not agree with the results by MURMANISand FOSTER. They claimed two-layered
walls. The difference is, perhaps, due to the harvesting method or observing method.
Besides, it may be due to the amorphous substance with which tylosis bud is covered
in early stages of development.
The following is the results on tyloses incubated in December. After the elongation
stages, the incubated tylosis walls had rather uniform thickness (0.3-0.5 pm thick, Fig. 6a
and b). The measurements were made on cross sections and at the sites where tyloses
touched to the inner surfaces of the vessels. Judged from scanning electron microscopical
observations, the wall was also thin and no pit-like structures were observed. Therefore,
it appears that incubated tylosis wall did not thicken after enlargement as far as this
incubation method is concerned. This phenomenon is probably due to the difference
between incubating conditions and natural ones. Lignification of incubated tylosis
wall was observed with phloroglucin-hydrochloric acid staining after about 10 days of
incubation. As for the stainability with KMnO4, however, lignification appeared to
begin partially before 10 days of the growth. Outer part of 6-day-old tylosis walls were
stained heavily only in the area where some tyloses were gathered but not touched one
another (Fig. 7). The tylosis walls of 14-day old had been lignified considerably, for
even in the inner part of the wall it was stained in the same manner as a vessel wall. The
lignification process on the incubated tylosis walls appears to be similar to that on other
cell walls. On the other hand, hemispherical materials were often observed on the
outer surface after about 6 days of growth.
(b) The difference in the structure or number of cell organelles prior to or in the process
of tylosis formation (in December)
After 16 hours of incubation, Golgi apparatus had still a few vesicles and showed dormant structure (Fig. 8). After 32 hours of incubation (at the developmental stage 1,
as defined above), Golgi apparatus began to increase in number and to be accompanied
with many large vesicles. After 50 hours of incubation, numerous Golgi apparatus
were scattered all over the bud (Fig. 9). Golgi vesicles were large and numerous. These
changes of Golgi apparatus were observed not only in the tylosis buds but also in the ray
parenchyma cells forming tyloses. Golgi apparatus kept the same structure until the
tyloses began to blockade the vessels. The nucleus and amyloplasts were sometimes
removed from the ray parenchyma cell to the tylosis. After 10 days of incubation, most
of Golgi apparatus had been transformed into the structure with a few vesicles (Fig. 10).
In the stage of incubated tylosis enlargement, the change of cell organelles and starch
grains almost agreed with the results by FujrrA et al. In these experiments, however,
dark (osmiophilic) precipitates were scarcely formed in this stage. This is probably
due to the longevity of cells thanks to the improvement of incubation method. Golgi
apparatus, ER, and mitochondria that had increased in number could be observed until
the later stages, even after 26 days of incubation, within most of tyloses and ray parenchyma
cells. However, it is still difficult to give a clear-cut answer why Golgi apparatus had
transformed into dormant structure (with a few small vesicles) in the lignification stage.
More minute investigation would be necessary for the structure change and the functions
of cell organelles.
The authors thank to the members of Wood Structure Laboratory in Department
of Wood Science and Technology in Kyoto University for their assistance during this
experiment. They also express their appreciation to Associate Professor Keizo OKAMURA,
Department of Wood Science and Technology, Kyoto University, for his critical reading
of the manuscript.
1) KORAN,Z. and COTE,W. A. JR.: The ultrastructure of tyloses.In "Cellular ultrastructure of woody
plants" (W. A. COTEed.) Syracuse Univ. Press. Syracuse, New York 319-333 (1965)
R. C.: Fine structure of tyloses in three speciesof the Myrtaceae Aust.J. Bot. 15 25-34(1967)
3) Jultr;k;'Ex,L.: Ptisobeni teploty a vlhkosti clieva na tvorbu thyl u buku Drev. Virskum3(1)5-13(1958)
4) KORAN,Z. and COTE,W. A. JR.: Ultrastructure of tyloses and a theory of their growth mechanism
I. A. W. A. News Bull. No. 2 3-15 (1964)
5) MEYER,R. W.: Tyloses development in white oak Forest Prod. J. 17 50-56 (1967)
L.: Formation of tyloses in felled Quercusrubra L. Wood Sci. Technol. 9 3-14(1975)
H.: Changes in parenchyma cell structure followed
by incubated tylosis development in Quercusserrata Timms. Bull. Kyoto Univ. Forests 47 144-151
H. : Ray-vessel pit pairs of Japanese Quercus
wood Bull. Kyoto Univ. Forests47 135-143(1975)
Fig. 3. Natural tylosis a: tangential view of a vessel lumen b: inner surface with pit-like structure
Fig. 4. Incubated tylosesin the current year at 35°C a: developmental stage 2 (after 24 hours), b: developmental stage 4 (after 48 hours)
Fig. 5. Incubated tylosis bud in the current year fixed with GA and 0s04 a: incubated at 20°C for 48 hours
in June, b: incubated at 20°C for 50 hours in December.
Fig. 6. Incubated tylosis wall fixed with GA and KMnO4 on cross section a: incubated at 20°C for 5 days
(5-day-old tylosis), the last stage of enlargement; b: 26-day-old tylosis, the last stage of lignification
Fig. 7. 6-day-old incubated tylosis walls fixed with GA and KMnO4
Fig. 8. A ray parenchyma cell contacted with a vesselafter 16 hours of incubation, fixed with GA and
Fig. 9. A part of a tylosis bud after 50 hours of incubation, fixed with GA and KMnO4
Fig. 10. 10-day-old incubated tyloses fixed with GA and KMnO4
T: tylosis Tw: tylosis wall
parenchyma cell
G: Golgi apparatus
PL: "protective layer"
R: ray parenchyma cell
Vw: vesselwall
Rs: secondary wall of ray