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  • 1
    Electronic Resource
    Electronic Resource
    Abnormal structure of protophloem sieve-element cell wall in colchicine-treated roots of Triticum aestivum L. (1994)
    Springer
    Planta 193 (1994), S. 266-274 
    Details
    ISSN: 1432-2048
    Keywords: Colchicine ; Cell wall (ingrowths) ; Microfibril ; Microtubule ; Protophloem sieve element ; Triticum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The structural aberrations of the cell walls of protophloem sieve elements (PSEs) in roots of wheat (Triticum aestivum L. cv. Maris Huntsman) caused by the anti-microtubule drug colchicine were investigated by electron microscopy. The initial effect of the drug on cell wall development was found to be an exceptionally rough wall surface, presumably caused by an uncontrolled fusion of Golgi vesicles with the plasma membrane. Cellulose microfibrils, which in normal PSEs are aligned transversely to the long axis and parallel to the cortical microtubules, in colchicine-treated PSEs display a predominant longitudinal orientation. The pattern of wall development is disturbed by deposition of wall material also within the sieve pores of the sieve-pore/plasmodesmata complexes, resulting in evenly thickened walls instead of the normal uneven layers, and in narrowing the sieve pores to the size of plasmodesmata. In prolonged and continuous colchicine treatment, PSEs develop unusual wall ingrowths projecting deeply into the cytoplasm, creating an extraordinary cell type not found in normal roots. The results confirm the view of microtubule involvement in the proper deposition and orientation of cellulose microfibrils, and in the normal patterning of the cell wall thickenings of differentiating PSEs.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00192540
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  • 2
    Electronic Resource
    Electronic Resource
    Abundance of microtubules in preprophase bands of some Triticum species (1985)
    Springer
    Planta 163 (1985), S. 175-182 
    Details
    ISSN: 1432-2048
    Keywords: Microtubule ; Ploidy level ; Preprophase band ; Triticum (microtubules)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Root tip procambial cells of Triticum speltoides, T. tauschii, T. turgidum and T. aestivum have been investigated ultrastructurally for the detection of preprophase microtubule bands (PMBs) and to estimate the number of microtubules comprising the bands. The species selected are phylogenetically related but differ in the ploidy level. It was found that all species develop well-defined PMBs prior to mitosis. Estimations of microtubule abundance in the PMBs was carried out in midpreprophase cells, a stage judged by a feature of the nucleus in which electron-transparent canals are formed around the initial condensations of the chromatin material and the nucleoli. Triticum speltoides bears the smaller average number of microtubules per PMB and T. aestivum the greater. The results indicate that the increase follows the upgrade of the number of chromosome sets. It is suggested that the average number of microtubules of PMBs is related to the ploidy level.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00393503
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  • 3
    Electronic Resource
    Electronic Resource
    Physiological and Ultrastructural Effects of Cadmium on Wheat (Triticum aestivum L.) Leaves (1997)
    Springer
    Archives of environmental contamination and toxicology 32 (1997), S. 154-160 
    Details
    ISSN: 1432-0703
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Medicine
    Notes: Abstract. The effects of a 7-day exposure of 3-day-old wheat plants to increasing Cd concentrations are described, with special attention being given to chloroplast ultrastructural changes, chlorophyll fluorescence responses, chlorophyll and nutrient concentration changes as well as growth changes of the whole plant. The plants treated with 1 mM Cd showed symptoms of heavy metal toxicity. The root, shoot-leaf length and the root, shoot-leaf biomass progressively decreased with increasing Cd in nutrient solution and in 1 mM of Cd an almost complete inhibition of growth was found. Shoot-leaf Cd accumulation increased under Cd-treatments, while a Fe, Mg, Ca, and K decline in the above ground parts was observed. The growth reduction and the inhibition of chlorophyll content and photosynthesis observed in the upper plant parts seemed principally due to indirect Cd effects on the content of essential nutrients. Cadmium treatment was shown to damage the structure of chloroplasts, as manifested by the disturbed shape and the dilation of the thylakoid membranes. These ultrastructural changes suggest that Cd probably induced premature senescence.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002449900168
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  • 4
    Electronic Resource
    Electronic Resource
    Sieve-element plastids ofTriticum andAegilops (Poaceae) (1984)
    Springer
    Plant systematics and evolution 145 (1984), S. 119-133 
    Details
    ISSN: 1615-6110
    Keywords: Poaceae ; Triticum ; Aegilops ; Sieve-element plastids ; crystalloid inclusions ; ultrastructure ; two- and three-dimensional patterns
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Fourteen taxa of the Triticum-Aegilops group have been investigated for their sieve-element plastids. At maturity they contain dense and thin crystalloid inclusions and are classified into the PIIc' plastid type; onlyAe. comosa var.biaristata lacked the thin crystalloids and thus conforms to the PII c type. The proteinaceous nature of the crystalloids was demonstrated by application of proteolytic enzymes. Ultrastructural evidence suggests that both kinds of crystalloid inclusions are involved in the sealing of sieve-plate pores of injured sieve tubes. Measurements and calculations of the spacings and angles carried out on crystalloid prints permitted the construction of a two- and three-dimensional pattern forT. aestivum thin crystalloids.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00984035
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  • 5
    Electronic Resource
    Electronic Resource
    Development of protophloem in roots ofAegilops comosa var.thessalica. II. Sieve-element differentiation (1982)
    Springer
    Protoplasma 113 (1982), S. 221-233 
    Details
    ISSN: 1615-6102
    Keywords: Aegilops ; Differentiation ; Nuclear disintegration ; Plastids ; Protophloem ; Sieve plates
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Protophloem sieve-element differentiation in roots of the grassAegilops comosa var.thessalica has been studied by light and electron microscopy. Sieve elements are arranged in vertical files and mature close to the root apex (about 450 μm). Nuclei have a nearly normal appearance until the last immature cell. In this cell, chromatin aggregates and becomes amorphous. Furthermore, nuclei are segmented in many parts with various appearance; the most condensed segments are retained in mature cells and treatment with proteolytic enzymes show that they are composed mostly of proteins. The ER does not aggregate into stacks, but some cisternae of it are appressed to the nuclear envelope. Smooth membranes of ER, plastids and mitochondria are retained at maturity. On the other hand, ribosomes and Golgi apparatus disappear completely. Vacuoles were not observed at any stage of development. Sieve-element cell walls develop wave-like thickenings, which in mature cells gradually become evenly thickened. These thickenings may serve as stores of wall material. Transformation of plasmodesmata canals into sieve plate pores is realized by removal of both callose and ER cisternae from the pore sites. The complete opening of pores occurs in the first mature sieve elements.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01280911
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  • 6
    Electronic Resource
    Electronic Resource
    Prospective companion cells differentiate into abnormal sieve elements in colchicine-treated roots ofTriticum aestivum (1993)
    Springer
    Protoplasma 176 (1993), S. 151-164 
    Details
    ISSN: 1615-6102
    Keywords: Triticum aestivum ; Roots ; Companion cells ; Colchicine ; Abnormal sieve elements ; Plastids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Companion cells (CCs) of seminal roots of wheat (Triticum aestivum L.) flank protophloem sieve elements (PSEs) on their inner side. In roots growing in the presence of 2 mM colchicine prospective CCs are induced to differentiate into abnormal sieve elements. The most convincing evidence that they deviate from their programmed developmental sequence is the deposition of dense crystalloid inclusions within their plastids, a feature characterizing sieve elements of gramineous species. These plastids, however, are ultrastructurally different from those of normal and abnormal PSEs in that they contain only one kind of crystalloid inclusion, exceptionally dense stroma, swollen vesicular structures and plastoglobuli. Mitochondria accumulate in large groups and appear unusually swollen and deformed. Walls develop abnormal thickenings which are deposited irrespective of the position of plasmodesmata. Nuclei become polyploid and appear highly lobed, but degenerate similarly to those in normal sieve elements. Aggregates of paracrystalline material occur in the cytoplasm between the nucleus and cell wall. The end walls display features characterizing developing sieve plates, callose is deposited around plasmodesmata, but sieve pores are not formed. Aberrant CCs may reach “maturity” and co-exist with colchicine-affected PSEs. Their arrangement may be similar to or differ from that of normal phloem poles. Not all cells in CC files are induced to deviate into abnormal sieve elements, nor does their development occur in sequence. Because developmental changes also occur in polyploid cells, which result from colchicine blocked cell divisions, it is concluded that cell division is not a prerequisite for cell differentiation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01378952
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  • 7
    Electronic Resource
    Electronic Resource
    Development of protophloem in roots ofAegilops comosa var.thessalica. I. Differential divisions and pre-prophase bands of microtubules (1982)
    Springer
    Protoplasma 113 (1982), S. 110-119 
    Details
    ISSN: 1615-6102
    Keywords: Protophloem ; Microtubules ; Pre-prophase band ; Cell division ; Root ; Aegilops
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The formative divisions of protophloem mother cells in roots of the grassAegilops comosa var.thessalica have been investigated by means of light and electron microscopy. Two successive differential divisions create protophloem poles consisting of a protophloem sieve element and two companion cells. Pre-prophase bands of microtubules appear in premitotic cells anticipating the plane of orientation of the cell plate and indicating the site where the daughter wall will join the parent one. Evidence is accumulated that the site previously occupied by pre-prophase band is bisected by the new wall. Structural asymmetries that could express polarity, like organelle displacement, were not observed in premitotic cells. A working hypothesis is proposed integrating the conclusions of the present study in a diagram correlating pre-prophase bands of microtubules and differential divisions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01281999
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  • 8
    Electronic Resource
    Electronic Resource
    An unusual feature of developing protophloem sieve elements in roots ofTriticum aestivum L. (1989)
    Springer
    Protoplasma 152 (1989), S. 14-21 
    Details
    ISSN: 1615-6102
    Keywords: Differentiation ; Heterochronic lysis ; Polarity ; Root protophloem sieve elements ; Triticum aestivum ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Developing protophloem sieve elements in roots of wheat are arranged in single vertical files. In the last immature differentiating sieve element bearing ribosomes the proximal end of the cytoplasm displays a diluted appearance in contrast to the distal end where the cytoplasm exhibits a considerably increased electron density. Differences can also be observed in ribosome quantity, organelle ultrastructure and the time of initiation of cell component degradation, those at the proximal end disorganizing first, suggesting a nonsimultaneous disorganization of the cell components in the two areas. This phenomenon, termedheterochronic lysis, is presumably an expression of an existing polarity not detectable in younger stages, but it might also be the result of an asynchronous enzymatic activity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01354235
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  • 9
    Electronic Resource
    Electronic Resource
    Development of mestome sheath cells in leaves ofAegilops comosa var.thessalica (1979)
    Springer
    Protoplasma 100 (1979), S. 139-153 
    Details
    ISSN: 1615-6102
    Keywords: Aegilops comosa var.thessalica ; Cell wall ; Development ; Mestome sheath cells ; Microtubules ; Suberized lamella
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The development of mestome sheath cells ofAegilops comosa var.thessalica was studied by electron microscopy. Anatomical and cytological observations show that this grass belongs to the C3 or non-Kranz plants. In the asymmetrically thickened walls of mestome sheath cells a suberized lamella is present. This lamella is deposited asynchronously. In the midrib and the large lateral bundles it appears first in the outer and inner walls and usually later in the radial walls. In the small lateral bundles its appearance is delayed in the inner walls of those cells situated on the xylem side. At maturity the suberized lamella is observed in all cell walls; however, in the small lateral bundles it is partly or totally absent from the walls of some cells situated on the xylem side. Tertiary wall formation is asynchronous as well, for it generally follows the deposition pattern of the suberized lamella. During the development of the mestome sheath cells microtubules show marked changes in their number and orientation, being fewer and longitudinal during suberin deposition. Dictyosomes are very active and may be involved in primary and tertiary wall formation. Endoplasmic reticulum cisternae are abundant and partly smooth, while plasmalemmasomes may function to reduce the plasmalemma extension. However, cytoplasmic structures that are clearly involved in suberin synthesis could not be identified. Suberized lamellae react strongly with silver hexamine. This is probably due to post-fixation with osmium tetroxide. On the basis of structural characteristics the mestome sheath may be regarded as an endodermis (cf., alsoFahn 1974). The significance of this view for water and assimilate exchange between the mesophyll and the bundle is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01283925
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  • 10
    Electronic Resource
    Electronic Resource
    Developmental features of protophloem sieve elements in roots of wheat (Triticum aestivum L.) (1996)
    Springer
    Protoplasma 193 (1996), S. 204-212 
    Details
    ISSN: 1615-6102
    Keywords: Golgi bodies ; Mitochondria ; Plastids ; Symmetrical divisions ; Protophloem sieve elements ; Triticum aestivum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Protophloem sieve elements (PSEs) in roots of wheat (Triticum aestivum L.) are arranged in single vertical files. The number of PSEs within the files increases by symmetrical divisions, which take place after the completion of asymmetrical (formative) divisions and before the initiation of differentiation. The divisions are preceded by well defined pre-prophase bands (PPB) of microtubules, which surround the nucleus in an equatorial position. In the cytoplasmic region between the nuclear surface and the PPB, perinuclear and endoplasmic microtubules were observed. The perinuclear microtubules are considered as part of the developing spindle, while the endoplasmic ones interlink the perinuclear microtubules with the PPB. Dividing cells do not show any signs of incipient differentiation. The first and most reliable indication of a commencing differentiation is provided by the sieve-element plastids that begin to accumulate dense crystalloid inclusions in the very young PSEs. In mature PSEs plastids contain two kinds of crystalloid inclusions, dense and thin, in a translucent stroma. Depending on the plastid-inclusions criterion it was shown that: (a) the PSEs of a given root do not initiate differentiation at exactly the same stage, (b) the developmental sequence extends to a span of 7–9 actively differentiating PSEs arranged in a single vertical file, and (c) each PSE needs about 16–21 h to pass through the whole developmental sequence. In the last two differentiating PSEs of a file, mitochondria were found to be enveloped by single cisternae of ER. The association is temporary as it is lost in the first PSEs with an autolysed lumen. During differentiation, Golgi bodies were abundant and active in producing vesicles involved in cell wall development. Golgi vesicles were also found among the microtubules of the PPB, but no local thickening was observed. Golgi bodies disorganize in the last stages of autolysis and disappear in mature sieve elements.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01276646
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