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1.
The tillering phase in Hordeum bulbosum L. is terminated whenthe newly-formed axillary buds no longer emerge as tillers,but differentiate into dormant regeneration buds. The patternof development of the axillary buds differs during the tilleringphase and the post-tillering phase. During the former, accumulationof leaf primordia corresponds to the age of the bud, i.e., leafnumber per bud increases basipetally along the shoot. Duringthe post-tillering phase, leaf number per bud decreases basipetallyfrom the base of the future bulb internode. This transitionis brought about by an acceleration in the rate of accumulationof leaf primordia which is more sustained in the buds situatedcloser to the base of the bulb internode. These positional differencesin the morphogenesis of the regeneration buds are reflectedin their physiological responses during the relaxation of dormancyand activation of the buds. 相似文献
2.
Genetic control of plant size and shape is a promising perspective,particularly in fruit trees, in order to select desirable genotypes.A recent study on architectural traits in an apple progeny showedthat internode length was a highly heritable character. However,few studies have been devoted to internode cellular patterningin dicotyledonous stems, and the interplay between the two elementarycell processes that contribute to their length, i.e. cell divisionand elongation, is not fully understood. The present study aimedat unravelling their contributions in the genetic variationof internode length in a selection of F1 and parent genotypesof apple tree, by exploring the number of cells and cell shapewithin mature internodes belonging to the main axes. The resultshighlighted that both the variables were homogeneous in samplescollected either along a sagital line or along the pith width,and suggest that cell lengthening was homogeneous during internodedevelopment. They allowed the total number of cells to be estimatedon the internode scale and opened up new perspectives for simplifyingtissue sampling procedures for further investigations. Differencesin internode length were observed between the genotypes, inparticular between the parents, and partly resulted from a compensationbetween cell number and cell length. However, genetic variationsin internode length primarily involved the number of cells,while cell length was more secondary. These results argue foran interplay between cellular and organismal control of internodeshape that may involve the rib meristem. Key words: Elongation, growth, histogenesis, Malusxdomestica Borkh, pith
Received 2 January 2008; Revised 22 January 2008 Accepted 29 January 2008 相似文献
3.
The effect of streaming speed on intercellular transport ofchloride has been studied using pairs of internodal cells ofChara. The rate of transport was measured by that fraction ofthe chloride that entered one internode which was transportedout of it into the cells of the node and the next internode.The speed of cytoplasmic streaming was altered by treating thefirst cell with cytochalasin B. The relative rate of intercellular transport depended markedlyon the streaming speed at all speeds up to those found in untreatedcells. The chloride influx into the treated cell did not dependon the streaming speed. It is concluded that the rate of intercellular transport oflow molecular weight solutes in Chara will be normally limitedby the rate at which cytoplasmic streaming brings solute tothe plasmodesmata, rather than by the diffusion permeabilityof the plasmodesmata. This conclusion may well apply to othercharophyte plants, and could in principle apply to higher plants. 相似文献
4.
Electrotonic Coupling between Adjacent Internodal Cells of Chara braunii: Transmission of Action Potentials beyond the Node 总被引:1,自引:0,他引:1
Many nodal cells are interposed between two internodal cellsof Chara braunii. When an action potential conducted in an internodereached the node, no electrical activation in the nodal cellscould be found, although an area of the membrane bordering thenodal cells in this internode was partially activated (end-membraneaction potential). When the action potential approached thenode along the stimulated internode, an electrotonic potentialchange (depolarization) was produced in the other internode.This depolarization was greatly depressed by the end-membraneaction potential of the stimulated internode, so that hardlyany transmission took place. The ratio of the potential changein the surface membrane of the adjoining ("postsynaptic") internode(cell b) to that of the stimulated one (cell a), the couplingratio, eb/ea, can be estimated from a simple equivalent circuitof the nodal region composed of two surface-membrane resistances(Ra, Rb) and intercellular resistance (Rn). If Rn remains thesame, a higher ratio should be produced with a larger Rb, butthe ratio does not depend on any change in Ra, which could beproved experimentally. Transmission of the action potentialbeyond the node was frequent when the coupling ratio was increasedand when the threshold that elicits the action potential waslowered by immersing the node in a K or Na salt solution.
1 Present address: Department of Physiology, Tohoku UniversitySchool of Dentistry, Sendai 980, Japan. (Received December 1, 1980; Accepted January 23, 1981) 相似文献
5.
The Initiation and Growth of Narcissus Bulbs 总被引:1,自引:0,他引:1
Plants of two Narcissus cultivars were dissected periodicallyover a year to study initiation, growth, and dry-weight changesof flowers and daughter bulb units in relation to the positionof the daughter bulbs in the branching system. A Narcissus bulbis a branching system comprising terminal and lateral bulb units;the former bear both terminal and lateral bulb units, but lateralscontain only terminal ones. This basic pattern may be modifiedby the failure of lateral bulb units or the development of supernumeraryones. Differences in bulb unit size, in scale and leaf number,and in flowering, related to position in the branching system,are probably due to the initiation of lateral bulb units somemonths after terminal ones. This affects the growth and behaviourof the laterals and daughter bulb units borne by these lateralsin the next generation. Bulb units live about four years; after the loss of their leafblades and flowers, the scales and leaf bases act as storageorgans whose weight increases or decreases according to thecarbohydrate status of the plant. Growth of bulb units showsan externally controlled alternation of rapid and slow growth.This is likely to be an effect of day length on bulbing. 相似文献
6.
Plasmolytic disruption of plasmodesmata interconnecting metaphloemsieve element-companion cell complexes with small and largephloem parenchyma cells in the elongating region of internode2 ofPhaseolus vulgarisL. seedlings did not affect accumulationof phloem-imported14C-photosynthates and86rubidium. The membrane-impermeantdye, 5(6) carboxyfluorescein, loaded into leaf phloem as themembrane-permeant diacetate ester, was found not to move radiallyout of the importing sieve elements in the internode elongationregion. In contrast, the apoplasmic tracer, Calcuofluor White,rapidly moved laterally throughout all tissues of the elongationzone. Hexoses, sucrose and potassium were identified as themain osmotica in internode apoplasmic sap. Label asymmetry in[14C](fructosyl)sucrose was retained on accumulation by excisedstem segments. Uptake of [14C]sucrose and86rubidium by stemsegments exhibited saturation kinetics. Sucrose uptake was inhibitedby the slowly penetrating sulphydryl reagent, para-chloromercuribenzenesulphonicacid.In vitrorates of sucrose uptake, at apoplasmic concentrations,corresponded to its predictedin vivorate of delivery to thestem ground tissues from mature sieve elements when respiratorylosses were assumed to be confined to the stem phloem. For potassium,the total delivery rate could be accounted for by itsin vitrorateof uptake. Overall, it was concluded that radial transport,in the elongation zone of internode 2 ofPhaseolus vulgarisL.seedlings, follows an apoplasmic route from mature sieve elementsto stem ground tissues.Copyright 1998 Annals of Botany Company PhaseoluLes vulgaris, apoplasm, elongating stem, French bean, photosynthates, potassium, radial transfer, symplasm. 相似文献
7.
Rate and pattern of migration of lineally-related olfactory bulb interneurons generated postnatally in the subventricular zone of the rat 总被引:4,自引:0,他引:4
A spatially discrete region of the anterior part of the postnataltelescephalic subventricular zone, referred to as the SVZa generatesvast numbers of lineally-related neurons destined for the olfactorybulb (Luskin, 1993). The cells originating in the SVZa migrateto the olfactory bulb along a highly restricted pathway whichis in a direction orthogonal to the orientation of radial glialfibers. In this study we analysed the number, distribution,orientation and rate of migration of SVZa-derived cells as theyapproach the olfactory bulb. In order to track the SVZa-derivedcells, a retroviral lineage tracer, encoding the reporter geneE.coli ß-galactosidase (lacZ) was injected preciselyinto the rat SVZa at postnatal day 1 (Pl). The lacZ-positivecells were visualized 1, 2 and 3 days later by X-Gal histochemistryin cryostat sections. As the number of SVZa-derived cells inthe pathway increased with survival time, their distributionchanged systematically. The distribution pattern of lacZ-positivecells by 2 and 3 days postinjection suggested that some of theprogeny of infected progenitor cells were undergoing neurogenesisas they proceeded to the olfactory bulb; a large percentageof the lacZ-positive cells were substantially displaced fromthe SVZa injection site. To investigate whether lacZ-positivecells migrate in a directed fashion, their orientation preferencewas scored. For the majority of lacZ-positive cells (>94%),their leading process was directed toward the olfactory bulb,possibly reflecting a response to migratory cues present alongthe pathway. The estimated average rate of cell migration tothe olfactory bulb was 23 µm/h, which is approximatelytwice the speed of radially directed neuronal migration fromthe telencephalic ventricular zone to the cortical plate (O'Rourkeet al, 1992). Collectively, these results suggest that SVZa-derivedintemeurons en route to the olfactory bulb may employ a novelmode of tangential migration. 相似文献
8.
In Nitella flexilis, a species belonging to the section Anarthrodactylaeof the genus Nitella (Characeae), some mature cells, with theexception of those of the nodal complex and the rhizoid, shownumerous spherical vacuoles occupying the entire central regionof the cell. These vacuoles are fairly uniform in size measuring3040 µm in diameter. Evidence is presented frominvestigations with the light and electron microscopes suggestingthat some mature cells of a certain group of Nitella speciesmay not have a huge central vacuole. Vacuolation in young cellsof the apex apparently begins by progressive dilation of theendoplasmic reticulum. The Golgi complex may also be involvedin vacuolation. The necessity for re-examination of certainbiological activities in the giant internode cell is explored. 相似文献
9.
Invertase Activity, Carbohydrate Metabolism and Cell Expansion in the Stem of Phaseolus vulgaris L. 总被引:2,自引:0,他引:2
In the stem of Phaseolus vulgaris L. the specific activity ofacid invertase was highest in the most rapidly elongating internode.Activity of the enzyme was very low in internodes which hadcompleted their elongation, in young internodes before the onsetof rapid elongation, and in the apical bud. From shortly afterits emergence from the apical bud the elongation of internode3 was attributable mainly to cell expansion. Total and specificactivities of acid invertase in this internode rose to a maximumat the time of most rapid elongation and then declined. Transferof plants to complete darkness, or treatment of plants withgibberellic acid (GA3), increased the rate of internode elongationand final internode length by stimulating cell expansion. Bothtreatments rapidly increased the total and specific activitiesof acid invertase in the responding internodes; peak activitiesof the enzyme occurred at the time of most rapid cell expansion. In light-grown plants, including those treated with GA3, rapidcell and internode elongation and high specific activities ofacid invertase were associated with high concentrations of hexosesugar and low concentrations of sucrose. As cell growth ratesand invertase activities declined, the concentration of hexosefell and that of sucrose rose. In plants transferred to darkness,stimulated cell elongation was accompanied by a rapid decreasein hexose concentration and the disappearance of sucrose, indicatingrapid utilization of hexose. No sucrose was detected in theapical tissues of light-grown plants. The results are discussed in relation to the role of acid invertasein the provision of carbon substrates for cell growth. Key words: Cell expansion, Acid invertase, Hexose, Sucrose, Phaseolus 相似文献
10.
MONDAL M. F.; BREWSTER J. L.; MORRIS G. E. L.; BUTLER HEATHER A. 《Annals of botany》1986,58(2):197-206
Bulb development was followed in four onion cultivars growingin controlled environments under 17 h days in factorial combinationsof photon-flux densities (PFD) of 111 and 333 µmol m2s1 with red: far-red spectral ratios (R : FR) of 2.88and 1.41. A PFD of 111with R : FR of 0.86 was used in a secondexperiment. The lower the R : FR or the higher the PFD the higherthe mean bulbing ratio and the ratio of bulb plus sheath toleaf blade dry weight and the earlier the bulb swelling. LowerR : FR accelerated scale initiation as did the higher PFD underR : FR 2.88 but not under R : FR 1.41. In high PFD bulb swellingoccurred before scale initiation because many sheaths of bladedleaves thickened, but in low PFD and low R : FR bulb swellingand scale initiation were concurrent. In the low PFD a low R: FR increased soluble carbohydrate concentrations in sheathsand scales compared to high R : FR. In high PFD, soluble carbohydrateconcentrations did not vary with R : FR and were higher thanunder low PFD. Onion, Allium cepa L., bulb, photon flux density, red: far-red ratio, light spectral quality, soluble carbohydrate 相似文献
11.
Mature tannin-containing coenocytes as long as the whole internodeare present in Sambucus racemosa, the longest being 32.8 cm.The shape of their nuclei and the structure of their chromatindiffer from those in adjacent parenchyma cells, whilst the cytoplasmalso differs both in electron density and in organelle fine-structure.In the seventh internode there are symptoms of nuclear and cytoplasmicdegeneration and loss of plastid and mitochondrial membranes. Tannin coenocyte, pith, Sambucus racemosa, cell structure, differentiation 相似文献
12.
The internodes of Sambucus racemosa L. shoot apices originatefrom a single layer of cells in which mononucleate mother tannincells are present. The mother tannin cells increase in lengthand differentiate together with the internodal growth. Sambucus racemosa L., shoot apices, internode, mother tannin cells, tannin coenocytes 相似文献
13.
Thigmomorphogenesis: Changes in Cell Division and Elongation in the Internodes of Mechanically-perturbed or Ethrel-treated Bean Plants 总被引:2,自引:1,他引:1
Examination of first internodes of young Phaseolus vulgarisL. plants which have been subjected to mechanical perturbationshows decreased elongation and increased radial growth. Thedecreased elongation can be attributed to both reduced cellelongation of epidermal and cortical cells and a reduced numberof cells in the vascular and pith tissues. The increased radialenlargement is due to increased cortical cell expansion andincreased secondary xylem production resulting from increasedcambial activity. All of these responses are observable withina few hours of a single mechanical perturbation. Treatment ofplants with ethrel mimics all of these effects of mechanicalperturbation. Phaseolus vulgarisL, Kidney bean, thigmomorphogenesis, mechanical perturbation, ethrel, (2-chloroethyl phosphonic acid), cell division, internode elongation 相似文献
14.
Alfalfa Stem Tissues: Cell-wall Development and Lignification 总被引:4,自引:0,他引:4
Alfalfa stems contain a variety of tissues with different patternsof cell-wall development. Development of alfalfa cell wallswas investigated after histochemical staining and with polarizedlight using light microscopy and scanning electron microscopy.Samples of the seventh internode, from the base of stems grownon cut stems, were harvested at five defined stages of developmentfrom early internode elongation through to late maturity. Internodeseven was elongating up to the third sample harvest and internodediameter increased throughout the entire sampling period. Chlorenchyma,cambium, secondary phloem, primary xylem parenchyma and pithparenchyma stem tissues all had thin primary cell walls. Pithparenchyma underwent a small amount of cell-wall thickeningand lignification during maturation. Collenchyma and primaryphloem tissues developed partially thickened primary walls.In contrast to a recent report, the formation of a ring shaped,lignified portion of the primary wall in a number of cells inthe exterior part of the primary phloem was found to precedethe deposition of a thick, non-lignified secondary wall whichwas degradable by rumen microbes. In numerous xylem fibres fromthe fourth harvest date onwards, an additional highly degradablesecondary wall layer was deposited against a previously depositedlignified and undegradable secondary wall. The pattern of lignificationobserved in alfalfa stem tissues suggests that polymerizationof monolignols by peroxidases at the luminal border of the primarycell wall creates an impermeable zone which restricts lignificationof the middle lamella region of tissues with thick primary walls.Copyright1998 Annals of Botany Company Alfalfa,Medicago sativaL., stem tissue, cell wall, development, lignification, degradation. 相似文献
15.
The anatomy was studied of the sugar-storing tissue of ninesugar-cane clones known to differ in their rates of sucroseuptake in vitro. Clones having a high rate of sucrose uptaketended to have smaller cells, thicker cell walls and more vascularbundles than clones having lower rates of sucrose uptake andthese differences in anatomy resulted in the high uptake cloneshaving storage tissue with a higher percentage of fibre thanthat of the low uptake clones. The findings are discussed inrelation to known associations between sugars and fibre andbetween sugars and the ratio of leaf weight to weight of nodeplus internode. 相似文献
16.
Partial submergence or treatment with either ethylene or gibberellicacid (GA3 induces rapid growth in deepwater rice (Oryza sativaL.). We correlated the synthesis of two cell wall componentswith two phases of internodal elongation, namely (13,14)-ß-glucanformation with cell elongation and lignification with differentiationof the secondary cell wall and cessation of growth. The contentof ß-glucan was highest in the zone of cell elongationin internodes of air-grown plants and plants that were inducedto grow rapidly by submergence. In the intercalary meristemand in the differentiation zone of the internode, ß-glucanlevels were ca. 70% lower than in the zone of cell elongation.The outer cell layers, enriched in epidermis, contained moreß-glucan in submerged, rapidly growing internodesthan in air-grown, control internodes. The ß-glucancontent of the inner, parenchymal tissue was unaffected or slightlylowered by submergence. The epidermis appears to be the growth-limitingstructure of rapidly growing rice internodes. We hypothesizethat elevated levels of ß-glucan contribute to elongationgrowth by increasing the extensibility of the cell wall. Lignificationwas monitored by measuring the content of lignin and the activitiesof two enzymes of the lignin biosynthetic pathway, coniferylalcohol dehydrogenase (CAD) and phenylalanine ammonia-lyase(PAL), in growing and non-growing regions of the internode.Using submerged whole plants and GA3-treated excised stem segments,we showed that lignin content and CAD activity were up to sixfoldlower in newly formed internodal tissue of rapidly growing ricethan in slowly growing tissue. No differences were observedin parts of the internode that had been formed prior to inductionof growth. PAL activity was reduced throughout the internodeof submerged plants. We conclude that lignification is one ofthe processes that is suppressed to permit rapid growth.
1 This work was supported by the National Science Foundationthrough grants No. DCB-8718873 and DCB-9103747 and by the Departmentof Energy through grant No. DE-FGO2-90ER20021. M.S. was therecipient of a fellowship from the Max Kade Foundation. 相似文献
17.
Extracellular recordings were performed from olfactory bulbneurons in the frog. The odour stimuli were the same as thosepreviously used for studying the receptor cells in the sameanimal species and were delivered at similar concentrations(Revial et al., 1982). The general properties of the neuronresponses are presented and discussed with reference to homologousproperties of olfactory receptor cells. The response rates elicitedby different stimuli from the bulbar neurons were found to behighly correlated with those elicited from receptor cells. Theindividual cell selectivity was better in the bulb than in theolfactory epithelium. The olfactory bulb neurons seemed to improvethe discrimination between stimuli (enantiomers) poorly distinguishedby the receptor cells. Reducing odor concentration caused therate of suppressive response to decrease faster than that ofexcitatory ones, suggesting that the manifestations of inhibitoryprocesses in some neurons requires a high level of excitationin others. 相似文献
18.
Vascular cambium ofBotrychium ternatum rhizome varied according to age, position and season was studied by light and electron microscopy. Cambium at the 6th internode (6-year-old cambium) had the greatest number of active cambial cells in August and September, thus it was in the most active stage. The active cells were characterized by the presence of a large vacuole, few storage materials such as starch grains within plastids or lipid droplets, a thin tangential wall; and various cell organelles in the thin peripheral layer of cytoplasm. When the 6-year-old cambium reached its dormant season after November, the dormant cells were filled with numerous storage materials and had few cell organelles. Our observations suggested that the initiation and cessation of cambial activity may be correlated with the annual life cycle of this plant: the vegetative and reproductive leaves began to emerge in June and July, respectively, and the sporophyll withered in November after the spore dispersal. Most cambial cells at the 10th internode, which remained in a dormant state throughout the year, were filled with numerous storage materials. Our results indicated that the activity of vascular cambium in the 10th internode was determinate. 相似文献
19.
Phaseolus vulgaris L. decapitated at the third internode showedaccelerated growth of the uppermost axillary bud remaining onthe stem (the first trifoliate axillary bud) after a lag periodof 35 h Much of the initial growth increment could beattributed to cell expansion Phaseolus vulgaris L, dwarf bean, correlative inhibition, cell expansion 相似文献
20.
Effects of the plant growth retardant, ancymidol, on the growthand morphology of the shoot system of cucumber (Cucumis sativusL. ) were investigated. Ancymidol inhibited stem elongation,reducing both number and length of internodes. Reduction inleaf area, attributable to a reduction in both cell size andnumber, was accompanied by an increase in chlorophyll per unitarea. The retardant decreased apical dominance and delayed anthesis.Gibberellic acid fully reversed ancymidol-induced inhibitionof stem elongation, internode length and production, and leafexpansion. GA4/7 and ancymidol gave a synergistic promotionof stem elongation by increasing elongation of younger internodesand increasing internode production. Synergistic promotion ofpetiole elongation by this combination was also observed. Ancymidol,applied 7 d previously either to the shoot or root, severelyreduced the level of gibberellin-like activity in bleeding sapcollected from decapitated plants. 相似文献