Impact of cytomixis on meiosis, pollen viability and pollen size in wild populations of Himalayan poppy (Meconopsis aculeata Royle). J Biosci

Department of Botany, Punjabi University, Patiala, India.
Journal of Biosciences (Impact Factor: 1.94). 10/2008; 33(3):371-80. DOI: 10.1007/s12038-008-0057-0
Source: PubMed

ABSTRACT We report the occurrence of cytomixis in wild populations of Himalayan poppy (Meconopsis aculeata Royle),which is considered to be an important and threatened medicinal plant growing in the high hills of the Himalayas. The impact of cytomixis on meiotic behaviour, reduced pollen viability and heterogeneous-sized pollen grains was also studied. Cytological studies in the seven wild populations from the high hills of Himachal Pradesh revealed that all the Himalayan populations exist uniformly at the tetraploid level (2n=56) on x=14. The phenomenon of chromatin transfer among the proximate pollen mother cells (PMCs) in six populations caused various meiotic abnormalities. Chromatin transfer also resulted in the formation of coenocytes, aneuploid, polyploid and anucleated PMCs. Among individuals that showed chromatin transfer, chromosome stickiness and interbivalent connections were frequently observed in some PMCs. The phenomenon of cytomixis in the species seems to be directly under genetic control; it affects the meiotic course considerably and results in reduced pollen viability.

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Available from: Puneet Kumar, Ph.D., Sep 03, 2015
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    • "Knight et al. 2010), cytology (e.g. Singhal & Kumar 2008) or ploidy level (e.g. Jacob & Pierret 2000; Pradeep & Jambhale 2000). "
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    ABSTRACT: This study undertook an investigation of an important problem, so far completely overlooked in the palynological literature - to determine the optimal sample size for pollen grain morphological studies. In other words, we investigated the number of pollen grains which should be measured in order to obtain a representative mean value of a given quantitative feature which, in consequence, would make it possible to more accurately describe the pollen of a given taxon. Investigations were conducted on a sample comprising 3850 Rosa canina L. pollen grains on the basis of the length of the polar axis (P), the equatorial diameter (E) and the P/E ratio, at the flower, specimen and population levels. The size of the pollen samples analysed reflected common sample numbers employed in previous pollen morphology studies, namely from five through 10, 20, 30, 50, 100 up to 200 pollen grains. The statistical analyses performed revealed a relatively low variability in pollen grain biometric features at the levels of flower, specimen and population. At the lowest level of variability analysed, it is sufficient to take measurements of several grains to obtain values satisfactorily representing the variability within the flower level. At the level of a specimen or population, the number of grains necessary to secure representative mean values should range from 15 to 20. However, when the research objective is not only information regarding mean values of pollen grain biometric features but also the analysis of their variability (min-max), then the sample size should include approximately 30 grains. The results obtained, apart from their significance in taxonomic studies, also possess important practical significance; measurements of pollen grain biometric features are very labour-intensive and costly and, sometimes, because of difficulties in obtaining satisfactory quantities of plant material (e.g. herbarium specimens, rare species, paleopalynological collections), also very sparse.
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    • "Cathcartia species also have 2n = 2x = 14, supporting the ITS phylogeny that places them outside Papaver, rather than within Meconopsis. Karyotype studies of Meconopsis species suggest that all are polyploid (2n = 8–12x = 56–84) [81], [85], [86], [87], but see Kumar et al. [88]. We suggest that the Meconopsis clade originated with the polyploid transition to 2n = 2x = 56, possibly via a tetraploid intermediate with 2n = 4x = 28 chromosomes that is now extinct. "
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    • "Cytomixis in this species results into the production of chromosomally hypo-and hyper-ploid PMC's along with some empty PMC's from which almost complete transfer of chromatin has taken place (Figs. 8 and 9). Most of these observations are in line with the fi ndings of Falistocco et al. (1995), Ghanima and Talaat (2003), Ghaffari (2006), Singhal et al. (2008) and Kumar et al. (2008) for other species of the Angiosperms. However, Omara (1976) believes that the role of cytomixis is to be properly assessed since the chances of production of aneuploid gametes is less, in strictly sexually diploid taxa. "
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