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The mitotic activity and chromosomal behaviour was observed in four different concentrations of magnesium sulphate at four different duration of treatment using Allium cepa as a biological system. Mito-inhibitory effect of the compound was observed in higher concentration. The compound was capable of producing various chromosomal abnormalities indicating the cytostatic and clastogenic properties of magnesium sulphate.

Chromosome number and karyomorphology of some species of the genus Desmodium Desv. and its related taxa, viz. D. concinnum DC. var. retusum (D. Don) H. Ohashi, D. heterocarpon (L.) DC. var. heterocarpon, D. laxiflorum DC., D. microphyllum (Thunb.) DC., D. podocarpum subsp. oxyphyllum var. mandschuricum Maxim., D. podocarpum DC. subsp. podocarpum and D. triflorum (L.) DC., Butea minor Buch.-Ham. ex Baker, Crotalaria cytisoides Roxb. ex DC. and Piptanthus nepalensis (Hook.) D. Don collected from different climatic regions of Nepal were observed. The basic numbers of chromosomes in Desmodium species was 11. It was recorded to be 9 in B. minor and P. nepalensis, and 8 in C. cytisoides. The chromosomes of the genus Desmodium were mostly medium and small in length throughout except in D. podocarpum. In D. podocarpum, B. minor, C. cytisoides and P. nepalensis chromosomes were large and medium. Desmodium Desv., Butea Koen ex Roxb., Crotalaria Linn. and Piptanthus D. Don. belonging to the family Papilionaceae Giseke. show remarkable diversity in morphological characters. Twenty-six species of Desmodium, 2 species of Butea, 19 species of Crotalaria and 1 species of Piptanthus are distributed in different geographical areas of Nepal (Press et al. 2000, Anonymous 1986). Piptanthus nepalensis is a cold temperate and sub-alpine plant. Remaining 3 genera are widely distributed in tropics and sub-tropics of the world. Economically the plants under study come under one of the most important families of flowering plants. Fourteen species of the family are endemic to Nepal (Shrestha and Joshi 1996). The chromosome counts and/or karyomorphology of some species of the genera under present study have been reported previously (

Cytotaxonomy of Smithia ciliata Royle, collected from Panighat (1700 msl), Kathmandu valley, is reported. The somatic chromosome number was found to be 2n = 38 with the basic number being n = 19.  Karyotype structure is predominated with medium sized chromosomes and with median constrictions. Key-words: chromosome count; karyotype; meiosis.DOI: 10.3126/botor.v6i0.2921 Botanica Orientalis - Journal of Plant Science (2009) 6: 111-113

Effect of triazophos (an organophosphorous insecticide) on mitotic activity and chromosomal behavior in the meristematic region of root tip cells of Allium cepa L. was assessed. The insecticide showed mitotic depression and positive chromo-toxic effects.Abnormalities, such as stickiness, plasmolysed cells, equatorial plate shifting, polar shifting, irregular chromosome arrangement, precocious arms formation, bridge formation, C-metaphase, fragmentation of chromosomes, unequal cytokinesis, diagonal cytokinesis, delayed cytokinesis and formation of binucleated cells, were recorded in the chemically pretreated root meristem.