Proc. Indian Acad. Sci. (Plant Sci.), Vol. 97, No. 3, June 1987, pp. 235-246. Printed in India. Anatomical contributŸ to the taxonomy of some Verbenaceae: Petiole LILLYAMMA MATHEW and G L SHAH* Departmr of Botany, Alphonsa College, Palai 686 574, India *Department of Biosciences, Sardar Patel University, Vallabh Vidyanagar 388 120, India Abstraer. The differentdimensional aspects of petiolar anatomy of 35 taxa of Verbenaceae has br traced with a view to reveal the structural diversity and to evaluate the cont¡ of petiolar anatomy to the taxonomy of Vr Seven parameters were quantitatively analysed for the patterns of variability. The different vascular configurations in va¡ taxa were found to be taxon specific and hence can be utilized asa taxonomic marker. The observation of intemal phloem in the petiole of Avicennia and Tectona is ah additional information relevant to the anatomy of Verbenaceae. The variation patterns in the l~tiolar anatomy of different taxa were found to have some adaptivr significance. Keywords. Pattems of variabifity; pr anatomy; structural diversity; taxonomy; Verbenaceae. 1. Introduction Verbenaceae is predominantly a tropical family exhibiting a wide range of growth habit and inhabiting diverse habitats. In India there are indigenous and introduced, wild and cultivated species. There is a considerable disagreement on the generic delimitation and relationships of different taxa in the family. Hence the present study has been taken up to supplement the exomorphic characters with anatomical studies in approaching the taxonomic problems of the family. Apart from the general study pertaining to the anatomy of Verbenaceae by Solereder (1908) and Metcalfe and Chalk (1950), limited studies on the petiolar anatomy of a few species of Cleroden- drum have been carried out by Inamdar (1968) and Inamdar and Patel (1969). 2. Materials and methods The taxa studied, their source and abbreviations used in the dice diagrams etc are given in table 1. The voucher mate¡ are deposited in the herbarium of the Depart- ment of Biosciences, Sardar Patel University, Vallabh Vidyanagar, Gujarat. Petiolar anatomy was studied from transections through the middle of the petiole. Small pieces of mature petiole were fixed in FAA, processed and embedded in paraffin (56-58~ following standard procedures (Berlyn and Miksche 1976). Sec- tions of 5-7 #m thick were cut on a rotary microtome, stained in toluidine blue O (O'Brien et al 1964) for general study and tannic acid-ferric chloride-resorcine blue (lacmoid) combination for testing internal phloem (Cheadle et al 1953). Sections were then dehydrated in Tertiary butyl alcohol (TBA)-xylene series, cleared in pure xylene and mounted in DPX. Quantitative characters such as (i) petiole length, (ii) cross sectional arca of the petiole, (iii) arca of the vascular bundle in TS, (iv) distance from vascular bundle to adaxial surface, (v) distance from vascular bundle to abaxial surface, (vi) number of pith bundles and (vii) number of vascular bundles were studied and statistically 235 236 Lillyamma Mathew and G L Shah Table 1. Taxa investigated and their source of collection. Code used in the dice Wild/ Names of the taxa Source diagram cultivated Avicennia marina Vierh. M AA W A. officinalis L. K AO W Callicarpa tomentosa Murr. K CT W Citharexylum subserratum Sw. C CS C Clerodendrum inerme Gaertn. G CI W/C C. multiflorum O. Ktze. G CM W C. indicum 0. Ktze. K CP C C. splendens G. Don G CE C C. thomsonae Balf. K CH C C. viscosum Vent. G CV W Duranta repens L. G DP C Gmelina arborea Roxb. G GA W G. philippensis Cham. G GP C Holmskioldia sanguŸ Retz. K HS C Lantana camara var. aculeata Mold. G LA W L. camara var. hybrida Mold. G LH C L. camara var. nivea Bailey G LN C Petrea volubilis Jacq. G PV W Phyla nodiflora (L.) Greene K PN W Premna latifolia Roxb. K PL W Stachytarpheta indica Vahl G SI W Tectona grandis L.f. G TG W/C T. hamiltoniana Wall. U TH C Verbena bipinnatifida Nutt. G VB C V. bonariensis L. GE VO C V. canadensis Britt. M VC C V. hispida Ruiz et Pav. GE VH C V. hybrida Voss M VY C V. incisa Hk. f. K VI C V. officinalis L. GE VP W/C V. stricta Vent. GE VS C V. urticifolia L. GE VU C Vitex negundo L. G VN W V. trifolia L. G VT W V. negundo var. intermedia L. M VX W M, Maharashtra; K, Kerala; G, Gujarat; U, Uttar Pradesh; GE, Seeds obtained from Germany and glown in the botanical garden; C, cultivated; W, Wild. analysed for the patterns of variability using range, mean and standard error. Areas were calculated using area calculating device (Chavan et al 1979). All measurements were based on an average of 100 readings. The values were graphically represented in the form of dice diagrams. Photomicrographs were taken on Carl Zeiss photomicroscope using Ilford 35 mm black and white film. 3. Observafions The transectional outline of the petiole is highly variable in different taxa (figures 1- 35). Epidermis is single layered, stomatiferous or estomatiferous with varying degree Contribution of petiolar anatomy to the taxonomy of Verbenaceae 237 ,,:~~ ~~- : s lO k:'::" xylem sc[erenchyma I ! ..... !..Y.Y .... Dhioern col~anchyrna I['2 . lOOq~rn Figures 1-13. Diagrammatic representation of petiole in cross section. 1. Avicem~ia marina. 2. A. officinalis. 3, CaIlicarpa tomentosa. 4. Citharexylum subserratum. 5. Clerodendrum inerme, 6, C, multiflorum. 7. C. indicum. 8. C. splendens. 9. C. thom- sonae. 10. C. viscosum. 11. Duranta repens. 12. Gmelina arborea. 13. G. philippensis. 238 Lillyamma Mathew and G L Shah 14 16 24 25 26 ~J '~~~s ~~ 1000AJm Figures 14-30. Diagrammatic representation of petiole incross section. 14. Holmskiotdia sanyuinea. 15, Lantana camara var. aculeata. 16. L. c. var. hybrida. 17. L. c. var. nivea. 18. Petrea t,olubilis. 19. Phyla nedifiora. 20. Premna latifolia. 21. Stachytarpheta indica. 22. V. bipinnatifida. 23. V. bonariensis. 24. V. canadensis. 25. V. hispida. 26. V. hybrida. 27. V. incisa. 28. V. o[~ficina/is. 29. V. urticifolia. 30. V. stricta. Contribution of petiolar anatomy to the taxonomy of Verbenaceae 239 ~~:~,i,,+i + " 34 [.~.-7 ~a ~\ t:!N ~b3S !+ ~ .| +. xylem 0 ~~otm sr.|erlr~l~yn~ ;'~~.. "+ : ++/ :ti 9o'91 +,;':,~ "2?Ÿ ,.t,t"'+*.*+;; "~'~~*'+[+,..', ' +~,:-+.+..... ,++*'.+ ;..,:++' Figures 31-35. Diagrammatic representation of petiole in cross section. 31. Tectona ,qrandis. 32. T. hamiltoniana. 33. Vitex negundo. 34. V. trifolia. 35. V. negundo var+ intermedia. of hairiness. In Avicennia trichomes are numerous on the abaxial surface and very few or absent on the adaxial surface (figures 36, 37). EpidermaI cells are mostly columnar, oval to oblong, rarely squarish of polygonal and usually with outer walls rounded, flat or rarely papillate as in Petrea (figure 39). 240 Lillyamma Mathew and G L Shah ...... : < ~a~91191237~" | : ~ N Figures 36-41. Photomicrographs of the structure of petio/e in cross section. 36. Avi- cennia marina (x 137). 37. A. oJficinalis (x 149). 38. V. incisa (x343). 39. Petrea votubilis ( x 514). 40. A. marina ( • 300). 41. C. inerme ( x 149). Contribution of petiolar anatomy to the taxonomy of Verbenaceae 241 The ground tissue is differentiated into hypodermal collenchyma which forms continuous or discontinuous strands and parenchyma. In Avicennia large intercel- lular spaces occur towards the adaxial side (figure 37). In Phyla nodiflora, Verbena bipinnatifida, V. bonariensis, V. incisa and V. stricta the dorsal margins of the petiole are dilated (figures 19, 22, 23, 27, 30) consisting of radially elongated parenchyma cells, containing denser contents and chloroplasts (figure 38). The patterns of vascular configurations observed in the middle region of the petiole are: (i) Crescent shaped in Clerodendrum inerme, Gmelina philippensis, Holmskioldia san9uinea, Phyla, Stachytarpheta and Verbena (figures 5, 13, 14, 19, 21- 30, 41). (ii) Crescentic with invaginated ends in Avicennia marina (figure 1). (iii) Crescentic with medullary bundles in Duranta repens, Lantana Camara vars. aculeata, hybrida and nivea and Vitex (figures 11, 15-17, 33-35). (iv) Two arcs with 4-5 dorsal bundles in Citharexylum subserratum (figure 4). (v) Dissected crescent of collateral bundles in Avicennia officinalis and Clerodendrum (except C. inerme and C. splendens) (figures 2, 6, 7, 9, 10, 43). (vi) Dissected crescent with invaginated ends in Callicarpa tomentosa and Premna latifolia (figures 3, 20). (vii) Dissected cylinder of collateral bundles without medullary bundles in Clerodendrum splendens and Gmelina arborea (figures 8, 12). (v¡ Dissected cylinder of collateral bundtes with medullary bundtes in both species of Tectona (figures 31, 32). (ix) Medullated cylinder in Petrea volubilis (figures 18, 45). The number of vascular bundles ranges from 1-many (figures 41, 43, 45). The maximum number 12-21 is observed in Tecwna 9randis (figure 31). Each bundle consists of an adaxial xylem and abaxial phloem with cambium in between (figure 44). Vessels may be solitary, in radial multiples or in clusters with the cross sectional outline circular or angular. The radial multiple arrangement is the prominent type in all the species studied. In Avicennia and Tectona additional groups of phloem occur internally towards the pith region (figures 40, 42). The perivascular sclerenchyma occurs asa continuous cylinder of 2-3 layers in Petrea oras discontinuous strands in A. officinalis, Citharexylum, Gmelina, Clerodendrum indicum, C. splendens, C. viscosum, Tectona and Vitex. One or two or seldom 4-5 lateral bundles are observed below each dorsal lateral rib in all taxa except Premna (figure 17). The lateral bundles are collateral and open in all the taxa (figure 47) except Callicarpa and Tectona where they are amphicribral or hardocentric (figure 46). Those taxa which have perivascular sclerenchyma are provided with a sclerenchymatous bundle cap outside the lateral bundles. In both species of Tectona the sclerenchymatous bundle sheath surrounds the whole bundle (figure 46).