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Influence of clavata3-2 mutation on early flower development in Arabidopsis thaliana: quantitative analysis of changing geometry.

Szczesny T, Routier-Kierzkowska AL, Kwiatkowska D - J. Exp. Bot. (2008)

Bottom Line: In particular, the shape of the adaxial primordium boundary varies and seems to be related to the shape of the space available for the given primordium formation, suggesting that physical constraints play a significant role in primordium shape determination.Moreover, there is only one tunica layer in both the meristem and in the primordium until it becomes a bulge that is distinctly separated from the meristem.Starting from this stage, the anticlinal divisions predominate in subprotodermal cells, suggesting that the distribution of periclinal and anticlinal cell divisions in the early development of the flower primordium is not directly affected by the clv3-2 mutation.

View Article: PubMed Central - PubMed

Affiliation: Institute of Plant Biology, University of Wrocław, Kanonia 6/8, 50-328 Wrocław, Poland.

ABSTRACT
Early development of the flower primordium has been studied in Arabidopsis thaliana clavata3-2 (clv3-2) plants with the aid of sequential in vivo replicas and longitudinal microtome sections. Sequential replicas show that, although there is no regular phyllotaxis in the clv3-2 inflorescence shoot apex, the sites of new primordium formation are, to a large extent, predictable. The primordium always appears in a wedge-like region of the meristem periphery flanked by two older primordia. In general, stages of primordium development in clv3-2 are similar to the wild type, but quantitative geometry analysis shows that the clv3-2 primordium shape is affected even before the CLAVATA/WUSCHEL regulatory network would start to operate in the wild-type primordium. The shape of the youngest primordium in the mutant is more variable than in the wild type. In particular, the shape of the adaxial primordium boundary varies and seems to be related to the shape of the space available for the given primordium formation, suggesting that physical constraints play a significant role in primordium shape determination. The role of physical constraints is also manifested in that the shape of the primordium in the later stages, as well as the number and position of sepals, are adjusted to the available space. Longitudinal sections of clv3-2 apices show that the shape of surface cells of the meristem and young primordium is different from the wild type. Moreover, there is only one tunica layer in both the meristem and in the primordium until it becomes a bulge that is distinctly separated from the meristem. Starting from this stage, the anticlinal divisions predominate in subprotodermal cells, suggesting that the distribution of periclinal and anticlinal cell divisions in the early development of the flower primordium is not directly affected by the clv3-2 mutation.

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Schematic surfaces representing different shapes exhibited by the flower primordium during its development: cone-like structure in which the tip of a cone is replaced by a rounded cap (A); nearly hemispherical shape (B); cavity-like shape (C); crease (D). Exemplary crosses, plotted on the surfaces, represent the principal directions of curvature. Cross arm lengths are proportional to the curvature in a given direction. The arm is plotted as a solid line if, in this direction, the surface is convex, and as a dashed line if it is concave.
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fig2: Schematic surfaces representing different shapes exhibited by the flower primordium during its development: cone-like structure in which the tip of a cone is replaced by a rounded cap (A); nearly hemispherical shape (B); cavity-like shape (C); crease (D). Exemplary crosses, plotted on the surfaces, represent the principal directions of curvature. Cross arm lengths are proportional to the curvature in a given direction. The arm is plotted as a solid line if, in this direction, the surface is convex, and as a dashed line if it is concave.

Mentions: Before analysing changes in primordium geometry it is convenient to describe the curvature of several characteristic shapes that a primordium may resemble (Fig. 2). A surface of nearly hemispherical bulge (Fig. 2B), at every point, is convex in all directions. Thus, the plots of its principal curvature directions are crosses with nearly equal arms and the curvature in these directions is positive, while the Gaussian curvature (a product of the principal curvatures) is almost uniform and positive on the whole surface. Another type of bulge resembles a cone-like structure, the tip having been replaced by a cap (Fig. 2A). Its curvature is different at different points on the surface, although the Gaussian curvature is positive everywhere. On the sides of the cone the directions of maximal curvature are meridional (perpendicular to the axis). There is a big difference between the maximal and minimal curvatures. On the cap part, the curvatures in the principal curvature directions are all similar to each other, while the value of the Gaussian curvature is elevated. A cavity-like surface (Fig. 2C) also has positive Gaussian curvature, but at every point it is concave in all directions and both the principal curvature values are negative. The last type of shape, a crease, resembles a saddle and is characterized by negative Gaussian curvature (Fig. 2D). At every point it is convex in one principal direction and concave in the other, meaning that the values of the principal curvatures are of opposite signs.


Influence of clavata3-2 mutation on early flower development in Arabidopsis thaliana: quantitative analysis of changing geometry.

Szczesny T, Routier-Kierzkowska AL, Kwiatkowska D - J. Exp. Bot. (2008)

Schematic surfaces representing different shapes exhibited by the flower primordium during its development: cone-like structure in which the tip of a cone is replaced by a rounded cap (A); nearly hemispherical shape (B); cavity-like shape (C); crease (D). Exemplary crosses, plotted on the surfaces, represent the principal directions of curvature. Cross arm lengths are proportional to the curvature in a given direction. The arm is plotted as a solid line if, in this direction, the surface is convex, and as a dashed line if it is concave.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC2651453&req=5

fig2: Schematic surfaces representing different shapes exhibited by the flower primordium during its development: cone-like structure in which the tip of a cone is replaced by a rounded cap (A); nearly hemispherical shape (B); cavity-like shape (C); crease (D). Exemplary crosses, plotted on the surfaces, represent the principal directions of curvature. Cross arm lengths are proportional to the curvature in a given direction. The arm is plotted as a solid line if, in this direction, the surface is convex, and as a dashed line if it is concave.
Mentions: Before analysing changes in primordium geometry it is convenient to describe the curvature of several characteristic shapes that a primordium may resemble (Fig. 2). A surface of nearly hemispherical bulge (Fig. 2B), at every point, is convex in all directions. Thus, the plots of its principal curvature directions are crosses with nearly equal arms and the curvature in these directions is positive, while the Gaussian curvature (a product of the principal curvatures) is almost uniform and positive on the whole surface. Another type of bulge resembles a cone-like structure, the tip having been replaced by a cap (Fig. 2A). Its curvature is different at different points on the surface, although the Gaussian curvature is positive everywhere. On the sides of the cone the directions of maximal curvature are meridional (perpendicular to the axis). There is a big difference between the maximal and minimal curvatures. On the cap part, the curvatures in the principal curvature directions are all similar to each other, while the value of the Gaussian curvature is elevated. A cavity-like surface (Fig. 2C) also has positive Gaussian curvature, but at every point it is concave in all directions and both the principal curvature values are negative. The last type of shape, a crease, resembles a saddle and is characterized by negative Gaussian curvature (Fig. 2D). At every point it is convex in one principal direction and concave in the other, meaning that the values of the principal curvatures are of opposite signs.

Bottom Line: In particular, the shape of the adaxial primordium boundary varies and seems to be related to the shape of the space available for the given primordium formation, suggesting that physical constraints play a significant role in primordium shape determination.Moreover, there is only one tunica layer in both the meristem and in the primordium until it becomes a bulge that is distinctly separated from the meristem.Starting from this stage, the anticlinal divisions predominate in subprotodermal cells, suggesting that the distribution of periclinal and anticlinal cell divisions in the early development of the flower primordium is not directly affected by the clv3-2 mutation.

View Article: PubMed Central - PubMed

Affiliation: Institute of Plant Biology, University of Wrocław, Kanonia 6/8, 50-328 Wrocław, Poland.

ABSTRACT
Early development of the flower primordium has been studied in Arabidopsis thaliana clavata3-2 (clv3-2) plants with the aid of sequential in vivo replicas and longitudinal microtome sections. Sequential replicas show that, although there is no regular phyllotaxis in the clv3-2 inflorescence shoot apex, the sites of new primordium formation are, to a large extent, predictable. The primordium always appears in a wedge-like region of the meristem periphery flanked by two older primordia. In general, stages of primordium development in clv3-2 are similar to the wild type, but quantitative geometry analysis shows that the clv3-2 primordium shape is affected even before the CLAVATA/WUSCHEL regulatory network would start to operate in the wild-type primordium. The shape of the youngest primordium in the mutant is more variable than in the wild type. In particular, the shape of the adaxial primordium boundary varies and seems to be related to the shape of the space available for the given primordium formation, suggesting that physical constraints play a significant role in primordium shape determination. The role of physical constraints is also manifested in that the shape of the primordium in the later stages, as well as the number and position of sepals, are adjusted to the available space. Longitudinal sections of clv3-2 apices show that the shape of surface cells of the meristem and young primordium is different from the wild type. Moreover, there is only one tunica layer in both the meristem and in the primordium until it becomes a bulge that is distinctly separated from the meristem. Starting from this stage, the anticlinal divisions predominate in subprotodermal cells, suggesting that the distribution of periclinal and anticlinal cell divisions in the early development of the flower primordium is not directly affected by the clv3-2 mutation.

Show MeSH
Related in: MedlinePlus