摘要:

Karyotypes of species forming the polyploid series (2x-10x) ofLeucanthemum vulgareaggr. in Italy have been defined. Observations have not given clues to the origin of polyploid species, but have revealed quantitative and structural differences, between genomes of different species, correlated with ploidy level. Such differences sem to consist mainly in a progressive reduction of the short arm of two chromosome types.

ISSN:0008-7114    

DOI:10.1080/00087114.1983.10797639

出版商:Taylor & Francis    

年代:1983

数据来源: Taylor

摘要:

Most Basidiomycetes are characterized by dolipores with parenthesomes that are multiperforate, imperforate or pauciperforate. Electron micrographs ofTremellae, however, show dolipore septa with banded material in the orifices and vesiculate parenthesomes. We have studied the fine structure ofTremella foliaceaPers. ex Fr. andTremellodon gelatinosum(Scop.) Pers. In these two species we describe several considerable differences which question the phylogeny suggested by some authors, within the Basidiomycetes. Ultrastructural similarities found in the dolipore ofTremella foliaceaand in the pore of a few Ascomycetes could suggest that the most primitive dolipore is theTremella-type.

ISSN:0008-7114    

DOI:10.1080/00087114.1983.10797640

出版商:Taylor & Francis    

年代:1983

数据来源: Taylor

摘要:

The duration of the mitotic cycle and its phases has been determined in the root tips of seedlings from brown and black caryopses ofHaynaldia villosa, by autoradiographic technique after labelling with m3H-thymidine. The total duration of the mitotic cycle was found to be 12h in brown caryopses and 9.5h in black caryopses. As to the time length of single phases, the greatest difference between the two kinds of caryopses was foun dat the level of G1phase. The possible significance of these differences is discussed.

ISSN:0008-7114    

DOI:10.1080/00087114.1983.10797641

出版商:Taylor & Francis    

年代:1983

数据来源: Taylor

摘要:

Meiotic and karyological studies on 5 taxa belonging to generaCephalantheraandEpipactisof sub-tribe Limodorinae (Neottieae) from the Western Himalayas were undertaken. Aneuploid races with 2n= 32 and 34 are recorded inCephalanthera ensifolia.Detailed karyotypic analysis is made in all the five taxa. Meiotic studies from PMC's as well as from EMC's were studied inEpipactis consimilisandE. latifolia.Chiasma frequency was higher in the embryo-sac mother cells than the pollen mother cells inE. consimiliswhile reverse was the case inE. latifolia.

ISSN:0008-7114    

DOI:10.1080/00087114.1983.10797642

出版商:Taylor & Francis    

年代:1983

数据来源: Taylor

摘要:

Cytological studies on 4 species belonging to the generaListeraandNeottiaof the sub-tribe Neottiinae (Orchidaceae) from the Western Himalaya were undertaken. Two species ofListera(L. longicaulis 2n= 46,L. tenuis2n= 40) are investigated for the first time. Detailed karyotypic studies were made on two species ofListeraand one species ofNeottia.Asymmetrical karyotypes are recorded. Meiotic behaviour in the PMC's ofListera longicauliswas very erratic. Clumping of chromosomes at M-I due to stickiness was frequent. There is only a slight difference in the chiasma frequencies of PMC's and EMC's inNeottia listeroides.

ISSN:0008-7114    

DOI:10.1080/00087114.1983.10797643

出版商:Taylor & Francis    

年代:1983

数据来源: Taylor

摘要:

Morphological, anatomical and ultrastructural differences have been observed in fronds of two months old cultures ofLemna minorL. These fronds are reduced in area and in thickness and never form colonies. They have been compared with normal and ABA treated fronds in order to determine if the above mentioned differences could be caused by ABA, which might have been released in the culture medium.

ISSN:0008-7114    

DOI:10.1080/00087114.1983.10797644

出版商:Taylor & Francis    

年代:1983

数据来源: Taylor

摘要:

The mechanism of adventive embryogenesis was studied at ultrastructural level. ThreeCitruscultivars were used as material, two poly-embryonic and one mono-embryonic. The adventive embryos inCitrusare initiated in the nucellar tissue adjacent to the embryo sac in the micropylar half and incidentally from the chalazal end. The nucellar embryoids derive from initial cells. Initial cells are present already at the time of flowering in the poly-embryonic cultivars: in the mono-embryonic cultivar initial cells are absent. At the mature embryo sac stage the initial cells have a « meristematic » character. Before division they develop new cell walls and become « zygote-resembling » cells. During this development they are isolated and their original cell walls are disintegrated. Simultaneously the surrounding nucellar cells degenerate and disappear and the initial cells become embedded in the endosperm.

ISSN:0008-7114    

DOI:10.1080/00087114.1983.10797645

出版商:Taylor & Francis    

年代:1983

数据来源: Taylor

摘要:

A somatic chromosome number ofeightis described inPelargonium elongatum(Cav.) Salisb. This is the lowest chromosome number reported in the genus, and species with 2n = 16, 18, 20, 22, previously regarded as diploids, may have had a polyploid origin. This finding is discussed with reference to the miniature variety « Kleine Liebling », which has 2n= 9, and has previously been described as a true haploid.

ISSN:0008-7114    

DOI:10.1080/00087114.1983.10797646

出版商:Taylor & Francis    

年代:1983

数据来源: Taylor

摘要:

The nuclei of the first node embryo ofTriticum durumshow the same amount of histone bound to DNA in young and in aged seeds in line with earlier findings of remaining metabolic activity. Furthermore the explants of the first node from the old seeds analyzed, are still able to generate calli and plantlets and might be usefull to recover embryos from aged seeds.

ISSN:0008-7114    

DOI:10.1080/00087114.1983.10797647

出版商:Taylor & Francis    

年代:1983

数据来源: Taylor