Apical Meristem Characteristics and Activity in Relation to Juvenility in Hedera

Hackett, Wesley P.; Cordero, Robert E.; Srinivasan, C.

doi:10.1016/b978-0-407-00570-9.50011-9

Cited by 11 publications

(11 citation statements)

References 8 publications

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“…The longest and most prominent files are typically associated with the incipient axillary bud adjacent to the primordium base, indicating that their formation and the inception of the bud may be related. It seems likely that cells in the inner tunica layers of the meristem (Stein and Fosket 1969;Hackett et al 1987) may be arranged accordingly, as in Daphne (Hara 1962), particularly since axillary buds commonly extend several layers deep as shown by the surrounding "shell zone" (Shah and Patel 1972) and the radial-longitudinal displacement undoubtedly involves both the surface and the subjacent layers.…”

Section: Discussionmentioning

confidence: 97%

“…More recent work (Green 1980(Green , 1986Hardham 1982;Jesuthasan and Green 1989;Nelson 1990) has focussed on the possible morphogenetic role of the surface cell layer of the shoot apical meristem. Our work with Hedera, a plant which is particularly suitable for these studies because a phyllotactic shift from spiral to distichous pattern can be induced by a single application of gibberellic acid (GA3) (Rogler and Hackett 1975;Hackett et al 1987), has resulted in several relevant findings. While the size of the primordium-free area of the meristem or the width of existing primordia do not seem to be causally involved, the phyllotactic transition is preceded and accompanied by an increased radiallongitudinal displacement of existing primordia away from the central region of the meristem (Marc and Hackett 1991).…”

Section: Introductionmentioning

confidence: 96%

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Changes in the pattern of cell arrangement at the surface of the shoot apical meristem in Hedera helix L. following gibberellin treatment

Marc

Hackett

1992

Planta

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The changes in the pattern of cell arrangement and surface topography at the shoot apical meristem of Hedera helix L., which occur during gibberellic acid (GA3)-induced transition from spiral to distichous phyllotaxis, were examined by scanning electron microscopy of rapidly frozen tissue. The technique preserves the original shape of the cells in their turgid state. It reveals distinct sets of radially oriented cell files, about four to eight cells wide, which extend from the central region of the meristem toward leaf primordia on the meristem flanks. In apices with spiral phyllotaxis, a new emerging primordium (0) appears as an acropetal bulge between the radial files adjacent to the third (3) and the second (2) older primordia. The bulging is associated with radial or oblique cell divisions while those located at the meristem flanks and in the radial files are oriented tangentially. As the displacement of existing primordia away from the central region increases following the GA3 treatment, radial and oblique divisions as well as acropetal bulging invade the radial files adjacent to the primordium 2; consequently the angular divergence of the emerging primordium from the youngest existing primordium (1) increases. In apices with distichous phyllotaxis, the earliest bulging appears on both sides of the radial files facing primordium 2, with a slight depression at the files. The radial files therefore correspond to regions of the meristem where acropetal bulging is generally delayed, although this effect apparently diminishes with increasing distance of existing primordia from the meristem center.

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Section: Discussionmentioning

confidence: 97%

Section: Introductionmentioning

confidence: 96%

Changes in the pattern of cell arrangement at the surface of the shoot apical meristem in Hedera helix L. following gibberellin treatment

Marc

Hackett

1992

Planta

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“…While leaf primordia that are initiated during the juvenile phase of growth are arranged in a distichous pattern, the arrangement changes to a spiral pattern as the plant matures (Hackett 1985;Hackett et al 1987; see also Poethig 1990). A reversion back to the juvenile distichous pattern can be induced by applying a single dose of gibberellic acid (GA3) to the base of an axillary bud (Robbins 1957;Rogler and Hackett 1975;Hackett et al 1987). We have examined this transition in detail by scanning electron microscopy of the shoot apical meristem from the expanding axillary shoot.…”

Section: Introductionmentioning

confidence: 99%

Gibberellin-induced reorganization of spatial relationships of emerging leaf primordia at the shoot apical meristem in Hedera helix L.

Marc

Hackett

1991

Planta

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The transition from spiral to distichous leaf arrangement during gibberellic-acid (GA3)-induced rejuvenation in Hedera was studied in detail by scanning electron microscopy of the shoot apical meristem. The transition, which involves the initiation of about 14 new leaf primordia, is accomplished by progressive increments in the divergence angle between the leaf primordia from an initial average value of 138.9 ° until it approaches 180 °. This process is preceded, as well as accompanied, by an increased radial displacement of young leaf primordia away from the apical meristem. Although the width of the leaf primordia also increases, this is unlikely to be a causal factor since it occurs only late in the transition. The size of the primordium-free area of the apical meristem is also unlikely to be involved. Quantitative analysis shows that the divergence angle of consecutive leaf primordia commonly fluctuates between relatively large and small values. Thus the transitional stages form a spirodistichous arrangement in which the divergence angle within each pair of leaves is large relative to that between leaf pairs. The stimulation of the radial displacement of the leaf primordia and the associated phyllotactic transition may involve GA3-induced modification in the spatial organization of cortical microtubules in the apical meristem and related changes in directional cell expansion.

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“…We know from experiments performed in the 1960s and 1970s that plant and animal tissues remember a determined state even after prolonged passage in culture (Hadorn 1968;Hackett et al 1987). Hadorn and colleagues showed that imaginal disc cells found in Drosophila larvae have an intrinsic memory, allowing them to remember determined states that are fixed in early embryogenesis.…”

Section: The Concept Of Cellular Memorymentioning

confidence: 99%

Transcriptional Silencing by Polycomb-Group Proteins

Grossniklaus

Paro

2014

Cold Spring Harbor Perspectives in Biology

228

202

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SUMMARYPolycomb-group (PcG) genes encode chromatin proteins involved in stable and heritable transcriptional silencing. PcG proteins participate in distinct multimeric complexes that deposit, or bind to, specific histone modifications (e.g., H3K27me3 and H2AK119ub1) to prevent gene activation and maintain repressed chromatin domains. PcG proteins are evolutionary conserved and play a role in processes ranging from vernalization and seed development in plants, over X-chromosome inactivation in mammals, to the maintenance of stem cell identity. PcG silencing is medically relevant as it is often observed in human disorders, including cancer, and tissue regeneration, which involve the reprogramming of PcGcontrolled target genes.

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Apical Meristem Characteristics and Activity in Relation to Juvenility in Hedera

Cited by 11 publications

References 8 publications

Changes in the pattern of cell arrangement at the surface of the shoot apical meristem in Hedera helix L. following gibberellin treatment

Changes in the pattern of cell arrangement at the surface of the shoot apical meristem in Hedera helix L. following gibberellin treatment

Gibberellin-induced reorganization of spatial relationships of emerging leaf primordia at the shoot apical meristem in Hedera helix L.

Transcriptional Silencing by Polycomb-Group Proteins

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