IAWA Bulletin n.s., Vol. 7 (1),1986 21

DEVELOPMENT OF VASCULAR CAMBIUM AND COMPRESSION WOOD FORMATION IN THE SHOOT OF YOUNG SPRUCE (PICEA JEZOENSIS V AR. HONDOENSIS)

by

Nobuo Yoshizawa, Yujiro Tanaka and Toshinaga Idei Faculty of Forestry, Utsunomiya University, Utsunomiya, Japan

Summary In the course of the righting movement in However, little is known on the development young spruce (Pieea jezoensis Carr. var. of the cambium cylinder associated with the hondoensis Rehd.) inclined at 45°, the occur• righting movement of the current shoot. Saiki rence of compression wood associated with the and Tachida (1973) reported in their observa• development of vascular cambium in the shoot tions of the current shoots of Pinus thunbergii was observed. In shoots, the recovery first took which exhibits rapid righting movements that place at the mid point, a few days after inclina• no compression wood cells occur within a spe• tion. The observations of serial cross sections cific distance of the shoot apex. A correlation taken from the apex downward revealed no ap• between the development of vascular cambium preciable difference in the development of the and that of compression wood within the in• procambium-cambium continuum between clined current shoots is of great interest. This the upper- and underside of the shoot. The for• paper is focused on the response of xylem tis• mation and structure of primary tracheary ele• sues to the stimulus of inclination in associa• ments were similar, irrespective of the site of tion with the early development of the cambial the procambium in the shoot. No compression system. wood cells occurred before the vascular cam• bium cylinder was complete. The stimulus of Materials and Methods compression wood formation is received only Materials in this experiment were taken from by the differentiating secondary xylem tissues the current shoots of 5 years old spruce trees derived from the cambium cylinder. (Pieea jezoensis Carr. var. hondoensis Rehd.), Key words: Apex, cell division, righting move• which were inclined at 45° in late May, and the ment, secondary xylem, tracheary elements. righting movement in the current shoots fol• lowing inclination was monitored using photo• Introduction graphic records taken periodically. The process of cell differentiation begins The whole current shoots were collected in with the formation of new cells beneath the early October, and were fixed with FAA after shoot apex (Foster, 1938; Cross, 1943; Eames separation into several pieces. They were em• & Mac Daniels, 1947). Below this portion, as bedded in paraffin by ordinary procedure, and growth and development proceed, the vascular serial cross sections of IS J-Lm thick were cu t at cambium system becomes established in a appropriate intervals from the apex to the base shoot (Esau, 1943, 1965; Larson, 1982). Con• of the shoot by using a rotary microtome. siderable controversy still exists in the literature These cross sections were double stained with as to when and where the cambium state begins safranin and light green, and observed with an and how this state can be identified. More in• ordinary light microscope. Longitudinal radial formation still should be accumulated concern• sections at several different heights along the ing the development of the vascular cambium shoot also were observed with a Nomarski dif• system. ferential interference microscope. On the other hand, recovery of the normal vertical position in tilted young stems takes Results and Discussion place at the top first and gradually proceeds In the course of the righting movement in downward (Westing, 1961; Archer & Wilson, young trees inclined at 45°, the recovery of the 1973; Fukazawa, 1973). The first recovery stems initiated in the current shoot, and gradu• seems to occur at the middle portion of the ally proceeded to the bottom thereafter, as in• current shoots (Yoshizawa et aI., in press). This dicated by earlier observations (Westing, 1961; fact interestingly suggests a certain relationship Archer & Wilson, 1973; Fukazawa, 1973). The between the development of vascular cambium first recovery took place at the middle portion and the occurrence of compression wood in the of the current shoots shortly after inclination shoot. (Fig. I). The righting of the shoot proceeded

Downloaded from Brill.com09/27/2021 08:41:26AM via free access 22 IAWA Bulletin n.s., Vol. 7 (1),1986

Fig. I. Righting movement in the shoot of Picea jezoensis var. hondoensis. - a: immediately after inclination; b: three days after inclination. Vigorous righting is found in the middle part of the current shoot (arrowhead).

rapidly from the middle area of the shoot to morphological changes in the resin canal shape. the base within a few days. This phenomenon With the development of the procambium is of interest in relation to the occurrence of downward, the number of radial cell files in compression wood cells associated with the de• each procambial bundle gradually increased. velopment of vascular cambium in shoots. Meanwhile, endarch development of primary Within the portion 0.2-0.5 em beneath the xylem, from protoxylem of spiral tracheids to apex, procambia consisting of cells with smaller metaxylem of pitted tracheids, proceeded (Fig. diameter appeared first in the periphery of the 5). However, the development and structure of central ground meristem, or future pith (Fig. 2). the primary tracheary elemen ts were similar ir• Meanwhile, cell divisions in the procambium respective of the si te of the proeam bium which were initiated randomly accompanying proto• produces such cells. It seems to be a general xylem formation in an endarch manner(Fig. 3). feature of primary traeheary elements that the In general, the procambia seem to show irregu• primary wall remains unlignified (Kuo et aI., lar eell divisions with no tangential continuity 1974; O'Brien, 1981). No remarkable differ• (Esau, 1977; O'Brien, 198 I; Larson, 1982). No ence in the intensity of lignification of the sec• marked anatomical differences between the up• ondary wall of the metaxylem cells, as well as per- and underside of the shoot could be ob• in the number of primary xylem cells, was ob• served in this part. The morphological differen• served between the upper- and underside of ces between the upper- and underside were first the shoot. In the case of Picea jezoensis var. observed in the cortex (Fig. 4). As far down to hondoensis, the number of radially aligned pri• the part 0.6 em below the apex, resin canals in mary xylem cells in each file was generally kept the cortex had irregular shapes irrespective of within a range of 2-5, by the gradual collapse upper- and underside of the shoot. However, of protoxylem cells inside and a corresponding further downward, resin canals became circular addition of metaxylem cells outside. or elliptic on the upperside although they retain• Further down the shoot, the remaining cells ed irregular shapes on the underside. An altera• between the procambial bundles became more tion in the internal pressure within the shoot meristematic, and periclinal divisions from fas• due to minute movement might be the cause of cicular to in terfascicular regions seemed to pro-

Downloaded from Brill.com09/27/2021 08:41:26AM via free access IAWA Bulletin n.s., Vol. 7(\),1986 23

Fig. 2. Transverse section of the shoot 0.2 cm below the apex. No difference in the upper- and underside of the shoot can be seen. - Fig. 3. Procambium viewed at a point 0.3 cm below the shoot apex. Note the protoxylem cells showing a more or less square outline in cross section (arrow• head).

Downloaded from Brill.com09/27/2021 08:41:26AM via free access 24 IAWA Bulletin n.s. , Vol. 7 (1),1986

@

Fig. 4. Transverse section of the shoot 0.6 cm below the apex. Note the irregular shape of resin canals on the underside (lower side of the photograph) of the shoot.

ceed actively during primary growth (Esau, zones of periclinal divisions spread almost con• 1943). In this way, many cells of the interfasci• tinuous across the procambium bundles (Fig. 6). cular residual meristem were incorporated in No difference in the development of both fasci• the developing and enlarging procambium bun• cular and interfascicular cambium between the dles. Further downward, with the advance in upper- and underside of the shoot could be ob• development of the interfascicular meristem, served (Fig. 6a & b).

Downloaded from Brill.com09/27/2021 08:41:26AM via free access IAWA Bulletin n.s., Vol. 7 (1),1986 25

ness, 3) development of the helical ridges and cavities, 4) the rounding of the cross-sectional shape, and 5) occurrence of intercellular spaces. Although mild compression wood cells in the transition zone had normal cell shapes and wall thickness, they lacked the S 3 layer and had a slightly excessive lignification in the outer re• gion of the S 2 layer at the cell corners. More• over, they tended to lack helical cavities in the transition zone. These tendencies in the transi• tion zone are in accordance with earlier obser• vations (Saiki & Tachida, 1973; Fujita et aI., 1979; Yumoto et aI., 1982; Yoshizawa et aI., 1982). The first occurrence of these compres• sion wood cells was located 2.5-3.5 cm below the apex, as suggested by Saiki and Tachida (1973). Thus, following the formation of such mild compression wood cells, typical compres• sion wood cells appeared on the underside (Fig. 9), at which site the recovery of the shoots from the displacements first initiated.

Summarising the above observations con• cerning the occurrence of compression wood and the development of vascular cambium in the shoots, the conclusion can be drawn that compression wood cells are formed correspond• Fig. 5. Longitudinal radial view of developing ing to the righting movement of the shoot a lit• primary xylem. Note the endarch development tle while after the continuity of vascular cam• of primary tracheary elements, from protoxy• bium cylinder has been completed. Compres• lem of spiral tracheids to metaxylem of pitted sion wood occurs following the formation of tracheids. The number of primary xylem cells normal wood cells, and the recovery of the in a radial file is generally kept within a range shoot follows a little later. No appreciable ana• of 2-5. tomical change due to the inclination was ob• served in the primary xylem cells. These facts indicate that the stimulus of compression wood formation is received only by a cambium with Shortly after the interfascicular cambium cylindrical continuity and/or by postcambial was completed, cambium developed complete differentiating tracheids in stems, as cylindrical continuity. At the portion 1- 2.5 suggested earlier by various investigators (Ken• cm below the apex, vigorous cambial activity nedy & Farrar, 1965;Timell, 1979a, b; Yumoto could be found. Only normal wood cells were et aI., 1982; Yoshizawa et aI., 1984, 1985). produced in this area at first on both sides, al• The relocation of auxin stimulates compres• though the frequency of cell divisions showed sion wood formation on the underside of the a tendency to be slightly higher on the under• shoots, but it seems to have no effect on the side (Fig. 7). Differences in the intensity of lig• development of the vascular cambium. Further nification of the secondary wall was not ob• investigations should be conducted on whether served between the metaxylem and normal or not a response of primary xylem tissues to secondary xylem cells. the stimulus of inclination occurs during the Following the formation of such normal completion of the procambium-cambium con• cells, mild compression wood cells with certain tinuum. features characteristic of compression wood cells were formed on the underside of the Acknowledgement shoot as the transitional stage from normal to Appreciation is expressed to Professor Dr. compression wood (Fig. 8). The changes of cell Ken Shimaji, Wood Research Institute, Kyoto wall structure during the transition from nor• University, Uji, Japan, for his consultation and mal to compression wood proceeded as follows: advice regarding this manuscript. I) disappearance of the S 3 layer, 2) increase in the intensity of lignification and cell wall thick- (text continued on page 29)

Downloaded from Brill.com09/27/2021 08:41:26AM via free access 26 I AWA Bulletin n.s., Vol. 7 (I), 1986

Fig. 6. Transverse section of the shoot 1.5 em below the apex. - a: upper side of the shoot; b: un• derside of the shoot. Differences in the development of cambium continuity are not found between either side. Zones of periclinal divisions spread almost continuously across the procambium bundles (arrowheads).

Downloaded from Brill.com09/27/2021 08:41:26AM via free access IAWA Bulletin n.s., Vol. 7 (1),1986 27

,. J,

y 4' •• .", ~ '. ; r ~. , J ./ • r • • r •

Fig. 7. Transverse section of the shoot 2 cm below the apex. A slightly higher production of xylem is found on the underside than on the upper side.

Downloaded from Brill.com09/27/2021 08:41:26AM via free access 28 IAWA Bulletin n.s., Vol. 7 (1),1986

Fig. 8. Transverse sections of the upper- (a) and underside (b) of the shoot 3 cm below the apex. Tracheids transitional between normal and compression wood in the underside have sligh tly thicker cell walls. Note the primary xylem cells with rounded outline (arrowheads).

Downloaded from Brill.com09/27/2021 08:41:26AM via free access IAWA Bulletin n.s., Vol. 7 (1),1986 29

Fig. 9. Transverse section of the shoot 3.5 cm below the apex. Compression wood cells are formed on the underside of the shoot (top in photograph).

References Fujita, M., H. Saiki, J. Sakamoto, N. Araki & Archer, R.R. & B.F. Wilson. 1973. Mechanics H. Harada. 1979. The secondary wall for• of the compression wood response. II. On mation of compression wood tracheids. IV. the location, action, and distribution of Cell wall structure of transitional tracheids compression wood formation. Physiol. between normal and compression wood. 51: 777-782. Bull. Kyoto Univ. For. 51: 247-256. Cross, G. L. 1943. Comparison of the shoot api• Fukazawa, K. 1973. Process of righting and xy• ces of the sequoias. Amer. J. Bot. 30: 130- lem development in tilted seedlings of Abies 142. sachalinensis. Res. Bull. College Exp. Hok• Eames, A.J. & L.H. MacDaniels. 1947. An in• kaido Univ. 30: 103-123 (in Japanese, with troduction to plant anatomy. Ed. 2. Mc• English summary). Graw-Hill, New York. Kennedy, R.W. & J.L. Farrar. 1965. Tracheid Esau, K. 1943. Origin and development of pri• development in tilted seedlings. In: Cellular mary vascular tissues in . Bot. ultrastructure of woody plants (ed. W.A. Rev. 9: 125-206. Cote Jr): 419-453. Syracuse Univ. Press, - 1965. Plant anatomy. Ed. 2. John Wiley & New York. Sons, New York. Kuo, J., T.P. O'Brien & M.J. Canny. 1974. Pit• - 1977. The anatomy of seed plants. Ed. 2. field distribution, plasmodesmatal frequen• John Wiley & Sons, New York. cy, and assimilate flux in the mestome sheath Foster, A. S. 1938. Structure and growth of the cells of wheat . Planta 121: 97-118. shoot apex in Ginkgo biloba. Bull. Torrey Larson, P. R. 1982. The concept of cambium. Bot. Club 65: 531-556. In: New perspectives in wood anatomy (ed.

Downloaded from Brill.com09/27/2021 08:41:26AM via free access 30 IAWA Bulletin n.s., Vol. 7 (1),1986

P. Baas): 85-121. Nijhoff/Junk Publ., The - , S. Koike & T. Idei. 1984. Structural changes Hague. of tracheid wall accompanied by compres• O'Brien, T.P. 1981. The primary cylem. In: Xy• sion wood formation in Taxus cuspidata lem cell development (ed. J. R. Barnett): and nucifera. Bull. Utsunomiya 14-46. Castle House PUbl., London. Univ. For. 20: 59-76. Saiki, H. & Y. Tachida. 1973. Proc. Jap. Wood - , - & -. 1985. Formation and structure Res. Soc. 23: 148 (in Japanese only). of compression wood tracheids induced by Timell, T.E. 1979a. Formation of compression repeated inclination in Taxus cuspidata. wood in balsam fir. I. Ultrastructure of the Mokuzai Gakkaishi 31: 325-333. active cambial zone and its enlarging deriva• - , Y. Okamoto & T. Idei. In press. Righting tives. Holzforschung 33: 137-143. movement and xylem development in tilted - 1979b. Formation of compression wood in young trees of . balsam fir. II. Ultrastructure of the differen• Yumoto, M., S. Ishida & K. Fukazawa. 1982. tiating xylem. Holzforschung 33: 181-191. Studies on the formation and structure of Westing, A.H. 1961. Changes in radial symmetry the compression wood cells induced by ar• in the leaders of eastern white pine follow• tificial inclination in young trees of Picea ing inclination. J. For. 59: 17-19. glauca. I. Time course of the compression Yoshizawa, N., T. Itoh & K. Shimaji. 1982. Vari• wood formation following inclination. Res. ation in features of compression wood Bull. College Exp. For. Hokkaido Univ. 39: among gymnosperms. Bull. Utsunomiya 137-162. Univ. For. 18: 45-64.

ASSOCIATION AFFAIRS and ANNOUNCEMENT

IAWA activities at the 18th IUFRO World Zur Morphologie der InterzeIluIaren. 1 - 4. gress L.J. Kucera, 1985. Vierteljahrschr. Naturf. Ges. In addition to the IUFROjIAWA symposia ZUrich 130: 35-74, 157-198,251-310, and which have been announced in detail in IAWA 374- 397. Author's address: Institut fUr Wald• Bulletin 6 (4), a program for the IAWA satellite und Holzforschung, ETH, ETH-Zentrum, 9092 meeting on Thursday evening, September 11 ZUrich, Switzerland. has now been fixed. It will include a short Although published in a journal of long IAWA business meeting, a prolonged social standing, wood anatomists may easily miss this hour, and a presentation by Dr. Niko Torelli series of four specialised papers on intercellular and Dr. Bozidar Petric entitled: 'A review of spaces in wood. The first instalment gives a com• xylotomic research in Yugoslavia.' All members prehensive literature review on morphology, oc• and accompanying persons are most welcome currence, terminology and functional impor• to attend this meeting. tance of intercellular spaces. Parts 2-4 report Minor changes in the programs of the sym• original observations on the three-dimensional posia on environmental pollution and wood network of intercellular spaces in beech and structure and quality, and of the contributed oak; part 2 gives SEM results; part 3 a statisti• paper session on natural variations in wood cal histological analysis, and part 4 reports on quality are still made as delegates submit their investigations using optical shuttle microscopy. final titles. However, this hardly affects the Intercellular spaces are often stepmotherly program outlines published in the previous treated in anatomical treatises. The present IAWA Bulletin issue. publications should remedy this situation.

Downloaded from Brill.com09/27/2021 08:41:26AM via free access