摘要:

1)Experimental mitosis stimulation in the differentiated root tissues in some species of Monocotyledons was obtained by treatment with some concentrations (generally, from 10 to 50 p. p. m.) of sodium 2,4-dichlorophenoxyacetate.2)In Tables I and II the percentages of polyploid mitoses in the cortex tissue in some of the species investigated herein are reported. In addition, a survey of the distribution of polyploidy in the various tissue layers in the roots of the species examined is given in the text.3)Polyploid cells showed 4nand 8nmitoses with « pairs » and « groups of four » chromosomes respectively. Only in one root inBellevalia romanapolyploid mitoses with single chromosomes, indicative of a second mitotic cycle in differentiated cells, were observed.A detailed description of the course of both 4nand 8nmitoses in differentiated root cells in the species studied is reported. The greatest variability in the behaviour of both centromere and relational coiling in 4nmitoses was observed in the roots ofAllium yunnanense.Spontaneous chromosome aberrations were met with in differentiated cells in bothAllium yunnanenseandNothoscordum fragrans.4)InGaltonia candicansandBulbinella Hookeri, notwithstanding the very intense pericyde stimulation for the production of lateral roots, mitosis stimulation in adult tissues was practically absent.5)The present observations are discussed in connection with our present knowledge on endopolyploidy and tissue differentiation and function. It is assumed that tetraploidy and octoploidy in differentiated tissues are the result of. respectively, a double and a triple chromosome reproduction in the resting stage, giving rise to « diplo » and « quadruplochromosomes ». The reasons for preferring the term « endopolyploidy » to « polyteny » are presented, with reference to a possible occurrence of an « endomitosis in a despiralized stage », as suggested by Geitler(1948).6)The following other points are also discussed:a)the chimerical constitution of differentiated plant tissues, 2n, 4n, 8nand probably higher polyploid nuclei occurring in different proportion in different tissues and in one and the same tissue in different species (or individuals in one species);b)the possible connection between size and shape of nuclei in adult tissues on one side and degree of « ploidy » on the other;c)the occurrence of spontaneous chromosome aberrations in differentiated cells and the possible significance of metabolites or some of their derivatives in the origin of the aberrations (cf. D'AMATO 1950b).

ISSN:0008-7114    

DOI:10.1080/00087114.1952.10797537

出版商:Taylor & Francis    

年代:1952

数据来源: Taylor

摘要:

E' stata studiata l'ovogenesi diAnilocra physodesnel periodo che va dal momento in cui gli ovogoni entrano in meiosi, fino alla formazione delle prime gocce di vitello nel citoplasma degli ovociti.

ISSN:0008-7114    

DOI:10.1080/00087114.1952.10797538

出版商:Taylor & Francis    

年代:1952

数据来源: Taylor

摘要:

E' stato studiato il corredo cromosomico di lombrichi provenienti da varie località: su quindici specie esaminate sono state riscontrate otto mutazioni poliploidi, viene così accertato che la poliploidia è fenomeno assai frequente nella famiglia.

ISSN:0008-7114    

DOI:10.1080/00087114.1952.10797539

出版商:Taylor & Francis    

年代:1952

数据来源: Taylor

摘要:

L'Autore in seguito all'osservazione di aberrazioni cromosomiche spontanee durante la mitosi negli apici radicali di plantule diReseda odoratasi è proposto di studiare un probabile effetto mutageno dell'« essenza di Reseda » sul testoAllium Cepa.

ISSN:0008-7114    

DOI:10.1080/00087114.1952.10797540

出版商:Taylor & Francis    

年代:1952

数据来源: Taylor

摘要:

Newts (Triturus viridescens) brought to the laboratory during the winter and kept on a limited diet of tubificid worms, developed an anemia characterized by the appearance in the peripheral blood of atypical erythrocytes, known as pseudoerythroplastids. The blood picture did not change after intraperitoneal injections with massive doses of vitamin B12(Merck). Animals collected during the summer did not show this anemia despite limited diet and repeated bleeding. It was suggested that the physiological condition of the newts at the time they are subjected to the anemia-inducing factors, may influence their susceptibility to the production of pseudoerythroplastids.

ISSN:0008-7114    

DOI:10.1080/00087114.1952.10797541

出版商:Taylor & Francis    

年代:1952

数据来源: Taylor

摘要:

The authors examined the influence of aqueous extracts ofPhaseolus vulgarison the root tip mitoses inAllium Cepa.Undiluted extracts of seeds, stored one year, induced an almost complete inhibition of mitotic activity after an 8 hrs'. treatment. After 60 hrs. recovery in tap water, mitotic activity was regained, but the new mitoses showed various chromosome aberrations, mainly fragmentations, The dilutions 1:2 and 1:4 induced similar effects in a lesser degree. Similar extracts of a variety ofPhaseolus vulgarisseeds, which had been stored for 5 to 6 years exerted an even stronger activity. The undiluted extract killed the roots after an 8 hrs'. treatment, while the dilution 1:2 inhibited mitosis completely after 8 hrs.; after 60 hrs. recovery in tap water 21,3% abnormal anaphases could be counted. The authors discuss the possible implications of their findings for an explanation of the origin of spontaneous chromosome aberrations in the primary roots of aged seeds.

ISSN:0008-7114    

DOI:10.1080/00087114.1952.10797542

出版商:Taylor & Francis    

年代:1952

数据来源: Taylor

摘要:

L'A. ha condotto ricerche citogenetiche sulle antere diDecana d'Inverno o Winter Doyenné(Pyrus communisL.), diKieffer Seedling(probabile incrocio traPyrus serotinaRehdere Pyrus communisL.) e su quelle di due esemplari F1dell'incrocioKieffer SeedlingXDecana d'Invernoe precisamente i due numeri17e22.

ISSN:0008-7114    

DOI:10.1080/00087114.1952.10797543

出版商:Taylor & Francis    

年代:1952

数据来源: Taylor