The numbers of leaflet primordia of each primary leaflet.

<p>A: Schematic of the branched structure of one half of a <i>R</i>. <i>aquatica</i> compound leaf. Circled numbers indicate the positions of primary leaflet (the horizontal axis in B), and theoretically derived recurrence formulas of each primary leaflet are shown by . The red numbers represent the numbers of leaflets formed on the 4^th primary leaflet (the vertical axis in B). B: A comparison between the experimentally observed data in actual plants and theoretically estimated numbers derived from mathematical formulae of leaflet on each primary leaflet. The magenta dots show the data from mature leaves. The number of leaflets at each stage was plotted as aligned at the center. The theoretical estimations are represented on a yellow planar graph, and the actual data in developing leaves as blue dots with columns.</p

Morphogenesis of <i>Rorippa aquatica</i> leaves.

<p>A, B: Mature leaf morphology of the simple leaf that was developed at 30°C (A) and the highly branched compound leaf that was developed at 20°C (B). Scale bar: 1 cm. C: Dissected shoot apex of a plant grown at 20°C, showing the nested group of leaf primordia with indented blade. D–F: Dissected primordial of a plant grown at 20°C for about 2 months. Each primodium has the 32th (D), 35th (E), and 39th (F) leaf primordium from the oldest (i.e. outermost) leaf of a plant. The larger leaf position numbers indicate younger leaves. Scale bar: 1 mm (C) and 200 µm (D–F). G: Comparison of the total number of leaflet primordial between experimentally observed and the theoretically estimated value.</p

Spatiotemporal plot and growth profiles for the BPM rings by pattern dependent expansion.

<p>A: Schematic of the modeling. B: Spatiotemporal plot for peak doubling by insertion. The value of reactant is represented by the gray scale. Each panel shows the first (C), second (D), third (E), and fourth (F) insertion. Each point indicate the middle point of segmented cell, then the color of points indicate the value of reactant <i>u</i>. Solid arrowheads indicate the points of peak insertion, and empty arrowheads are points of side branch generation.</p

Simulations of leaf primordia and branches.

<p>Each panel shows the simulated whole leaves (A–C) and primary leaflets (D–H). The simulated branches were crossover. Each branch was independently formed nested regular branches. The inserted number shows the time of iterative calculations (), and the arrowheads indicate each leaflet; filled, flamed, and dotted arrow heads represent the first, second, and third primary leaflet respectively.</p

Spatiotemporal plot and growth profiles for the BPM rings by Expansion inhibition.

<p>A: Spatiotemporal plot for peak doubling by splitting. The value of reactant is represented by the gray scale. Each panel shows the first (B), second (C), third (D), and fourth (E) splitting. Each point indicate the middle point of segmented cell, then the color of points indicate the value of reactant <i>u</i>. Solid arrowheads indicate the points of peak splitting, and empty arrowheads are points of side branch generation.</p

A Decrease in Ambient Temperature Induces Post-Mitotic Enlargement of Palisade Cells in North American Lake Cress

<div><p>In order to maintain organs and structures at their appropriate sizes, multicellular organisms orchestrate cell proliferation and post-mitotic cell expansion during morphogenesis. Recent studies using Arabidopsis leaves have shown that compensation, which is defined as post-mitotic cell expansion induced by a decrease in the number of cells during lateral organ development, is one example of such orchestration. Some of the basic molecular mechanisms underlying compensation have been revealed by genetic and chimeric analyses. However, to date, compensation had been observed only in mutants, transgenics, and γ-ray–treated plants, and it was unclear whether it occurs in plants under natural conditions. Here, we illustrate that a shift in ambient temperature could induce compensation in <i>Rorippa aquatica</i> (Brassicaceae), a semi-aquatic plant found in North America. The results suggest that compensation is a universal phenomenon among angiosperms and that the mechanism underlying compensation is shared, in part, between Arabidopsis and <i>R</i>. <i>aquatica</i>.</p></div

Observation of epidermal cells from plants grown at 30°C and 20°C.

<p>(A) Epidermal cells in LN6 of <i>Rorippa aquatica</i> grown at 30°C (left) and 20°C (right). The upper panels show images of epidermal cells, and the lower panels show the silhouettes of randomly selected cells. Scale bars = 50 μm. (B) Epidermal cell area. (C) Dissection index (DI) of epidermal cells. Error bars represent the standard error (SE); * = <i>p</i> < 0.05 by Student’s <i>t</i>-test (<i>n</i> = 6).</p

Cellular phenotypes of leaves from plants grown at 30°C and 20°C.

<p>(A) Palisade cells in LN6 of <i>Rorippa aquatica</i> grown at 30°C (left) and 20°C (right). The upper panels show differential interference microscopy images, and the lower panels show the silhouettes of randomly selected cells. Scale bars = 100 μm. (B–D) Leaf area, number of cells per 100 mm², and palisade cell area, respectively. Error bars represent the standard error (SE); * = <i>p</i> < 0.05; ** = <i>p</i> < 0.01 by Student’s <i>t</i>-test (<i>n</i> = 6).</p

Expression analyses of orthologous genes related to compensation.

<p>(A) Schematic presentation of three classes of compensation. (B) Expression levels of Ra <i>AN3</i>, Ra <i>ERECTA</i>, Ra <i>FUGU2</i>, Ra <i>FUGU5</i>, and Ra <i>KRP2</i> in leaf primordia of <i>Rorippa aquatica</i> grown at 30°C and 20°C. Error bars represent the standard error (SE). * = <i>p</i> < 0.05 by Welch’s <i>t-</i>test (<i>n</i> = 4).</p

Observation of inner structure of leaves of <i>Rorippa aquatica</i> grown at 30°C and 20°C.

<p>(A) Inner cells in LN6 leaf blade of <i>R</i>. <i>aquatica</i> grown at 30°C (left) and 20°C (right). Cross-sections in the upper panels show images of inner leaf tissue cells, and the lower panels show the silhouettes of randomly selected cells. Scale bars = 100 μm. (B) Area of inner cells. (C) Thickness of leaves. Error bars represent the standard error (SE) (<i>n</i> = 6).</p