Indian J. Applied & Pure Bio. Vol. 29(2), 343-360 (2014). Leaf architecture in some Euphorbiaceae Sarala C. Tadavi and Vijay V. Bhadane* *Department of Botany, Pratap College, Amalner-425401, (India) E-mail: [email protected] Abstract The present study deals with the leaf architectural study of 44 species distributed over 20 genera of the Euphorbiaceae to provide comprehensive account on the leaf architecture of Euphorbiaceae and its taxonomic significance. The leaves are simple except in Anda and Hevea where leaves are 3-5 foliate. The leaf shape, apex, base, number of areoles and vein endings entering the areoles are species specific. Major venation pattern is pinnate-craspedodromous, pinnate- camptodromous with brochidodromous, weak brochidodromous, festooned brochidodromous, eucamptodromous and reticulodromous secondaries and actinodromous. The highest degree of vein order is up to 6º. Quantitative parameters like the numbers of secondary veins, areoles and vein endings per unit area have using analyzed. The veinlets terminations are mostly conventional tracheids or occasionally dilated. The presence of bundle sheath is common around 1º to 5º veins. Leaf architectural characteristics such as presence of major venation categories, nature of marginal ultimate venation, areoles, presence or absence of bundle sheath and type of leaf margins are found to the helpful in delimiting the taxa study. Key words: Leaf architecture, taxonomy, Euphorbiaceae. Leaf architecture including venation conclusions on a survey of dicotyledonous and pattern has been studied in 20 genera and 44 angiospermous leaves respectively. A perusal species of the Euphorbiaceae. Though the of the past literature revealed that studies on study of leaf architecture is more than a leaf architecture in Euphorbiaceae are almost century old, due importance was not given to negligible1,2,4,8,9,11,13. Therefore, the present it in the systematic studies of the dicotyledons. investigation has been carried out to provide However, the work of Hickey5,6 gave a new a detailed account on the same besides its impetus and precision to the subject. Hickey evaluation for taxonomic purpose. and Wolfe7 and Melville10 based most of their (344) The plant materials were collected Major venation pattern : from various places like Bangalore, Castlerock (Goa), Waghai Botanical garden and Thrissur Major venation pattern is pinnate- (Kerala). The leaves of the material fixed in craspedodromous, pinnate-camptodromous acetic alcohol are cleared in a supersaturated with brochidodromous, weak brochidodromous, solution of chloral hydrate for 2 or 3 days. festooned brochidodromous, eucamptodromous However, the leaves of the herbarium material and reticulodromous secondaries and actinodromous. are first boiled in 5% sodium hydroxide for a few minutes and then kept in 10% potassium In pinnate craspedodromous type hydroxide at 30ºC for 2-3 days. Permanent single primary vein originate from base of the Canada balsam mounts of the cleared leaves leaf lamina and traverse towards its apex. The are prepared after dehydration in alcohol and thickness of the primary vein gradually staining them with alcoholic Kores stamp pad decreases from base to the apex. The primary purple ink Rao et al.12. In those taxa with vein gives rise to secondary veins on either compound leaves, the middle leaflets of a side in opposite, sub-opposite or alternate mature leaf are selected and the leaflet is fashion. Secondaries after originating from the referred to as leaf. The terms described are primary are traverse towards the margin. If adapted from Hickey5 and Hickey and Wolfe7. the secondaries directly terminate at the margin the venation pattern is simple craspe- Morphological description : dodromous. Such pattern is observed in Phyllanthus acidus and Vernicia fordii (Plate Leaves simple, unlobed, 3-lobed, I, Figs. 1-2). Secondaries branch just inside pinnately lobed or palmate; alternate, opposite the margin, with one arm terminating at the margin and the other join the super-adjacent or subopposite; the leaves ovate, elliptic, obovate secondary. This is called semicraspedo- or oblong; margin entire dentate or undulate; dromous found in Acalypha ciliata, A. apex acute, acuminate, mucronate, rounded or fruticosa, A. hispida and Baliospermum (Plate attenuate; base rounded, truncate, decurrent, I, Figs. 3-5). In Agrostistachys indica peltate or cordate; texture herbaceous, coria- semicraspedodromous venation having one ceous or chartaceous. additional set of loops outside the branch that joins the supra-adjacent secondary this is In all the taxa studied, the venation is called festooned semicraspedodromous (Plate unicostate and multicostate reticulate and may I, Fig. 6). In pinnate camptodromous type be differentiated into a number of size classes. secondaries do not terminate at the margin, The veins of first, second and third categories but join together in a series of prominent are considered under the major venation pattern arches and forms brochidodromous type. It is and the veins of the subsequent categories – seen in Aporosa, Breynia nivosa, B. retusa, the minor venation pattern that forms the Croton, Euphorbia fulgens, E. indica, E. milii, reticulum. The species wise qualitative leaf Glochidion, Hevea, Jatropha integerrima, features are given in the Table 1a and 1b. Mallotus nudiflorus, M. philippensis, (345) Pedilanthus, Phyllanthus airy-shawii, P. decreases gradually towards the apex and it debilis, P. indofischeri, P. polyphyllus, P. gives off other degree veins on either side. The reticulatus, P. urinaria, Putranjiva (Plate I, primary vein is stout to moderate or weak. It Figs. 7-9 and Plate II, Figs. 1-3). If the arches runs straight or bends into a small curve in of secondaries are not prominent it is weak the lamina. The primary veins are simple and brochidodromous type found in Anda, remain unbranched. Euphorbia neriifolia and E. umbellata (Plate II, Fig. 4). Primary loops having a set of Secondary veins: secondary loops outside and forms festooned brochidodromous type in Flueggea leucopyrus The secondary veins (2°) arises on and F. virosa (Plate II, Fig. 5). When secondaries either side of the primary vein in alternate upturned and gradually diminishing apically fashion and sometime opposite manner, which inside the margin, connected to the supra- diverge uniformly at a moderate acute angle adjacent secondaries by a series of cross veins from the primary vein and extend towards the without forming prominent marginal loops, margin bending in a smooth or abrupt curve. such eucamptodromous type is found in The secondaries are present more on one side Phyllanthus maderaspatensis and P. virgatus of the primary vein in leaves with oblique base. (Plate II, Fig. 6). If the secondaries losing their The number of secondary veins varies within identity towards the leaf margin by repeated the same species. The angle of divergence of branching into a vein reticulum the venation the secondary veins is acute wide, acute pattern is reticulodromous. It is observed in moderate or acute narrow and varies from Euphorbia heterophylla and E. tirucalli (Plate species to species and even within the same II, Fig. 7). species from base to apex. In B. retusa, J. podagrica, the basal secondary veins are acute In actinodromous type three or more wide. Some secondary veins become more primary veins diverging radially from a single acute wide at the apical of lamina in A. ciliata, point. The position of the first point of primary Euphorbia indica, Euphorbia tirucalli, vein radiation is at the base (basal). Ramifi- Flueggea leucopyrus, Glochidion, Phyllanthus cation of the lateral actinodromous veins airy-shawii, P. debilis, P. indofischeri, P. covering at least 2/3 of the blade area (perfect) polyphyllus, and P. urinaria (Plate II, Figs. 2- and actinodromous veins reaching at the 3). The secondaries may or may not show margin (marginal). Such pattern is observed branching into two towards tip. These are in Chrozophora prostrata, C. rottleri, interconnected by supra adjacent secondaries. Jatropha curcas, J. gossypiifolia, J. multifida, J. podagrica, Manihot and Tragia (Plate II, The inter secondaries are present Figs. 8-9). running parallel or nearly so to the secondaries as in Breynia nivosa, B. retusa, Euphorbia Primary vein: fulgens, E. umbellata, Fluggea leucopyrus, F. virosa, Glochidion, Jatropha gossypiifolia, J. The primary vein (1°) is the thickest integerrima, Phyllanthus maderaspatensis vein of the leaf/leaflets and its thickness and Putranjiva (Plate I, Fig. 7 and Plate II, (346) Figs. 4, 6). The freely ending ultimate veins are called veinlets. The number of veinlets Agrophic veins which are comb like entering an areole also varies from species to complex of veins comprised of a lateral 1° or species and within the same species. 2° secondaries with two or more exmedial 2° veins that travel roughly parallel courses The marginal venation: towards the margin present in Acalypha ciliata, A. fruticosa, A. hispida, Baliospermum, The marginal ultimate venation is Croton, Jatropha integerrima, Mallotus incomplete in Acalypha ciliata, A. fruticosa, nudiflorus, M. philippensis and Vernicia (Plate Agrostistachys, Breynia nivosa, B. retusa, I, Figs. 2-5, 8 and II, Fig. 1). In Vernicia they Chrozophora prostrata, C. rottleri, Croton, are compound and straight and simple and Euphorbia fulgens, E. heterophylla, E. indica, looped in others. E. milii, E. neriifolia, E. tirucalli, E. umbellata, Flueggea leucopyrus, Jatropha