IAWA Journal, Vol. 15 (4), 1994: 399-406

FUSIFORM PARENCHYMA CELLS IN THE YOUNG WOOD OF PINACEAE, AND THEIR DISTINCTION FROM MARGINAL PARENCHYMA

by

Shuichi Noshiro and Tomoyuki Fujii Wood Anatomy Laboratory, Forestry and Forest Products Research Institute, Tsukuba Norin, P. O. Box 16, Ibaraki 305, Japan

Summary Fusiform parenchyma cells found in sev• ray tracheids, and the proportion of ray tra• eral genera of Pinaceae are described and cheid pit border types. Recently, Anagnost compared with marginal parenchyma. Fusi• et al. (1994) restudied all these features using form parenchyma cells are mostly fusiform world-wide sam pIes of Picea and Larix, and in shape, with occasional smooth horizontal confirmed the results of Bartholin (1979) that walls. They form discontinuous tangential ray tracheid pit border types were the most bands in complete or incomplete circ1es in the reliable characteristic. However, because of innermost growth rings of Larix, Abies, and restricted growth in branches, it was difficult Tsuga. Fusiform parenchyma always con• to use these stemwood characteristics in iden• tains resinous material, and is more conspic• tifying branchwoods. uous in branchwoods than in stern woods. Modern branchwood materials gathered Marginal parenchyma cells were observed in for comparative purposes, however, revealed Cedrus, Keteleeria, Pseudolarix, and Pseudo• the conspicuous occurrence of resinous paren• tsuga as weIl as in Larix, Abies, and Tsuga, chyma cells in the inner growth rings of Larix and very rarely in Picea. Marginal paren• and their absence in Picea. Occurrence of chyma cells are scattered along growth ring resinous parenchyma ceHs was also observed boundaries. They are always in strands with in the Quaternary branchwoods, and was used nodular horizontal walls with conspicuous to distinguish Larix branchwoods from Picea simple pits. Cell wall structure of these two branchwoods. Resinous parenchyma cells in types of parenchyma differs in the intensity Larix were fusiform, and differed from strand of the birefringence of the secondary walls. parenchyma occurring along growth ring Fusiform parenchyma cells are distinct from boundaries of several Pinaceous genera. We marginal parenchyma with which they were observed fusiform parenchyma in the young previously confused, and should be regarded stemwood of Larixand branchwood of Abies as a new component of coniferous wood. and Tsuga (also Pinaceae); fusiform parenchy• Key words: Abies, Larix, Picea, Tsuga, Pina- ma was most conspicuous in Larix branch• ceae, fusiform parenchyma cells, young wood. Budkevich (1956, 1961) did a com• wood, marginal parenchyma. prehensive study of the wood anatomy of Pinaceae, and described the presence ofaxial Introduction parenchyma in the latewood of Abies, Cedrus, While identifying Quaternary fossil branch• Keteleeria, Larix, Pseudolarix, Pseudotsuga, woods, the first author encountered difficulty Tsuga and Ducampopinus (most taxonomists in distinguishing between branchwood of inc1ude this genus in Pinus, e.g. Farjon 1984; Larix and Picea. Stemwoods of these two Mabberley 1987), and absence ofaxial paren• genera have been distinguished by transition chyma from Cathaya, Picea and Pinus. He from earlywood to latewood, pit seriation of distinguished axial parenchyma with nodular longitudinal tracheids, number of epithelial end walls from axial parenchyma with smooth cells surrounding horizontal resin canals, end walls, and described parenchyma dis• presence or absence of spiral thickenings in tribution in Abies, Pseudotsuga, Larix, and

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Table 1. Occurrence of fusiform and marginal parenchyma in the secondary xylem of Pinaceae.

Species Specimen fusifo11ll parenchyma marginal nurnber parenchyrna growth ring

Abies firma Sieb. et Zucc. branch 1WTw-12974 + 2-3 ± do branch 1WTw-12975 + 2-6 do branch 1WTw-12976 ± 2 do stern 1WTw-433 do stern TWfw-14714 ++ 2-3 Abies sachalinensis (Fr. Schrn.) Masters branch 1WTw-5694 ++ 1-6 ± do branch 1WTw-5695 ++ 1-7 ± do branch 1WTw-5695 ++ 1-7 ± Cedrus deodara (Roxb.) G. Don branch 1WTw-12963 ++ do branch 1WTw-12964 + do branch 1WTw-12965 ++ Keteleeria davidiana (Bertr.) Beissn. branch 1WTw-12962 ++ do banch 1WTw-12969 ++ do branch 1WTw-12970 ++ Larix gmelinii (Rupr.) Rupr. var. japonica (Regel) Pilger branch 1WTw-2906 ++ 1-3 ++ do branch 1WTw-2913 ++ 1-3 ++ do branch 1WTw-2914 ++ 2-3 ++ Larix kaempferi (Lamb.) Carr. branch 1WTw-2905 ++ 1-3 ++ do branch 1WTw-2911 ++ 1-4 ++ do branch 1WTw-2912 ++ 1-6 ++ do stern K-l60 + 1-2 ++ do stern K-l84 + 2-3 + do stern Sn-l27 + 2-3 + do stern Sn-37 + 2 ++ do stern Sn-48 + 4-6 + Picea glehnii (Fr. Schrn.) Masters branch 1WTw-3903 do branch 1WTw-2907 do branch 1WTw-2908 Piceajezoensis (Sieb. et Zucc.) Carr. branch 1WTw-2904 do branch 1WTw-2909 do branch 1WTw-2910 Picea maximowiczii Regel ex Masters stern 1WTw-835 ± do stern Kan-9135 Pinus densiflora Sieb. et Zucc. branch 1WTw-12966 do branch 1WTw-12967 do branch 1WTw-12968 Pseudolarix amabilis (Nelson) Rehder branch 1WTw-12977 ++ Pseudotsuga japonica (Shirasawa) Beissn. branch 1WTw-12971 ++ do branch 1WTw-12972 ++ do branch 1WTw-12973 ++ Tsuga canadensis (L.) Carr. branch 1WTw-6790 ++ 3-4 ++ do branch 1WTw-6791 + 3-4 ++ Tsuga diversifolia (Maxim.) Masters branch 1WTw-6795 ++ 1-4 ++ do branch 1WTw-6796 ++ da branch 1WTw-6797 ++ do branch 1WTw-6798 + 3-4 ++ do stern 1WTw-593 + 8 +

-: not observed; ±: less than ten per specirnen; +: incornplete circlc; ++: cornplete circle.

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Cedrus. He also noted a more marked occur• ture of parenchyma cells was observed both rence ofaxial parenchyma in branchwoods between cross nicols of a polarised light mi• than in stemwoods. However, he did not croscope and with a phase contrast micro• mention fusiform parenchyma cells. Our ob• scope on thin transverse and tangential sec• servations indicate a distinction between fusi• tions (0.5 microns) of branchwoods and form parenchyma with rare smooth horizon• stemwoods of Larix that were prepared using tal walls and marginal stranded parenchyma epoxy-embedding. with nodular end walls. Fusiform parenchy• ma cells in secondary xylem are so far known to occur in Ephedra (Esau 1964) and several Results dicotyledons (panshin & De Zeeuw 1980; Fusiform parenchyma cells occur in Abies IAW A Committee 1989), but not in conifers firma, Abies sachalinensis, Larix kaempferi, (Phillips 1948; Greguss 1955; Panshin & De Larix glehnii, Tsuga canadensis, and Tsuga Zeeuw 1980). diversifolia, and were not observed in the In this paper we describe the morphology other six genera studied (Table 1). They are and distribution of fusiform parenchyma in mostly found in the latter half of the earlywood Pinaceae, and compare it to marginal stranded or in the latewood, and are occasionally scat• parenchyma. tered throughout the innermost growth rings (Figs. 1, 6, 9). They usually form irregular, Materials and Methods discontinuous tangential bands in complete or Branchwoods and stemwoods of 14 spe• partial circles within growth rings, mostly cies of nine genera of Pinaceae (47 sampies) occurring as single cells. These cells always were studied (Table 1). Sampies were collect• contain resinous material, and can be easily ed from plantations and natural habitats in recognised in transverse sections (e.g., Figs. Japan. We were unable to collect materials of 2, 3). The diameters of these parenchyma Cathaya and Nothotsuga. Nomenclature fol• cells are equal to those of the surrounding lows that of Farjon (1984, 1990). Specimens tracheids, or slightly sm aller (Fig. 2), and were sectioned on a sliding microtome for their length exceeds 1 mm (Fig. 7). They have light microscopy, including pith and inner• sparse simple pits on radial walls, and lack most rings, and were double-stained with pits on tangential walls (Figs. 4, 8). They are Safranin and Gentian Violet. Cell wall struc- basically fusiform in shape without subdivi-

-) Figs. 1-5. Fusiform and marginal parenchyma in the branchwood of Larix kaempferi. - 1: TS x 20; fusiform parenchyma making complete circles in the innermost rings. - 2: RLS x 200; mar• ginal parenchyma cells in astrand (m), and a fusiform one with rcsinous content (f). - 3: TS x 400; fusiform parenchyma cens with resinous content, and a marginal one with simple pits on a hori• zontal wall (arrow). - 4: RLS x 400; sparse simple pits on a radial wall of a fusiform parenchy• ma cell. - 5: TLS x 400; nodular horizontal walls (arrows) and simple pits on tangential walls of a marginal parenchyma cello - Scale bar = 200 11m in Fig. 1, and 50 11m in Figs. 2-4.

-) -) Figs. 6-8. Fusiform parenchyma in the branchwood of Abies sachalinensis. - 6: TS x 40; fusi• form parenchyma in the latewood nearly parallel to growth ring boundaries. - 7: RLS x 100; fusiform parenchyma cells (f) more than 1 mm long. - 8: TLS x 400; a smooth horizontal wall in fusiform parenchyma and absence of pits on tangential walls. - Fig. 9. Fusiform parenchyma in the branchwood of Tsuga diversifolia. TS x 40. - Figs. 10 & 11. Marginal parenchyma in the branchwood of Pseudolarix amabilis. - 10: TS x 200; marginal parenchyma cells (arrows) on growth ring boundaries.- 11: TLS x 200; nodular horizontal walls and simple pits on tangential and radial walls. - Sc ale bar = 100 11m in Figs. 6, 7 & 9, and 50 11m in Figs. 8, 10 & 11.

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Figs. 12 & 13. Cell wall structure of fusifollTI and marginal parenchyma in branchwood of Larix kaempferi. - 12: Phase-contrast micrograph. - 13: Polarised light micrograph showing fusifollTI (f) and marginal (m) parenchyma. si on (Fig. 7), but thin smooth horizontal walls renchyma forms complete circles in all the are occasionally observed in sam pies of Abies branchwoods, but is sparse and scattered in sachalinensis (Fig. 8). In Larix their occur• restricted parts of growth rings in stemwoods rence is independent of the distribution of (Table 1). Occurrence of fusiforrn parenchyma vertical resin canals (Fig. I). is constant and most conspicuous in Larix spe• FusifollTI parenchyma cells are usually eies, but differs between species and also be• more conspicuous in branchwoods than in tween individuals in Abies and Tsuga. Fusi• stemwoods. In Larix kaempferi, fusiform pa- form parenchyma is found between the first

Downloaded from Brill.com09/27/2021 11:05:37PM via free access Noshiro & Fujii -- Fusiform parenchyma in Pinaceae 405 ------and eighth growth rings, and OL:curs most walls of fusiform parenchyma cells are com• commonly between the second to fourth rings posed of more densely-packed microfibrils (Table 1). In sam pIes where fusiform paren• orientated in obtuse angles than marginal pa• chyma is found over three or more growth renchyma cells. rings, it occurs in all the rings; once it disap• pears, it will never occur again in subsequent Discussion rings. Duration of fusiform parenchyma for• Fusiform parenchyma in Pinaceae is dis• mation is longest in Abies sachalinensis. tinct from marginal parenchyma, with which Marginal parenchyma occurs in 11 species it has been confused, and differs in morphol• of 10 genera, and is not observed in two spe• ogy and its distribution within growth rings. cies of Picea or in Pinus densiflora (Table 1). This parenchyma should therefore be regard• Among the species having fusiform paren• ed as a new component of coniferous wood. chyma, marginal parenchyma is abundant in According to recently proposed phylogenies Larix and Tsuga (Figs. 2, 3), but rather rare of conifers, the three genera having fusiform in Abies. Among the species without fusiform parenchyma are not dosely related (Hart 1987; parenchyma, Cedrus deodara, Keteleeria da• Price et al. 1987; Chase et al. 1993). Because vidiana, Pseudolarix amabilis (Fig. 10), and the outgroup of Pinaceae is in controversy, Pseudotsuga japonica have abundant marginal and because occurrence of fusiform paren• parenchyma. Among the Picea species that chyma in the secondary xylem has not been usually lack axial parenchyma (Sudo 1968), surveyed in all genera and species, it is not one stemwood sam pIe of Picea maximowiczii dear if this character is paraphyletic and re• had rare marginal parenchyma cells (Table 1). presents parallel evolution. Fusiform paren• The observed occurrence of marginal paren• chyma of Pinaceae occurs only in juvenile chyma in Pinaceae conforms with the descrip• wood, not in mature wood, and does not tions of Phillips (1948), Greguss (1955), see m to be homologous with fusiform pa• Budkevich (1961) and Sudo (1968). Marginal renchyma occurring in the mature wood of parenchyma cells are scattered along growth Ephedra and several dicotyledons. Further ring boundaries (Figs. 2, 3, 10), and are al• information on the distribution of this charac• ways in strands with nodular horizontal walls ter in conifers is necessary to assess its phylo• having conspicuous simple pits (Figs. 5, 11). genetic significance in Pinaceae. Even in radial sections, it is apparent that All the sampies with fusiform parenchyma strands of marginal parenchyma on growth forming compIete rings were collected either ring boundaries are distinct from fusiform pa• in Hokkaido or northem Honshu, excepting renchyma without sub divisions (Fig. 2). Mar• an Abies firma stemwood of uncertain origin. ginal parenchyma cells usually lack resinous Both of these regions are in the cool-temper• contents, and have sparse simple pits on both ate or subalpine zone, and severe winter may radial and tangential walls (Fig. 11). promote formation of fusiform parenchyma. Both fusiform and marginal parenchyma Abies firma branchwoods collected in middle cells had obviously thinner cell walls than Honshu show less conspicuous occurrence tracheids (Fig. 12). In contrast with the typi• of fusiform parenchyma than Abies sachali• cal three-layered sUlIcture of tracheid second• nensis branchwoods collected in Hokkaido. ary walls, walls of fusiform parenchyma cells Branchwoods of Tsuga diversifolia, collected show alm ost uniform and high birefringence from the same natural habitat in the subalpine between cross nicols, but the bright layers zone, however, show inconsistency in fusi• are divided by a very narrow dark layer (Fig. form parenchyma formation, and do not indi• 13), indicating the crossed tlat-helix layered cate that there is a direct correlation between structure of the secondary wall. The second• dimate and fusiform parenchyma formation. ary walls of marginal parenchyma cells are Fusiform parenchyma seems to be a specific a little thinner with alm ost uniform birefrin• character useful for identification of young gence. The difference in the birefringence of sterns, but determining whether it has eco• the secondary walls between the two types of logic significance awaits study of additional parenchyma cells suggests that the secondary material.

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