Leaf Micromorphology and Leaf Glandular Hair Ontogeny of Myoporum Bontioides A

Feddes Repertorium 2013, 124, 50–60 DOI: 10.1002/fedr.201300020

RESEARCH PAPER Leaf micromorphology and leaf glandular hair ontogeny of Myoporum bontioides A. Gray

Sauren Das1, Chiou-Rong Sheue2, Yuen-Po Yang3, 4

1 Agricultural and Ecological Research Unit, Indian Statistical Institute, 203 Barrackpore Trunk Road, Kolkata 700108, India 2 Department of Life Sciences & Research Center for Global Change Biology, National Chung Hsing University, 250 Kuo Kuang Road, Taichung 40227, Taiwan 3 Department of Biological Sciences, National Sun Yat-sen University, Kaohsiung 804, Taiwan 4 Department of Bioresources, Dayeh University, Changhua 515, Taiwan

Myoporum bontioides A. Gray (Myoporaceae), a red list plant in Japan, is restricted to only Submitted: November 14, 2013 a few East Asian countries like China, Japan and Taiwan, associated to some true man- Revised: March 8, 2014 groves. The leaf is isolateral and has a thick cuticle; stomata are anomocytic, sunken and Accepted: April 30, 2014 have a beak-shaped cuticular outgrowth at the inner and outer side of the stomatal pore (ledges); profuse glandular hairs are scattered on both leaf surfaces of young leaves. The mesophyll is compact with palisade and spongy parenchyma cells in the young stage, but at maturity profuse intercellular spaces can be observed. Secretory ducts occur in young leaves. Pear-shaped glandular hairs protrude from the epidermal layer. Hair primordia are well distinct by their larger size and undergo divisions to produce two laterally placed basal cells, two stalk cells and four radiating terminal cells. The cuticle layers of the terminal cells are often separated from the cell wall to form a space, in which ions accumulate for excretion. Inner walls of the basal cells are connected with the mesophyll. Though ontogeny and structure of glandular hairs have resemblance to typical mangroves, considering leaf micromorphology, this plant is better termed as “mangrove associate” instead of “true mangrove”.

Keywords: Glandular hairs, leaf anatomy, morphology, Myoporum bontioides, ultrastructure

1 Introduction* et al. 2013). There are about 32 species within the genus, which is spread from Mauritius, across Australia to Myoporum Banks & Sol. ex G. Forst is a figwort plant the Pacific Islands and up to China. Myoporum bon- genus, formerly placed in Scrophulariaceae (Gray 1862). tioides (Sieb. & Zucc.) A. Gray, was considered as syn- Olmstead et al. (2001) opined that there is a close rela- onymous to Pentacoelium bontioides by Siebold & Zuc- tionship of Myoporaceae with two other families, Buddle- carini (1846). Later on, this taxon was classified as jaceae and Scrophulariaceae s. str. They further consid- Myoporum bontioides A. Gray under the genus ered the genus as paraphyletic and included both Myoporum. The genus includes about 30 species which Buddlejaceae and Myoporaceae in the family Scrophu- are distributed from Eastern Asia to the Pacific Islands lariaceae. But recently it has again been segregated as and Australia (Gray 1862).The plants are mostly distrib- a separate family, Myoporaceae (Mabberley 2000; Ma uted in wet places near the sea in islands of Kyushu (western coast and Tanegashima) and Ryukyus of Ja- Correspondence: Dr. Das, 203, B.T. Road, Kolkata, pan, Formosa and China. The geobotanical and ecologi- West Bengal 700108 cal descriptions of this species were done by Hiroki E-Mail: [email protected] Phone: +91 33 2575 3220 (1985), considering it as a semi-mangrove. This species Fax: +91 33 2577 3049 is regularly recorded amongst the typical mangroves,

50 © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim Feddes Repertorium 2013, 124, 50–60 Leaf anatomy and leaf gland ontogeny of Myoporum bontioides along the sandy seashores in Vietnam, particularly in the cules extracted from this plant (Fraga 2001; He et al. north-eastern zone along with Scyphiphora hydrophyl- 2004; Kanemoto et al. 2008), a detailed anatomical laceae (Hong & Hoang 1993). They also recorded this investigation of this rare species is insufficient. Anatomi- plant from South Japan, Taiwan, Central to Southern cal and morphological features serve as a trustworthy China and Northern Vietnam. The family Myoporaceae pointer towards the understanding of the ecological was monographed, and Pentacoelium was re-installed adaptation of a plant. The influence of different ecologi- as a genus distinct from Myoporum Banks & Sol. ex G. cal factors (microclimate) on plants is best reflected by Forst. by Chinnock (2007). Pentacoelium is similar to the its leaf morphology and anatomical organization, as species of Myoporum in respect to vegetative character- compared to the other vegetative organs (Krstić et al. istics, though the flowers are much larger and the fruits 2002). M. bontioides grows in saline/estuarine soil asso- are quite different (Chinnock 2007). The fruits of Penta- ciated to some mangroves, and thus the leaf micromor- coelium are large and structurally more complex than in phology resembles some typical mangrove leaf architec- the other members of this family (Li 2002). The family tures and signifies the ecological niches of the taxa. The Myoporaceae was documented by Li (1998), and he leaf micromorphology of this taxon is still pertinent to concluded that the genus Myoporum has about 30 spe- plant biologists. The present work deals with the detailed cies distributed from Eastern Asia to the Pacific islands leaf anatomical account to find out the degree of similar- and Australia, and Myoporum bontioides (Sieb. & Zucc.) ity with typical mangrove species. Structural architecture A. Gray being the only species reported from Taiwan. and developmental pathway of glandular hairs on leaves Hongbin et al. (2011) reported Myoporum bontioides are of special interest in comparison to other salt- (Sieb. & Zucc.) A. Gray (synonym M. chinense (A. Can- secreting plants (especially mangroves). The structural dolle) A. Gray; Polycoelium bontioides (Sieb. & Zucc.) resemblance of leaf glandular hairs often signifies the A. Candolle; P. chinense A. Candolle) from the sandy harmony in the mechanism of secretion (Levering & sites along the coasts, near the sea levels of Eastern Thomson 1971; Oross & Thomson 1982). Hence, the Fujian, South Guangdong, South Guangxi, Tainan (West ontogeny of glandular hairs with the aid of ultra- Taiwan) and East Zhejiang (South Japan). In Taiwan, microscopy (SEM and TEM) was also carried out for the plant was reported from two places, I. Tungshih better understanding. (Ton-Shou) mangrove wetland, a west coast of Chiayi County (Chen & Lee 1978; Wu 1986; Lin et al. 1987a) and II. Tatu Estuary, northwest of Changhua County 2 Material and methods (Karpowicz 1985; Lin et al. 1987b). Theisen & Fischer (2004) concluded that the family Myoporaceae included Myoporum bontioides was collected from the Tungshih four genera with ca. 330 species, with a center of diver- mangrove wetland at the west coast of Chiayi County in sity in Australia, extending to the islands of the Pacific southern Taiwan (Fig. 1B). The location comprises sev- and Indian ocean, and few species in tropical America, eral small patches of mangroves with adjacent intertidal Hawaii, Caribbean islands and Japan. According to mudflats. The vegetation is a mixture of typical man- Global Biodiversity Information Facility (GBIF 2013), groves like Avicennia marina, Kandelia obovata and M. bontioides A. Gray is distributed only in Taiwan Rhizophora stylosa, with stray communities of Atriplex (23.5° N 121° E), two regions of Japan, Kagoshima nummularia and Myoporum bontioides. The climate is (30° N 130° E) and Nagasaki (36° N 138° E), and north- humid tropical with an average annual rainfall of about west China (Fig. 1A). This species has been considered 2,000 mm. as a red list plant by the Threatened Species Committee, For anatomical investigation, leaf samples were cut Japan Society of Plant Taxonomists (Yahara et al. into small pieces (2 × 2 mm2 approximately) and fixed in 1997). According to the IUCN (1994), M. bontioides 2.5% glutaraldehyde in 0.1 M sodium phosphate buffer A. Gray has been declared as a globally threatened (pH 7.3) for 4 h at room temperature. After washing (EW, CR, EN or VU) Red List Category plant. thrice in buffer for 30 min, the specimens were seconda- M. bontioides is widely considered as a folk medicinal rily fixed in 1% OsO4 in the same buffer for 4 h. De- plant in the northwest of China and known as a superfi- hydration was carried out through ethanol series starting cies-syndrome drug (Wang et al. 2000). Deng et al. from 30%, the material was infiltrated for 3 days and (2008) reported that the stem and leaf extracts of embedded in Spurr’s resin (DER = 6.0) (Spurr 1969). M. bontioides show inhibitory effects against seven The embedded material was then polymerized in an fungi, with >58% of inhibition at 10 g L−1 after 72 h of oven at 70 °C for 12 h. Semi-thin sections (1 μm) were incubation, and the compound was identified as epin- cut with a MTX Ultra microtome (RMC, Tucson, Arizona, gaione. Myoporum bontioides is a rare coastal species USA). The sections were stained with 1% toluidine blue and can be used as potential soil binder. Though a num- for light microscopy (Olympus BH-2, Tokyo, Japan). Leaf ber of papers have been published on bioactive mole- surfaces were examined by scanning electron micro-

Figure 1. Distribution of Myoporum bontioides A. Gray. (A) Global distribution (source: Global Biodiversity Information Facility, 2013) [http://www.discoverlife.org/mp/20m?kind=Myoporum+bontioides.]; (B) Collection site of the species (map of Taiwan in inset). (Source: Google Earth).

Figure 2. Photographs of the species. (A) natural habit; (B) closer view of a twig; (C) twig bearing seeds; (D) closer view of a flowering twig. scopy (SEM, Hitachi S 2400, Tokyo, Japan) following the surface lustrous, midrib slightly projected on lower sur- protocol by Bozzola (2007) and were photographed. face, lateral nerves obscure. Flowers appear from Janu- Ultra-thin sections (about 75 nm) were cut and sections ary to May, 2–4, fascicled in leaf axils. Pedicel slender, were stained (Ellis 2007) with uranyl acetate (5% in 50% 2 cm long at flowering, up to 3 cm long in fruiting stage. methanol) and lead citrate (1% in water) for transmission Calyx campanulate, 10 mm long, deeply 5-lobed; lobes electron microscopic examination (TEM, Hitachi H 600, lanceolate, acuminate, 5 mm long. Corolla campanulate Tokyo, Japan) and then photographed. to funnel-shaped, white, with purple spots, 2–2.5 cm long, more or less fleshy; tube stout, 10–15 mm long, 5-lobed; lobes elliptic, obtuse or acute, 10 mm long, 3 Results reflexed. Stamens 4, slightly didynamous, exert, 18– 25 mm long; filaments glabrous, divergent. Style filiform, 3.1 Plant morphology 18–25 mm long. Fruits are drupe, ovoid to globose, acute, 10–15 mm long, 8–10 mm in diameter, reddish Plants of Myoporum bontioides are evergreen, erect brown at ripening (Fig. 2A–D). shrubs, 1–2 m tall. Branches are fleshy, with swollen leaf scars. Leaves are alternate, coriaceous, fleshy; petioles 3.2 Micromorphology of the leaf are 1–2 cm long; blades are oblong to elliptic, 5–12 cm long, 2–4 cm wide, the apex acute or acuminate, base In transverse sections, the leaves are isolateral; mature acute, gradually tapering into the petiole, entire; upper leaves have profuse intercellular spaces in the mesophyll

© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim 53 S. Das et al. Feddes Repertorium 2013, 124, 50–60 region (Fig. 3A). Mesophyll tissues of young leaves are the thin-walled phloem occurs adaxially. Metaxylem is in compactly arranged and have spherical secretory cavities the anterior and protoxylem in the posterior position lined with an epithelial layer of small, isodiametric pa- (Fig. 3A). The leaf anatomy shows that the mesophyll ranchymatous cells (Fig. 3B, C). Glandular hairs are pre- zone lacks any hyaline water storage tissues in the sent on both the adaxial and abaxial surface of the young endodermal region as commonly found in typical man- leaves, but at maturity they are absent (Fig. 4A, B). Ma- grove leaves; bundle sheath extensions and terminal ture glandular hairs appear as pear-shaped structures, tracheids are also absent. encrypted in the epidermal layer (Fig. 3H, I; 4D). Mature leaves are 0.605 mm ± 0.011 thick; the cuticle is promi- 3.3 Ultrastructure nent, wavy and more or less equal in thickness on both surfaces of the leaf (0.039 mm ± 0.004). Leaves are The leaf surface is rough and undulating; in younger amphistomatic, but the frequency of stomata is lower on leaves, numerous glandular hairs are present on both the adaxial surface (19.7mm–2 ± 1.16 and 25.8 mm–2 the adaxial and abaxial surface, the frequency is higher ± 1.81 on the adaxial and abaxial surface, respectively). on the adaxial side. The anterior wall of anomocytic The sunken stomata are anomocytic, surrounded by 3–4 stomata is more cutinized than the posterior wall epidermal cells of varying size (Fig. 3D; 4A–C). The ante- (Fig. 4A–C). Glandular hairs are encrypted within the rior walls of the stomatal guard cells are much cutinized epidermal layer, the basal cells (two in number) are (Fig. 3D; 4C). In transverse sections of the leaf, mature embedded in the leaf epidermis, and the inner walls of stomata show a distinct beak-shaped cuticular outgrowth the basal cells are connected with the mesophyll. The overarching the stomatal pore at the outer and inner stalk cells and radiating terminal cells protrude from the side, termed as ledges (Fig. 3E). The epidermal layer is leaf surface (Fig. 4D). Large secretory cavities, encircled 0.107 mm ± 0.016 thick on the upper surface and by a single layer of barrel-shaped, thin-walled epithelium 0.074 mm ± 0.14 on the lower surface, more cutinized at cells, occur in the upper part of the mesophyll zone in the outer tangential wall than at the lateral wall (Fig. 3E; young leaves (Fig. 4E). 4F). The epidermal cells are mostly rectangular, and the The transmission electron microscopy observations outer wall is more cutinized and sinuous at the tangential also confirm that the glandular hairs differ prominently wall (Fig. 3A, E). from the surrounding epidermal cells as they protrude The mesophyll is composed of thin-walled chloren- from the latter. They lack chloroplasts, have centrally chyma, differentiated distinctly into one or two layers of located vacuoles and a large nucleus. Abundance of elongated, anticlinally extending palisade cells on both other cell organelles like mitochondria, golgi apparatus adaxial and abaxial sides, and between the adaxial and and endoplasmic reticulum are noticed (Fig. 5A–D). adaxial palisade there are 4–6 layers of isodiametric Based on the ultra-structural studies, each mature gland spongy parenchyma cells (Fig. 3A). In young leaves, the consists of two basal cells, two stalk cells and four radi- mesophyll is compact without any intercellular space ating terminal cells. The basal cells are large, embedded (Fig. 3B), but at maturity, palisade and spongy cells are in the leaf tissue, and assumed to be the collecting cells loosely arranged with profuse intercellular spaces. Veins for the excretory substances (mainly excess salts). Ra- are placed in the middle of the transversal leaf section. diating terminal cells protrude from the laminar surface Younger leaves show numerous circular secretory cavi- and have a secretory function (Fig. 5A–C). In longitudi- ties with a layer of narrow epithelial cells (Fig. 3B, C; 4E) nal section, the cuticle of the terminal cells gets sepa- and occur at any level within the mesophyll. In mature rated from the cell wall and forms a space, probably leaves, these cavities are absent. Vascular bundles are serving towards the accumulation of secretory products sheathed by one layer of small polygonal sclerenchyma prior to excretion (Fig. 5D). The extreme outer portion of cells. Xylem strands are present on the abaxial side, and the periplasm of the terminal cells appears as a darker

Figure 3. Photomicrographs of semi-thin transverse sections of leaves. (A) mature leaf; (B) young leaf; (C) enlarged ᭤ secretory cavity; (D) stoma with subsidiary cells (top view); (E) stoma with cuticular outgrowth forming a beak-like structure on both inner and outer side of the stomatal pore (ledges); (F)–(I). Developmental stages of leaf glandular hairs. (F) Single glandular hair primordial cell with dark nucleus and upwardly elevated from the normal epidermis; (G) primordial cell undergoes a periclinal division to form one terminal cell and one basal cell. It is a dividing cell, after division, the two nucleus are placed at the two opposite poles (indicated with double arrow); (H) basal cell divides longitudinally to form two basal cells, and terminal cell divides to form one stalk cell and one terminal cell; (I) basal cells encrypted within the epidermis, after division two stalk cells and four radiating terminal cells are produced. (Bc – basal cells, Cu – cuticle, Ep – epidermis, Et C – epithelium cell layer, Gc – guard cells, Gh Pr – glandular hair primordial, Gl H – glandular hair, L – ledges, Mx – metaxylem, Ph – phloem, Pp – palisade parenchyma, Px – protoxylem, Sc – secretory cavity, Sp – spongy parenchyma, St – stomata, St C – stalk cell, Su C – subsidiary cell, Tc – terminal cell, Vb – vascular bundle).

© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim 55 S. Das et al. Feddes Repertorium 2013, 124, 50–60 layer, the electron-dense portion of the periplasm of iii) absence of sclerotic bundle sheaths and iv) presence terminal cells (Fig. 5D). of sclereids of different shapes. In mature leaves, the investigated taxon has a loosely arranged mesophyll 3.4 Ontogeny of glandular hairs tissue. The complete absence of any definite water storage cells, sclereids and terminal tracheids can be as- The glandular hair primordia differ remarkably from the cribed towards the non-mangrove characters of the other neighboring epidermal cells in their level of eleva- taxon, but some other leaf anatomical features of the tion from the epidermal cells, they are larger in size studied taxon surely can be considered as associated to with an enlarged, deeply stained nucleus, lack of chloro- mangroves. Terminal tracheids and branched sclereids plasts and a central vacuole in the cytoplasm as well as in mangroves provide mechanical support and capillary abundant mitochondria and other cellular organelles water storage function (Zimmermann 1983; Tomlinson (Fig. 5A–C). Transverse sections show that the mature 1986). The present taxon shows secretory cavities in the hair consists of four radiating terminal cells, two stalk mesophyll region of young leaves, lined with a layer of cells and two basal cells (Fig. 3I; 4F; 5A–C). The hair epithelium cells which are absent in the mature leaf. primordia protrude from the epidermal layer (Fig. 3F). Karrfalt & Tomb (1983) opined that all members of The first division of the primordia takes place in periclinal Myoporaceae possess secretory cavities, except Oftia. plane to form a terminal and a basal cell (Fig. 3G). The They observed that the secretory cavities in Bontia basal cell undergoes another periclinal division to form a daphnoides (Myoporaceae) are homologous to the air stalk cell and a basal cell, while the terminal cell remains spaces in Leucophyllum minus, where cellular separa- undivided. The stalk cell then undergoes one transverse tion and disintegration are not preceded by cell division division to produce two stalk cells; the basal cell under- (lysigenous origin). They also concluded that the air goes a longitudinal division, and two basal cells are space in Leucophyllum differs from the secretory cavi- formed. The terminal cell undergoes two longitudinal ties of Bontia, principally in the lack of secretory function divisions to form four radiating cells (Fig. 3H, I). At ma- and absence of cell division during their development. turity, the basal cells are embedded in the leaf epider- Later, Lersten & Beaman (1998) did not notice any ana- mis, and the inner parts remain attached to the meso- tomical evidence of transitory epithelial cells or lysis of phyll (Fig. 3H, I; 4F; 5A–C). The mature glandular hairs cells in developing air spaces in five species of Leuco- remain enclosed within the uninterrupted cuticular layer. phyllum, thus the hypothesis that air spaces are trans- From the surface view, the four terminal cells appear as formed secretory cavities is not supported. They also a radiating fan (Fig. 3I; 4F; 5C). reported epithelium-lined cavities scattered abundantly in leaves from three species of Myoporaceae (Bontia daphnoides L., Eremophila longifolia (R. Br.) F. Muell. 4 Discussion and Myoporum sandwichense A. Gray). Hence, the origin of this secretory cavity is yet to be resolved. The presence of a considerably thick cuticle on the leaf Theisen & Fischer (2004) also described the secretory can be attributed to a constraint device of the plant cavities in younger leaves of some members of Myopo- against non-stomatal water loss, which is a typical halo- raceae. philic character (suffice by its natural habitat). Waisel The longitudinal sections of mature glandular hairs (1972) deliberated that the thick cuticular layer is an are composed of three different types of cells – radial adaptive feature of mangroves. The stomata are anomo- terminal cells, lateral stalk cells and laterally placed cytic and sunken. Distinct beak-like cuticular outgrowths basal cells. The entire glandular hair is encircled by occur on both inner and outer side of the stomatal pore cuticular layer. These features are similar to the glandu- (ledges). Das (2002) reported that this structure is a lar hairs of some true mangrove species such as common character in true mangroves and provides an Avicennia sp. and Aegiceras corniculatum and a man- extra protective means against water loss through the grove-associated taxon, Acanthus ilicifolius (Das 1999; stomatal pore during transpiration. Considering the leaf 2002). The salt glands in all salt secreting mangroves anatomical features, M. bontioides was described as show some structural similarities in having basal cells, ‘mangrove shrub’ by Toyama & Itow (1975). Though the stalk cells and a capitate group of radiating terminal leaf micromorphology of M. bontioides has some re- cells, and all these can be correlated to the convergent semblances with typical mangroves, the present obser- evolutionary character among the different mangrove vation reveals some disparities, too. Earlier works (Tom- taxa (Das & Ghose 1993). Fahn & Shimony (1977) stud- linson 1986; Das 1999) described four unique leaf ied the ontogeny of glandular and non-glandular hairs of anatomical features of typical mangroves, such as i) Avicennia marina and opined that the both types of leaf presence of colorless water storage tissue in the hypo- hairs follow the same developmental pattern, at least up dermal layer, ii) short terminal tracheids at vein endings, to the three-celled stage. Metcalfe & Chalk (1950), in

Figure 4. SEM images of the leaf. (A) lower leaf surface; (B) upper leaf surface; (C) stomata with subsidiary cells; (D) single glandular hair, (E) transverse section of leaf showing secretory cavity; (F) longitudinal section of glandular hair. (BC – basal cells, Cu – cuticle, E – epidermis cell, Et C – epithelial cell layer, Gl H – glandular hair, LE – Lower epidermis, M – midrib of leaf, SC – secretory cavity, SGC – stomatal guard cell, Su C – subsidiary cell, St C – stalk cell, TC – terminal cell, UE – upper epidermis).

Figure 5. TEM images of glandular hairs (transverse section of leaf) (A) young stage of glandular hair with single terminal cell, single stalk cell and two basal cells; (B) glandular hair with premature terminal cells; (C) mature view with distinct four terminal cells, two stalk cells and two basal cells; (D) magnifies terminal cells showing cellular organelles. (BC – basal cell, CU/Cu – cuticle, CC – collecting cavity, El – electron-dense layer, ER – endoplasmic reticulum, G – golgi bodies, M – mitochondria, N – nucleus, ST C – stalk cells, TC – terminal cell, V – vacuole).

58 © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim Feddes Repertorium 2013, 124, 50–60 Leaf anatomy and leaf gland ontogeny of Myoporum bontioides their extensive leaf anatomical study, commented that 5 References the structural differences of glandular and non-glandular leaf are rather in function and not in early development. Barhoumi, Z.; Djebali, W.; Abdelly, C.; Chaïbi, W. & Smaoui, A. 2008: Ultrastructure of Aeluropus littoralis leaf salt glands Waisel (1972) described that the glandular hairs in halo- under NaCl stress. Protoplasma 233: 195–202. phytes lack chloroplasts and that central vacuoles are Bozzola, J. J. 2007: Conventional specimen preparation tech- rich in cellular organelles. The present observation is niques for Scanning Electron Microscopy of biological conform with this. A common feature in leaf glandular specimens. In: John Kuo (ed.) Electron Microscopy: methods and protocols, 2nd ed. Humana Press, Totowa, New hairs of some monocots and some dicots is the large Jersey. 608 p. space between the outer wall of the cells and the cuticle Campbell, N. & Thomson, W. 1976: The ultrastructural basis of (Oross & Thomson 1982). Campbell & Thomson (1976) chloride tolerance in the leaf of Frankenia. Ann. Bot. 40: opined that this cavity apparently represents a collecting 687–693. compartment where salts, after being sequestrated by Chen, M. Y. & Lee, Y. C. 1978: Tungshih Mangrove Forest and the gland cells, accumulate prior to emission through the Egretry. J. Sci. Eng. 15: 117–128. cuticle. The glandular hairs of dicotyledonous plants are Chinnock, R. 2007: Eremophila and allied genera: A monograph of the plant family Myoporaceae. Rosenberg Publishing multicellular and more complex than those of monocots Limited, NSW, Australia, 672 p. like some grasses (Liphschitz & Waisel 1974). The pre- Das, S. 1999: An adaptive feature of some mangroves of sent observation is in conformity with the earlier views. Sundarbans, West Bengal. J. Plant Biol. 42(2): 109–116. The glandular hairs are present on both surfaces of Das, S. 2002: On the ontogeny of stomata and glandular hairs young leaves, but disappear at leaf maturity. Karrfalt in some Indian mangroves. Acta Bot. Croat. 61(2): 199–205. & Tomb (1983) worked on the leaf hairs of Bontia Das, S. & Ghose, M. 1993: Morphology of stomata and leaf hairs of some halophytes from Sundarbans, West Bengal. daphnoides (Myoporaceae) and commented that the Phytomorphology 43: 59–70. leaf hairs were found on the leaf bud and were absent Deng, Y.; Zhen, Y.; Yanzhen, Y. U. & Xiulian, B. 2008: Inhibitory on unfolded mature leaves. The ultrastructure shows activity against plant pathogenic fungi of extracts from that the two basal cells are embedded in the leaf meso- Myoporum bontioides A. Gray and identification of active ingredients. Pest Management Sci. 64(2): 203–207. phyll and that they are assumed to be the collecting cells. The capitate terminal part formed by four cells is Ellis, A. E. 2007: Poststaining grids for Transmission Electron Microscopy. Conventional and alternative protocols. In: John responsible for the excretion of ions, primarily in the Kuo (ed.), 2nd edn. Electron microscopy: methods and pro- space (collecting chamber) between the cuticle and tocols, Humana Press, Totowa, New Jersey. 608 p. the outer wall of the terminal cells. Finally it passes out- Fahn, A. & Shimony, C. 1977: Development of the glandular side the cuticle. Barhoumi et al. (2008) explained that and non-glandular leaf hairs of Avicennia marina (Forssk.) Vierh. Bot. J. Linn. Soc. 74: 37–46. such a periplasmic space in the terminal cells signifies Fraga, B. M. 2001: A novel sesquiterpene, mucrotan have been that secreted ions (mineral salts) can be preferentially found in extracts of Myoporum bontioides. Nat. Prod. Rep. transported from the basal cells, through stalk cells 18: 650–673. and ultimately to the terminal cells (following the Global Biodiversity Information Facility (GBIF) 2013: Web address: apoplastic pathway). Osmand et al. (1969) opined that http://www.discoverlife.org/mp/20m?kind=Myoporum+bontio ides the superfluous salt is collected from the mesophyll by Gray, A. 1862: Myoporaceae. Proceedings of the American the basal or collecting cells and secreted by the terminal Academy of Arts and Sciences 6: 52. cells of the glandular hairs into the subcuticular space He, Y.; He, T.; Gu, W.; Xian, J.; Zhang, M. & Feng, L. 2004: around them, and ultimately the terminal cells dry out Bioactivity of volatile oils from Myoporum bontioides on and salt is left on the leaf surface as a white powdery Plutella xylostella. J. Appl. Ecol. 15: 140–152. layer. Hiroki, N. 1985: Geobotanical and ecological studies on three Considering the comparatively weaker leaf anatom- semi-mangrove plants in Japan. Jap. J. Ecol. 35: 85–92. ical features (such as a reduced amount of packed Hong, P. N. & Hoang, T. S. 1993: Mangroves in Vietnam. IUCN, Bangkok, Thailand. 177 p. chlorophyllous cells within the mesophyll region, devoid Hongbin, C.; Hong, D. & Chinnock, R. J. 2011: Myoporaceae. of any water storage tissues, sclerotic bundle sheaths In: Zhengyi, W.; Raven, P. H. & Hong, D. (eds.) Flora of and sclereids) in comparison to typical mangrove taxa, China, Vol. 19, Science Press and Missouri Botanical Gar- the taxon diverges much from the latter. Tomlinson den Press, Beijing and St. Louis. 492 p. (1986) opined that, in spite of assemblage of different International Union for Conservation of Nature (IUCN) 1994: Directory of Indo-Malayan Protected Areas. IUCN Conser- families, mangroves have some uniqueness and are vation Monitoring Centre, Cambridge. readily identified by their leaf anatomical features. The Kanemoto, M.; Matsunami, K.; Otsuka, H.; Shinzato, T.; Ishi- total disappearance of glandular hairs on mature leaves gaki, C. & Takeda, Y. 2008: Chlorine-containing iridoid and of M. bontioides, conceivably can be attributed to man- iridoidglucoside, and other glucosides from leaves of Myoporum bontioides. Phytochem. 69: 2517–2522. grove-associated plants rather than to a true mangrove Karpowicz, Z. 1985: Wetlands in East Asia – A Preliminary and is thus a considerably weaker adaptation for their Review and Inventory. ICBP Study Report No. 6. Cam- natural saline habitat. bridge: International Council for Bird Preservation.

Karrfalt, E. E. & Tomb, A. S. 1983: Air space, secretory cavities Oross, J. W. & Thomson, W. W. 1982: The ultrastructure of the and the relationship between Leucophylleae (Scrophulari- salt glands of Cynodon and Distichlis (Poaceae). Am. J. aceae) and Myoporaceae. Systematic Bot. 8: 29–32. Bot. 69: 939–949. Krstić, L. N.; Merkulovand, L. S. & Boža, P. P. 2002: The vari- Osmand, C. B.; Lüttge, U.; West, K. R.; Pallaghy, C. K. & ability of leaf anatomical characteristics of Solanum nigrum Shacher-Hill, B. 1969: Ion absorption in Atriplex leaf tissue: L. (Solanales, Solanaceae) from different habitats. Proceed. II, Secretion of ions to epidermal bladders. Aust. J. Biol. Sci. Nat. Sci. Matica. Srpska. Novi. Sad. 102: 59–70. 22: 797–814. Lersten, L. R. & Beaman, J. M. 1998: First report of oil cavities Siebold, P. F. & Zuccarini, J. G. 1846: Florae Japonicae familae in Scrophulariaceae and reinvestigation of air spaces in naturales adjectis generum et specierum exemplis selectis. leaves of Leucophyllum frutescens. Am. J. Bot. 85: 1646– Sectio altera. Plantae dicotyledoneae et monocotyledonae. 1649. Abhandelungen der mathematischphysikalischen Classe Levering, C. A. & Thomson, W. W. 1971: The ultrastructure of der Königlich Bayerischen Akademie der Wissenschaften the salt gland of Spartina foliosa. Planta 97: 183–196. 4(3): 123–240. Li, H. 1998: Myoporaceae. In: T. C. Huang (ed.), Flora of Tai- Spurr, A. R. 1969: A low viscosity epoxy resin embedding wan, 2nd Edn. Vol. 4. Dept. of Botany, National Taiwan Uni- medium for electron microscopy. J. Ultrastruct. Res. 26: versity, Taipai, Taiwan. p. 731–732. 31–43. Li, Z. 2002: Myoporaceae. In: Hu, Chiachi (ed.), Flora Reipubli- Theisen, I. & Fischer, E. 2004: Myoporaceae. In: J. W. Kadereit cae Popularis Sinicae. Science Press, Beijing 70: 310–313. (ed.), Flowering Plants: Dicotyledons. The Families and Lin, Y. S., Lue, K. Y., Chen, M. Y. & Chen C. H. 1987a. Wet- Genera of Vascular Plants. Springer, Heidelberg, Berlin. lands of Taiwan (R.O.C.). Report prepared for the Asian p. 289–292. Wetlands Inventory and presented at the Conference on Tomlinson, P. B. 1986: The Botany of Mangroves. Cambridge Wetland and Waterfowl Conservation in Asia, Malacca, University Press, New York, USA. Malaysia, 23–28 February 1987. Toyama, S. & Itow, S. 1975: The distribution and ecology of a Lin, Y. S.; Lue, K. Y; Chen, M. Y. & Lee, Y. C. 1987b: Tungshih mangrove-like plant, Myoporum bontioides A. Gray (Myo- Mangrove Forest and Egretry. J. Sci. Eng. 15: 117–128. poraceae), in western Kyushu, Japan. Hickobia 7: 117– Liphschitz, N. & Waisel, Y. 1974: Existence of salt glands in 124. various genera of Gramineae. New. Phytol. 73: 507–513. Waisel, Y. 1972: Biology of halophytes. Academic Press, New Ma, K.; Ji, L.; Qin, H.; Liu, J. Y.; Yao, Y.; Lin, C.; Yan, H.; Wang, York, USA. L.; Qiao, H. & Li, R. 2013: Catalogue of Life China (version 2012). In: Roskov, Y.; Kunze, T.; Paglinawan, L.; Orrell, T.; Wang, Q. G.; Ma, C. L. & Zhai, J. J. 2000: Furanoeudesmane- Nicolson, D.; Culham, A.; Bailly, N.; Kirk, P.; Bourgoin, T.; B, a new eudesmanese sesquiterpenoid from Myoporum Baillargeon, G.; Hernandez, F.; De Wever, A. (eds.), Spe- bontioides. Acta Crystal. 56: 569. cies 2000 & ITIS Catalogue of Life, 11th March 2013 Digital Wu, C. A. 1986: Coastal Protected Areas in Taiwan. Paper resource at www.catalogueoflife.org/col/. Species 2000: presented at the International Seminar on Coastal Parks Reading, UK. and Protected Areas. Taiwan National Normal University, Mabberley, D. J. 2000. The Plant Book: A portable dictionary of Taipei, Taiwan, 12–29 April, 1986. the vascular plants, 2nd Ed., Cambridge University Press, Yahara, T.; Kato, T.; Inoue, K.; Yokota, M.; Kadono, Y.; Seri- UK. 858 p. zawa, S.; Takahashi, H.; Kawakubo, N.; Nagamasu, H.; Su- Metcalfe, C. R. & Chalk, L. 1950: Anatomy of the dicotyledons, zuki, K.; Ueda, K. & Kadota, Y. 1997: Red List of Japanese vol. 1 and 2. Oxford University Press, London, UK. Vascular Plants. The Threatened Species Committee, Ja- pan Society of Plant Taxonomists, Tokyo, Japan. Olmstead, R. G.; Depamphilis, C. W.; Wolfe, A. D.; Young, N. D.; Elisons, W. J. & Reeves, P. A. 2001: Disintegration of Zimmermann, M. H. 1983: Xylem structure and the ascent of the Scrophulariaceae. Am. J. Bot. 88: 348–361. sap. Springer-Verlag, Berlin.