scholarly journals Experimental investigations of the shoot apex of Dryopteris aristata Druce

1947 ◽  
Vol 232 (589) ◽  
pp. 343-384 ◽  
Keyword(s):  
Shoot Apex ◽  
Apical Meristem ◽  
Vascular Tissue ◽  
Normal Development ◽  
Vascular System ◽  
Leaf Primordia ◽  
Terminal Region ◽  
Main Shoot ◽  
Marked Contrast ◽  
Medullary Parenchyma

A method whereby the apical meristem of the fern Dryopteris aristata Druce can be partially isolated from the adjacent lateral organs and tissues is described. This procedure has been adopted as a means of investigating growth and morphogenesis at the shoot apex. The technique involves the severance of the incipient vascular tissue which originates immediately below the apical meristem; the isolated meristem is thus seated on a plug of growing medullary parenchyma. Leaf primordia can be similarly isolated. Meristems treated in this way are capable of growth. They develop into short vasculated shoots bearing leaves. The nutrients sustaining this growth must reach the apical meristem from below by diffusing through medullary parenchyma at the base of the isolated terminal region. Above the parenchymatous region a solenostelic vascular system is present in the new axis; this is in marked contrast to the dictyostelic configuration of the parental shoot below. On the further growth of the isolated meristem leaves are produced and the stele becomes dictyostelic. The new leaves, of which as many as fourteen have been observed after 11 weeks’ growth, show the normal phyllotactic arrangement, and this is continuous with that of the main shoot below. The procedure adopted has the effect of removing the physiological dominance of the apical meristem relative to the main shoot; thus numerous large buds develop on the lateral segments of the parental shoot but none on the isolated terminal region. The growth of isolated leaf primordia is very limited. The vascular system develops as a solenostele, foliar gaps are not formed in the region of confluence with the shoot stele, axillary buds are developed, and the leaf apex becomes directed outwards. These several features are in marked contrast to the normal development. The isolated lateral segments are also capable of further growth. The experimental procedure adopted involves the severance of the vascular tissues at various levels. An account is given of new and hitherto unrecorded morphological developments observed in these segments. Interesting features include the formation of large solenostelic buds, the solenostelic development of isolated meristeles, medullation of meristeles and the induction of a polycyclic stelar condition, in one instance by a process of cambium-like activity. These are all in marked contrast to the normal development of the intact shoot. The data which have been obtained are discussed with special reference to the path of translocation of nutrients to the terminal meristem and to leaf primordia, morphogenetic processes at the shoot apex, the factors influencing the differentiation of the vascular system, and theories of shoot formation and constitution. The results of these experiments give no support to phytonic theories but emphasize the difference in potentiality for development between shoot and leaf primordia. In this connexion the factors which determine the shape and system of segmentation of the apical initials of shoot and leaf are seen to require further investigation. The hypotheses that lateral buds are inhibited by substances proceeding from the apical meristem, that the initial differentiation of vascular tissue can be attributed to the basipetal diffusion of a substance or substances from the actively growing apical meristem, and that under conditions of tensile stress incipient vascular tissue undergoes a parenchymatous development, are supported by the data of these experiments. The observations afford a clear indication of the diversity of the morphogenetic activity in the growing region. Nutritional, mechanical and other factors are seen to be important in influencing the distribution of tissues during development. The view entertained by comparative morphologists that the vascular system in ferns is of a highly conservative nature and therefore of great value in phyletic studies is to some extent opposed by the data of these experiments. But notwithstanding the several unusual vascular configurations produced as a result of the experimental treatment, there is eventually a return to the typical vascular arrangements of the normal shoot. There is thus a need for harmonizing the data of the causal and phyletic aspects. The more thoroughly the operation of morphogenetic factors extrinsic to the specific hereditary substance is understood, the more critical will be the selection of criteria of comparison for phyletic purposes.

scholarly journals Single-cell analysis resolves the genetic program of primary vascular system formation in hybrid poplar

2021 ◽  
Author(s):  
Daniel Conde ◽  
Paolo M. Triozzi ◽  
Wendell J. Pereira ◽  
Henry W. Schmidt ◽  
Kelly M. Balmant ◽  
...  
Keyword(s):  
Gene Expression ◽  
Single Cell ◽  
Shoot Apex ◽  
Vascular Tissue ◽  
Vascular System ◽  
Developmental Trajectories ◽  
Specific Gene ◽  
Cell Type ◽  
Woody Perennials ◽  
Cell Type Specific

Despite the enormous potential of novel approaches to explore gene expression at a single-cell level, we lack a high-resolution and cell type-specific gene expression map of the shoot apex in woody perennials. We use single-nuclei RNA sequencing to determine the cell type-specific transcriptome of the Populus vegetative shoot apex. We identified highly heterogeneous cell populations clustered into seven broad groups represented by 18 transcriptionally distinct cell clusters. Next, we established the developmental trajectories of epidermal cells, leaf mesophyll, and vascular tissue. Motivated by the high similarities between Populus and Arabidopsis cell population in the vegetative apex, we created and applied a pipeline for interspecific single-cell expression data integration. We contrasted the developmental trajectories of primary phloem and xylem formation in both species, establishing the first comparison of primary vascular development between a model annual herbaceous and a woody perennial plant species. Our results offer a valuable resource for investigating the basic principles underlying cell division and differentiation conserved between herbaceous and perennial species, which also allows the evaluation of the divergencies at single-cell resolution.

scholarly journals Growth and development of shoot apex in barley I. Morphology and histology of shoot apex in vegetative phase

2014 ◽  
Vol 49 (1-2) ◽  
pp. 21-31
Author(s):  
Zygmunt Hejnowicz ◽  
Wiesław Włoch
Keyword(s):  
Shoot Apex ◽  
Growth And Development ◽  
Apical Part ◽  
Leaf Primordia ◽  
Main Shoot ◽  
Vegetative Phase ◽  
Tunica Layer ◽  
Bulge Formation

The vegetative phase of development of the main shoot apex lasts over 5 plastochrons after germination. The endosperm has a sufficient store of nutrition for this period. At the beginning of this phase the apex has a one-layer tunica. The cells of the latter divide above the level of bulge formation for leaf primordia, exclusively anticlinally, although somewhat lower within the leaf bulge periclinal divisions may occur. The cells immediately under the first tunica layer in the apical part grow tangentially to the surface. These cells divide only anticlinally forming gradually the second tunica layer. In the course of the entire phase the shape of the meristeanatic caulis from the tip to the 4th frustum remains unchanged.

In situ localization of storage protein mRNAs in developing meristems of Brassica napus embryos

Development ◽  
1991 ◽  
Vol 111 (2) ◽  
pp. 299-313 ◽  
Author(s):  
D.E. Fernandez ◽  
F.R. Turner ◽  
M.L. Crouch
Keyword(s):  
Brassica Napus ◽  
Storage Protein ◽  
Shoot Apical Meristem ◽  
Apical Meristem ◽  
Vascular Tissue ◽  
Leaf Primordia ◽  
Root Apical Meristem ◽  
Cdna Clones ◽  
Final Maturation

Probes derived from cDNA clones of napin and cruciferin, the major storage proteins of Brassica napus, and in situ hybridization techniques were used to examine changes in the spatial and temporal distribution of storage protein messages during the course of embryogeny, with a special emphasis on the developing apical meristems. Napin mRNAs begin to accumulate in the cortex of the axis during late heart stage, in the outer faces of the cotyledons during torpedo stage and in the inner faces of the cotyledons during cotyledon stage. Cruciferin mRNAs accumulate in a similar pattern but approximately 5 days later. Cells in the apical regions where root and shoot meristems develop do not accumulate storage protein messages during early stages of embryogeny. In the upper axis, the boundary between these apical cells and immediately adjacent cells that accumulate napin and cruciferin mRNAs is particularly distinct. Our analysis indicates that this boundary is not related to differences in tissue or cell type, but appears instead to be coincident with the site of a particular set of early cell divisions. A major change in the mRNA accumulation patterns occurs halfway through embryogeny, as the embryos enter maturation stage and start drying down. Final maturation of the shoot apical meristem is associated with the development of leaf primordia and the accumulation of napin mRNAs in the meristem, associated leaf primordia and vascular tissue. Cruciferin mRNAs accumulate only in certain zones of the shoot apical meristem and on the flanks of leaf primordia. Neither type of mRNA accumulates in the root apical meristem at any stage.

The shoot apical meristem and development of vascular architectureThis review is one of a selection of papers published on the Special Theme of Shoot Apical Meristems.

2006 ◽  
Vol 84 (11) ◽  
pp. 1660-1671 ◽  
Author(s):  
Nancy G. Dengler
Keyword(s):  
Arabidopsis Thaliana ◽  
Shoot Apical Meristem ◽  
Apical Meristem ◽  
Leucine Zipper ◽  
Vascular Tissue ◽  
Vascular System ◽  
Expression Patterns ◽  
Three Dimensional ◽  
Integrative Model ◽  
Class Iii

The shoot apical meristem (SAM) functions to generate external architecture and internal tissue pattern as well as to maintain a self-perpetuating population of stem-cell-like cells. The internal three-dimensional architecture of the vascular system corresponds closely to the external arrangement of lateral organs, or phyllotaxis. This paper reviews this correspondence for dicotyledonous plants in general and in Arabidopsis thaliana (L.) Heynh., specifically. Analysis is partly based on the expression patterns of the class III homeodomain-leucine zipper transcription factor ARABIDOPSIS THALIANA HOMEOBOX GENE 8 (ATHB8), a marker of the procambial and preprocambial stages of vascular development, and on the anatomical criteria for recognizing vascular tissue pattern. The close correspondence between phyllotaxis and vascular pattern present in mature tissues arises at early stages of development, at least by the first plastochron of leaf primordium outgrowth. Current literature provides an integrative model in which local variation in auxin concentration regulates both primordium formation on the SAM and the first indications of a procambial prepattern in the position of primordium leaf trace as well as in the elaboration of leaf vein pattern. The prospects for extending this model to the development of the complex three-dimensional vascular architecture of the shoot are promising.

Developmental potentialities of leaf primordia of Osmunda cinnamomea. VI. The expression of P1

1971 ◽  
Vol 49 (11) ◽  
pp. 1941-1945 ◽  
Author(s):  
Thomas H. Haight ◽  
Charles Carroll Kuehnert
Keyword(s):  
Phase I ◽  
Phase Ii ◽  
Shoot Apex ◽  
Shoot Apical Meristem ◽  
Apical Meristem ◽  
Leaf Primordia ◽  
Phase Iii ◽  
Developmental Phase ◽  
Experimental Conditions ◽  
Three Phases

Data from culture experiments presented strongly suggest that the development of leaf primordia at the shoot apex may be divided into three phases in Osmunda cinnamomea. Phase I lasts from inception (Im) to some point in time during P1. Phase II probably begins somewhere between Im and I1, and may be retained as long as P9. Phase III is evident as early as P1 and continues through the entire primordial sequence to include Pn. In nature, or under experimental conditions where physiological continuity between the primordium and shoot apical meristem complex is maintained, O. cinnamomea primordial expression is phase III expression (leaf only). However, if the primordia produced at the shoot apex are removed from certain external biological influences (specifically the shoot apical meristem and certain older primordia) terminal expression of the primordia may be either phase I, phase II, or phase III depending upon the developmental phase of the primordia at the time of their isolation.

Cytological and histological changes induced by cold temperature in the young shoots of Marquillo × Kenya Farmer wheat dwarf 1

1972 ◽  
Vol 50 (3) ◽  
pp. 403-408 ◽  
Author(s):  
J. D. Mahon ◽  
D. T. Canvin
Keyword(s):  
Apical Meristem ◽  
Leaf Primordia ◽  
Vascular Bundles ◽  
Vascular Differentiation ◽  
Main Shoot ◽  
Histological Changes ◽  
Whole Plant ◽  
Meristematic Activity ◽  
Extensive Cell ◽  
Extent Of Damage

The growth of Marquillo × Kenya Farmer 1 heat plants has been shown to be irreversibly terminated if they are exposed to a 16° temperature when 10 days old and it has been proposed that this low temperature sensitivity proceeds through a rapid inactivation of the shoot apical meristem. Histological and microautoradiographic techniques were used to study the effects of 16° treatment on the morphology and meristematic activity of the young shoots of both Marquillo × Kenya Farmer 1 and normal Marquillo plants.Within 12 h of the beginning of 16° treatment, damaged cells were visible in the young developing leaf and stem tissues and such cells became numerous after longer periods at 16°. The cells most rapidly destroyed were those surrounding the vascular bundles in both leaf primordia and stem tissues and the extent of damage in a tissue was closely related to the stage of vascular differentiation in the adjacent bundles.Cell division in the apical meristem of the main shoot was inhibited even more rapidly. The proportion of cells dividing and the incorporation of 3H-thymidine into the nuclei of meristem cells decreased rapidly at 16° and the reversibility of these effects was similar to that of the whole plant effects.It is suggested that the cessation of growth in Mql × KF 1 exposed to 16° is due to the lack of cell division and that the permanence of this effect is due to the extensive cell destruction that occurs in the meristematic regions.

The comparative investigation of apices of vascular plants by experimental methods

1950 ◽  
Vol 234 (620) ◽  
pp. 583-602 ◽  
Keyword(s):  
Shoot Apex ◽  
Vascular Plants ◽  
Vascular Tissue ◽  
Vascular System ◽  
Subsequent Development ◽  
Comparative Investigation ◽  
Lateral Organs ◽  
Experimental Treatments ◽  
Leaf Insertion ◽  
Axial Growth

A considerable diversity of histological constitution is to be found in the apices of seed plants, and these again differ notably from those of eusporangiate and leptosporangiate ferns. Yet, in their growth and morphogenetic activity, the vegetative apices of all classes of vascular plants have much in common, i.e. they give rise to a vasculated axis with regularly disposed lateral members. Comparative investigations of apices by strictly anatomical methods have definite limits which are soon reached. In the present investigation the aim was to see if, when the same experimental treatments are applied to very differently constituted apices, closely comparable or divergent organographic developments ensue. When the shoot apex in selected eusporangiate and leptosporangiate ferns and in species of Primula was isolated by vertical incisions from the lateral organs and tissues, with concomitant severing of the incipient vascular tissue or procambium, the apex continued to grow and gave rise to a short vasculated leafy shoot in which the normal anatomical pattern was soon reconstituted. Relevant data for Dryopteris aristata have appeared in earlier volumes of these Transactions . Comparable data for eusporangiate and other leptosporangiate ferns are now described and illustrated. In Primula , in and just above the region of the incisions, the vascular tissue of the new axial growth was in the form of an uninterrupted ‘cylinder’, conforming in outline with the triangular or rectangular contour of the isolated plug. The experimental materials have afforded clear evidence of a basipetal development of vascular tissue from pith cells, strands of the new vascular system eventually becoming conjoined with those of the parent shoot. In the leaf-bearing region of the new shoot the vascular cylinder was interrupted by leaf gaps as in the normal development in Primula and in ferns. A prevascular ring, with foliar gaps in the regions of leaf insertion, is present at the shoot apex in Primula , this being comparable with the arrangements in ferns such as Dryopteris. When all the very young leaf promordia were successively removed, the shoot was found to have an uninterrupted ring of vascular tissue, as in equivalent experiments with Dryopteris and other ferns. The experimental data so far obtained thus show that when the same treatments are applied to very differently constituted apices, closely comparable results are obtained. The implications of this finding are discussed in relation to (i) the importance of the cellular constitution of apices in organogenesis, (ii) the the diversity of apical constitution in vascular plants at large, (iii) the apex as a self-determining region, (iv) the inception and subsequent development of the vascular system in different classes of plants, and (v) the relative contributions of axis and leaves to the vascular system.

THE EFFECT OF LIGHT INTENSITY AND TEMPERATURE ON FLORAL INITIATION AND INFLORESCENCE DEVELOPMENT OF MARQUIS WHEAT

1963 ◽  
Vol 41 (12) ◽  
pp. 1663-1674 ◽  
Author(s):  
D. J. C. Friend ◽  
J. E. Fisher ◽  
V. A. Helson
Keyword(s):  
Light Intensity ◽  
Apical Meristem ◽  
High Light ◽  
Leaf Primordia ◽  
Leaf Number ◽  
Continuous Illumination ◽  
Floral Initiation ◽  
Main Shoot ◽  
Inflorescence Development ◽  
Effect Of Light

Under continuous illumination, floral initiation was earlier with each increase in light intensity from 200 to 2500 ft-c, and with each increase in temperature between 10 and 30 °C. This effect of light intensity is attributed to promotion of floral initiation by energy in the far-red (730 mμ).The rate of formation of leaf primordia was accelerated by increases in light intensity to a greater extent than floral initiation, so that the final leaf number on the main shoot was greatest for the plants grown at high light intensities. Between 10 and 25 °C an increase in temperature had similar effects on the rate of formation of leaf primordia and floral initiation, so that the final leaf number was not altered. The final leaf number was lower at 30 °C than at 25 °C because leaf primordium formation was retarded.After floral initiation, the growth of the apical meristem was most rapid at 30 °C and 2500 ft-c, resulting in the earliest heading and anthesis (33 and 38 days). Low temperatures strongly retarded the later stages of ear development and emergence.

scholarly journals Extended expression of MaKN1 contributes to the leaf morphology in aquatic forms of Myriophyllum aquaticum

Botany ◽  
2015 ◽  
Vol 93 (9) ◽  
pp. 611-621
Author(s):  
M.D. Shafiullah ◽  
Christian R. Lacroix
Keyword(s):  
Apical Meristem ◽  
Leaf Morphology ◽  
Expression Patterns ◽  
Homeobox Gene ◽  
Leaf Primordia ◽  
Leaf Primordium ◽  
Myriophyllum Aquaticum ◽  
Knox Gene ◽  
Leaf Morphogenesis

Myriophyllum aquaticum (Vell.) Verdc. is heterophyllous in nature with highly dissected simple leaves consisting of several lobes. KNOX (KNOTTED1-LIKE HOMEOBOX) genes are believed to have played an important role in the evolution of leaf diversity. Up-regulation of KNOX during leaf primordium initiation can lead to leaf dissection in plants with simple leaves and, if overexpressed, can produce ectopic meristems on leaves. A previous study on KNOX gene expression in the aerial form of this species showed that this gene is expressed in the shoot apical meristem (SAM), as well as in leaf primordia P0 to P8. Based on these results, it was hypothesized that the prolonged expression of the MaKN1 (Myriophyllum aquaticum Knotted1-like homeobox) gene beyond P8, might play an important role in the generation of more lobes, longer lobes, and hydathode formation in the aquatic leaves of M. aquaticum. The technique of in situ hybridization was carried out using a previously sequenced 300 bp fragment of MaKN1 to determine the expression patterns of this gene in the shoot of aquatic forms of the plant. Expression patterns of MaKN1 revealed that the SAM and leaf primordia of aquatic forms of M. aquaticum at levels P0 (youngest) to P4 were distributed throughout these structures. The level of expression of this MaKN1 gene progressively became more localized to lobes in older leaf primordia (levels P5 to P12). Previous studies of aerial forms of this plant showed MaKN1 expression until P8. Our results with aquatic forms show that the highly dissected leaf morphology in aquatic forms was the result of the prolonged expression of MaKN1 beyond P8. This resulted in the formation of elongated and slightly more numerous lobes, and hydathodes in aquatic forms. These findings support the view that KNOX genes are important developmental regulators of leaf morphogenesis and have played an important role in the evolution of leaf forms in the plant kingdom.

Phyllotaxis of the palm Euterpe oleracea Mart. at the level of the shoot apical meristem

Botany ◽  
2010 ◽  
Vol 88 (5) ◽  
pp. 528-536 ◽  
Author(s):  
Denis Barabé ◽  
Laura Bourque ◽  
Xiaofeng Yin ◽  
Christian Lacroix
Keyword(s):  
Shoot Apical Meristem ◽  
Fundamental Theorem ◽  
Apical Meristem ◽  
Leaf Primordia ◽  
Leaf Primordium ◽  
Divergence Angle ◽  
Euterpe Oleracea ◽  
The Mean ◽  
The Relationship ◽  
Euterpe Oleracea Mart

Previous studies on palm phyllotaxis deal mainly with the mature trunk. The goals of this study are (i) to determine the relationship between the number of parastichies, the divergence angle, and the plastochrone ratio at the level of the shoot apical meristem; (ii) to examine whether there are fluctuations in the divergence angle; (iii) to interpret the significance of phyllotactic parameters with respect to the mode of growth of the apex. The tubular base of the leaf primordium is more or less asymmetrical, and completely surrounds the shoot apical meristem. The phyllotactic system corresponds to a (2, 3) conspicuous parastichy pair. The mean divergence angle per apex varies between 126.9° ± 9.3° (mean ± SD) and 135. 8° ± 8.0°. Divergence angles for all apices fluctuate within a range of 115.89° to 157.33°. The mean plastochrone ratios between apices varies from 1.35 ± 0.18 to 1.58 ± 0.12. The plastochrone ratio at each plastochrone for all apices ranges from 1.09 to 2.00. There is no correlation between the angle of divergence and the plastochrone ratio. There is a fluctuation in the value of the divergence angle that falls within the range predicted by the fundamental theorem of phyllotaxis. The high value of the ratio of the diameter of leaf primordia over the diameter of the apex, and the long plastochrone might explain the lack of correlation between certain phyllotactic parameters.

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