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Journal ArticleDOI

Reazioni di natura auxinica ed effetti rizogeni in Allium Cepa L.

01 Jan 1948-Plant Biosystems (Taylor & Francis Group)-Vol. 55, Iss: 2, pp 161-213
TL;DR: No relation has been found between degree of macroscopical growth responses and intensity of lateral root formation: treatments inducing the most intense growth reactions may show very poor « root-forming » effects.
Abstract: Summary The authors have studied growth responses and induction of laterals in onion roots subjected to various experimental treatments. The following reactions have been observed: C-tumours, coiling and bending responses, basal thickening, root hair formation and browning of roots. Fasciation, sometimes present in onion roots, is brought to greater evidence by many chemical treatments; none of these seems, however, to enhance its frequency. A more or less complete inhibition of growth and induction of lateral roots are generally concomitant phenomena; an exception to this rule are sulfathiazole and the threshold concentrations of 2,4-D (2,4-dichlorophenoxyacetic acid) and its sodium salt (see Table I). No relation has been found between degree of macroscopical growth responses and intensity of lateral root formation: treatments inducing the most intense growth reactions may show very poor « root-forming » effects (for ex., nicotinic acid and moist air). For most of the chemicals tested the threshold valu...
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Journal ArticleDOI
TL;DR: The cytogenetics of plant cell and tissue cultures and their regenerates will be discussed, and nuclear processes at and during callus induction will be followed.
Abstract: After a short introduction, the cytogenetics of plant cell and tissue cultures and their regenerates will be discussed. In the first section discussion will focus on cytogenetic conditions “in vivo”, i.e., in the original explant: (I) widespread ocurrence of polysomaty as a consequence of endoreduplication; (2) aneusomaty, an important, though rare, cause of chromosome number variation in vivo; (3) occurrence of chromosome structural changes in differentiated tissues, especially in association with aging; (4) mixoploidy and/or gene mutations, either nuclear or organellar, present as mosaics or periclinal chimeras, especially in vegetatively propagated plants. In section two the discussion will follow with nuclear processes at and during callus induction: (1) mitosis induction in diploid (haploid) and endoreduplicated cells and initiation of cell lines with different ploidy levels; (2) chromosome endoreduplication prior to mitosis induction as a mechanism of polyploidization; (3) nuclear fragmentation (ami...

278 citations

Journal ArticleDOI
TL;DR: It is shown that morphogenetic changes were induced by the fungus in the root system of the host during the first 105 days after sowing by Glomus sp.
Abstract: SUMMARY Morphometric analysis, modelling and histological techniques were used to study root morphogenesis in nonmycorrhizal and mycorrhizal plants of Allium porrum infected by a Glomus sp., strain E3, during the first 105 days after sowing. They showed that morphogenetic changes were induced by the fungus in the root system of the host. Adventitious roots of mycorrhizal plants became more numerous and shorter than those of controls, as mycorrhizal infection proceeded. Increase in number was fitted by logistic curves in mycorrhizal and control plants; increase in length was fitted in both cases by logistic curves. Mycorrhizal roots became progressively more branched than controls: branching increased linearly with time in mycorrhizas, whereas in the controls it showed an almost constant frequency from day 49 onwards and was fitted by a logistic curve. There was a significant depression of mitotic index demonstrated in the apical meristems of vesicular-arbuscular mycorrhizas.

207 citations

Journal ArticleDOI
TL;DR: The most common mechanism of polyploidization acting in plant tissues and cells appears to be supernumerary chromosome reproduction, which is responsible for polysomaty in root and shoot meristems as well as forpolyploidy in any type of differentiated tissues and for nuclear growth in general.
Abstract: SUMMARYThe actually available data on the occurrence of polyploidy in plant tissues and cells have been critically reviewed. The incidence of polyploidy in the plant body, the cytological mechanisms by which the polyploid condition is produced, the physiological and general significance of polyploidy in the « soma » of plant organisms and related questions have been considered.The most common mechanism of polyploidization acting in plant tissues and cells appears to be supernumerary chromosome reproduction. This is responsible for polysomaty in root and shoot meristems as well as for polyploidy in any type of differentiated tissues and for nuclear growth in general. During the development of ephemeral tissues, such as the anther tapetum, supernumerary chromosome reproduction has been sometimes found to occur intermingled with monochromosome mitoses and/or typical endomitosis of the Gerris-type.Abortive mitoses due to spindle disturbances and chromosome stickiness or both are a very common polyploidization...

194 citations

Journal ArticleDOI
TL;DR: Riassuni riassunte le attuali conoscenze sulla distribuzione e sul modo di origine della endopoliploidia nei tessuti vegetali and viene discusso il possibile significato oferta dell'endopoli Ploida nella differenziazione istologica.
Abstract: RIASSUNTOVengono riassunte le attuali conoscenze sulla distribuzione e sul modo di origine della endopoliploidia nei tessuti vegetali e viene discusso il possibile significato della endopoliploidia nella differenziazione istologica.

167 citations

Journal ArticleDOI
TL;DR: The length of the mitotic cycle and the time spent in mitosis are calculated for six regions of the apical meristem of roots of Zea using the measurement of the rates of labelling nuclei with radioactive thymidine and the rate of accumulation of metaphases in roots grown in colchicine.
Abstract: SUMMARY The length of the mitotic cycle and the time spent in mitosis are calculated for six regions of the apical meristem of roots of Zea. The two methods used are the measurement of the rates of labelling nuclei with radioactive thymidine and the rates of accumulation of metaphases in roots grown in colchicine. The mitotic cycle lasts from 12 hours in the cap initials to about 200 hours in the quiescent centre of the same roots. Some points about the organization of apices are discussed in the light of these estimates.

134 citations

References
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Journal ArticleDOI
01 Jan 1942-Nature
Abstract: THROUGHOUT plants and animals the cell nucleus has a uniformity of structure corresponding to the uniformity of its work. This structure has to reconcile the mechanical requirements of cell division and reproduction with the physiological requirements of heredity and development. Its primary importance has led to its study by a great variety of physical and chemical techniques; indeed, a greater variety than has been brought to bear on any other type of structure. Differential staining, X-ray diffraction and X-ray destruction, double refraction, micro-dissection, micro-incineration, ultraviolet spectroscopy and differential digestion as wellas bulk analysis and the vast magnifications of geneticexperiment have been used. They have all played their different parts in the solution of the problem.

120 citations