Limits...
Morphogenesis at the inflorescence shoot apex of Anagallis arvensis: surface geometry and growth in comparison with the vegetative shoot.

Kwiatkowska D, Routier-Kierzkowska AL - J. Exp. Bot. (2009)

Bottom Line: Although the shapes of all the three types of primordia are very similar during their early developmental stages, areal growth rates and anisotropy of apex surface growth accompanying formation of leaf or bract primordia are profoundly different from those during formation of flower primordia.The replica method does not enable direct analysis of growth in the direction perpendicular to the apex surface (anticlinal direction).Moreover, the position of this slowly growing zone with respect to cells is not stable in the course of the meristem ontogeny.

View Article: PubMed Central - PubMed

Affiliation: Department of Biophysics and Morphogenesis of Plants, University of Silesia, Jagiellońska 28, 40-032 Katowice, Poland. Dorota.Kwiatkowska@us.edu.pl

ABSTRACT
Quantitative analysis of geometry and surface growth based on the sequential replica method is used to compare morphogenesis at the shoot apex of Anagallis arvensis in the reproductive and vegetative phases of development. Formation of three types of lateral organs takes place at the Anagallis shoot apical meristem (SAM): vegetative leaf primordia are formed during the vegetative phase and leaf-like bracts and flower primordia during the reproductive phase. Although the shapes of all the three types of primordia are very similar during their early developmental stages, areal growth rates and anisotropy of apex surface growth accompanying formation of leaf or bract primordia are profoundly different from those during formation of flower primordia. This provides an example of different modes of de novo formation of a given shape. Moreover, growth accompanying the formation of the boundary between the SAM and flower primordium is entirely different from growth at the adaxial leaf or bract primordium boundary. In the latter, areal growth rates at the future boundary are the lowest of all the apex surface, while in the former they are relatively very high. The direction of maximal growth rate is latitudinal (along the future boundary) in the case of leaf or bract primordium but meridional (across the boundary) in the case of flower. The replica method does not enable direct analysis of growth in the direction perpendicular to the apex surface (anticlinal direction). Nevertheless, the reconstructed surfaces of consecutive replicas taken from an individual apex allow general directions of SAM surface bulging accompanying primordium formation to be recognized. Precise alignment of consecutive reconstructions shows that the direction of initial bulging during the leaf or bract formation is nearly parallel to the shoot axis (upward bulging), while in the case of flower it is perpendicular to the axis (lateral bulging). In future, such 3D reconstructions can be used to assess displacement velocity fields so that growth in the anticlinal direction can be assessed. In terms of self-perpetuation, the inflorescence SAM of Anagallis differs from the SAM in the vegetative phase in that the centrally located region of slow growth is less distinct in the inflorescence SAM. Moreover, the position of this slowly growing zone with respect to cells is not stable in the course of the meristem ontogeny.

Show MeSH

Related in: MedlinePlus

The developmental sequence of a second inflorescence shoot apex of Anagallis arvensis exhibiting spiral Fibonacci phyllotaxis, illustrating the earliest stages of bract primordium development (primordium P2) and the origin of flower primordium (primordium F3). Scanning electromicrographs (A–C) and curvature plots (D–F) for the sequence of three replicas are shown. Labelling as in Fig. 1. Bar=30 μm.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
getmorefigures.php?uid=PMC2724690&req=5

fig2: The developmental sequence of a second inflorescence shoot apex of Anagallis arvensis exhibiting spiral Fibonacci phyllotaxis, illustrating the earliest stages of bract primordium development (primordium P2) and the origin of flower primordium (primordium F3). Scanning electromicrographs (A–C) and curvature plots (D–F) for the sequence of three replicas are shown. Labelling as in Fig. 1. Bar=30 μm.

Mentions: During the next stage, the bract primordium is separated from the SAM (the separation stage). This leads to formation of a distinct, saddle-shaped crease between the primordium and SAM, i.e. the future bract axil. The crease is usually composed of two to three latitudinal rows of cells. It is concave in the meridional direction and convex in the latitudinal direction (like the axil of P3 in Fig. 1C, G; or P3 in Fig. 2A, B, D, E). The duration of the separation stage is again about half the plastochron. Cells contributing to formation of the crease are the cells assigned to the bract primordium at the earlier developmental stage and often also SAM cells adjacent to the primordium (compare P3 in Fig. 1A, E and C, G; and P2 in Fig. 2B, E and C, F). During the separation stage, the bract primordium attains a flattened shape. Once the saddle-shaped crease, i.e. the future axil, is formed, flower primordium formation begins.


Morphogenesis at the inflorescence shoot apex of Anagallis arvensis: surface geometry and growth in comparison with the vegetative shoot.

Kwiatkowska D, Routier-Kierzkowska AL - J. Exp. Bot. (2009)

The developmental sequence of a second inflorescence shoot apex of Anagallis arvensis exhibiting spiral Fibonacci phyllotaxis, illustrating the earliest stages of bract primordium development (primordium P2) and the origin of flower primordium (primordium F3). Scanning electromicrographs (A–C) and curvature plots (D–F) for the sequence of three replicas are shown. Labelling as in Fig. 1. Bar=30 μm.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC2724690&req=5

fig2: The developmental sequence of a second inflorescence shoot apex of Anagallis arvensis exhibiting spiral Fibonacci phyllotaxis, illustrating the earliest stages of bract primordium development (primordium P2) and the origin of flower primordium (primordium F3). Scanning electromicrographs (A–C) and curvature plots (D–F) for the sequence of three replicas are shown. Labelling as in Fig. 1. Bar=30 μm.
Mentions: During the next stage, the bract primordium is separated from the SAM (the separation stage). This leads to formation of a distinct, saddle-shaped crease between the primordium and SAM, i.e. the future bract axil. The crease is usually composed of two to three latitudinal rows of cells. It is concave in the meridional direction and convex in the latitudinal direction (like the axil of P3 in Fig. 1C, G; or P3 in Fig. 2A, B, D, E). The duration of the separation stage is again about half the plastochron. Cells contributing to formation of the crease are the cells assigned to the bract primordium at the earlier developmental stage and often also SAM cells adjacent to the primordium (compare P3 in Fig. 1A, E and C, G; and P2 in Fig. 2B, E and C, F). During the separation stage, the bract primordium attains a flattened shape. Once the saddle-shaped crease, i.e. the future axil, is formed, flower primordium formation begins.

Bottom Line: Although the shapes of all the three types of primordia are very similar during their early developmental stages, areal growth rates and anisotropy of apex surface growth accompanying formation of leaf or bract primordia are profoundly different from those during formation of flower primordia.The replica method does not enable direct analysis of growth in the direction perpendicular to the apex surface (anticlinal direction).Moreover, the position of this slowly growing zone with respect to cells is not stable in the course of the meristem ontogeny.

View Article: PubMed Central - PubMed

Affiliation: Department of Biophysics and Morphogenesis of Plants, University of Silesia, Jagiellońska 28, 40-032 Katowice, Poland. Dorota.Kwiatkowska@us.edu.pl

ABSTRACT
Quantitative analysis of geometry and surface growth based on the sequential replica method is used to compare morphogenesis at the shoot apex of Anagallis arvensis in the reproductive and vegetative phases of development. Formation of three types of lateral organs takes place at the Anagallis shoot apical meristem (SAM): vegetative leaf primordia are formed during the vegetative phase and leaf-like bracts and flower primordia during the reproductive phase. Although the shapes of all the three types of primordia are very similar during their early developmental stages, areal growth rates and anisotropy of apex surface growth accompanying formation of leaf or bract primordia are profoundly different from those during formation of flower primordia. This provides an example of different modes of de novo formation of a given shape. Moreover, growth accompanying the formation of the boundary between the SAM and flower primordium is entirely different from growth at the adaxial leaf or bract primordium boundary. In the latter, areal growth rates at the future boundary are the lowest of all the apex surface, while in the former they are relatively very high. The direction of maximal growth rate is latitudinal (along the future boundary) in the case of leaf or bract primordium but meridional (across the boundary) in the case of flower. The replica method does not enable direct analysis of growth in the direction perpendicular to the apex surface (anticlinal direction). Nevertheless, the reconstructed surfaces of consecutive replicas taken from an individual apex allow general directions of SAM surface bulging accompanying primordium formation to be recognized. Precise alignment of consecutive reconstructions shows that the direction of initial bulging during the leaf or bract formation is nearly parallel to the shoot axis (upward bulging), while in the case of flower it is perpendicular to the axis (lateral bulging). In future, such 3D reconstructions can be used to assess displacement velocity fields so that growth in the anticlinal direction can be assessed. In terms of self-perpetuation, the inflorescence SAM of Anagallis differs from the SAM in the vegetative phase in that the centrally located region of slow growth is less distinct in the inflorescence SAM. Moreover, the position of this slowly growing zone with respect to cells is not stable in the course of the meristem ontogeny.

Show MeSH
Related in: MedlinePlus