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  • 1
    Electronic Resource
    Electronic Resource
    Light enhances differentiation of the vascular system in the fruit of Actinidia deliciosa (1996)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 98 (1996), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Light is recognized as crucial in determining high quality of fleshy fruits, for example, kiwifruit [Actinidia deliciosa var. deliciosa (A. Chev.) C. F. Liang et A. R. Ferguson]. Among the possible mechanisms through which light improves the quality of kiwifruit berry, there may be a direct morphogenic role on the differentiation of the fruit's vascular system, though this has not yet been investigated.The present study's aim was to determine (1) whether light positively affects the differentiation of the vascular system of the fruit and/or the pedicel, and, if so, (2) which component (xylem, phloem, or both) is more affected, and (3) in which period of the berry's development the improvement of the vascular differentiation (if any) occurs. To this end, fruit morphogenesis of kiwifruit was studied in two developmental environments (i.e., in full sunlight and in paper bags that reduced the full sunlight to 10%), and in two phases of fruit development (i.e., 1 and 5 months [harvest] after anthesis). During the growth period, the type of environment did not affect the differentiation pattern of the vascular system in the three types of bundles present in the fruit. However, in comparison with shade, light improved the vasculature in the fruit pericarp and pedicel, inducing a consistently higher extent of the xylary component in the main bundles of the fruit and pedicel, principally due to an increase in the number of xylem elements. The phloic component was also increased by light, but to a much lesser extent than that of the xylary. During the entire period of development, light-grown fruits contained higher concentrations of calcium and magnesium, as compared with shade-grown fruits.In conclusion, in the berry of Actinidia deliciosa, light enhances the differentiation of the vascular system, in particular the xylary component. The hypothesis that fruit quality is improved through a more efficient translocation of specific mineral nutrients (e.g., calcium) via the xylem is presented.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1996.tb00672.x
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  • 2
    Electronic Resource
    Electronic Resource
    Protease activity, organisation of vegetative primordia and effect of putrescine in tobacco thin layers (1996)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 98 (1996), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Since in tobacco thin layers exogenous putrescine alters the physiological and mor-phogenic responses induced by IAA (indole-3-acetic acid) and/or BA (benzylade-nine), the effect of this polyamine on protease activity and on the formation of meristemoids and vegetative primordia was studied during morphogenesis. Superficial thin layer explants, excised from the stem of tobacco (Nicotiana tabacum L. cv. Samsun) plants in the vegetative stage, were cultured under various hormonal conditions (IAA, IAA+BA, BA) and in a hormone-free medium, in the presence or absence of 100 μM putrescine. Histological analysis showed that no meristemoids were formed on the control medium or with putrescine alone and only a few were formed on IAA-treated explants with or without putrescine. An increasing number of meristemoids was observed in IAA+BA and BA treatments during culture; in both cases this number was enhanced by the presence of exogenous putrescine. Protease activity was evaluated spectrophotometrically using two synthetic substrates, azocasein and N-benzoyl-DL-arginine-p-nitroanilide (BAPNA). In the former, maximum protease activity was observed in IAA+BA- and BA-treated explants on days 10 and 15, respectively, while with IAA activity was lowest, the maximum occurring on days 5–10. In this case exogenous putrescine enhanced protease activity in the presence of IAA alone or with BA, while it decreased it in the presence of BA. BAPNA-mediated proteolytic activity (serine-proteases) was highest in IAA+BA-treated explants, intermediate in BA- and not different from controls in IAA-treated explants. Putrescine only affected proteolytic activity in IAA+BA treatments. The use of specific inhibitors of protease activities indicated that these enzymes belong to two main classes of proteases, that is serine- and thiol-proteases. The pattern of proteolytic activities during culture appeared to be related to the differentiation of meristemoids into vegetative primordia. The effect of exogenous putrescine on protease activity was different depending on different synthetic substrates, developmental patterns, pH and ionic strength.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1996.tb05722.x
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  • 3
    Electronic Resource
    Electronic Resource
    Polyamine conjugate levels and ethylene biosynthesis: inverse relationship with vegetative bud formation in tobacco thin layers (1999)
    Copenhagen : Munksgaard International Publishers
    Physiologia plantarum 105 (1999), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The effects of two inhibitors of polyamine (spermidine and spermine) biosynthesis, cyclohexylamine (CHA; 5 and 10 mM) and methylglyoxal(bis-guanylhydrazone) (MGBG; 0.1, 0.5 and 1 mM), on the organogenic response in vegetative bud-forming tobacco (Nicotiana tabacum L. cv. Samsun) thin layer explants were evaluated micro- and macroscopically at different times during culture. The final number of buds formed and the percentage of organogenic explants was significantly reduced by both inhibitors, but much more so by MGBG than CHA. This inhibitory effect was already evident in MGBG-treated explants on day 5, in terms of the number of meristemoids per explant. On the contrary, in the presence of CHA, the number of meristemoids on day 5 was higher than that in the controls. Between days 9 and 13, meristemoid formation slowed down considerably in inhibitor-treated explants compared with controls. On day 13, the number of bud primordia was similar in control and CHA-treated explants, but significantly lower in MGBG-treated explants. This inhibitor also induced peculiar cytohistological events, such as a reduced formation of oval-shaped cell aggregates on the explant surface and more frequent cases of nucleolar extrusion, while CHA led to the appearance of hypertrophic epidermal cells; callus formation at the basal end of the explant and xylogenesis were also affected by the inhibitors. Ethylene biosynthesis, measured as [〈displayedItem type="mathematics" xml:id="di-fml-1" numbered="no"〉〈mediaResource alt="image" href="urn:x-wiley:00319317:PPL105223:PPL_105223_mu1"/〉C]methionine incorporation, was stimulated 2- (day 2) to 3-fold (15 h) by 0.5 mM MGBG, whereas CHA (10 mM) had little effect and aminoethoxyvinylglycine (AVG; 0.1 μM), an ethylene synthesis inhibitor, was strongly inhibitory. In control explants, the incorporation of labelled methionine into ethylene and spermidine followed an inverse trend up to day 8. In these explants, free putrescine increased 32-fold and spermidine increased about 10-fold between days 0 and 8. Trichloroacetic acid (TCA)-soluble conjugated putrescine also accumulated dramatically during culture. While CHA provoked a decline in spermidine levels, MGBG caused an unexpected increase in free spermidine and spermine titres; however, its most conspicuous effect was on the further enhancement of putrescine conjugate accumulation, while CHA and AVG had the opposite effect. Results are discussed in view of establishing a putative link between MGBG-enhanced ethylene synthesis, increased conjugate titres and inhibition of meristemoid formation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1034/j.1399-3054.1999.105223.x
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  • 4
    Electronic Resource
    Electronic Resource
    The histogenesis of somaclones from tomato (Lycopersicon esculentum Mill.) cotyledons (1988)
    Springer
    Protoplasma 142 (1988), S. 156-163 
    Details
    ISSN: 1615-6102
    Keywords: Tomato ; Lycopersicon esculentum ; Somaclonal variation ; Plant regeneration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary A histological study ofin vitro cultured cotyledonary expiants of tomato (Lycopersicon esculentum) was performed in order to determine the site (differentiated tissue or developing callus) and the mode of plant regeneration. Results have shown that callus develops at the excision sites of cotyledonary expiants and that shoots are formed exclusively within the unorganized callus: excision areas are the only morphogenetic sites and the proximal excision is the preferred site for plant regeneration. Shoots differentiate by organogenesis within the superficial region of the callus. Few neocambial cells cooperate in the neoformation. Origin from a single cell is highly unlikely since rarely observed single activated cells never developed into shoots. Regenerated plants may be chimeras if invitro culture induces genetic diversity in the initial cells.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01290872
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  • 5
    Electronic Resource
    Electronic Resource
    Root histogenesis from tobacco thin cell layers (1991)
    Springer
    Protoplasma 161 (1991), S. 31-42 
    Details
    ISSN: 1615-6102
    Keywords: Adventitious roots ; Histogenesis ; Thin cell layers ; Tobacco stem
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Internode stem expiants ofNicotiana tabacum cv. Samsun, consisting of eight cell layers: epidermis, subepidermal chlorenchyma, collenchyma and cortical parenchyma (i.e., thin cell layers), were cultured under conditions inducing rhizogenesis. The aim was to investigate the histological sequence of adventitious root formation in this system. The earliest cytological events in culture (12 h) were nucleolar extrusions and amitotic nuclear divisions. Though not restricted to a specific cell layer, the two phenomena were more frequent in the subepidermal chlorenchyma, and characterized the first phases (12-96 h) of cell proliferation mainly occurring in this layer. Amitoses were followed by the formation of thin walls within the original cells, resulting in the formation of intracellular clusters. These subepidermal clusters were separated by enlarged cells of the parent tissue, whose nuclei showed nucleolar extrusion. At day 3 the first mitoses were observed in cells having abundant starch inclusions. Amitotic divisions also continued, but less frequently. The increasing frequency of mitoses in the subepidermal chlorenchyma (day 4), as well as in the two underlying collenchymatous layers, contributed to the growth of the superficial clusters, in which small clumps of meristematic cells were formed; these, later (day 9), gave rise to root domes. The 5th cell layer remained undivided for a relatively long time (two weeks). The 6th and 7th layers proliferated mitotically later (from day 8 onwards) than the superficial layers and formed root domes following the same histological sequence. Wound callus, generated by the innermost layer, increased markedly in the last two weeks of culture and concomitantly formed vascular clumps surrounded by meristematic layers; these produced root primordia which were frequently anomalous (day 26–27). Regardless of its origin (i.e., superficial or deep layers of the expiant, or wound callus cells), root tip formation was always preceded by the differentiation of a sheath of starch-containing cells, from which the root cap developed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01328895
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  • 6
    Electronic Resource
    Electronic Resource
    Histological study of embryogenesis and organogenesis from anthers ofVitis rupestris du Lot cultured in vitro (1992)
    Springer
    Protoplasma 171 (1992), S. 134-141 
    Details
    ISSN: 1615-6102
    Keywords: Anther culture ; Caulogenesis ; Histological analysis ; Rhizogenesis ; Somatic embryogenesis ; Vitis rupestris Scheele cv. du Lot
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Anthers ofVitis rupestris du Lot were cultured in vitro at the uninucleate stage of the microspore, in order to investigate the histology of embryogenic and organogenic processes in this genotype. Microspores divided in the anther loculi resulting in the formation of globular structures with a ruptured exine. Somatic embryogenesis and, occasionally, caulogenesis and rhizogenesis occurred in calli produced from all anther tissues except the endothecium. The initial cell of the embryoid was surrounded by a jacket layer when situated deep within the callus. When the embryoid's initial cell was situated in the peripheral callus, a cutinized wall was present and the three-celled proembryoid was almost always segmented, showing the same embryonal type as the zygotic proembryo. Root differentiation and elongation and cap differentiation occurred during the growth phase in liquid medium. The mature root was diarch and contained cells with calcium-oxalate raphides, as seen in vivo. No starch or tannin deposition was ever observed in the mature embryoids.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01403728
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  • 7
    Electronic Resource
    Electronic Resource
    Early phases in in vitro culture of tomato cotyledons: Starch accumulation and protein pattern in relation to the hormonal treatment (1994)
    Springer
    Protoplasma 182 (1994), S. 59-64 
    Details
    ISSN: 1615-6102
    Keywords: In vitro culture ; Tomato ; Starch accumulation ; Protein pattern
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Tomato cotyledon explants, cultured in vitro in the presence of sucrose, were subjected to different hormonal treatments to establish whether the induction of different organogenic programmes could be correlated with differences in starch accumulation and protein electrophoretic pattern. The cytohistological changes in explants over the first 15 days of culture were studied by light and electron microscopy. It was found that starch accumulation occurs under all conditions, though varying in duration and amount. Over the first 2 days of culture the protein electrophoretic pattern changes in a similar way under all conditions, while after 7 days changes take place which are probably related to the different developmental programmes induced by the treatments.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01403689
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  • 8
    Electronic Resource
    Electronic Resource
    Cytological events induced by the inhibition of polyamine biosynthesis in thin cell layers of tobacco (1993)
    Springer
    Protoplasma 175 (1993), S. 9-16 
    Details
    ISSN: 1615-6102
    Keywords: Cell expansion ; Nicotiana tabacum ; Nucleolar extrusion ; Polyamine biosynthesis inhibitors ; Rhizogenesis ; Thin cell layers
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The proliferative growth of thin cell layers ofNicotiana tabacum cultured on a rhizogenic medium was markedly disturbed when polyamine biosynthesis was inhibited. Treatments with polyamine inhibitors led to cell expansion, accompanied by thinning of the cell wall and inhibition of cell division, and frequent cases of nucleolar extrusion, mainly in the parenchymal layer in contact with the medium. Nucleolar extrusion was not correlated with cell expansion. The highest incidence of nucleolar extrusion occurred when the pathways of putrescine biosynthesis were inhibited and when spermidine synthesis, via S-adenosylmethionine decarboxylase, was blocked. The duration of the growth phase with nuclear amitotic divisions was prolonged in the presence of the inhibitors and root meristem formation delayed. When polyamines were added with the inhibitors, all reactions proceeded as in the controls.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01403280
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  • 9
    Electronic Resource
    Electronic Resource
    Ethylene involvement in vegetative bud formation in tobacco thin layers (1998)
    Springer
    Protoplasma 202 (1998), S. 134-144 
    Details
    ISSN: 1615-6102
    Keywords: Ethylene ; Ethylene inhibitors ; Meristemoids ; Nicotiana tabacum ; Thin layers ; Vegetative buds
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The role of ethylene in vegetative bud regeneration was studied in cultured tobacco (Nicotiana tabacum L. cvSamsun) thinlayer expiants. The experimental approach consisted in supplementing the bud-inducing medium with an inhibitor of ethylene biosynthesis, aminoethoxyvinylglycine (AVG), an ethylene antagonist, silver thiosulphate (STS), or an ethylene-releasing compound, 2-chloroethylphosphonic acid (CEPA), at various concentrations. The organogenic response was assessed both macroscopically (percentage of bud-forming expiants, final number of buds per expiant) and cytohistologically (number, characteristics, and localisation of meristemoids and bud primordia). The time course of ethylene production during culture was also evaluated. At the end of culture (day 27) all the expiants treated with these compounds had a lower number of buds compared to controls. STS was detrimental to meristemoid initiation at all the concentrations tested. In contrast, 0.5 μM AVG, which strongly inhibited ethylene production, provoked a large increase in the formation of meristemoids early in culture and the appearance of anomalous (“twin”) buds. CEPA reduced meristemoid formation but, at the lower concentrations (1 and 10 μM) speeded up bud emergence. On the whole it mainly favoured disorganised growth and xylogenesis. The results of this work highlight the contrasting effects of ethylene in relation to the two critical stages of the organogenic process, i.e., meristemoid formation and bud primordium development.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01282541
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  • 10
    Electronic Resource
    Electronic Resource
    TherolD gene fromAgrobacterium rhizogenes is developmentally regulated in transgenic tobacco (1997)
    Springer
    Protoplasma 197 (1997), S. 111-120 
    Details
    ISSN: 1615-6102
    Keywords: Agrobacterium rhizogenes ; rolD promoter ; GUS gene ; Nicotiana tabacum ; Development
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary TherolD gene fromAgrobacterium rhizogenes has recently been shown to induce striking precocity of flowering in transgenic tobacco. A transcriptional fusion between 578 bp of therolD upstream regulating sequence and the GUS reporter gene has been transferred to tobacco plants and its expression analysed throughout the whole life cycle of the plant. A detailed histological analysis revealed thatrolD is strongly expressed in elongating and differentiating tissues of each organ, from the mature embryo to the adult plant. In organs with determinate growth, such as cotyledons, leaves and floral parts,rolD expression follows the age gradient of the tissues. In mature tissues,rolD expression is high, begins to decrease with ageing and is switched off when senescence occurs.RolD is also active in the vascular system, in the procambium, pith- and receptacular-meristems. Our data show that expression ofrolD is under developmental control as it correlates with, and may represent a molecular marker for, the elongation/expansion and maturation phases of the plant tissues.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01279889
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