Publisher Summary This chapter discusses the B-chromosome systems in flowering plants and animal species. The term B chromosome is introduced to describe extra chromosome which have little if any effect on visible characters of the plant, which are not homologous with the A chromosomes of the normal complement, and which are extremely irregular in their meiotic distribution. B Chromosomes are now known under a variety of different names, including supernumerary and accessory, which are the most common alternatives. B chromosomes are dispensable and nonhomologous with A chromosomes. These two characteristics above all others most sharply differentiate them from members of the basic A-chromosome complement. The distribution of B chromosome in plant and animal species is discussed. In many plants and animals the B chromosomes are completely stable during the cell cycle and are inherited in a constant and unchanging form along with the A chromosomes. Some plant species have an apparent order in their instability, which results in exclusion and/or accumulation of B chromosomes in specific tissues and organs. The significance of B-chromosome effects in flowering plants and animals is discussed.

B-Chromosome Systems in Flowering Plants and Animal Species

RIASSUNTOL'A delinea l'importanza delle modificazioni cromosomiche del soma nel problema della speciazione delle piante che si riproducono vegetativamente

https://www.tandfonline.com/doi/pdf/10.1080/00087114.1956.10797584

A New Concept of a Means of Speciation in Plants

Karyotypes and electrophoretic pattern of 15 strains of taro were studied. Strains collected from the northeast India hill state, Meghalaya were diploids and triploids whereas those from the plains of south India were diploids and of north India was a triploid. The diploids had 2n=28 and triploids showed 2n=42 chromosomes. The wild taro had the most asymmetrical karyotype. The protein content varied from 4.2 to 11.4 mg/g dry wt. The maximum protein content was found in a triploid strain 8 (11.4 mg/g dry wt) and minimum in the wild taro (4.2 mg/g dry wt). The number of protein bands was 7 in the wild taro (diploid) and 12 in one of the cultivated triploid strain. Meghalaya strains showed great variation with respect to leaf size and tuber shape and size. All the strains have diverged at morphological, karyotypic and genotypic levels. It is suggested that taro might have originated in the north-eastern India.

Karyotypic and electrophoretic studies on taro and its origin

Further cytological study of Colocasia taro in the Pacific utilizing karyotypic data has produced a hypothesis for two separate lineages of the plant within contemporary populations. This provides support for domestication in the western Pacific independent of diffusion of Asian cultigen forms, but it is indicated that confirmation awaits more comprehensive karyotyping of Indian and Southeast Asian material.

Chromosome variation in taro, Colocasia esculenta: implications for origin in the Pacific.

Flowers of 23 species representing six subfamilies of Araceae were studied by means of serial cross sections, special attention being given to vascular patterns and to taxa of supposed phylogenetic importance. Floral structure is shown to be extremely diverse with no unifying pattern common to all subfamilies. Conclusions include the following: (1) Lysichiton has a specialized gynoecial vascular pattern which differs from others encountered in the survey and which weighs against the primitive position attributed to this genus by Hutchinson. (2) Philodendron, with its multiple stylar canals, cannot have originated from subfamily Pothoideae, as Engler's phylogenetic concept would require of all Araceae; instead, it appears that several synearpous evolutionary lines have evolved independently from extinct apocarpous members of the family. (3) In Acorus, stamens are introrse and dorsal carpellary bundles are lackiing; these characters and others justify the recognition of Acorus as a separate subfamily Acoroideae. In addition, the survey revealed a peculiar deterioration of the inner ovary wall and the septa in several taxa, apparently a normal feature of floral development. Spathiphyllum solomonense Nicolson is described in an appendix. LITERATURE ON comparative anatomy of flowers has accumulated over the past several decades into a sizeable body of information; in Rao's (1961) bibliography of more than 800 entries, most families of angiosperms are represented by at least one publication. It appears, however, that no modern botanist has undertaken a special investigation of vasculature and histology in flowers of Araceae. This is rather surprising, because the family is large and widely distributed with many familiar ornamental species. Moreover, most of the families commonly suggested as allies of Araceae have been studied, at least in an introductory way, from the standpoint of floral structure: al-Rawi (1945), Bosch (1947), and Morrow (1963, 1965) investigated the palms; Harling (1946, 1958) and Garcin (1958), the Cyclanthaceae; Gatin (1920), Anderson (1940), and el-Hamidi (1952), the Liliaceae. The anatomy of araceous flowers is not totally unknown, for the authoritative monographs of Engler (1905, 1911, 1912, 1915, 1920a, 1920b), Krause (1908, 1913), and Engler and Krause (1908, 1920) are replete with drawings and descriptive comments relating to floral structure. For the most part, however, these observations are derived from the earlier works of Schott (in particular his Genera Aroidearum, 1858) and Engler (see especially his 1884 contribution on floral morphology), in which no information is given on vascular patterns. Apparently, the only 19th century worker to examine floral vasculature of Araceae was van 1 Received for publication May 31, 1966. The authors thank Dr. Donald R. Kaplan for reading the manuscript critically. Tieghem (1867), who reported on the -arrangement of bundles in pistillate flowers of Zantedeschia, Alocasia, and Aglaonema, later (1907, p. 315) offering an interpretation of the staminate flower of Aglaonema. Possibly the only contribution since van Tieghem's time is Saunders' (1939) brief commentary, expressed in the terms of her long discredited theory of "carpel polymorphism." We have not found that any author on Araceae has compared vascular systems and other microscopic floral characters in genera selected for possible phylogenetic interest, as we attempt to do in this paper. Our investigation is meant to be no more than an introductory survey. It was planned as a summer project only (the laboratory work was completed during the summer of 1965, while the third author was a research assistant in the Smithsonian Summer Program for Graduate Students), and because of other research commitments we do not expect to carry it further. Our aims are to point out the diversity in internal floral structure of the Araceae, particularly in those groups claimed to be primitive by various authors, to compile pertinent literature, and to raise questions of phylogeny that should be considered in subsequent studies of the family. We hope thus to attract the attention of other investigators to an interesting and, from the anatomical standpoint, neglected group of monocotyledons. Accordingly, the second author will be happy to share his collections of inflorescences with any worker who wishes to use them for further anatomical research. M-ATERIALS-Specimens used in this investigatiorn were selected from an assemblage of about

A survey of floral anatomy in araceae

(1955). Cytology of Different Species of Aroids with a View to Trace the Basis of their Evolution. Caryologia: Vol. 7, No. 2, pp. 221-291.

Cytology of Different Species of Aroids with a View to Trace the Basis of their Evolution

(1955). Cytology of Amaryllids as an Aid to the Understanding of Evolution. Caryologia: Vol. 7, No. 1, pp. 1-71.

https://www.tandfonline.com/doi/pdf/10.1080/00087114.1955.10797483

Cytology of Amaryllids as an Aid to the Understanding of Evolution

RIASSUNTONel presente lavoro si sono studiati gli effetti sui costituenti cellulari di sei diversi ormoni e cioe dell'acido β-naftossiacetico, dell'ac. 1-naftilacetico, dell'ac. fenilacetico, dell'ac. indoloacetieo, dell'ac. indolpropionico, dell'ac. indolbutirrico.Come l'acido 1-naftilacetico, i cui risultati erano gia stati osservati da LEVAN, anche questi altri ormoni hanno un'azione mutagena sulle piante. Si sono messi in evidenza gli effetti di questi ormoni sulla struttura dei cromosomi, in conseguenza dell'alterata viscosita del plasma e della diversa contrazione dei segmenti cromosomici. Sono stati pure osservati gli effetti delle varie concentrazioni (minimum, maximum ed optimum) per ogni ormone, e si e notato che l'optimum e indicato dalla prevalenza della maggior percentuale di metafasi ben distese con morfologia ben distinta.Non sembra esistere nessun rapporto tra la solubilita e la concentrazione necessaria per ottenere l'effetto ottimale. E stato pero notato che la concentrazione necessaria ...

Archana Mookerjea

Papers

Cytology of Different Species of Aroids with a View to Trace the Basis of their Evolution

Cytology of Amaryllids as an Aid to the Understanding of Evolution

Possibilities of use of Hormones in Chromosome Analysis: (With Plates II and III)