Pleione 10(2): 288 - 296. 2016. ISSN: 0973-9467 © East Himalayan Society for Spermatophyte

Leaf architecture of some of Linnaeus found in Assam,

Nibedita Das1 and S. K. Borthakur Department of , Gauhati University, Guwahati – 781014, Assam, India 1Corresponding author: [email protected] [Received 28.10.2016; Revised 14.12.2016; Accepted 17.12.2016; Published 31.12.2016]

Abstract architectural attributes of six species of Clerodendrum Linnaeus (sensu lato) [C. bracteatum Wallich ex Walpers; C. indicum (Linnaeus) Kuntze; C. inerme (Linnaeus) J.Gaertner (i.e. inermis Linnaeus); C. laevifolium Blumea; C. serratum Moon (i.e. serrata (Linnaeus) Steane & Mabberley); and C. trichotomum Thunberg], occurring naturally in Assam, were studied to ascertain their taxonomic relationships using leaf architectural characters. Different parameters like leaf attachment, length, blade class, laminar shape, margin, apex and base, 20 and 30 vein categories, spacing and angle were studied. A dichotomous key of these species was constructed and detailed description based on the architectural characters for each species are provided. From the produced data no sufficient difference could be identifies to isolate and from Clerodendrum Linnaeus. Key words: Clerodendrum, Leaf architecture, Blade class, Vein category, Assam

INTRODUCTION The Clerodendrum Linnaeus was placed under in most of the angiosperm classifications (Bentham & Hooker 1862–1883; Cronquist 1981). But, in recent classifications, based mostly on molecular data, has re-classified the genus as a member of (Chase & Reveal 2009; Haston et al. 2009). The genus was established in 1753 by Linnaeus based on the type species Clerodendrum infortunatum Linnaeus from India (Shrivastava & Patel 2007). The genus is now classified in the subfamily , as several genera are transferred from Verbenaceae to Lamiaceae in the 1990s, based on phylogenetic analysis of morphological and molecular data (Chakraborthy et al. 2013). Clerodendrum is widely distributed in the tropical and subtropical regions of the world with few species extending to the temperate regions. The number of species under the genus is about 560 (Moldenke 1971) or 580 (Munir 1989) or 400 (Mabberley 2005). In India Clerodendrum Linnaeus is represented by about 23 species (Srivastava & Choudhury 2008). Kanjilal et al. (1939) described only 13 species of Clerodendrum from Assam including Arunachal Pradesh, Meghalaya, Nagaland and Manipur. As most of the members of Clerodendrum are ethnomedically important (Shrivastava & Patel 2007) their proper identification is very important. Leaf architecture is the aspect of morphology that helps to study leaf structure, including shape, marginal configuration, apex, base, venation pattern, etc., allowing more rigorous comparisons among different taxa (Metcalfe & Chalk 1950; Inamdar 1971). Such characters have great significance in delimitation of closely related species. The leaf architectural features Nibedita Das & SK. Borthakur 289 in Clerodendrum have not been studied so far for use as source of taxonomic characters. Thus, this study defines taxonomic usefulness of leaf architectural characters ofClerodendrum Linnaeus. The binomial Volkameria inermis was established by Linnaeus in 1753 in his . In most of the literature this is now referred as Clerodendrum inerme (Linnaeus) J. Gaertner though its Linnaean name is the currently accepted one (www.theplantlist.org). Similarly, the species Volkameria serrata was established by Linnaeus in 1767. Later on the species was recombined as Clerodendrum serratum by Moon in 1924. However, now the species is again transferred to the newly established genus Rotheca by Steane & Mabberley (1998) and the accepted binomial is Rotheca serrata (Linnaeus) Steane & Mabberley (www.theplantlist.org) which is also kept under Ajugoideae of Lamiaceae. Both these species are quite common in the study area and an attempt will be made to understand their closeness with different other species of Clerodendrum under study. So, here, the genus Clerodendrum Linnaeus is treated sensu lato with six species from Assam those are, in many local floras (Kanjilal et al. 1939; Rajendran & Daniel 2002, Giri et al. 2008), treated under this genus including two which are now nomenclaturally accepted under two other different genera.

MATERIALS AND METHOD Mature of the six species of Clerodendrum Linnaeus [C. bracteatum Wallich ex. Walpers; C. indicum (Linnaeus) Kuntze; C. inerme (Linnaeus) J.Gaertner (Volkameria inermis Linnaeus); C. laevifolium Blumea; C. serratum Moon (Rotheca serrata (Linnaeus) Steane & Mabberley); and C. trichotomum Thunberg] ccurring in Assam were collected from different parts of the state. The inclusion of C. inerme and C. serratum in the list was done to understand their closeness with Clerodendrum in respect to their leaf-architectural data. The voucher specimens have been processed as per standard methods of Jain and Rao (1977) and deposited in the Herbarium of Botany Department, Gauhati University (GUBH) for future reference. To study the leaf architecture fresh leaves were cleared following the technique of Bersier & Bocquet (1960) and for description terminologies used are as suggested by Hickey (1973) and Leaf Architecture Working Group (LAWG 1999). The characters described were leaf attachment, leaf organization, petiole features, laminar size, blade class, laminar shape and symmetry, laminar ratio, base and apex angle, base and apex shape, position of petiolar attachment, margin type, lobation and vein orders. The leaf-vein orders were also examined. The laminar size was measured using a centimeter scale. The result of the laminar size gives the idea of what type of blade class of the leaves were. The base and apex angles were measured using a protractor. A dichotomous key to the six species of Clerodendrum Linnaeus (sensu lato) was then constructed and the descriptions were based uniquely on leaf-architectural characters.

RESULTS Key to the six species of Clerodendrum (sensu lato) based on leaf architectural characters

1a. Leaves sessile or sub-sessile ………. 2 1b. Leaves distinctly petiolate ……. 3 2a. 20 veins weak, brochidodromous; 20 vein spacing decreasing towards base, weak intersecondaries ………………………… C. serratum [= Rotheca serrata] 290 Leaf architecture of Clerodendrum spp.

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A B C

D E F

PLATE - I. Leaf shape of Clerodendrum species (A - F): A. C. indicum; B. C. inerme; C. C. serratum; D. C. trichotomum; E. C. bracteatum; F. C. laevifolium Nibedita Das & SK. Borthakur 291 2b. 20 vein strong brochidodromous; 20 vein spacing irregular, strong intersecondaries …. C. indicum 3a. Lamina entire ……...... 4 3b. Lamina erose; 20 brochidodromous, weak intersecondaries, 20 vein spacing irregular, areolation well developed …………………………………… C. laevifolium 4a. Lamina acuminate ………... 5 4b. Lamina retuse; 20 weak brochidodromous, 20 vein spacing decreasing towards base, areolation moderately developed ...... C. inerme [=Volkameria inermis] 5a. 20 vein spacing decreasing regularly towards base, weak intersecondaries, areolation moderately developed ………………………………………… C. trichotomum 5b. 20 vein spacing irregular, strong intersecondaries, areolation well developed ...... C. bracteatum

Leaf architectural characteristics of the six species of Clerodendrum Linnaeus (sensu lato)

Clerodendrum bracteatum Wallich ex Walpers [PLATE-I, Fig. E; PLATE-II, Fig. E] Leaves decussate, petiolate; Blade: 135-190×46-104 mm with 1.8:1 ratio, symmetrical, ovate, acuminate, base concave, mesophyll and entire. Venation: Pinnate 1° vein, 2°s weak brochidodromous; angle of divergence, smoothly decreasing towards base; inter-2°s Strong; 3° sinuous; angle with respect to 1° vein, perpendicular, increasing basally; alternate percurrent 40 and regular polygonal reticulate 5°; well developed areolation. Exsiccatae: Kumarikata, Baksa District, Assam, India, 15.05.2013, N. Das 2856 (GUHB).

Clerodendrum indicum (Linnaeus) Kuntze [PLATE-I, Fig. A; PLATE-II, Fig. A] Leaves whorled, sessile or sub-sessile; Blade: 150-180×20-30 mm with 6:1 ratio, symmetrical, elliptic, acuminate, base decurrent, notophyll and entire. Venation: Pinnate 1° vein, 2°s brochidodromous; angle of divergence, one pair of acute basal secondaries; inter-2°s strong; 3° exmedially ramified; angle with respect to 1° vein obtuse, incosistent; alternate, percurrent 4° and regular polygonal reticulate 5°; well-developed areolation. Exsiccatae: Pamohi, Kamrup Disrict, Assam, India, 03.07.2013, N. Das 2845 (GUBH).

Clerodendrum inerme (Linnaeus) J.Gaertner [i.e. Volkameria inermis Linnaeus] [PLATE- I, Fig. B; PLATE-II, Fig. B] Leaves decussate, petiolate; Blade: 30 37×25-29 mm with 1.8:1 ratio, symmetrical, obovate, retuse, base cuneate, microphyll and entire. Venation: Pinnate 1° vein, 2°s weak brochidodromous; angle of divergence, uniform; inter- 2°s weak; 3° admedially ramified; angle with respect to 1° vein, perpendicular, uniform; regular polygonal reticulate 4° and 5°; moderately developed areolation. Exsiccatae: G.U. Campus, Jalukbari, Kamrup District, Assam, India, 12.04.2013, N. Das 2812 (GUBH).

Clerodendrum laevifolium Blume [PLATE-I, Fig. F; PLATE-II, Fig. F] Leaves decussate, petiolate; Blade: 130-175×25-35 mm with 5:1 ratio, symmetrical, elliptic, acuminate, base cuneate, notophyll and erose. 292 Leaf architecture of Clerodendrum spp.

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A B

C D

E F

PLATE - II. Leaf architecture of Clerodendrum species (A - F): A. C. indicum; B. C. inerme; C. C. serratum; D. C. trichotomum; E. C. bracteatum; F. C. laevifolium Nibedita Das & SK. Borthakur 293 Venation: Pinnate 1° vein, 2°s brochidodromous; angle of divergence, one pair of acute basal secondaries; inter-2°s Weak; 3° exmedially ramified; angle with respect to 1° vein, obtuse, increasing exmedially; regular polygonal reticulate 40 and dichotomizing 5°; well developed areolation. Exsiccatae: Haflong, N.C. Hills, Assam, India, 03.04.2013, N. Das 2825 (GUBH).

Table 1. Leaf-blade architecture of the six species of Clerodendrum Linnaeus (sensu lato)

Species Leaf Petiole Laminar Attachm- Features Blade Shape L:W Margin Apex Base ent class Ratio C. indicum Whorled Sessile to Notophyll Elliptic 6:1 Entire Acumi- Decurrent subsessile nate C. inerme Decussate Petiolate Microphyll Obovate 1.8:1 Entire Retuse Cuneate

C. serratum Decussate Sessile to Mesophyll Obovate 2.4:1 Serrate Acumi- Cuneate subsessile nate C. trichotomum Decussate Petiolate Mesophyll Ovate 2:1 Entire Acumi- Rounded nate C. bracteatum Decussate Petiolate Mesophyll Ovate 1.8:1 Entire Acumi- Concave nate C. laevifolium Decussate Petiolate Notophyll Elliptic 5:1 Erose Acumi- Cuneate nate

Clerodendrum serratum (Linnaeus) Moon [i.e. Rotheca serrata (Linnaeus) Steane & Mabberley] [PLATE-I, Fig. C; PLATE-II, Fig. C] Leaves decussate, sessile or sub sessile; Blade: 150-220×55-92 mm with 2.4:1 ratio, symmetrical, obovate, acuminate, base cuneate, mesophyll and serrate. Venation: Pinnate 1° vein, 2°s weak brochidodromous; angle of divergence, smoothly decreasing towards base; inter-2°s weak; 3° exmedially ramified; angle with respect to 1° vein, obtuse, increasing exmedially; alternate percurrent 40 and regular polygonal reticulate 5°; moderately developed areolation. Exsiccatae: Hajo, Kamrup District, Assam, India, 22.12.2013, N. Das 2865 (GUHB).

Clerodendrum trichotomum Thunberg [PLATE-I, Fig. D; PLATE-II, Fig. D] Leaves decussate, petiolate; Blade: 130-190×40-95 mm with 2:1 ratio, symmetrical, ovate, acuminate, base rounded, mesophyll and entire. Venation : Pinnate 1° vein, 2°s weak brochidodromous; angle of divergence, smoothly decreasing towards base; inter-2°s weak; 3° sinuous; angle with respect to 1° vein, perpendicular, increasing basally; opposite percurrent 40 and regular polygonal reticulate 5°; moderately developed areolation. Exsiccatae: Charaipung RF, Digboi Forest Division, Tinsukia District, Assam, India, 20.04.2013, N. Das 2815 (GUBH).

DISCUSSION Details of the data recorded through the study of leaf characters from four species now accepted under Clerodendrum, Volkameria inermis and of Rotheca serrata has been 294 Table 2. Leaf architecture characters of the six species of Clerodendrum Linnaeus (sensu lato) Leafarchitectureof Clerodendrum spp. Nibedita Das & SK. Borthakur 295 presented in Tables 1 and 2 exhabit that these characters are indeed good taxonomic markers in plant identification. The most important characters which separate species from each other were leaf attachment; petiole features; laminar shape, margin, apex and base, blade class, 2° and 3° vein categories, spacing and angle of emergence of these veins. Tables 1 and 2 illustrate the uniqueness of these leaf architecture characters of six species examined. Leaf architectural characters can be very good taxonomic marker especially during off- flowering times and sterile plant specimens. Photographs of the collected species have been provided in the Figure 1 (A to F) and Figure 2 (A to F). It can be concluded from the data generated from leaf-architecture study that there is no marked recognizable difference of Volkameria inermis and Rotheca serrata to keep out these two species from the genus Clerodendrum. Further systematic studies using other parameters may through light in this regard.

Acknowledgements The authors are thankful to the UGC for providing financial assistance under its Special Assistance Program [SAP-DRS-I].

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