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. 2018 Apr 23;7:e34460. doi: 10.7554/eLife.34460

Figure 4. A mechanical conflict at the petiole-blade junction in cotyledons.

(A–D) Z-projections (maximal intensity) of confocal stacks from representative, propidium iodide stained, 3-day (A) or 5-day (B) old WT cotyledons and 3-day (C) or 5-day (D) old qua1-1 cotyledons grown on 1% (A, C) and 2.5% (B,D) agar medium. (E–H) Surface signal extracted from confocal stacks, of representative GFP-MBD cotyledons grown on 1% (E,G; n = 12 cotyledons) and 2.5% (F,H; n = 13 cotyledons) agar medium. Red lines are the output of the FibrilTool macro for the blade region (E (n = 898 cells), F (n = 639 cells)) and petiole-blade junction (G (n = 550 cells), H (n = 425 cells)). The polar histograms in C and D show the global distribution of cell separation orientation in qua1-1 cotyledons (respectively 12 and 8 samples from three biological replicates); the polar histograms in E-H show the distribution of microtubule array orientations for 12 samples. (I) Schematic representation of the effect of differential growth from the cotyledon and the petiole resulting in a mechanical conflict at the junction with higher tensile stress. The close-up image is extracted from a petiole-blade junction in the qua1-1 mutant. Scale bars, 100 µm.

Figure 4.

Figure 4—figure supplement 1. Mechanical assessment of the cotyledon’s petiole-blade junction by AFM.

Figure 4—figure supplement 1.

Box plots of the turgor pressure P (A), cell wall elastic modulus E (B), apparent stiffness k (C) and cell wall tension σ (D) comparing cells at the blade and at the petiole-blade junction (see Figure 4) from wild-type seedlings grown on 2.5% agar medium. Measurements on each domain were done pairwise on 10 cotyledons. Circles indicate Tukey’s outliers. Student’s t-test, *** indicates p-value<0.001; *, p-value<0.05; n, number of measured cells.
Figure 4—figure supplement 2. Gaping pattern in the third leaf of qua1-1 seedlings.

Figure 4—figure supplement 2.

(A–B) Z-projections (maximal intensity) of confocal stacks from, propidium iodide stained young leaves from qua1-1 seedlings grown on 1% agar medium. In panel A, the top right corner leaf is the third leaf, and the bottom left corner leaf is the fourth leaf. Leaf in B is the third leaf. Note the presence of longitudinal cracks at the base of the leaves and radial cracks around trichomes. Scale bars, 50 μm.