REDUCTION OF CHROMOSOME NUMBER IN ROOT TIP CELLS OF MEDICAGO

1974 ◽  
Vol 16 (1) ◽  
pp. 219-227 ◽  
Author(s):  
R. S. Sadasivaiah ◽  
K. Lesins
Keyword(s):  
Chromosome Number ◽  
Ploidy Level ◽  
Chromosome Numbers ◽  
Plant Evolution ◽  
Root Tip ◽  
Aneuploid Chromosome ◽  
Tip Cells ◽  
Root Tip Cells ◽  
In Cells

Cytological studies on progenies obtained from intercrosses between colchicine-induced octoploid (2n = 8x = 64) plants of alfalfa showed normal, haploid and aneuploid chromosome numbers in cells of the same root tip. Critical observations on cells at different divisional stages revealed the occurrence of meiosis-like mitotic divisions, resulting in a reduction of chromosome number. The frequency of cells showing reductional divisions appeared to vary with the ploidy level of the material. The possible significance of chromosome reduction in plant evolution is indicated.

scholarly journals Ploidy Levels of Hardy Actinidia Accessions in the U.S. Determined by Flow Cytometry

HortScience ◽  
1997 ◽  
Vol 32 (3) ◽  
pp. 439D-439 ◽  
Author(s):  
Mary Ann Start ◽  
James Luby ◽  
Robert Guthrie ◽  
Debby Filler
Keyword(s):  
Flow Cytometry ◽  
Ploidy Level ◽  
Interspecific Variation ◽  
Root Tip ◽  
Interspecific Crosses ◽  
Ploidy Levels ◽  
Haploid Chromosome Number ◽  
Tip Cells ◽  
Root Tip Cells ◽  
The U.S

The hardy Actinidia species represent a source of genetic diversity for improving A. deliciosa (kiwifruit) as well as for creating new economically important cultivars through intra- and interspecific crosses. Attempts at breeding in Actinidia have been complicated by the existence of intraspecific as well as interspecific variation in ploidy. The haploid chromosome number in Actinidia is 29 and diploid (2n=2x=58), tetraploid (2n=4x=116), and hexaploid (2n=6x=174) levels have been identified. Because of the problems encountered when crossing parents differing in ploidy level, it is desirable to know the ploidy levels of plants to be used in breeding. We determined the ploidy levels of 61 Actinidia accessions currently available in the U.S., including primarily accessions of relatively winter-hardy species. The 61 accessions, representing eight species and three interspecific hybrids, were screened for ploidy using flow cytometry. Mitotic root tip cells from one plant from each putative ploidy level were examined microscopically to confirm the ploidy level derived from flow cytometry. There were 17 diploids, 40 tetraploids, and 4 hexaploids. Intraspecific variation was not found among accessions of the species arguta, callosa, deliciosa, kolomikta, melanandra, polygama, or purpurea. All kolomikta and polygama accessions were diploid. All arguta, callosa, melanandra, and purpurea accessions were tetraploid. Actinidia deliciosa was hexaploid. One chinensis accession was tetraploid. Two accessions (NGPR 0021.14 and 0021.3), acquired as chinensis, were hexaploid and may, in fact, be A. deliciosa based on their morphology. `Issai' (arguta × polygama) was hexaploid and `Ken's Red' and `Red Princess' (both melanandra × arguta) were tetraploid.

scholarly journals Chromosome Number and Karyotype Variation in Codiaeum variegatum Cultivars

HortScience ◽  
2010 ◽  
Vol 45 (4) ◽  
pp. 538-540 ◽  
Author(s):  
Min Deng ◽  
Jianjun Chen ◽  
Richard J. Henny ◽  
Qiansheng Li
Keyword(s):  
Chromosome Numbers ◽  
Genetic Basis ◽  
Morphological Diversity ◽  
Root Tip ◽  
Limited Information ◽  
Ornamental Foliage Plants ◽  
Wide Range ◽  
Codiaeum Variegatum ◽  
Tip Cells ◽  
Root Tip Cells

Codiaeum variegatum (L.) Blume is one of the most popular ornamental foliage plants. It encompasses more than 300 recognized cultivars valued by their wide range of leaf shapes and vivid foliage colors. Thus far, only limited information is available regarding the genetic basis of their leaf morphological variation. This study investigated the chromosome numbers and karyotypes of seven phenotypically diverse cultivars. Root-tip cells were fixed, mounted, and observed under light microscopy. Results showed that chromosome numbers in the mitotic metaphase of the seven cultivars were high and variable and ranged from 2n = 66, 70, 72, 76, 80, 82, 84, to 2n = 96, indicating that the cultivars are polyploid and some could be aneuploid. Genetic mosaics occurred in one of the seven cultivars. Additionally, each cultivar had its own karyotype. There were no relationships between chromosome numbers or karyotypes and leaf morphology. Results from this study suggest that the morphological diversity among cultivars of this species could be in part attributed to high variation in chromosome numbers and karyotypes.

scholarly journals New chromosome numbers in Pilocarpus Vahl (Rutaceae)

2000 ◽  
Vol 14 (1) ◽  
pp. 11-24
Author(s):  
Ladislau A. Skorupa
Keyword(s):  
Chromosome Numbers ◽  
Room Temperature ◽  
Basic Number ◽  
Root Tip ◽  
Root Tips ◽  
Chromosome Counts ◽  
Pre Treatment ◽  
First Time ◽  
Tip Cells ◽  
Root Tip Cells

Chromosome counts for eight species of Pilocarpus Vahl (Rutaceae) a native of Brazil are reported for the first time. Chromosome numbers were determined from mitotic root tip cells of seedlings derived from field collections and grown in the greenhouse. Feulgen staining was used. Initial pre-treatment of root tips was done by using a saturated aqueous solution of alpha-bromonapthalene for two hours at room temperature (20-25ºC). Chromosome numbers of 2n=44 and 2n=88 were determined for the examined taxa. The present results suggest the occurrence of tetraploidy in P. spicatus St.-Hil. and P. carajaensis Skorupa, and a possible basic number x=22 to the genus Pilocarpus.

scholarly journals Study of crossability and F1 of interspecific hybridization between Brassica rapa (B. campestris) and B. nigra

2008 ◽  
Vol 32 (3) ◽  
pp. 445-449
Author(s):  
MA Malik
Keyword(s):  
Chromosome Number ◽  
Interspecific Hybridization ◽  
Female Parent ◽  
Pollen Sterility ◽  
F1 Hybrids ◽  
Root Tip ◽  
Intermediate Morphology ◽  
Pale Colour ◽  
Tip Cells ◽  
Root Tip Cells

Interspecific hybridization between yellow seeded variety, Binasarisha-6 of B. rapa var. Yellow Sarson (2n=20; AA) and Nigra-1 of B. nigra (2n=16; BB) were made. The crosses with Binasarisha-6 of B. rapa var. Yellow Sarson as a female parent were only successful. Chromosome number in root tip cells of the F1 hybrids was 18, which was half of the sum total of the somatic chromosome number of the parents and indicated hybrid nature. Hybrids exhibited intermediate morphology between the parents. All the hybrids showed complete pollen sterility with shrivelled, pointed tip, and pale colour anthers and reduced filaments and failed to set siliquae and seeds.DOI: http://dx.doi.org/10.3329/bjar.v32i3.546Bangladesh J. Agril. Res. 32(3) : 445-449, September 2007

scholarly journals THE RELATION BETWEEN DNA SYNTHESIS AND CHROMOSOME STRUCTURE AS RESOLVED BY X-RAY DAMAGE

1963 ◽  
Vol 18 (3) ◽  
pp. 525-540 ◽  
Author(s):  
H. J. Evans ◽  
J. R. K. Savage
Keyword(s):  
Tritiated Thymidine ◽  
Root Tip ◽  
X Rays ◽  
Type B ◽  
Physical Separation ◽  
X Irradiation ◽  
Tip Cells ◽  
Root Tip Cells ◽  
Chromosome Regions ◽  
In Cells

Vicia faba root tip cells were treated for short periods with tritiated thymidine, either immediately before or after exposure of roots to x-rays, and autoradiograph preparations were analysed in an attempt to test the hypothesis that chromatid type (B') aberrations are induced only in those chromosome regions that have synthesized DNA prior to x-irradiation, whereas chromosome type (B'') aberrations are induced only in unduplicated chromosome regions. Studying the relation between presence or absence of label at loci involved in aberrations, in cells irradiated at different development stages, and the pattern of labelling in cells carrying both types of aberration leads to the conclusion that B'' aberrations are induced only in unreplicated chromosome regions. Following replication, only B' aberrations are induced, but these aberrations are also induced in chromosome regions preparing to incorporate DNA. It is suggested that the doubled response of the chromosome to x-rays prior to DNA incorporation might reflect a physical separation of replicating units prior to replication. The aberration yields in damaged cells which were irradiated in G1 S, and early G2 were in the ratio of 1.0:2.0:3.2. The data indicate that the increased yield of B' in early G2 relative to S cells may be a consequence of changes in the spatial distribution of the chromosomes within the nucleus.

Short Communication. A robust method for chromosome quantification and ploidy determination in woody species

2009 ◽  
Vol 57 (2) ◽  
pp. 87 ◽  
Author(s):  
Harshi K. Gamage ◽  
Susanne Schmidt
Keyword(s):  
Light Microscopy ◽  
Chromosome Numbers ◽  
Nuclear Dna ◽  
Accurate Determination ◽  
Nuclear Dna Content ◽  
Root Tip ◽  
Root Tips ◽  
Ploidy Determination ◽  
Tip Cells ◽  
Root Tip Cells

Accurate determination of ploidy level of putative polyploid plants is essential for tree breeding and other applications. Methods for ploidy determination include quantification of chromosome numbers in root-tip cells via light microscopy and indirect assessment via anatomical and morphological traits. Flow cytometry is potentially a high-throughput method to quantify nuclear DNA content; however, it does not allow determining chromosome numbers and interfering compounds often prevent its use. Microscopy-based quantification of chromosomes in active root-tip cells remains the most unambiguous method for ploidy determination, although root tips are difficult to obtain from field-grown plants, and light microscopy can result in insufficient resolution in species with many and small chromosomes. Here, we present a robust technique that uses 2, 4-diamidino-2-phenylindole (DAPI) dye and 1000-fold magnification fluorescence microscopy for quantification of chromosomes in root and shoot tips of woody angiosperms and gymnosperms, and overcomes the reported difficulties. Rather than the conventional tip squashing, spreading tips on glass slides resulted in very good chromosome separation in diverse species, with up to 56 chromosomes and a chromosome size of 2–20 μm. Chromosome counts were performed in diploid Agathis robusta, Elaeocarpus angustifolius, Eucalyptus robusta, Paulownia tomentosa, Pongamia pinnata and Toona ciliata, and di- and tetraploid Acacia crassicarpa and Citrus species.

Cytological investigation of the Achillea millefolium complex (Compositae) in Quebec

1977 ◽  
Vol 55 (7) ◽  
pp. 796-808 ◽  
Author(s):  
Camille Gervais
Keyword(s):  
Chromosome Numbers ◽  
Pollen Grains ◽  
Achillea Millefolium ◽  
Root Tip ◽  
Herbarium Specimens ◽  
Cytological Investigation ◽  
Mitotic Abnormalities ◽  
Small Pollen ◽  
Tip Cells ◽  
Root Tip Cells

The study of the chromosome numbers of over 112 individuals belonging to the Achillea millefolium L. complex (Compositae) and the examination of the pollen of about 200 herbarium specimens have led to the following conclusions; the A. millefolium complex, in Quebec, includes tetraploids (2n = 36), hexaploids (2n = 54), and various hybrid types. Tetraploids could be divided into two taxa: the southernmost is A. lanulosa Nutt. with small pollen grains and light brown or yellowish-margined phyllaries while the northern or alpine plants, corresponding to A. nigrescens (E. Mey.) Rydb., possess large pollen grains and dark-margined phyllaries. The two species, in contact zones, seem to hybridize freely. Hexaploids comprise purple-flowered introduced individuals escaping from cultivation, white or pink individuals, also introduced, and possibly a native taxon. The introduced hexaploids belong to A. millefolium s.str. and the purple-flowered variety frequently hybridizes with A. lanulosa giving rise to pentaploids (2n = 45) apparently almost sterile. A few plants from Maine (U.S.A.) have also been studied. This paper finally reports cytological observations related particularly to spontaneous mitotic abnormalities (fragmentation, fusion of chromosomes) affecting root tip cells of seedlings.

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