POLLEN MORPHOLOGICAL STUDIES IN TWENTY ACCESSIONS OF JASMINUM SAMBAC (L.)AIT. FROM KERALA

* Smitha S Nair 1 , Devipriya V 2 and Regy Yohannan 1 . 1. Post Graduate & Research Department of Botany, Sree Narayana College, Kollam, Kerala. 2. Department of Botany, Sree Narayana College, Chempazhanthy, Thiruvananthapuram, Kerala. ...................................................................................................................... Manuscript Info Abstract ......................... ........................................................................ Manuscript History

The pollen morphology of 20 accessions of Jasminum sambac L.(Ait) collected from different parts of Kerala State were studied. The major palynological features relating to the pollen shape, aperture and exine ornamentation are conserved within the species. The pollen grains were in general spheroidal, medium-sized and 3(4)zonocolporate with reticulate exine ornamentation. SEM analysis revealed microvariations relating to the exine components such as muri and lumina. Although these variations were not adequate enough to classify the taxa into palynological groups, certain character associations were observed such as the link between homobrochate condition and oval or ellipsoidal lumina. Four accessions with very short lumina and almost porous exine had spiny projections or pyramidal tapering from their upper mural ends. The phylogenetic significance of such microstructural variations in the pollen exine remain to be evaluated based on SEM studies of the exine architecture including more taxa belonging to the group.
Jasminum sambac (L.) Ait., commonly referred to as Arabian Jasmine, is native to southern Asia (Green and Miller, 2009). The species exhibits a wide range of morphological variation relating to its vegetative and floral features, and has a number of cultivars known by differing vernacular names such as kuttimulla, kudamulla, arimulla, iruvachimulla, moonnadukkumulla, adukkumulla etc., grown all over the State of Kerala as garden ornamentals. Earlier studies on the pollen morphology of the species have focused largely on light microscopic observations. But the advent of high end tools such as the Scanning Electron Microscope has enabled in-depth analysis of the intricate patterns of exine ornamentation, opening up new vistas of exploration. Nair and Kapoor (1974) demonstrated that statistical evaluation of pollen variations can be used as an effective tool in the categorization of varieties, and also in the understanding of the hybridity status of the cultivars within a taxon. Hence the present study is undertaken to ISSN: 2320-5407 Int. J. Adv. Res. 5(9), 1726-1733 1727 make a detailed comparative intraspecific analysis of the pollen from twenty accessions of Jasminum sambac from Kerala using LM and SEM studies, and to evaluate the significance of palynology in the systematics of the speciescomplex.

Materials and Methods:-
Twenty accessions of Jasminum sambac (L.) Ait. were collected from various locations in the State of Kerala. Polliniferous materials from the collected specimen were fixed in glacial acetic acid. The details regarding the 20 taxa included in the present study are furnished in Table 1. Palynological analysis:-Fresh anthers from mature unopened flower buds were fixed in glacial acetic acid. Pollen preparations were made by the acetolysis method standardized by Erdtman (1952) and modified by Nair (1970). The pollen shape and size classes were ascertained following the classifications suggested by Erdtman(1966) and Walker & Doyle (1975) respectively. The terminologies suggested by Punt et al. (1994) were adopted for describing the aperture types and exine ornamentation patterns. Measurements relating to the following characters were taken using an ocular micrometer. In each case, the mean values of the measurements were taken from a random sample of 30 pollen grains.    The major qualitative palynological features were also conserved within the species with the members having mostly spheroidal, 3-zonocolporate, medium-sized pollen with reticulate exine ornamentation (Tables 3a-b). Only one accession (AC 5) showed occasionally 4-zonocolporate pollen in addition to the more frequent 3-zonocolporate ones. Although the lumina were irregular in size due to varying mural traits, the pollen could be broadly categorized into homobrochate and heterobrochate types (Figs. 1, 20). The former was observed in only three taxa (AC 2, 3 and 10). Muri were very tall, narrow or broad, with upper end flat and smooth in most accessions, except in AC 5 where it was pyramidal (Fig. 11). Small granular warts were observed on the mural surface in some taxa -AC 2, 3, 4, and 17. The accession AC 12 showed slight granulation on its mural surfaces, with the granules not assuming the form of warts. The accessions AC 8, 14 and 15 showed spiny projections from the mural wall (Plate III).
The lumina were very deep with the luminal floor not clearly visible due to the tallness of the mural walls in almost all cases, except in AC 20 where few warts and perforations were noted in the lumina. Even in this case, the mural walls were tall. In homobrochate forms the lumina appeared oval or ellipsoidal, while the heterobrochate pollen had narrow and irregularly elongated lumina. Interestingly, the four taxa with pyramidal projection or spiny outgrowths from the mural wall had very short and irregularly narrow lumina giving a porous appearance to the pollen exine. In all other taxa, the lumina were more prominent giving a reticulate appearance. The lumina appeared to be plugged with waxy material in three accessions -AC 4, 5 and 15.

Conclusions:-
The pollen observed from 20 accessions of Jasminum sambac L.(Ait) collected from different parts of Kerala State were in general spheroidal, medium-sized and 3(4)zonocolporate with reticulate exine ornamentation. These characters are largely consistent with the pollen features reported for the genus and its family, the Oleaceae. Thus the major palynological features are conserved within the species and its higher level groups. Erdtman (1971) and Nilsson (1988) had earlier opined that pollen characters are not good taxonomic markers for the family Oleaceae.
The results from the present study corroborate their findings. However, the fine exine architecture revealed through SEM analysis reflected the microvariations with regard to exine components such as the muri and lumina. These microvariations were not adequate enough to group the taxa studied into palynological classes. Certain character associations were also observed such as the correlation between homobrochate condition and oval or ellipsoidal lumina. In addition, spiny projections or pyramidal tapering from the upper mural ends were noted in the four accessions with very short lumina and almost porous exines. The phylogenetic significance of such microstructural variations in the pollen exine remain to be evaluated based on SEM studies on more taxa belonging to the group.