Thaiszia - J. Bot., Košice, 21: 73-83, 2011 http://www.bz.upjs.sk/thaiszia Systematic value of foliar epidermal morphology in some taxa of the tribes: Urticeae and Parietariae of the West African Urticaceae 1* 2 2 AKEEM BABALOLA KADIRI , BOLA OBOH & CHIMA OHA 1 Department of Botany, University of Lagos, Akoka Yaba, Lagos, Nigeria; abkadiri2001@yahoo.com 2 Department of Cell Biology and Genetics, University of Lagos, Akoka Yaba, Lagos, Nigeria; bolaoboh@yahoo.co.uk *Corresponding author Kadiri A. B., Oboh B. & Oha C. (2011): Systematic value of foliar epidermal morphology in some taxa of the tribes: Urticeae and Parietariae of the West African Urticaceae. – Thaiszia – J. Bot. 21: 73-83. – ISSN 1210-0420. Abstract: The foliar epidermal characteristics of all West African species of the tribe Parietarieae and some taxa in the tribe Urticeae were investigated by the means of light microscopy for the purposes of easy identification and justification of recent taxonomic merging of Fleurya with Laportea. In the tribes, cell number is higher on the adaxial surface (52 to 110) than on the abaxial surface (19 to 96), stomata number varies from 31 to 42 per mm² while cell size ranged from 60.8 - 70.4 µm x 22.4 - 32.0 µm on the adaxial surface and 32.0 - 40.0 µm x 16.0 - 22.4 µm on the abaxial surface. Generally, all the species have hypostomatic leaves and anomocytic stomatal type but paracytic and anisocytic types are diagnostic for Laportea aestuans, Laportea ovalifolia, Parietaria laxiflora, and Laportea alatipes. Glandular and simple trichomes of different sizes were observed in all the taxa except in Girardinia heterophylla and L. ovalifolia. The cell shape, anticlinal wall pattern, and stomatal type which correlate to a reasonable extent have supported the amalgamation of Laportea and Fleurya. Crystal sands of calcium oxalate were found in L. ovalifolia, Girardinia condensata, and Parietaria laxiflora while peltate scales distinguished P. laxiflora from other species. The species have medicinal and economic values. An artificial indented dichotomous taxonomic key for separating the taxa is presented. Keywords: Urticaceae, Urticeae, Parietariaeae, leaf epidermis, morphology, West Africa. 73 Introduction Urticaceae, the nettle plant, is a family of flowering plants consisting of herbs, shrubs and trees (HUTCHINSON & DALZIEL 1963; HUTCHINSON 1967; HEYWOOD 1978). The family has 45 genera with about 700 species (HEYWOOD 1978). There are eleven genera in West Africa and four of these which are grouped in two tribes (Urticeae and Parietarieae) were selected for the present study. The taxa were specifically selected for study because of the recent taxonomic change, lack of sufficient information on leaf endo-morphological characteristics and synonymy problem. Fleurya Gaud. has been merged with Laportea Gaud. (LOWE & SOLADOYE 1990). There is a very thin line of distinction between Parietarieae and Boehmerieae (HEYWOOD 1978) and perhaps because of the ecological preference (montane areas) of Parietarieae, taxonomic information about it is scanty in West Africa; furthermore, the two species of Girardinia are often regarded as synonyms and Droguetia is poorly represented in and taxonomic information about it is almost lacking (HUTCHINSON & DALZIEL 1963). The following taxa were investigated, Urticeae: Droguetia iners (Forsk.) Schweinf., Laportea aestuans (Linn.) Chew., syn. Fleurya aestuans (Linn.) Miq., Laportea ovalifolia (Schumach.) Chew., syn. Fleurya ovalifolia (Schum. & Thonn.) Dandy, Laportea alatipesHook f., Laportea mooreana (Hiern.) Chew., Girardinia heterophylla (Vahl.) Decne, Girardinia condensata (Hochst. ex Steud.) Wedd., syn. Girardinia diversifolia (Link.) Friis, and Parietarieae: Parietaria debilis Forst. f. and Parietaria laxiflora Engl. were studied. These species have culinary, clothing and aesthetic uses (BURKILL 1997; HUTCHINSON & DALZIEL 1963). Based on exo-morphology, BENTHAM & HOOKER (1965) grouped all taxa in the family in one tribe Urereae while HEYWOOD (1978) subdivided the family into six tribes and our genera were grouped into two tribes Urticeae and Parietarieae. In the later account documented by LOWE & SOLADOYE (1990), the genus Fleurya Gaud. was changed to Laportea Gaud. and all the species were transferred based on exo-morphological traits. The present investigation therefore aims at justifying the merging of Fleurya with Laportea using endomorphological features of the leaf and also to document the leaf epidermal features of other species in order to facilitate their delimitation and ease their recognition even if leaf samples are available in fragments. The only existing report on leaf endo-morphology in the group is the general family account by METCALFE & CHALK (1950, 1979) with scanty information on few taxa of the tribes: Urticeae and Parietarieae, which are the major focus of the present work; however, other taxa in family are not also sufficiently accounted for. The present study will therefore contribute more taxonomic data that will enhance taxonomic understanding of the group. In order to facilitate this, an artificial indented dichotomous taxonomic key is therefore presented to assist in taxa delimitation. Material and methods Preserved specimens obtained from the herbarium of the Forestry Research Institute of Nigeria, Ibadan (FHI) and fresh specimens collected from field trips 74 were used for the study. Specimens deposited in the herbarium of the University of Lagos (LUH) were visited for authentication and study. Herbarium abbreviations follow HOLMGREN et al. (1990). The herbarium indices of the investigated species are given as follow: D. iners (FHI 8889), F. eastuans (FHI 33365), F. ovalifolia (FHI 51098), L. alatipes (FHI 29958), L. mooreana (LUH 3163), L. ovalifolia (FHI 101554), G. heterophylla (FHI 97877), G. condensata (FHI 42715), P. debilis (FHI 97893) and P. laxiflora (FHI 39217). Specimens of synonymous taxa were compared. Methods follow ADEDEJI (2004), AKHIL & SUBHAN (1997), KADIRI et al. (2007), KOTRESHA & SEETHARAM (2000), OGUNDIPE & W UJEK (2004), REJDALI (1991). Portions of 2–5 cm² were cut from the standard median part of the leaf lamina near the mid-rib, or the whole leaf was used. Dried leaves were boiled in water for thirty minutes and subsequently soaked in either concentrated trioxonitrate (v) acid (HNO3) in capped specimen bottles for about 8–24 hrs to macerate the mesophyll, or irrigated in sodium hypochlorite solution (commercial bleach) for 30–120 minutes to bleach the leaf portions. Tissue disintegration was indicated by bubbles and the epidermal layers were separated and transferred into Petri dishes containing water for cleansing. In case of fresh materials, the leaves were scraped with razor blade to separate epidermis. Tissue debris was cleared off the epidermis with fine-hair brush and washed in several changes of water. Drops of different grades of ethanol, 50 % – 100 %, were added in turn to dehydrate the cells. The preparations were later stained with Safranin O in 50 % alcohol for about five minutes before being mounted in glycerine on glass slides. The epidermal layers were mounted on glass slides with the uppermost surfaces facing up, covered with cover-slips and ringed with nail varnish to prevent dehydration. Photographs of epidermal features of the leaf were obtained with the aid of digital Motic camera attached to a microscope and Pentium IV computer while line diagrams of structures were made with camera lucida. Results D. iners has the highest number of trichomes on the adaxial surface. Trichomes occur on both surfaces of the leaves of D. iners, L. aestuans, L. alatipes, G. condensata and Parietaria spp. while L. ovalifolia and G. heterophylla are glabrous (Plates 1 and 2, Tab. 1). The epidermal cell shape is polygonal on both surfaces of D. iners, G. condensata and Parietaria spp., but it is irregular on both surfaces of L. ovalifolia and L. aestuans. It is polygonal/irregular on the surfaces of L. alatipes, L. mooreana and specimens of L. ovalifolia (Fig. 1, Plate 1, Tab. 1). The two species of Parietaria showed limited variations in their foliar epidermal features. The leaf is pubescent on both surfaces; the anticlinal wall is undulate while the cell shape is also uniform on both surfaces (Fig. 1, Plates 1 and 2, Tab. 1). Mean cell size is 45.2 - 107.8µm x 20.5 -40.6µm and stomatal size is 18.9 µm x 7.7 - 10.6 µm. Cell wall thickness varies from 4.3 – 8.8 µm on both surfaces (Tab. 2). The species grouped under the tribe: Urticeae are more variable in their foliar epidermis than the species of Parietarieae. The leaf is either glabrous on both surfaces in G. heterophylla and 75 L. ovalifolia or pubescent on both surfaces in D. iners, G. condensata, L. aestuans, L. alatipes, L. mooreana and Parietaria spp. (Tab. 1). Intra-generic differences in these features were also recorded. Mean cell size is 27.0 - 57.8 µm x 10.5 - 27.2µm and stomatal size is 13.4 - 20.8 µm x 6.7 – 11.9 µm. Cell wall thickness varies from 3.1 – 4.8µm on both surfaces (Tab. 2). Stomatal types recorded included the anomocytic type which is present in all species (Plate 1), anisocytic which is restricted to Laportea species: L. alatipes, L. aestuans and L. ovalifolia and paracytic type which occurred only in P. laxiflora (Tab. 1). Cystoliths filled the cell lumen in all Laportea species including specimens regarded as Fleurya (Fig. 1 D, E, F, H, K). B A G F E I D C K J H L Fig. 1: Line drawings of some taxonomically useful foliar epidermal features of some members of West African Urticaceae. A: D. iners (short conical trichomes), B: P. debilis (bulbous base glandular trichome), C: P. laxiflora (large cell size in Parietaria spp.), D, E (L. aestuans ), F (L. ovalifolia), G, H (specimen designated as Fleurya ovalifolia at FHI) and K (L. alatipes) have cystoliths within cell lumen; C, D (L. aestuans); F, H, J (G. heterophylla) and L (L. alatipes): show anomocytic stomata, the common stomatal type in the two tribes. The leaf is hypostomatic. I: P. laxiflora (scar of bulbous base glandular trichome). Adaxial surface: A, B, E, G, I and K; abaxial surface: C, D, F, H, J, and L. Scale is 50µm. 76 Tab. 1: Relative quantitative and qualitative characteristics of foliar epidermis of the species of the tribes: Urticeae and Parietarieae of the West African Urticaceae. Species Tribe: Urticeae Droguetia iners Laportea aestuans syn. Fleurya aestuans Laportea alatipes 77 Laportea mooreana syn. Fleurya mooreana Laportea ovalifolia syn. Fleurya ovalifolia Girardinia heterophylla Girardinia condensata Tribe: Parietarieae Parietaria debilis Parietaria laxiflora Surface Cell shape Wall pattern Stomatal type Trichome type Cell no. 2 (x) per mm Stomatal no. 2 (x) per mm Trichome no. 2 (x) per mm adaxial abaxial adaxial abaxial adaxial abaxial adaxial abaxial adaxial abaxial adaxial abaxial adaxial abaxial polygonal polygonal irregular irregular polygonal/irregular polygonal/irregular polygonal/irregular irregular irregular irregular irregular polygonal/irregular polygonal polygonal curved curved curved curved straight/curved straight/curved straight/curved straight/curved curved curved straight/curved straight/curved straight straight absent anomocytic absent anomocytic, anisocytic absent anomocytic, anisocytic absent anomocytic absent anomocytic, anisocytic absent anomocytic absent anomocytic present present present present present present present present absent absent absent absent present present 110 62 41 33 39 27 30 26 46 19 34 49 45 97 absent 3 absent 15 absent 14 absent 10 absent 32 absent 42 absent 10 16 3 1 8 7 7 7 6 absent absent absent absent 14 55 adaxial abaxial adaxial abaxial polygonal polygonal polygonal polygonal undulate undulate undulate undulate absent anomocytic absent anomocytic, paracytic present present present present 64 24 16 20 absent 12 absent 5 1 75 7 6 Tab. 2: Relative quantitative characteristics of foliar epidermis of the species of the tribes: Urticeae and Parietarieae of the West African Urticaceae. Species Tribe: Urticeae Droguetia iners Surface 78 adaxial abaxial Laportea aestuans adaxial syn. Fleurya aestuans abaxial Laportea alatipes adaxial abaxial Laportea mooreana adaxial syn. Fleurya mooreana adaxial Laportea ovalifolia adaxial syn. Fleurya ovalifolia abaxial Girardinia heterophylla adaxial abaxial Girardinia condensata adaxial abaxial Tribe: Parietarieae Parietaria debilis adaxial abaxial Parietaria laxiflora adaxial abaxial S.E= Standard error Epidermal cell length Epidermal cell width Epidermal cell thickness Stomatal length Stomatal width Min(Mean±S.E)Max (µm) Min(Mean±S.E)Max (µm) Min(Mean±S.E)Max (µm) Min(Mean±S.E)Max (µm) Min(Mean±S.E)Max (µm) 32.0(36.6±4.12)48.0 32.0(35.5±1.72)40.0 29.0(36.1±4.0)48.0 32.0(39.6±4.4)52.0 29.0(37.7±4.2)48.0 19.2(27.0±5.3)42.0 27.0(35.7±4.1)45.0 16.2(25.0±5.0)40 48.0(50.9±2.2)56.0 35.0(41.9±3.4)48.0 38.0(43.5±7.1)64.0 38.0(45.1±3.1)51.0 22.0(29.1±4.1)42.0 22.0(31.3±1.3)32.0 16.0(17.6±0.8)19.0 21.0(10.5±0.5)13.0 8.0(11.2±1.1)13.0 10(11.8±1.1)14.4 13.0(17.9±2.3)24.0 10.0(13.4±2.3)19.0 11.0(16.9±2.2)22.0 8.0(10.2±2.1)16.0 22.4(25.6±2.1)32.0 16.0(17.9±2.4)26.0 16.0(21.7±2.3)25.6 14.0(18.5±1.6)22.4 8.0(10.6±1.2)12.8 13.0(17.6±2.4)24 4.0(4.7±0.2)5.1 4.0( 4.6±0.2)4.8 1.6(3.4±0.8)4.8 3.2(3.6±0.2)4.8 3.2(3.5±0.7)4.4 2.9(3.3±0.2)4.0 3.0(2.9±0.6)4.0 2.4(3.0±0.3)4.0 3.2(4.3±0.7)6.0 3.2(3.7±0.8)4.0 3.7(4.3±0.8)4.8 4.0(4.6±0.2)4.8 3.2(3.5±0.1)3.8 2.4(3.4±0.5)4.8 absent 12.8(15.3±1.0)16 absent 12.8(15.4±1.0)16.0 absent 11.2(13.4±0.7)14.0 absent 10.2(11.4±0.8)13.0 absent 16(16.6±1.2)18.0 absent 16.0(17.9±1.2)21.0 absent 11.0(16±3.0)24.0 absent 6.4(6.7±0.1)8 absent 8.0(9.3±0.7)9.6 absent 6.2(8.3±0.8)9.6 absent 5.2(6.3±0.7)7.8 absent 8.0(9.3±0.8)11.0 absent 8.0(11.5±1.7)16.0 absent 6.4(8.6±0.9)11.2 37.0(45.2±3.2)51.0 35.0(40.3±3.2)48.0 69.0(91.9±8.7)112.0 96.0(107.8±9.0)136.0 19.2(20.5±2.8)29 16(21.1±4.5)25 32(40.6±6.1)56.0 32(40.0±4.6)51.0 4.8(5.2±0.3)5.6 3.2(4.3±0.8)4.8 6.4(8.8±1.4)12.8 4.8(7.2±1.3)9.6 absent 11.2(18.9±1.1)16.0 absent 14.4(18.9±2.1)22.4 absent 6.4(7.7±0.7)8.0 absent 8.0(10.6±1.1)13.0 Plate1: Foliar epidermal surfaces of some species of Urticaceae. A, B: Girardinia heterophylla; C, D: Droguetia iners; E, F: Laportea mooreana. A, C, and E: adaxial surface, B, D, F: abaxial surface. Scale bar is 25µm. 79 Plate 2: Trichome types recorded within the tribes: Urticeae and Parietarieae. A: Simple multiseriate acicular trichome found in Girardinia condesata, B: Multicellular glandular trichome reported in Laportea spp., C: Unicellular nonglandular acicular type recorded in Drougetia iners, D: Unicellular tip-bent glandular trichome found in Parietaria spp.. Scale is 75µm. Discussion In the general anatomical account of Urticaceae, METCALFE & CHALK (1950, 1979) reported the occurrence of laticiferous elements, glandular, non glandular and stinging hair types, hypostomata, presence of hydathodes, fluid-loaded epidermis, silicified and calcified cell walls which occur as cystoliths of different forms. Lumen-filled cystoliths were encountered in all the Laportea species. There were variations in the length and type of trichomes observed among these species; simple multiseriate acicular trichomes were found in Girardinia, 80 multicellular glandular type was recorded in Laportea spp., simple non-glandular long acicular type was found in D. iners and multicellular tip-bent glandular type was recorded in Parietaria spp. and L. alatipes has the longest trichomes of 60.1µm. These features were found to have reliable systematic value. The amalgamation of Laportea and Fleurya is supported by the foliar epidermal characteristics especially all the qualitative features as these features correlate to a large extent. DAVIS & HEYWOOD (1963) have described qualitative features as those characters which are limitedly influenced by environmental factors as they are under strict genetic control. However, DAVIS & HEYWOOD (1963); HEYWOOD (1973) and DILCHER (1947) cautioned the application of trichomes in making taxonomic decisions as its expression can be influenced by environmental factors. In the quantitative characters, there was a considerable overlap in all measurements; the mean values of epidermal cell and stomatal size are reasonably close; therefore, the merging of these species as documented by LOWE & SOLADOYE (1990) is strongly supported. Generally, all the species have hypostomatic leaves and anomocytic stomatal type but paracytic and anisocytic types were also recorded in L. aestuans, L. alatipes, L. ovalifolia and P. laxiflora. The taxonomic relevance of trichomes in Urticaceae and the systematic relevance of epidermal features has been articulated in angiosperms (AKHIL & SUBHAN 1997, KADIRI et al. 2007, KOTRESHA & SEETHARAM 2000, METCALFE & CHALK 1950 1979, OGUNDIPE & W UJEK 2004 and REJDALI 1991). Crystal sands of Calcium oxalate was found in L. ovalifolia, G. condensata, L. ovalifolia, and P. laxiflora while peltate scales distinguish P. laxiflora from other species. However, the variations recorded in these features have pointed to the fact that these species cannot be lumped together in a single tribe as done by BENTHAM & HOOKER (1965). The species of Parietaria share many features in common; therefore their grouping in the same tribe Parietariaeae is supported. An artificial indented dichotomous taxonomic key for separating the taxa is presented as follows: Artificial intended dichotomous key for separating the species of the two West African tribes: Urticeae and Parietariae of the family Urticaceae 1. Cell shape polygonal/irregular, anticlinal wall pattern straight/curved. Stomatal types anomocytic, anisocytic and paracytic. Leaf pubescent on either surface, mean cell size 27.0 - 57.8 µm x 10.5 - 27.2 µm, stomatal size 13.4 - 20.8 µm x 6.7 – 11.9µm. Cell wall thickness varies from 3.1 – 4.8 µm, cystoliths present…………………………………………………………………Tribe Urticeae 1. Cell shape polygonal, anticlinal wall pattern undulate, stomatal types anomocytic and paracytic. Leaf pubescent on both surfaces, Mean cell size 45.2 - 107.8µm x 20.5 - 40.6µm and stomatal size is 18.9 µm x 7.7 - 10.6 µm. Cell wall thickness varies from 4.3 – 8.8 µm on both surfaces, cystoliths absent………….………………………………………………..….Tribe Parietariae Tribe Urticeae: 1. Epidermal cell shape undulate, leaf surface glabrous….Girardinia heterophylla 1. Epidermal cell shape polygonal/ irregular , leaf surface pubescent 81 2. Stoma more than twice as long as wide, mean trichome number on the abaxial surface 55 per mm²………………………………Girardinia condesata 2. Stoma twice as long as wide, mean trichome number on the abaxial surface 3 per mm²…………………………………………………………Droguetia iners 3. Cell shape irregular on both surfaces, 4. Trichome present………………………………..…..…Laportea aestuans 4. 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