Pteris Vittata in India Has Been Reported to Have 29, 58 and 87 Bivalents at Meiosis with the Basic Number 29 (Mehra and Verma 1960, Verma and Khullar 1965)
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Cytologia 48: 21-25, 1983 Intraspecific Polyploidy in Pteris vittata Linn.1 P. B. Khare and Surjit Kaur National Botanical Research Institute, Lucknow, India Received December 22, 1980 Pteris vittata in India has been reported to have 29, 58 and 87 bivalents at meiosis with the basic number 29 (Mehra and Verma 1960, Verma and Khullar 1965). Sexual tetraploid (n=58) is of wide occurrence in the himalayan ranges while diploid and hexaploid are reported from Nainital and South India (Verma 1961, Abraham et al. 1962). The tetraploid form is also reported from Ceylon (Manton and Sledge 1954). The presence of different cytotypes in the species suggest that like P. ensiformis and P. quadriaurita (Abraham et al. 1962) P. vittata also constitute a coeno species which in India has reached a very high degree of cytological complexity. Variation in shape of the spores in P. vittata cultivated at National Botanical Re search Institute, Lucknow, has been reported by Devi (1974) as also some meiotic instability in a plant from Calcutta (Sharma and Majumdar 1955). Cytological evaluation of the different collection belonging to the taxon main tained at different places in Lucknow revealed triploid, tetraploid and pentaploid forms, of which the triploid and pentaploid are being reported for the first time. Some details of their morphology and cytology form the subject matter of this com munication. Materials and methods Samples of the young sporophylls were collected from different localities of Lucknow (National Botanical Research Institute, C. S. I. R. Colony, Nirala Nagar and Moti Mahal Campus) and fixed in 1:3 acetic alcohol. These were subsequently squashed in aceto-carmine for cytological observations. Leaf surface studies were made by epidermal peel stained with safranin. Size of stomata is based on mean of 20 measurements taken at random. Observations 1. Cytology The spore mother cell of C. S. I. R. Colony plant showed 29 II+29 I whereas, that from NBRI showed 29 II+87 I indicating triploid and pentaploid level of ploidy, respectively (Figs. I and 5). The univalents are conspicuous because of their minute size and thus can easily be distinguished from the bivalents. Those from Moti Mahal Campus showed 58 bivalents and thus indicated tetraploidy (Fig. 3). These chro mosome numbers in Pteris vittata prove the existence of intraspecific polyploidy. Irregular meiosis was observed in both pentaploid and triploid plants. At metaphase 1 NBRI Research Publication No . 154 (N. S.). 22 P. B. Khare and Surjit Kaur Cytologia 48 I bivalents remain at equatorial plate while the univalents tend to be distributed all over the cytoplasm. A few lagging univalents at both the anaphase stages were frequent (Fig. 7). Figs. 1-6. 1, meiosis in triploid. •~1000. 2 , explanatory diagram to Fig. 1 (outlined chromosomes are univalents). 3, meiosis in tetraploid . •~1000. 4, explanatory diagram to Fig . 2. 5, meiosis i n pentaploid. •~1000. 6, explanatory diagram to Fig . 5 (outlined chromosomes are univalents) . 2. Spores Spores of triploid and tetraploid plants are typically tetrahed ral with a rugulose to reticulate type of ornamentation of the sporoderm . The two spore faces are clearly 1983 Intraspecific Polyploidy in Pteris vittata Linn. 23 separated by a prominent equatorial collar which girdles the spore (Devi 1974). In addition to the normal trilete form the pentaploid also included tetrahedral, bilateral and some intermediate forms of spores. Such heterogenecity comes from the highly irregular and uncertain meiosis of the pentaploid genome. Figs. 7-10. 7, anaphase II in pentaploid. •~1000. 8, lower epidermis in tetraploid.•~1000. 9, lower epidermis in triploid. •~1000. 10, lower epidermis in pentaploid.•~1000. 24 P. B. Khare and Surjit Kaur Cytologia 48 3. Epidermis The mean stomatal size was 34.8•~22.4ƒÊm in tetraploid, 35.7•~22.4ƒÊm in triploid and 46.4•~27.6ƒÊm in pentaploid. The frequency of stomata was highest in tetraploid, ie. 89.2per sq. mm and lowest in pentaploid, ie. 54.5per sq. mm. (Table 1). This data shows that the pentaploid possesses larger stomata with less frequency while the tetraploid has smaller stomata with higher frequency (Figs. 2, 3 and 4). In the triploid on the other hand, the size and frequency of stomata was intermediate of the two. Epidermal cell size was largest in pentaploid, smallest in tetraploid and intermediate in triploid (Table 1). Table 1. Showing variation in size and frequency of stomata and length of epidermal cell in three different cytotypes of Pteris vittata Discussion Pteris vittata complex consists of five distinct entities corresponding to different level of ploidy, namely diploid, triploid, tetraploid, pentaploid and hexaploid. Triploid and pentaploid are being reported by the present authors (Table 2) for the first time. Triploid and pentaploid plants are phenotypically much similar to one another, the tetraploid is much smaller in size and bushy in nature. Significant differences in the size of stomata and their frequency have been observed in the three cytotypes, the size of stomata apparently being correlated with ploidy level. However, no such correlation between size of stomata and ploidy level (4•~, 5•~ and 6•~) has been observed in Diplazium subsinuatum which may partly be due to the high grade of ploidy level (Nakato and Mitui 1979). Pentaploid in the present investigation is easily distinguished by the production of many abnormal spores in contrast to normal spores of other cytotypes. Thus spore morphology is very helpful in the separation of the cytotypes as it has been shown true for Diplazium subsinuatum by Nakato and Mitui (1979). The presence of univalents in addition to bivalents in the triploid and pen taploid leads to the belief that these plants have resulted from hybridization between two genotypes. Triploid cytotype showed 'n' bivalent and 'n' univalent. This number in dicates the hybridization of a tetraploid with a diploid. Normally a condition of n pair+n univalent (AAB) is supposed to occur when a diploid (AB) or a tetraploid (AABB) has backcrossed with one of its parents. 1983 Intraspecific Polyploidy in Pteris vittata Linn . 25 Pentaploid hybrid showed 2n bivalents and 3n univalents. It is assumed that pentaploid is synthesized in nature by the hybridization of hexaploid and a tetraploid. If hexaploid is designated by AABBCC and tetraploid AADD, the hybrid pentaploid will be AABCD, which ultimately gives rise to 2n bivalents and 3n univalents in meiotic configuration. Table 2. Showing different cytotypes of P. vittata Acknowledgement The authors are indebted to Dr. T. N. Khoshoo, Director, NBRI, Lucknow for encouragement during the course of these investigations. References Abraham, A., Ninan, C. A. and Mathew, P. M. 1962. Studies on the cytology and phylogeny of the Pteridophytes VII. Observations on one hundred species of South Indian ferns. J. Ind. Bot. Soc. 41: 339-421. Devi, S. 1974. On the occurrence of bilateral spores in cultivated Pteris longifolia L. Grana 14: 1-3. Manton, I. and Sledge, W. A. 1954. Observation on the cytology and taxonomy of Pteridophyte flora of Ceylon. Phil. Trans. Roy. Soc. London Ser. B. N. 654; 238: 127-185. Mehra, P. N. 1961. Chromosome numbers in himalayan ferns. Res. Bull. Punjab Univ. 12: 139-169.- and Verma, S. C. 1960. Cytotaxonomic observations on some west himalayan Pteridaceae. Caryologia 13: 619-650. Nakato, N. and Mitui, K. 1979. Intraspecific polyploidy in Diplazium subsinuatum (Wall.) Tagawa. J. Jap. Bot. 54: 129-136. Sharma, A. K. and Majumdar, A. 1956. Cytological peculiarities of Pteris longifolia L. and its importance in evolution. Sci. and Cult. 21: 338-339. Verma, S. C. and Khullar, S. P. 1965. Cytology of some west himalayan Adiantaceae (Sensu Alston) with taxonomic comments. Caryologia 18: 85-106..