Botanical Journal of the Linnean Society (2001), 135: 1—11. With 21 figures doi:10.1006/bojl.2001.0417, available online at httpWwww.idealibrary.com on IDE

Observations on the vegetative anatomy of : habital, organographic and phylogenetic conclusions

SHERWIN CARLQUIST FLS

Santa Barbara Botanic Garden, 1212 Mission Canyon Road, Santa Barbara, California 93105, U.S.A.

Received December 1999; accepted for publication April 2000

For the single species of Austrobaileya (Austrobaileyaceae), quantitative and qualitative data are offered on the basis of a mature stem and a root of moderate diameter. Data available hitherto have been based on stems of small to moderate diameter, and roots have not previously been studied. Scanning electron microscope (SEM) photographs are utilized for roots, and show compound starch grains. Roots lack sclerenchyma but have relatively narrow vessels and abundant ray tissue. Recent phylogenies group Austrobaileyaceae with the woody families , , and (these four may be considered ), and somewhat less closely with the vesselless families Amborellaceae and Winteraceae and the aquatic families Cambombaceae and Nymphaeaceae. The vessel-bearing woody families above share vessels with scalariform perforation plates; bordered bars on plates; pit membrane remnants present in perforations; lateral wall pitting of vessels mostly alternate and opposite; tracheids and/or septate fibre-tracheids present; axial parenchyma vasicentric (sometimes abaxial); rays Heterogeneous Type I; ethereal oil cells present; stomata paracytic or variants of paracytic. Although comparisons between vessel- bearing and vesselless families must depend on fewer features, Amborellaceae and Winteraceae have no features incompatible with their inclusion in an expanded Illiciales. © 2001 The Linnean Society of London

ADDITIONAL — KEYWORDS: — — Amborellaceae ethereal — cells — oil Illiciaceae Schisandraceae stomata —

— tracheid — — dimorphism Trimeniaceae vessel origin Winteraceae — wood anatomy.

INTRODUCTION considered by most authors to belong to (see Metcalfe, 1987, for a survey). Several authors have Vegetative anatomy of Austrobaileya scandens C. T. favoured a placement in (e.g. Endress, White, sole species of Austrobaileyaceae, was first 1980). Loconte & Stevenson (1991) regarded Austro studied by Bailey & Swamy (1949); their work has baileyaceae as a sister group to the remainder of been included in the summary of the family in Metcalfe Magnoliales. Some recent workers have grouped Au (1987). Although vegetative anatomy of the species is strobaileya in or near Illiciales, along with Illiciaceae relatively well known, important new details can be and Schisandraceae (Nandi, Chase & Endress, 1998; added here because new kinds of material—liquid- Renner, 1999). Trimeniaceae are included in this al preserved mature stems as well as roots of small to liance by Renner (1999); the Angiosperm Phylogeny moderate diameter—were available. New records for Group (1998), Nandi, Chase & Endress (1998), and anatomical feature character states in Austrobaileya Renner (1999) also place Arnborellaceae, Ca are offered below. bombaceae, Nymphaeaceae, and Winteraceae close to New information concerning Austrobaileya is of spe Illiciales. This group of families was left phylo cial interest because of the many primitive features genetically unplaced and without an ordinal name by the genus has been claimed to possess (Bailey & the Angiosperm Phylogeny Group (1998). The pre Swamy, 1949; Dickinson & Endress, 1983). New in sentations of Nandi, Chase & Endress (1998) who call formation on Austmbaileya is also of potential value the group “Magnoliid II” and Renner (1999), who calls because the phylogenetic position of the genus has the group “expanded Nymphaeales”, clearly consider shifted considerably in recent years, depending on the this group of families as basal in and evidence adduced. Previous to 1980, Austrobaileya was therefore in angiosperms as a whole. 1 0024—4082/01/010001 + 11 $3500/0 © 2001 The Linnean Society of London __ __

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Figures 1—4. Wood sections from mature E,• stem of Austrobaileya scandens. Fig. 1. Transverse section; vessels increase in diameter from near pith (below) to near cambium (above). Scale bar =100 tim. Fig. 2. TS. Axial parenchyma is abaxial to vessels. Scale bar=50 am. Fig. 3. Tangential section; in additional to two wide multiseriate rays, less conspicuous uniseriate rays are present. Scale bar = 100 urn. Fig. 4. Radial section; upright, square, and procumbent cells are about equally abundant. Scale bar= 100 jam.

upright cells as sheathing and tip cells (Fig. 3). No walls are lignified; pits are commonly bordered as seen quantitative data for ray width and height are given in sectional view (Fig. 5). Starch is common in septate because of great variability in these features. Ray cell fibre-tracheids, axial parenchyma and ray cells. Dark- A USTROBAILEYA VEGETATIVE ANATOMY 5

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Figures 5—9. Sections of Austrobaileya sccindens. Figs 5—6. Mature stem secondary xylem radial section. Scale bar = 20 jim. Fig. 5. Portions of ray cells from radial section to show bordered nature of pits. Fig. 6. Fibre-tracheid with small bordered pits and (above) a septum. Figs 7—9. TS medium-diameter root. Fig. 7. TS secondary xylem, pith below; multiseriate ray very wide. Scale bar =100 jim. Fig. S. Portion of transection, secondary xylem (lower right) and secondary phloem (upper right), with phloem ray (upper left) and xylem ray (lower left). Scale bar=50jim. Fig. 9. Bark transection with phellem at top and secondary phloem below; sclerenchyma is absent. Scale bar =100 jim. 6 S. CARLQUIST coloured phenolic compounds in some septate fibre cortical cells are stretched tangentially, and some of tracheids and in some ray cells (Fig. 4). No ethereal these cells are subdivided by a radial division. At the oil cells were observed in stem secondary xylem. inside of the cortex is a ring of sclerenchyma. The sclerenchyma consists of strands of phloem fibres (cor Root wood anatomy responding to fascicular areas of the primary stem) between which brachysclereids are intercalated. As the Growth rings absent (Fig. 7). Vessels mostly solitary, stem increases in diameter, the ring remains unbroken mean number of vessels per 1.17. group is Vessels are because brachysclereids are continually added. In not in tangential or radial groupings. Mean vessel ternal to the ring of selerenchyma is secondary phloem, diameter ranges from 18 un pm. to 70 Mean vessel including dilated phloem rays. The phloem rays are element length, 551 aim. All vessel elements have scal composed of thin-walled cells that contain abundant ariform perforation plates (Figs 16—19). Bars of per compound starch grains. The axial secondary phloem foration plates comparatively with wide respect to the consists of nearly tangential bands of phloem par rather narrow perforations (Figs 16—19, especially Figs enchyma alternating with bands of nonfunctional sieve 17 and 19). Pit membrane remnants present in a few cells, except close to the cambium, where sieve cells perforations (Fig. 17). Number of bars per plate, 5—18; are still functional. Within the secondary phloem are mean number, 10.3. Mean vessel wall thickness, axially elongate idioblasts containing dark phenolic 2.2 pm. Mean number of vessels mm2 was not de compounds (Fig. 12). These idioblasts are in vertical termined because of abundance of ray tissue. Lateral strands of one to three cells. Scalariform sieve areas wall pitting vessels of is mainly alternate (Fig. 16), are conspicuous in radial sections of secondary phloem although opposite, transitional, and scalariform pat (Fig. 13). No companion cells in the ordinarily accepted terns are occasional. Circular lateral vessel wall pits sense of the term were observed in the material ex are 7 jim in diameter. Imperforate tracheary elements amined (Fig. 11). are tracheids and fibre-tracheids; septa are clearly seen in at least some of the fibre-tracheids. Mean tracheid length, 780 pm. Mean tracheid wall thickness, Root cortex, bark, and phloem anatomy 5.2 pm. Tracheid pits are circular, pit cavity diameter The outer surface of the root is clothed with layers of about 7 jim (Fig. 18, left). Apertures of the pits as seen phellem (Fig. 9); phellem cells are filled with deposits from the lumen side of the tracheid pits are slitlilce of dark phenolic compounds which give the root a (Fig. 20). Fibre-tracheids are often adjacent to rays. brown colour in gross aspect. Internal to the phellem Mean fibre-tracheid length, 763 jim. Fibre-tracheid and phellogen are several layers of phelloderm, most wall thickness, 0.9 jim (Fig. 21). Pits of fibre-tracheids of which lack deposits of phenolic compounds. Cortical have narrow borders; pit cavity diameter is about 4 jim. parenchyma cells and phloem ray cells with compound Septa in fibre-tracheids, where seen, consist of a thin starch grains. Parenchyma cells in both cortex and ray primary wall. Axial parenchyma vasicentric or abaxial, regions are stretched tangentially and many of them in strands of two cells. Rays are uniseriate and narrow are subdivided by radial divisions (Figs 8, 9). There is to wide multiseriate; multiseriate rays tend to become no sclerenchyma of any kind in the cortex or phloem. very wide toward the cambium, so that ray tissue is Axial secondary phloem consists of phloem par more abundant than fascicular tissue in the secondary enchyma cells and sieve cells; no companion cells were xylem (Fig. 7). Ray cells are upright to square, rarely observed. In all but the youngest portions of the sec procumbent, either with thin primary walls (Fig. 8, ondary phloem, crushed sieve cells are intermixed with left), or with moderately thin lignified walls. Scattered persistent phloem parenchyma (Figs 8, 9). The phloem ethereal oil cells are present in the multiseriate rays, ray cells have thin nonlignified walls. Ethereal oil cells starch grains abundant in the septate fibre-tracheids are present in phloem rays and cortex (Fig. 5, arrow). (Fig. 21), axial parenchyma, and rays. Deposits of yellowish amorphous compounds are abundant in Pitk anatomy early-formed vessels, occasional in other cells as drop lets. In the mature stem, pith cells are circular in transverse section but when seen in longitudinal sections are elongate, rectangular in outline. Pith cells decrease in Stem cortex, bark, and phloem anatomy diameter toward the periphery of the pith (Fig. 1). The mature stem of Austrobaileya (Fig. 10) features Many of the pith cells have horizontally-orientated several layers of phellem, filled with dense ac septa with thin primary walls only. cumulations of dark phenolic compounds. There are The root studied (Fig. 7) has a pith composed of several layers of phelloderm, some cells of which con slender sclereids that are elongate as seen in lon tain phenolic compounds. Internal to the phelloderm gitudinal section. No ethereal oil cells were observed are large cortical cells. During expansion of the stem, in pith of either the stem or the root. A USTROBAILEYA VEGETATIVE ANATOMY 7

112

Figures 10—15. Sections of Austrobaileya scandens. Fig. 10. TS outer portion of mature stem, secondary xylem below, bark above. Scale bar= 100 lam. Fig. 11. TS secondary phloem with portion of secondary xylem, below; no companion cells evident. Scale bar = 20 jam. Fig. 12. Radial section from young stem with a little secondary growth; cells with dark contents are elongate idioblasts containing phenolic compounds. Scale bar =100 am. Fig. 13. Sieve areas on sieve element from radial section of mature stem. Scale bar = 20 tm. Figs 14, 15. Stomata and adjacent epidermal cells from paradermal section of leaf. Scale bar = 201am. Fig. 14. Stoma with subsidiary cell above upper guard cell, subdivided epidermal cells below. Fig. 15. Stoma with subdivided cell above upper guard cell; no other subsidiary cells definable. 8 S. CARLQUIST

Figures 16—21. SEM photographs of radial section of secondary xylem of medium-diameter root of Austrobaileya scanclens. Fig. 16. Portions of two perforation plates; lateral wall pitting at upper left. Fig. 17. Four perforations, with pit membrane remnants present in the central two. Fig. 18. Scalariform perforation plate at right; at left, tracheids with outer surfaces exposed, showing circular pit membranes. Fig. 19. Vessel with narrow perforations, left; tracheid at right. Fig. 20. Inner surface of tracheid, showing slitlike pit apertures. Fig. 20. Portions of fibre-tracheids filled with compound starch grains. Magnification scale at lower right in each figure = 5 jim. A USTROBAILEYA VEGETATIVE ANATOMY 9

Leaf anatomy and stomata & Tupper, 1918). Another possible factor in this regard The observations on leaf anatomy offered by Bailey & is that scandent species accumulate secondary xylem Swamy (1949) were confirmed in the present study. relatively slowly, and thus may exhibit a more juvenile The stomata of Austrobaileya have been reported to wood; in typical woody species, length of vessel ele be paracytic or anomocytic. That description is con ments increases with amount of secondary growth firmed by the present study. Two stomata are il (Bailey & Tupper, 1918). lustrated here. The stoma in Figure 14 would be The differences between stem wood and root wood paracytic ifthere were a true subsidiary cell paralleling of Austrobaileya may be explained by function: the the lower guard cell in the photograph. Instead, there roots evidently serve more for storage (judging from are two epidermal cells that appear to have cut off abundance of ray tissue and abundance of starch), the derivatives that parallel the lower guard cell. Above stems more for water conduction. Thus, the root vessels the guard cell pair in Figure 15 is a subsidiary cell that of Austrobaileya are narrower than those of the stem, has been subdivided. These stomata do not correspond which runs contrary to the generalization of Patel exactly to the concept of paracytic subsidiary cells (1965) that within a give species, root vessels are wider (or to the equivalent in other systems of stomatal than those of stem. The narrowness of perforations in terminology), but could be considered intermediate perforation plates of roots of Austrobaileya may also between paracytic and anomocytic. be also indicate that the root structure is less adapted to meet high conductive rates of water in comparison to the stem, in which perforations are relatively wide DISCUSSION and bars comparatively thin. There are ethereal oil cells in the cortex and phloem Habit and organography rays of the root in Austrobaileya, whereas ethereal oil Correlations between habit and wood anatomy must be cells have not been reported in comparable tissues of examined before characters likely to reflect taxonomic the stem (Table 1). Perhaps the abundance of starch relationships can be identified. The data in Table 1 storage in the root and the presence in the soil of starch- highlight wood modifications related to habit. Austro consuming pathogens provide reasons for a selective baileya is a . The nature of wood with respect to value of ethereal oil cells in the root. Likewise, the the lianoid habit in possibly related genera has been dark-coloured phenolics in phellem of the root may examined in a series of papers that cover the three deter predation or entry of pathogens. Ethereal oil other families of the revised order Illiciales. All species cells are present in wood of Schisandraceae (Table 1), of Schisandraceae are scandent, albeit variously, and but not in wood of Illiciaceae. Mucilage cells, a sort of their wood has been studied by Cariquist (1999). Pip close vicarious equivalent to oil cells, are present in tocalyx of the Trimeniaceae is a liana, and data on its fibre-like axial xylem cells of and in ray cells wood may be found in Carlquist (1984). All Illiciaceae of Piptocalyx. The lack of oil cells in wood is (Carlquist, 1982b) and the genus Trimenia Carlquist, not a significant taxonomic character; oil cells are 1984) of Trimeniaceae are or and have located elsewhere in the in Illicium (Table 1). wood patterns typical of nonscandent woody Idioblasts (crystals, laticifers, etc.) are always more and therefore offer good comparisons for study of wood common closer to the surface of a plant, and are least modifications of the scandent genera. The samplings of common in wood (deposition of deterrent compounds woods of lianas by Carlquist (1975) show the following in the lumina of dead heartwood cells forms a barrier characteristics for the lianoid species: vessels wider, to rot or predation equivalent to the idioblasts near the stems beginning with narrower vessels but pro the plant surface). ducing increasingly wider vessels as secondary growth proceeds; (2) vessel density (number of vessels mm2 of transection) relatively great when one takes the Phylogeny wide vessel diameter into account; (3) vessel elements Austrobaileyaceae are grouped with the vessel-bearing shorter; (4) in those families with scalariform per families Illiciaceae, Schisandraceae, and Trimeniaceae foration plates (e.g. Dilleniaceae, in which Tetracera into an order that could be called an expanded version is scandent), fewer bars per perforation plate. The of Illiciales, by the Angiosperm Phylogeny Group vessel elements of Austrobaileya may not seem short, (1998), and other recent authors (see Introduction). but when compared to those of Illicium, they are Features that link Austrobaileyaceae, Illiciaceae, Schi shorter. Length of vessel elements in scandent species sandraceae, and Trimeniaceae with respect to wood may not represent the scandent habit per se, but may anatomy are (Table 1): vessels with scalariform per be related to the degree of phylogenetic specialization foration plants (chiefly with more than 10 bars); of the scandent genus, since more specialized di- bordered bars on perforation plates; pit membrane cotyledons tend to have shorter vessel elements (Bailey remnants in perforation (see Cariquist, 1992); vessels 10 S. CARLQUIST with mostly alternate or opporsite lateral wall pits; Stomata are paracytic or possibly some related type tracheids with large circular bordered pits (both in the woody families of the expanded Illiciales except tracheids and septate fibre-tracheids in Austro for Austrobaileya (which has mixed anamocytic and baileyaceae; septate fibre-tracheids and no tracheids in paracytic) Illiciaceae (paracytic and laterocytic) and Trimeniaceae); vasicentric axial parenchyma (tending Schisandraceae (haplocheilic) according to Metcalfe towards abaxial in Austrobaileyaceae and Sch (1987). In the haplocheilic type, the subsidiary cells isandraceae, some diffuse parenchyma in Illiciaceae); are cut from adjacent epidermal cells rather than from rays corresponding to Heterogeneous Type I of Kribs the mother cell of the guard cell, and some stomata in (1935); and ethereal oil cells or mucilage cells (see Austrobaileya may correspond to an incipient haplo comments in above paragraph). This is a surprising cheilic type. More study of ontogeny of stomata, with list of shared features, and all of them except for the appropriate terminological corrections, is needed. presence of septate fibre-tracheids are best interpreted Chloranthaceae are said to have “paracytic variants” as primitive character states (plesiomorphies). The in stomata of leaves (Metcalfe, 1987), and this term development of fibre-tracheids in Austrobaileya has might be applied to Austrobaileya and Schisandraceae been interpreted as an apomorphy here. The ray type as well. in all four families is the same. The scalariform end- Thus, vegetative anatomy as a whole supports the wall pitting of tracheids in Amborella (Metcalfe, 1987) concept of an expanded Illiciales. The differences other may be a precursor to development of vessels with than those related to habit are relatively minor, and scalariform perforation plates, as in Austrobaileya and the degree of identity or close identity in wood and Illiciaceae. other vegetative features (Table 1) is greater than one A striking feature of considerable phylogenetic sig might expect for a group of relatively ancient families of nificance is the presence of porose pit membrane rem dicotyledons. If, as recent molecular evidence suggests, nants in Austmbaileya, Illiciaceae (Carlquist, 1992) Nymphaeales are basal to Illiciales, the anatomy of and Schisandraceae (Carlquist, 1999). Trimeniaceae Nymphaeales is very difficult to compare to that of have not been studied in this respect. The porose pit Illiciales because so many of the differences between membrane remnants seem just a small step beyond the two orders are attributable to the aquatic (or near the porose pit membrane (presumably intact) of tra aquatic, Barclaya) habit of Nymphaeales. cheids of Bubbia (Carlquist, 1983). The lack of companion cells in Austrubaileya claimed by Bailey & Swamy (1949) was essentially confirmed by REFERENCES Huber & Graf (1955), who found only a few companion Angiosperm Phylogeny Group. 1998. An ordinal clas cells. No companion cells were identified in the present sification for the families of flowering plants. Annals of the study. Srivastava (1970) claimed that Austrobaileya Missouri Botanical Garden 85: 531—553. has companion cells but he used an altered definition Bailey 1W, Swamy BGL. 1949. The morphology and re of that terms. Companion cells have traditionally been lationships of Austrobaileya. 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