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Retamales, Hernan Alfonso, Scherson, Rosa, & Scharaschkin, Tanya (2014) Micromorphology and anatomy of leaves of ’Syzygium floribundum’ (Myr- taceae: Syzygieae), a rainforest tree endemic to eastern Australia. Proceedings of the Royal Society of Queensland, 119, pp. 45-52.
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Notice: Please note that this document may not be the Version of Record (i.e. published version) of the work. Author manuscript versions (as Sub- mitted for peer review or as Accepted for publication after peer review) can be identified by an absence of publisher branding and/or typeset appear- ance. If there is any doubt, please refer to the published source. 1 Micromorphology and anatomy of leaves of Syzygium floribundum (Myrtaceae:
2 Syzygieae), a rainforest tree endemic to eastern Australia
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4 Hernan A. RetamalesA, Rosa SchersonB, Tanya ScharaschkinA
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6 ASchool of Earth, Environmental and Biological Sciences, Science and Engineering Faculty.
7 Queensland University of Technology. Brisbane, QLD 4001, Australia.
8 BPlant Biology Laboratory, Faculty of Forest Sciences and Nature Conservation, University
9 of Chile, P.O. Box 9206, Santiago, Chile.
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29 ABSTRACT
30 Although species of Syzygium are abundant components of the rainforests in Queensland and
31 New South Wales, little is known about the anatomy of the Australian taxa. Here we describe
32 the foliar anatomy and micromorphology of Syzygium floribundum (syn: Waterhousea
33 floribunda) using standard protocols for scanning electron microscopy (SEM) and light
34 microscopy. Syzygium floribundum possesses dorsiventral leaves with cyclo-staurocytic
35 stomata, single epidermis, internal phloem, rhombus-shaped calcium oxalate crystals and
36 complex-open midrib. In general, leaf anatomical and micromorphological characters are
37 common with some species of the tribe Syzygieae. However, this particular combination of
38 leaf characters has not been reported in a species of the genus. The anatomy of the species is
39 typical of mesophytic taxa.
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41 INTRODUCTION
42 Syzygium Gaertn. is a large genus in the family Myrtaceae that comprises approximately
43 1200 species (Craven and Biffin, 2010). Species of the genus are predominantly trees
44 occurring in rainforests from China and southeast Asia to south eastern Australia (Hyland,
45 1983; Craven et al., 2006). These species are abundant components in the upper and medium
46 strata of rainforests of eastern Australia (Hyland, 1983). Syzygium floribundum F.Muell (sect.
47 Waterhousea) (Weeping Lilly Pilly) is a tree up to 30 m tall (FIG 1 A). It is endemic to
48 Australia and occurs in southeastern Queensland and northeastern New South Wales, mainly
49 along creeks and rivers in microphyll rainforests (Hyland, 1983). The species is regarded as a
50 horticulturally important tree, adequate for streets and gardens and appears to be relatively
51 tolerant to myrtle rust (Queensland Government, 2014). As with other species of Myrtaceae,
52 it is also important for local fauna as a food source, particularly birds and insects (Wilson,
53 2011).
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55 Syzygium floribundum was formerly placed in the genus Waterhousea B. Hyland, which was
56 recognized as an exclusively Australian genus with four species. It has recently been
57 transferred to Syzygium on the basis of molecular and morphological phylogenetic evidence
58 (Biffin et al., 2006; Craven et al., 2006; Craven & Biffin 2010). Waterhousea (B.Hyland)
59 Craven & Biffin, comb. nov. is now considered a section in subgenus Acmena (DC.) Craven
60 & Biffin, comb. nov., in the genus Syzygium.
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62 Anatomical and micromorphological characters have shown to be relevant for taxonomic
63 delimitation in the family (Schmid, 1980; Fontenelle et al., 1994), but only a few species
64 have been examined. The leaf anatomy of a number of species of Syzygium, but not S.
65 floribundum, was investigated by Soh & Parnell (2011) and shown to be taxonomically
66 useful for the infrageneric classification of the genus. The leaf surface micromorphology has
67 not been described for any species in the genus. This investigation aims to undertake a
68 complete anatomical and micromorphological description of the leaves of Syzygium
69 floribundum so as to determine if there are any taxonomically important characters that
70 differentiate this species from others in the genus.
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72 MATERIAL AND METHODS
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74 SAMPLING
75 Mature leaves of Syzygium floribundum were collected as fresh material from the natural
76 habitat of the species (FIG 1 B). Leaves were collected from sun-exposed branches from
77 randomly selected individual trees in a riverside forest in Enoggera, QLD (27° 26' 27" S /
78 153° 0' 45" E) and a small rainforest 2 km away from the coast in Noosa, QLD (26° 38' 52" S
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79 / 153° 2' 36" E). Specimens (Reta-056.1, Reta-056.2, Reta-056.3 and Reta-056.4) are
80 currently housed at the Queensland Herbarium (BRI). The location of sampling localities and
81 the geographical distribution of the species are shown in the FIG 2.
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83 SCANNING ELECTRON MICROSCOPY
84 Leaves were fixed in FAA for 24-48h, dehydrated using a graded ethanol series and then
85 critical point dried (Anderson, 1951) in an Autosamdri-815 automatic critical point drier.
86 Samples were mounted on stubs with self-adhesive double-sided carbon discs and sputter-
87 coated with gold palladium for 175 sec using a Leica EM SCD005 Gold Coater. Examination
88 and photography were conducted using a FEI Quanta 200 SEM/ESEM operated at 10kV.
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90 LIGHT MICROSCOPY
91 Leaves were fixed in FAA for 24-48h prior to being dehydrated through a graded ethanol
92 series and embedded in paraffin wax (Johansen, 1940; Ruzin, 1999). Transverse sections
93 (5µm thickness) were cut using a Leica rotary microtome. Staining of sections was performed
94 using a 0.05% (w/v) of ruthenium red in distilled water and a counterstaining with 0.1%
95 (w/v) solution of toluidine blue (TBO) in distilled water (O’Brien et al., 1964; Chaffey et al.,
96 2002). Leaf clearings were prepared by immersing tissue fragments of 1-2 cm2 in 10% KOH
97 at room temperature for 48 h followed by 7% NaClO for 2 h or until leaves turned transparent.
98 Cleared leaves were washed five times with distilled water, stained with 0.1% safranin and
99 mounted with lactoglycerol (lactic acid-glycerol 1:1). Sections were dried and mounted with
100 Entellan mounting medium. Slides were observed using a Nikon SMZ 800 Stereo light
101 microscope (Nikon eclipse 50i compound) and images captured using the NIS Elemental
102 digital image analysis software.
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104 TERMINOLOGY
105 Terminology for general anatomical descriptions, including glands, stomatal complex types
106 and cell types were based on Esau (1953) and Gifford and Foster (1989). Myrtaceae-specific
107 terminology was based on previous work on this family (Schmid, 1980, 1984; Keating, 1984;
108 Cardoso et al., 2009; Soh & Parnell, 2011 and da Silva et al., 2012).
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110 RESULTS
111 GROSS MORPHOLOGY OF LEAVES
112 The leaves of S. floribundum are simple, opposite, lanceolate-elliptical in shape. The apex is
113 acuminate and the base attenuate. Both surfaces are punctuated. Leaves have numerous
114 secondary and tertiary reticulate veins. Venation is pinnate and weakly to strongly
115 brochidodromus. Intramarginal veins are visible on both adaxial and abaxial surfaces (FIG. 3
116 A).
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118 CUTICLE, EPIDERMAL CELLS AND STOMATA
119 The adaxial cuticle is thicker than the abaxial cuticle. The cuticle contains polyphenols as
120 indicated by bluish-green staining with TBO. Epicuticular waxes are mainly granules and
121 flakes and randomly distributed on the surface (FIG. 3 B).
122 Adaxial and abaxial epidermal cells are small, compressed, plano-convex and mainly
123 isodiametric. Adaxial epidermal cells are rounded and have straight cell walls, while abaxial
124 epidermal cells are irregularly rounded and the anticlinal cell walls are strongly sinuous (FIG.
125 3 C).
126 Stomatal complexes are cyclo-staurocytic and randomly distributed on the abaxial surface of
127 the leaf (Fig. 3 B), but also can occur in groups above midrib. Guard cells are kidney-shaped
128 and the pore between them is narrow at the equatorial region. Stomata are circular to
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129 elliptical and are located at the same level of the epidermal cells. The length of the guard
130 cells is 8–13 m long.
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132 MIDRIB
133 The midrib of S. floribundum is a mixture of closed and complex open, with two or more
134 vascular bundles packed in the centre of the leaf (FIG. 4 A, B). The leaf blade is impressed
135 on the adaxial surface above the midrib. The bundle sheath extension is composed of
136 rounded-polygonal cells and is clearly developed, particularly on the abaxial side (FIG. 4 A).
137 The midrib is arc-shaped with a deep curvature. The abaxial side is convex and the adaxial is
138 slightly concave to straight (FIG. 4 B). Fibres are continuous around the midrib. Xylem
139 vessels of the midrib show scalariform perforation plates and helical wall thickenings. This
140 species has internal phloem, with a well-developed adaxial phloem partition. Incurved
141 margins of the phloem are poorly developed. Phloem sieve tubes and companion cells have
142 thin primary cell walls. Phloem fibres have evident and thick secondary cell walls.
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144 MESOPHYLL
145 The mesophyll is dorsiventral and is formed by a 1-2 layered palisade parenchyma and a
146 spongy parenchyma with abundant intercellular spaces. The palisade parenchyma layer is
147 somewhat loose and composed of rectangular, attenuated and vertical cells. These cells
148 possess thin primary cell walls and numerous chloroplasts. The spongy parenchyma is
149 composed of irregular shaped cells (rounded to star-shaped). Both palisade and spongy
150 parenchyma contain mucilage (FIG 4 C). Subepidermal idioblasts with rhombus-shaped
151 calcium oxalate crystals occur throughout the palisade parenchyma (FIG. 4 D). Secretory
152 cavities are present on both sides of the leaf, are abundant throughout the mesophyll and have
153 variable dimensions (62 ± 25 m of diameter). They are composed of large spaces
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154 surrounded by a sheath of peripheral epithelial cells. These cells are almost completely
155 disintegrated in mature leaves (FIG. 4 E). In paradermal view, secretory cavities are observed
156 as one overlying cell surrounded for 6-8 elongated cells. There are no stomata in the vicinity
157 of the secretory cavities (FIG. 3 D).
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159 DISCUSSION
160 Syzygium floribundum shares a number of anatomical and micromorphological characters
161 with other Myrtaceae. Some of these features include the presence of calcium oxalate crystals,
162 internal phloem and schizogenous secretory cavities. Anatomical characters described here
163 largely agree with Keating (1984) and Soh & Parnell (2011) for Syzygium/Waterhousea.
164 Nonetheless, the combination of some features such as cyclo-staurocytic stomata, rhombus-
165 shaped crystals, midrib with a well-developed adaxial phloem partition and poorly developed
166 incurved margins of the phloem are not found in other species of the genus.
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168 Calcium oxalate crystals have been reported in practically all the Myrtaceae studied (Cardoso
169 et al., 2009; Gomes et al., 2009; Soh & Parnell, 2011). However, rhombus-shaped calcium
170 oxalate crystals as those found in this study have been reported in a few Myrtaceae, mainly
171 some species of Syzygium (Soh & Parnell, 2011). The function of these crystals is not
172 completely clear, but has been related to the regulation of calcium and other minerals (Volk
173 et al., 2002), as well as protection against herbivores and pathogens (Franceschi & Nakata,
174 2005; Korth et al., 2006).
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176 Internal phloem was found in all vascular bundles of leaves, either as continuous tissue or as
177 different degrees of adaxial phloem partition. This feature is regarded as a typical anatomical
178 character in the order Myrtales (Takhtajan, 1980; Cronquist. 1981) and is widely present in
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179 Myrtaceae (Schmid, 1980; Cardoso et al., 2009). Further investigation is needed to determine
180 whether the internal phloem is derived from the procambium, or from mesophyll cells
181 (ground tissue). This developmental difference is regarded as a potentially informative
182 taxonomic character (Patil et al., 2009).
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184 Secretory cavities follow the typical schizogenous pattern commonly observed in Myrtaceae
185 (Alves et al., 2008; Donato & Morretes, 2009; Gomes et al., 2009). The schizogenous pattern
186 can be identified by the presence of elongated epithelial cells surrounding the secretory space
187 in mature leaves (Cicarelli et al. 2008). Other patterns identified in Myrtaceae include
188 schizolysigenous secretory cavities (a mixture of schizogenous and lysigenous, the latter due
189 to disintegration of cells) in Myrtus communis (Cicarelli et al. 2008). Secretory cavities are
190 the structures referred by Hyland (1983) as oil dots on the surface of the leaves, which are
191 regarded as very numerous. Volatile oils secreted by these structures in Myrtaceae, have been
192 identified as flavonoids (Wollenweber et al., 2000) and terpenoids (Tanaka et al., 1996; Lee,
193 1998; Judd et al., 1999). Chemical compounds produced by secretory cavities were not
194 characterized in this study.
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196 Leaf anatomical characters are generally regarded as homoplaseous in the genus Syzygium.
197 However some have been shown to be useful for species identification, such as shape of the
198 midrib, type of crystals and stomatal complexes (Soh & Parnell, 2011). Anatomical
199 characters described here are similar to those described by Soh and Parnell (2011) in the
200 subgenus Acmena (DC.) Craven & Biffin, where the species previously treated as
201 Waterhousea are included. In ecological terms, a thin cuticle, a loose palisade parenchyma
202 and superficial stomata suggest a mesophytic anatomy of the leaves (Esau, 1959). This
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203 assumption matches with the common habitats of S. floribundum, which are mainly
204 rainforests, creeks and other riparian environments (Hyland, 1983; Wilson, 2011).
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206 In this study, the leaf micromorphology and anatomy of Syzygium floribundum has been
207 described for the first time. There are anatomical similarities between the species and other
208 Myrtaceae taxa, particularly in terms of typical characters of the family. Certain anatomical
209 characters are coincident with other species previously named as Waterhousea, which
210 supports the grouping of these species. Combination of anatomical characters is unique for
211 this taxon within the genus, which is relevant for identification purposes. More anatomical
212 and micromorphological studies in the group could enhance the understanding of the
213 ecophysiology of species of Myrtaceae occurring in Australasian rainforests.
214
215 ACKNOWLEDGEMENTS
216 We are very grateful to Amy Carmichael, Rachel Hancock and technician staff from QUT for
217 valuable help and technical advice. Thanks to members of the Plant Structure and
218 Systematics group at QUT for feedback and advice. Funding for this investigation has been
219 provided for CONICYT-Government of Chile and QUT.
220
221 LITERATURE CITED
222
223 ALVES, E.; TRESMONDI, F. & LONGUI, E. 2008. Análise estrutural de folhas de Eugenia
224 uniflora L. (Myrtaceae) coletadas em ambientes rural e urbano, SP, Brasil. Acta Botanica
225 Brasilica 22 (1): 241-248.
226
9
227 ANDERSON, T. 1951. Techniques for the preservation of three-dimensional structure in
228 preparing specimens for the electron microscope. Transactions of the New York Academy of
229 Sciences 13: 130.
230
231 AUSTRALIA’S VIRTUAL HERBARIUM. 2014. Map output. Council of heads of
232 Australasian Herbaria. Viewed 02 of September 2014.
233
234 BIFFIN, E.; CRAVEN, L.; CRISP, M. & GADEK, P. 2006. Molecular systematics of
235 Syzygium and allied genera (Myrtaceae): evidence from chloroplast genome. Taxon 55(1):
236 79-94.
237
238 CARDOSO, C.; PROENCA, S. & SAJO, M. 2009. Foliar anatomy of the subfamily
239 Myrtoideae (Myrtaceae). Australian Journal of Botany 57: 148-161.
240
241 CHAFFEY, N.; CHOLEWA, E.; REGAL, S. & SUNDBERG. 2002. Secondary xylem
242 development in Arabidopsis: a model for wood formation. Physiologia Plantarum: 114: 594-
243 600.
244
245 CICCARELLI, D.; GARBARI, F. & PAGNI, A. 2008. The flower of Myrtus communis
246 (Myrtaceae): Secretory structures, unicellular papillae, and their ecological role. Flora –
247 Morphology, Distribution, Functional Ecology of Plants 203: 85-93.
248
249 CRAVEN, L.; BIFFIN, E. & P. ASHTON. 2006. Acmena, Acmenosperma, Cleistocalyx,
250 Piliocalyx and Waterhousea formally transferred to Syzygium (Myrtaceae). Blumea 51: 131-
251 142.
10
252
253 CRAVEN, L. & E. BIFFIN. 2010. An infrageneric classification of Syzygium (Myrtaceae).
254 Blumea 55: 94-99.
255
256 CRONQUIST, A. 1988. The evolution and classification of flowering plants. 2nd Edition.
257 New York Botanical Garden, Bronx. 555 pp.
258
259 DA SILVA, C.; BARBOSA, L.; MARQUES, A.; BARACAT-PEREIRA, M.; PINHEIRO, A.
260 & MEIRA, R. 2012. Anatomical characterization of the foliar colleters in Myrtoideae
261 (Myrtaceae). Australian Journal of Botany 60: 707-717.
262
263 DONATO, A. & MORRETES, B. 2009. Anatomía foliar de Eugenia florida DC.
264 (Myrtaceae). Revista Brasileira de Farmacognosia 19: 759-770.
265
266 ESAU, K. 1953. Plant anatomy. (John Wiley & Sons, Inc, New York).
267
268 FONTENELLE, G.; COSTA, G. & MACHADO, R. 1994. Foliar anatomy and
269 micromorphology of eleven species of Eugenia L. (Myrtaceae). Botanical Journal of the
270 Linnean Society 115: 111-133
271
272 FRANCESCHI, V.R. & NAKATA, P. 2005. Calcium oxalate in plants: formation and
273 function. Annual Review of Plant Biology 56: 41-71.
274
275 GIFFORD, E.M. & FOSTER, A.S. 1989. Morphology and evolution of vascular plants. Third
276 edition. (Freeman, New York).
11
277
278 GOMES, S.; SOMAVILLA, N.; GOMES-BECERRA, K.; MIRANDA, S.; DE-CARVALHO
279 & GRACIANO-RIBEIRO. 2009. Anatomía foliar de espécies de Myrtaceae: contribuicoes á
280 taxonomía e filogenia. Acta Botanica Brasileira 23(1): 223-238.
281
282 HYLAND, B. 1983. A revision of Syzygium and allied genera (Myrtaceae) in Australia.
283 Australian Journal of Botany Supplementary Series 9: 1-164.
284
285 JOHANSEN, D. 1940. Plant microtechnique. (McGraw Hill Book, New York).
286
287 JUDD, W.; CAMPBELL, C.; KELLOGG, E. & STEVENS, P. 1999. Plant systematics: a
288 phylogenetic approach. (Sinauer Associates, Sunderland, MA).
289
290 KEATING, R. 1984. Leaf histology and its contribution to relationships in the Myrtales.
291 Annals of the Missouri Botanical Garden 71(3): 801-823.
292
293 KORTH, K.; DOEGE, S.; PARK, S.; GOGGIN, F.; WANG, Q.; GOMEZ, S.; LIU, G.; JIA,
294 L. & NAKATA, P. 2006. Medicago truncatula mutants demonstrate the role of plant calcium
295 oxalate crystals as an effective defense against chewing insects. Plant Physiology 141 (1):
296 188-195.
297
298 LEE, C. 1998. Ursane triterpenoids from leaves of Melaleuca leucadendron. Phytochemistry
299 49 (4): 1119-1122.
300
12
301 O’BRIEN, T.; FEDER, N. & MCGULLY, E. 1964. Polychromatic staining of cell walls by
302 Toluidine blue O. Protoplasma 59: 368-373.
303
304 PATIL, V. S.; RAO, K. & RAJPUT, K. 2009. Development of intraxylary phloem and
305 internal cambium in Ipomoea hederifolia (Convolvulaceae). Journal of the Torrey Botanical
306 Society 136: 423-432.
307
308 QUEENSLAND GOVERNMENT, 2014. Business and Industry Portal – Known plants
309 affected by myrtle rust. URL: 310 management/health-pests-weeds-diseases/weeds-and-diseases/identify-myrtle-rust/plants- 311 affected-myrtle-rust> Visited: 09 July 2014. 312 313 RUZIN, S. 1999. Plant microtechnique and microscopy. (Oxford University Press, New 314 York). 315 316 SCHMID, R. 1980. Comparative anatomy and morphology of Psiloxylon and Heteropyxis, 317 and the subfamilial and tribal classification of Myrtaceae. Taxon 29(5-6): 559-595. 318 319 SCHMID, R. 1984. Reproductive anatomy and morphology of Myrtales in relation to 320 systematics. Annals of the Missouri Botanical Garden 71 (3): 832-835. 321 322 SOH, W. & PARNELL, J. 2011. Comparative leaf anatomy and phylogeny of Syzygium 323 Gaertn. Plant Systematics and Evolution 297: 1-32. 324 13 325 TAKHTAJAN, A. 1980. Outline of the classification of flowering plants (Magnoliophyta). 326 The Botanical Review 46 (3): 225-359. 327 328 TANAKA, T.; ORII, Y.; NONAKA, G.; NISHIOKA, I. & KOUNO, I. 1996. Syzyginins A 329 and B, two ellagitannins from Syzygium aromaticum. Phytochemistry 43 (6): 1345-1348. 330 331 VOLK, G.; LYNCH-HOLM, V.; KOSTMAN, T.; GOSS, L. & FRANCESCHI, V. 2002. The 332 role of druse and raphide calcium oxalate crystals in tissue calcium regulation in Pistia 333 stratiotes leaves. Plant Biology 4 (1): 34-45. 334 335 WILSON, P. 2011. Myrtaceae. In Kubitzki, K. (eds.), The families and genera of vascular 336 plants. Vol. X. Flowering plants Eudicots: Sapindales, Cucurbitales, Myrtaceae, pp. 212-271. 337 (Springer-Verlag, Heidelberg) 338 339 WOLLENWEBER, E.; WEHDE, R.; DÖRR, M.; LANG, G. & STEVENS, J. 2000. C- 340 Methyl-flavonoids from the leaf waxes of some Myrtaceae. Phytochemistry 55 (8): 965-970. 341 342 AUTHOR INFORMATION 343 Hernan Retamales is PhD candidate at QUT working on the systematics of Australasian and 344 South American Myrtaceae using molecular and morpho-anatomical data. His PhD is funded 345 by the Government of Chile (CONICTY). Dr Rosa Scherson is a Lecturer at the School of 346 Forestry in the University of Chile and is the external supervisor of Mr Retamales. Dr Tanya 347 Scharaschkin is a Senior Lecturer at the School of Earth, Environmental and Biological 348 Sciences at QUT. She has recused herself from the review and editorial process for this 349 article, due to conflict of interest as Editor of PRSQ, which has been handled by Dr. Geoff 350 Edwards (President RSQ) instead. 14 351 352 353 FIG. 1. Syzygium floribundum, habit and leaf morphology. A, Tree. B, Detail of leaves. 354 355 356 FIG 2. Geographical distribution of S. floribundum showing sampling localities. Red dots- 357 geographical distribution of the species. Green dots- sampling localities. Map obtained and 358 adapted from: Australia’s Virtual Herbarium (2014). 359 15 360 FIG. 3. 361 Light (LM) and scanning electron micrographs (SEM) of leaves of S. floribundum. A, Leaf 362 clearing showing reticulate tertiary venation. B, SEM micrograph showing distribution of 363 stomata on the leaf surface. C, SEM micrograph showing detail of cyclo-staurocytic stomata 364 and surrounding epidermal cells. D, SEM micrograph of secretory cavity on the abaxial 365 surface showing overlying cell (arrow) surrounded by 6-8 elongated cells. Scale bars = 500 366 µm in A, 20 µm in C. 367 368 369 370 371 372 373 16 374 375 FIG. 4. Transverse light micrographs (LM) of leaves of S. floribundum. A, General view of 376 the anatomy of the leaf blade showing slight depression above the midrib. B, Detail of the 377 midrib showing xylem (stained green-blue), phloem (pink) and fibres (purple). C, 378 Dorsiventral mesophyll showing palisade and spongy parenchyma. D, Detail of the 379 mesophyll containing subepidermal idioblasts with rhombus-shaped calcium oxalate crystals. 380 E, Secretory cavity composed of a large space surrounded by epithelial cells. cr- calcium 381 oxalate crystals, fi- fibres, ph- phloem, pp- palisade parenchyma, sc- secretory cavities, sp- 382 spongy parenchyma, xy- xylem. Scale bars = 100 µm 17