DOI : 10.15740/HAS/AJBS/12.2/223-232 ASIAN JOURNAL OF BIO SCIENCE e ISSN-0976-8343 | Visit us : www.researchjournal.co.in Volume 12 | Issue 2 | Oct., 2017 | 223-232 RESEARCH PAPER Morphology of flower, pollen and orbicules ofMeghalayan Dioscorea L. (Dioscoreaceae), North-East India: A pivotal taxon in the evolution of monocot NILOFER SHEIKH AND YOGENDRA KUMAR Department of Botany, North Eastern Hill University, SHILLONG (MEGHALAYA) INDIA Email : [email protected]; [email protected] Article Info : Received : 26.06.2017; Revised : 20.08.2017; Accepted : 18.09.2017 Flowers, pollen and orbicules morphology is an important source of information for systematic and evolutionary studies among different species, genera and families level. In the present study the floral, pollen and orbicules morphology of 80 samples of the genus Dioscorea L. representing 8 species native to Meghalaya were studied. Trichopus and Tacca, the allied genera with Burmannia of Burmanniaceae, nearest family of Dioscoreaceae were selected as an outgroup for the present study. Variation in floral, pollen and orbicules characters were observed and 62 descriptors or traits were selected for morphometric analysis. Pollen of Dioscorea is monosulcate or bisulcate with perporate or microrecticulate sexine sculptures. Orbicules were mostly spherical with smooth surface. Key words : Floral morphology, Pollen aperature, Sexine ornamentation, Orbicule morphology, Morphometric analysis How to cite this paper : Sheikh, Nilofer and Kumar, Yogendra (2017). Morphology of flower, pollen and orbicules of Meghalayan Dioscorea L. (Dioscoreaceae), North-East India: A pivotal taxon in the evolution of monocot. Asian J. Bio. Sci., 12 (2) : 223-232.DOI : 10.15740/HAS/ AJBS/12.2/223-232. INTRODUCTION Ayensu (1972) have classified the genus based on seed morphology, floral characters, underground organs and Dioscorea L., one of the core genus of the family anatomical characters, yet the systematic of the genus is Dioscoreaceae are mainly distributed in the tropics and confusing and not completely resolved. Floral and pollen subtropical regions of the world, of which India accounts morphology plays an important role in taxonomic for 50 species of Dioscorea (Anonymous, 1952) in identification at species, generic or even higher level of distribution. Meghalaya, one of the eight states of North- classification. The arrangement, size, nature and numbers East India is rich in biodiversity and has luxuriant growth of different floral parts are included in taxonomic of Dioscorea species in wild habitat. Nearly 16 species identification. Few workers who suggested the taxonomic of Dioscorea has been reported from Meghalaya (Sheikh significance of pollen morphology within Dioscoreaceae et al.,2009). This genus of the family Dioscoreaceae were Su (1987); Caddick et al. (1998) and Xifreda occupies a basal position among all extant monocoty- (2000). Others who contributed to the palynological data ledonous plants (Dahlgren, 1989 and Chase et al., 2006). of Dioscorea species using light microscopy (LM) were Despite of its large morphological diversity, this genus Selling (1947); Kuprianova (1948); Sharma (1967); lacks in proper taxonomic treatment. Several workers Erdtman (1969); Heusser (1971); Huang (1972) and like Knuth (1924); Burkill (1960); Coursey (1967) and Chavez et al. (1991). Microphological data remained HIND INSTITUTE OF SCIENCE AND TECHNOLOGY NILOFER SHEIKH AND YOGENDRA KUMAR scarce untill Schols et al. (2001 and 2003) examined longest axis (LA) and the shortest equatorial axis (SEA) pollen of 96 Dioscorea species with light microscopy were measured using LM slides of acetolyzed pollen and (LM), Scanning electron microscopy (SEM) and additional measurement was taken by SEM. Transmission electron microscopy (TEM) and concluded that pollen of Dioscorea are monosulcate or disulculate Morphometric analysis : with perporate, perporate to microreticulate or striate A total of 62 descriptors (qualitative and quantitative) exine and suggested that aperature number and sexine traits were selected from floral, pollen and orbicule ornamentation to be frequently consistent within samples morphology (Table A). Species means for 32 quantitative from each section. Schols et al. (2005) with correspond characters were calculated and the differences among to the combine work of Wilkin et al. (2005) and Caddick the means were statistically significant at p<0.0001. All et al. (2002) presented the pollen characters evolution in tests were performed using STATGRAPHICS centurion the genus Dioscorea. Though pollen characters XVI Version 16.0.09. Qualitative characters were scored assessment for phylogenetic study are comparatively rare as binary state or unordered multistate characters at generic level but are mostly within family or at higher whereas quantitative characters were scored as level. Such study made an approach for using multistate characters. A maximum parsimony based micromorphological characters in systematic study of phylogenetic tree was constructed using NONA ver 1.6 large genera. (Goloboff, 1993). Morphological data matrix were With support to the work of Schol et al.( 2001, 2003 incorporated into Winclada ver. 1.00.08 (Nixon, 2002) and 2005), the present paper considers the importance and submitted into NONA using “spawn”. A heuristic of detailed floral, pollen and orbicules morphological study search was conducted employing the multiple TBR+TBR and aims at not only considering micromorphological strategy, with 1000 replication and 999 random seeds. characters but also incorporating the neglected floral characters and implicating the use of these characters Outgroup selection: for the proper systematics and evolutionary studies of Trichopus and Tacca, the allied genera of large genera like Dioscorea. Dioscorea from Dioscoreaceae and Burmannia of Burmanniaceae, nearest family of Dioscoreaceae was RESEARCH METHODOLOGY selected as an outgroups for the present study. Data for morphometric study of these outgroups was taken from Fresh flowers were collected from wild habitat of available literature viz., Caddick et al. (1998, 2000, 2002a Meghalaya. A total of eight species (Dioscorea alata and b); Huber (1998) and Kunth (1924). L., Dioscorea belophylla (Prain) Haines, Dioscorea bulbifera L., Dioscorea glabra Roxb, Dioscorea pentaphylla L., Dioscorea pubera Bl., Dioscorea RESEARCH FINDINGS AND ANALYSIS oppositifolia L., Dioscorea lepcharum Prain et Burk) The results obtained from the present investigation were collected (appendix for voucher specimen number). as well as relevant discussion have been summarized under following heads : LM and SEM : Approximately 10 pollen grains belonging to each Floral morphology : species were acetolyzed following the protocol of Plant is usually dioecious in the genus Dioscorea Shivanna and Rangaswamy (1993) for LM and then but other allied genera such as Tacca, Trichopus are acetolyzed pollen were dehydrated through an acetone hermaphrodite belonging to same family Dioscoreaceae. series before critical point drying (CPD). The dried pollen The female flowers are borne in small numbers in axillary was mounted on specimen stubs and micrographs were spikes and male in larger numbers in panicles. Both male taken using digital imaging on JSM- 6360, JEOL scanning and female flower bear one large floral bract and small electron microscope at Sophisticated Analytical bracteoles. The sepal and petal are usually similar in size Instrument Facility, North Eastern Hill University, Shillong. and appearance and are arrange in two whorls (Fig.1). Micrographs were also taken for whole male flower, Floral colour also shows variation between the species anther lobes, style and staminode. For each species, the generally being white, purplish, creamish or greenish Asian J. Bio Sci., 12 (2) Oct., 2017 : 223-232 224 Hind Institute of Science and Technology MORPHOLOGY OF FLOWER, POLLEN & ORBICULES OF MEGHALAYAN Dioscorea L. (DIOSCOREACEAE) Table A: List of qualitative and quantitative characters used in morphometric analysis Sr. No. Traits acronym Characters/descriptors Score code-descriptor code Qualitative / Quantitative traits 1. FT Flower type 1-dioecious; 2- hermaphodite Male inflorescence 2. InfS Inflorescence smell 0-absent;1-present 3. NoInf/INT Number of inflorescence per internode 1-One or two;2-many 4. InfG/P Inflorescence glabrous/pubescent 1-glabrous;2-pubescent 5. InfPo Inflorescence position 1-upward;2-downward 6. MFC Male flower colour 1-whitish purple;2-pale green;3-yellow 7. FLBS Floral bract shape 1-ovate acuminate;2-orbicular;3-ovate 8. FLBrS Floral bracteoles shape 1-broadly lanceolate;2-ovate acuminate; 0-others 9. OTS Outer tepal shape 1-ovate;2-obovate;3-lanceolate;0-others 10. ITS Inner tepal shape 1-linear oblong;2-oblong obovate;3-ovate 11. TG/P Tepal glabrous/pubescent 1-glabrous;2-pubescent 12. STA No. of stamen 1-3stamens;2-6stamens 13. STAMA/P Staminode absent/present 0-absent;1-present 14. LMspk Average length of spike 1-(1-10cm); 2-(11-20cm);3->20cm 15. MFL Male flower length 1-(2mm); 2->2mm 16. MFP Male flower peduncle length 1-(1.1-2cm);2-(2.1-3cm);3-(3.1-4cm); 4-(4.1-5cm) 17. MFPe Male flower pedicle length 1-(0.6-1.5mm); 2-(1.6-2.5mm); 3-(2.6-3.5mm) 18. FLBL Floral bract length 1-(1mm); 2->1mm 19. FLBW Foral bract width 1-(1mm); 2->1mm 20. FLBrL Floral bracteoles length 1-(0.1-1.0mm); 2->1mm 21. FLBrW Foral bracteoles width 1-(0.1-1.0mm); 2->1mm 22. OTL Outer tepal length 1-(1.5-3mm); 2->3mm 23. OTW Outer tepal width 1-(0.1-1.0mm); 2->1mm 24. ITL Inner tepal length 1-(0.1-3.1mm); 2->3.1mm 25. ITW Inner tepal width 1-(0.1-1.0mm); 2->1mm Female inflorescence 26. FNoInf/INT Number of inflorescence per internode 1-One or two;2-many 27. FInfG/P Inflorescence glabrous/pubescent 1-glabrous;2-pubescent 28. FInfPo Inflorescence position 1-upward;2-downward 29. FFC Female flower colour 1-greenish brown;2-white;3-yellowish 30. FFLBS Floral bract shape 1-ovate acuminate;2-orbicular;3-ovate 31. FFLBrS Floral bracteoles shape 1-broadly lanceolate;2-ovate acuminate 32. FOTS Outer tepal shape 1-ovate;2-obovate;3-lanceolate 33. FITS Inner tepal shape 1-linear oblong;2-oblong obovate;3-ovate 34.