Male meiosis, morphometric analysis and distribution pattern of 2× and 4× cytotypes of Ranunculus hirtellus Royle, 1834 (Ranunculaceae) from the cold regions of northwest Himalayas (India).

Vijay Kumar Singhal,Puneet Kumar

doi:10.3897/compcytogen.v5i3.1359

Abstract

In this study, we examined the chromosome number, detailed male meiosis, microsporogenesis, pollen fertility and morphological features and distribution of 2× and 4× cytotypes of Ranunculus hirtellus Royle, 1834. The majority of the populations scored now from cold regions of the northwest Himalayas showed tetraploid (n=16) meiotic chromosome count and one of the populations studied from the Manimahesh hills existed at diploid level (n=8). The individuals of diploid cytotype exhibited perfectly normal meiotic course resulting in 100% pollen fertility and pollen grains of uniform sizes. On the other hand, the plants of the tetraploid cytotype from all the populations in spite of showing normal bivalent formation and equal distribution to the opposite poles at anaphases showed various meiotic abnormalities. The most prominent among these meiotic abnormalities was the cytomixis which involved inter PMC (pollen mother cell) chromatin material transfer at different stages of meiosis-I. The phenomenon of cytomixis induced various meiotic abnormalities which include chromatin stickiness, pycnotic chromatin, laggards and chromatin bridges, out of plate bivalents at metaphase-I, disoriented chromatin material at anaphase/telophase and micronuclei. Consequently, these populations exhibited varying percentages of pollen sterility (24 - 77 %) and pollen grains of heterogeneous sizes. Analysis of various morphometric features including the stomata in 2× and 4× cytotypes showed that increase in ploidy level in the species is correlated with gigantism of vegetative and floral characters and the two cytotypes can be distinguished from each other on the basis of morphological characters. The distribution patterns of the 2× and 4× cytotypes now detected and 2×, 3×, 4× cytotypes detected earlier by workers from other regions of the Indian Himalayas have also been discussed.

Highlights

Ranunculus hirtellus Royle, 1834 (Ranunculaceae), a perennial erect or decumbent herb, distinctly pubescent with fibrous and shortly fusiform root stock is endemic to Himalayas, and distributed in the temperate, sub-alpine and alpine slopes in NorthWest to North-East Himalaya, temperate to subalpine slopes at 2000 – 4500 m in the states of Jammu & Kashmir, Himachal Pradesh, Uttarakhand, Sikkim, and Arunachal Pradesh and in Afghanistan, Pakistan, Nepal and Tibet (Sharma et al 1993, Srivastava 2010)
The population scored from the Manimahesh hills was found to be diploid while rest of the six populations studied from Kullu, Chamba and Lahaul-Spiti districts existed at tetraploid level
The impact of cytomixis and chromatin transfer in inducing various meiotic abnormalities in R. hirtellus resulting into abnormal sporad formation, and some pollen malformation seem to be under some genetic factors (Singhal and Gill 1985, Bellucci et al 2003, Haroun et al 2004, Lattoo et al 2006, Singhal et al 2007, 2008, 2009a, b, 2010, in press, Kumar and Singhal 2008, Singhal and Kumar 2008a, b, 2010 Kumar et al 2008a, b 2010, in press, Himshikha et al 2010) or the genetic imbalance in the 4× cytotype, high altitude and low temperature stress conditions prevailing in the cold deserts, where temperature during the months of May - July dips to below freezing, the time the plants enters the reproductive/ flowering bud stage

Summary

Introduction

Ranunculus hirtellus Royle, 1834 (Ranunculaceae), a perennial erect or decumbent herb, distinctly pubescent with fibrous and shortly fusiform root stock is endemic to Himalayas, and distributed in the temperate, sub-alpine and alpine slopes in NorthWest to North-East Himalaya, temperate to subalpine slopes at 2000 – 4500 m in the states of Jammu & Kashmir, Himachal Pradesh, Uttarakhand, Sikkim, and Arunachal Pradesh and in Afghanistan, Pakistan, Nepal and Tibet (Sharma et al 1993, Srivastava 2010). The species is used to cure skin diseases and wounds, and as a vermifacient, cooling agent and anthelmintic in other parts of the Himalayas in India (Jain 1991, Iyer 1992, Kumar 2010, Pharswan et al 2010). The information gathered from various Indexes to Plant Chromosome Numbers (Goldblatt 1981, 1984, 1985, 1988, Kumar and Subramanian 1986, Khatoon and Ali 1993) revealed that the species is variable in terms of chromosome number (2n=14, 16, 24, 28, 32) and level of ploidy (2×, 3×, 4×).

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