TROCHODENDRANAE Takht

Trochodendrineae Engl., Syllabus, ed. 2: 116. Mai 1898; Trochodendranae Takht. ex Reveal in Phytologia 79: 71. 29 Apr 1996

Fossils Nordenskioeldia is represented by leaves and reproductive organs from the Paleocene (and possibly earlier) to the Miocene of western North America, Spitsbergen and Central and East Asia. The fruit is a sessile schizocarp having ten to 20 single-seeded and probably nutlike mericarps in a ring.

Habit Bisexual or androdioecious, evergreen trees. Buds large, covered with numerous imbricate scales.

Vegetative anatomy Phellogen ab initio superficial. Vessel elements with scalariform or reticulate-scalariform perforation plates; vessels usually approx. same length and width as tracheids. Imperforate tracheary xylem elements tracheids or fibre tracheids, tracheids in young wood with scalariform bordered pits, in older wood with circular bordered pits. Wood rays uniseriate or multiseriate, heterocellular. Axial parenchyma apotracheal diffuse or diffuse-in-aggregates. Sieve tube plastids S type. Nodes 1–7:1–7, unilacunar to multilacunar, with one or more leaf traces (often 3:3, trilacunar with three traces). Idioblasts secretory (non-sclerenchymatous) or sclerenchymatous (non-secretory), present in cortex. Crystals?

LeavesAlternate (spiral or distichous), simple, entire, with supervolute ptyxis. Stipules present at petiole base or absent; leaf sheath absent. Petiole vascular bundle transection arcuate to almost annular, with wing bundles. Venation pinnate, brochidodromous, or palmate, actinodromous; secondary veins running together with lateral veins into persistent transparent cap. Stomata paracytic, tetracytic, cyclocyti or laterocytic. Cuticular wax crystalloids as clustered tubuli (Berberis type), chemically dominated by nonacosan-10-ol. Mesophyll with sclerenchymatous idioblasts with sclereids of different types, or sclerenchymatous idioblasts replaced by resin-producing idioblasts. Idioblasts with ethereal oils absent. Leaf margin serrate to crenate, with chloranthoid teeth (secondary veins running together with lateral veins into translucent persistent cap).

Inflorescence Terminal, racemose, botryoid or reduced panicle, cymose, or flowers four together in axillary catkin- or spike-like inflorescences. Floral prophylls (bracteoles) absent.

Flowers Actinomorphic. Hypogyny or half epigyny. Tepals 2+2, with imbricate? aestivation, sepaloid, free, or absent in open flowers. Nectaries present on horizontally expanded dorsal/abaxial ovary walls. Disc absent.

Androecium Stamens 2+2, antetepalous, or c. 40 to more than 100, spiral. Filaments thin, free from each other and from tepals. Anthers basifixed, non-versatile, tetrasporangiate, latrorse, longicidal-valvicidal (dehiscing by longitudinal slits at each end expanding into two transverse lines, resulting in two wing-shaped valves). Tapetum secretory. Staminodia absent.

Pollen grains Microsporogenesis simultaneous. Pollen grains usually tricolpate or tricolpor(oid)ate (sometimes tetracolp[or]ate), shed as monads, bicellular at dispersal. Exine tectate, with columellate infratectum, perforate to rugulate-reticulate at mesocolpia, striate (with more or less parallel striae) near apertures.

Gynoecium Carpels four to eleven (to 17), in a single whorl, connate at base; carpel plicate, postgenitally partially fused laterally (sometimes free), with or without secretory canal. Ovary semi-inferior, 4–11(–17)-locular at base; ovaries unilocular elsewhere (apocarpy). Stylodia erect, recurved. Stigma decurrent, papillate, Dry type. Pistillodium absent.

Ovules Placentation apical to axile (lateral/marginal). Ovules five to c. 30 per carpel, anatropous, pendulous, apotropous, bitegmic, crassinucellar, expanded at chalazal end (integument elongate). Inner integument thicker than outer integument. Micropyle bistomal (or endostomal?), prolonged. Hypostase present. Megagametophyte monosporous, Polygonum type. Endosperm development cellular or nuclear. Endosperm haustoria? Embryogenesis caryophyllad.

Fruit A multifolliculus-like ventricidal and somewhat loculicidal syncarpous capsule. Adaxial side of free carpel segments developing faster than abaxial side during maturation, making stylodia expanding horizontally and often recurving (stylodia finally basal on abaxial side).

Seeds Aril absent? Seed coat thin, endotestal-exotegmic. Exotestal cells wider than inner cells. Endotesta palisade, with short sclerotic and somewhat thickened cell walls. Tegmen unspecialized. Exotegmen tracheidal, with thick-walled elongate cells. Chalazal outgrowth present, with hairpin-shaped vascular bundle. Perisperm not developed. Endosperm copious, oily and proteinaceous. Embryo small, straight, well or little differentiated, without chlorophyll. Cotyledons two. Germination phanerocotylar.

Phytochemistry Flavonols (kaempferol, quercetin, myricetin), cyanidin, chalcones or dihydrochalcones, proanthocyanidins (prodelphinidins), dhurrin and other cyanogenic compounds, and oleanolic acid derivatives present. Ellagic acid not found.

Fossils Fossils of Tetracentron have been found in Eocene to Miocene layers in western North America and in the Miocene of Iceland.

Habit Bisexual, deciduous trees, with leaves and inflorescences on short shoots arising from long-shoots.

Vegetative anatomy Phellogen ab initio superficial. Vessel elements with scalariform or reticulate-scalariform perforation plates; vessels usually approx. same length and width as tracheids. Imperforate tracheary xylem elements tracheids, in young wood with scalariform bordered pits, in older wood with circular bordered pits. Wood rays uniseriate or multiseriate, heterocellular. Axial parenchyma apotracheal diffuse (in short tangential rows). Sieve tube plastids S type. Nodes 3:3, trilacunar with three leaf traces. Idioblasts secretory (non-sclerenchymatous); also present in cortex. Crystals?

LeavesAlternate (distichous), simple, entire, with supervolute ptyxis. Stipules inserted at petiole base; leaf sheath absent. Axillary bud entirely covered by laterobasal petiole flange. Petiole rounded toward base; leaf scar more or less encircling short shoots. Petiole vascular bundle transection arcuate to almost annular, with three bundles and wing bundles. Venation palmate, actinodromous; secondary veins running together with lateral veins into persistent transparent cap. Stomata paracytic, tetracytic or laterocytic. Cuticular wax crystalloids as clustered tubuli (Berberis type), chemically dominated by nonacosan-10-ol. Mesophyll sclerenchymatous idioblasts replaced by large branched resin-producing idioblasts. Idioblasts with ethereal oils absent. Leaf margin serrate, with chloranthoid teeth.

Inflorescence Axillary, catkin- or spike-like; flowers in groups of usually four. Floral prophylls (bracteoles) absent.

Flowers Actinomorphic, small. Hypogyny or half epigyny. Tepals 2+2, with imbricate? aestivation, sepaloid, free. Idioblasts secretory (non-sclerenchymatous). Nectaries present on horizontally expanded dorsal/abaxial ovary walls. Disc absent.

Androecium Stamens 2+2, antetepalous. Filaments free from each other and from tepals. Anthers basifixed, non-versatile, tetrasporangiate, latrorse, longicidal-valvicidal (dehiscing by longitudinal slits expanding into two transverse lines at each end, resulting in two wing-shaped valves). Tapetum secretory, with binucleate? cells. Staminodia absent.

Pollen grains Microsporogenesis simultaneous. Pollen grains tricolpate or tricolporate (to tricolporoidate), shed as monads, bicellular at dispersal. Exine tectate, with columellate infratectum, perforate to rugulate-reticulate at mesocolpia, striate (with more or less parallel striae) near apertures.

Gynoecium Carpels four, alternitepalous, in a single whorl, connate at base; carpel plicate, postgenitally partially fused, with or without secretory canal. Ovary superior or semi-inferior, quadrilocular at base; unilocular elsewhere (apocarpy). Stylodia four, short, subulate, expanded, finally subbasal and recurved. Stigma decurrent, papillate, Dry type. Pistillodium absent.

Ovules Placentation axile (lateral/marginal). Ovules five or six per carpel, anatropous, pendulous, apotropous, bitegmic, crassinucellar, expanded at chalazal end. Micropyle bistomal (or endostomal?), prolonged. Outer integument two cell layers thick. Inner integument at least three cell layers thick. Hypostase present. Megagametophyte monosporous, Polygonum type. Endosperm development ab initio nuclear. Endosperm haustoria? Embryogenesis?

Fruit A multifolliculus-like ventricidal and somewhat loculicidal syncarpous capsule with persistent stylodia. Adaxial side of free part of carpel developing faster than abaxial side during fruit maturation, making stylodia expanding horizontally and recurving (stylodia finally basal on abaxial side).

Seeds Aril absent? Seed with outgrowth. Seed coat thin, endotestal-exotegmic. Testa multiplicative. Exotestal cells wider than procumbent inner cells? Mesotestal cell walls lignified. Endotesta palisade, with short sclerotic and somewhat thickened lignified cell walls. Tegmen unspecialized. Exotegmen tracheidal, with thick-walled cells. Chalazal outgrowth present. Vascular bundle hairpin-shaped. Perisperm not developed. Endosperm copious, oily and proteinaceous. Embryo small, straight, little differentiated, chlorophyll? Cotyledons two. Germination phanerocotylar?

Phytochemistry Flavonols (kaempferol?, quercetin), cyanidin, chalcones or dihydrochalcones, proanthocyanidins (prodelphinidin?), dhurrin (a cyanogenic glycoside), and oleanolic acid derivatives present. Ellagic acid not found.

Systematics Tetracentron (1; T. sinense; eastern Nepal to Arunchal-Pradesh, northern Burma, southwestern and central China).

Tetracentron is sister to Trochodendron (Trochodendraceae).

Fossils Trochodendron is known from many Eocene to Miocene records in western North America and Europe.

Habit Androdioecious, evergreen tree, exclusively with long-shoots. Buds large, covered with numerous imbricate scales.

Vegetative anatomy Phellogen ab initio superficial. Young stem with separate vascular bundles. Wide primary medullary strands alternating with narrow strands. Vessel elements with scalariform or reticulate-scalariform perforation plates; vessels usually approx. same length and width as tracheids. Imperforate tracheary xylem elements fibre tracheids and tracheids, tracheids in young wood with scalariform bordered pits, in older wood with circular bordered pits, fibre tracheids with crossfield pit pairs. Wood rays uniseriate or multiseriate, heterocellular. Axial parenchyma apotracheal diffuse or diffuse-in-aggregates. Sieve tube plastids S type. Nodes 1:1 to 7:7, unilacunar to multilacunar, with one or more leaf traces (often 3:3, trilacunar with three traces). Sclerenchymatous idioblasts (also in cortex), with sclereids of different kinds, often branched, non-secretory. Crystals?

LeavesAlternate (spiral), simple, entire, coriaceous, with supervolute? ptyxis. Stipules and leaf sheath absent. Petiole vascular bundle transection arcuate, with three bundles and wing bundles. Venation pinnate, brochidodromous; secondary veins running together with lateral veins into persistent transparent cap. Stomata paracytic, cyclocytic or laterocytic, surrounded by one pair of hippocrepomorphic (U-shaped) subsidiary cells. Cuticular wax crystalloids as clustered tubuli (Berberis type), chemically dominated by nonacosan-10-ol. Mesophyll with sclerenchymatous idioblasts, often branched, with sclereids of different kinds (also asterosclereids, non-secretory). Idioblasts with ethereal oils absent. Leaf margin serrate to crenate, with chloranthoid teeth.

Inflorescence Terminal, racemose botryoid or reduced panicle, cymose, with terminal flower. Floral prophylls (bracteoles) absent.

Flowers Actinomorphic. Half epigyny. Tepals absent, or up to five rudimentary, scale-like in early bud, early caducous. Nectaries present on horizontally expanded dorsal/abaxial ovary walls. Disc absent.

Androecium Stamens c. 40 to c. 70 (to more than 100), spiral. Filaments free. Anthers basifixed, non-versatile, tetrasporangiate, latrorse, longicidal-valvicidal (dehiscing by longitudinal slits expanding into two transverse lines at each end, resulting in two wing-shaped valves); connective slightly prolonged. Tapetum secretory, with binucleate cells. Staminodia absent.

Pollen grains Microsporogenesis simultaneous. Pollen grains usually tricolp(or)ate (sometimes tetracolp[or]ate), shed as monads, bicellular at dispersal. Exine tectate, with columellate infratectum, perforate to rugulate-reticulate at mesocolpia, striate (with more or less parallel striae) near apertures.

Gynoecium Carpels (four to) six to eleven (to 17), in a single whorl, connate at base; carpel plicate, postgenitally partially fused, with or without secretory canal. Ovary semi-inferior, (quadri- to) sexa- to 11(–17)-locular at base; ovaries unilocular elsewhere (apocarpy). Stylodia erect, conduplicate, recurved, with ventral secretory canal. Stigma adaxially decurrent, papillate, Dry type. Pistillodium absent.

Ovules Placentation apical-axile (lateral/marginal). Ovules c. 15 to c. 30 per carpel, anatropous, pendulous, apotropous, bitegmic, crassinucellar, expanded at chalazal end. Micropyle bistomal (or endostomal?), prolonged. Outer integument two cell layers thick. Inner integument at least three cell layers thick. Hypostase present. Megagametophyte monosporous, Polygonum type. Endosperm development ab initio cellular. Endosperm haustoria? Embryogenesis caryophyllad.

Fruit A multifolliculus-like ventricidal and somewhat loculicidal syncarpous capsule (sometimes also abaxially dehiscent). Adaxial side of free carpel segments developing faster than abaxial side during fruit maturation, making stylodia expanding horizontally (stylodia finally basal on abaxial side).

Seeds Aril absent? Seed with outgrowth, pendant. Seed coat thin, endotestal-exotegmic. Exotestal cells wider than inner cells. Endotesta palisade, with short sclerotic and somewhat thickened cell walls. Tegmen unspecialized. Exotegmen tracheidal, with thick-walled cells. Chalazal outgrowth present. Vascular bundle hairpin-shaped. Perisperm not developed. Endosperm copious, oily and proteinaceous. Embryo small, straight, well differentiated, without chlorophyll. Cotyledons two. Germination phanerocotylar.

Phytochemistry Flavonols (kaempferol, quercetin, myricetin), cyanidin, proanthocyanidins (prodelphinidins), tyrosine-derived cyanogenic compounds, dhurrin (a cyanogenic glycoside) and oleanolic acid derivatives present. Ellagic acid not found.

Systematics Trochodendron (1; T. aralioides; southern Korean Peninsula, Japan, the Ryukyu Islands, northern Taiwan).

Trochodendron is sister to Tetracentron (Tetracentraceae).

Bailey IW, Nast CG. 1945. Morphology and relationships of Trochodendron and Tetracentron I. Stem, root, and leaf. – J. Arnold Arbor. 26: 143-153.

Bailey IW, Thompson WP. 1918. Additional notes upon the angiosperms Tetracentron, Trochodendron, and Drimys, in which vessels are absent from the wood. – Ann. Bot. 32: 503-512.

Bonderson W. 1952. Entwicklungsgeschichte und Bau der Spaltöffnungen bei den Gattungen Trochodendron Sieb. et Zucc., Tetracentron Oliv., und Drimys J. R. et G. Forst. – Acta Horti Berg. 16: 169-217.

Chaw S-M. 1992. Pollination, breeding syndromes, and systematics of Trochodendron aralioides Sieb. et Zucc. (Trochodendraceae), a relictual species in eastern Asia. – In: Peng C-I (ed), Phytogeography and botanical inventory of Taiwan, Botanical series 12, ROC, Taipei, pp. 63-77.

Chen L, Ren Y, Endress PK, Tian X-H, Zhang X-H. 2007. Floral organogenesis in Tetracentron sinense (Trochodendraceae) and its systematic significance. – Plant Syst. Evol. 264: 183-193.

Crane PR. 1984. A re-evaluation of Cercidiphyllum-like plant fossils from the British early Tertiary. – Bot. J. Linn. Soc. 89: 199-230.

Crane PR, Manchester SR, Dilcher DL. 1991. Reproductive and vegetative structure of Nordenskioldia (Trochodendraceae): a vesselless dicotyledon from the early Tertiary of the northern hemisphere. – Amer. J. Bot. 78: 1311-1334.

Croizat L. 1947. Trochodendron, Tetracentron, and their meaning in phylogeny. – Bull. Torrey Bot. Club 74: 60-76.

Doweld AB. 1998. Carpology, seed anatomy and taxonomic relationships of Tetracentron (Tetracentraceae) and Trochodendron (Trochodendraceae). – Ann. Bot. 82: 413-443.

Endress PK. 1986. Floral structure, systematics, and phylogeny in Trochodendrales. – Ann. Missouri Bot. Gard. 73: 297-324.

Endress PK. 1993. Trochodendraceae. – In: Kubitzki K, Rohwer JG, Bittrich V (eds), The families and genera of vascular plants II. Flowering plants. Dicotyledons. Magnoliid, hamamelid and caryophyllid families, Springer, Berlin, Heidelberg, New York, pp. 599-602.

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Hara H, Kanai H. 1964. The discovery of Tetracentron in West Nepal. – J. Jap. Bot. 39: 193-195.

Harms H. 1897. Über die Stellung der Gattung Tetracentron Oliv. und die Familie der Trochodendraceen. – Ber. Deutsch. Bot. Ges. 15: 350-360.

Hsu Y-C, Jane W-N, Chen S-H. 2013. Microsporogenesis and exine structure in Trochodendron aralioides Siebold and Zuccarini (Trochodendraceae). – Plant Syst. Evol. 299: 1057-1064.

Hsu Y-C, Jane W-N, Chen S-H. 2017. Inflorescence and floral development in Trochodendron aralioides (Trochodendraceae). – Plant Syst. Evol. 303: 403-412.

Huang SF, Lin TP. 2006. Migration of Trochodendron aralioides (Trochodendraceae) in Taiwan and its adajacent areas. – Bot. Stud. 47: 83-88.

Jørgensen LB, Møller JD, Wagner P. 1975. Secondary phloem of Trochodendron aralioides. – Svensk Bot. Tidskr. 69: 217-238.

Keng H. 1959. Androdioecism in the flowers of Trochodendron aralioides. – J. Arnold Arbor. 40: 158-160.

Kubitzki K, Reznik H. 1966. Flavonoid-Muster der Polycarpicae als systematisches Merkmal I. Übersicht über die Familien. – Beitr. Biol. Pflanzen 42: 445-470.

Li H-F, Chaw S-M, Du C-M, Ren Y. 2011. Vessel elements present in the secondary xylem of Trochodendron and Tetracentron (Trochodendraceae). – Flora 206: 595-600.

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Manchester SR, Crane PR, Dilcher DL. 1991. Nordenskioldia and Trochodendron (Trochodendraceae) from the Miocene of Northwestern North America. – Bot. Gaz. 152: 357-368.

Mohana Rao PR. 1981. Seed and fruit anatomy of Trochodendron aralioides. – Phytomorphology 31: 18-23.

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Nast CG, Bailey IW. 1946. Morphology of Euptelea and comparison with Trochodendron. – J. Arnold Arbor. 27: 186-192.

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“TROCHODENDRIDAE”

TROCHODENDRALES Takht. ex Cronquist

TETRACENTRACEAE A. C. Sm.

TROCHODENDRACEAE Eichler