Figure 1.
Seedlings of Polaskia chichipe and Echinocactus platyacanthus at three developmental stages and two water availability conditions.
DAG: days after germination. Scale bar 1 mm for all images.
Figure 2.
Morphometric analysis of seedling shape and size.
A,B: 30-point template to capture the shape of both Polaskia chichipe and Echinocactus platyacanthus seedlings. Open circles correspond to primary landmarks which are placed on recognizable features of the seedlings (base, cotyledonary areoles, and apex); filled circles correspond to secondary landmarks evenly spaced between primary landmarks. C: Example of the 30-point model template fitted onto a photographed seedling. D: Principal Component Analysis of Polaskia chichipe (PCAPol) and Echinocactus platyacanthus (PCAEch) seedlings. Mean shapes with and without procrustes for size are shown. SD: Standard deviation. PC1Pol shows elongation of the apex with size effects.
Figure 3.
Quantification of the morphology and the anatomy in cacti seedlings.
A–C: The morphology of Polaskia chichipe expressed as PCPol. D–E: The number and area of xylem vessels in Polaskia chichipe. F–H: The morphology of Echinocactus platyacanthus represented as PCEch. I–J: The number and area of vessels in Echinocactus platyacanthus. D–E,I–J: Significant PCs from the regression yi = βPC1+βPC2+βPC3+εi are highlighted. * p<0.5, *** p<0.0005. Error bars represent standard error. DAG: days after germination.
Figure 4.
Histological sections and schematic representations of Echinocactus platycanthus hypocotyls.
Transversal sections were obtained 3–4 mm above the base of the shoot. A: Seedling of a Control treatment. B Seedling of a Stress treatment. C Vascular bundle area showing details of the collapsible cells and areas of collapsible tissue. D: Section of parenchyma showing turgid cells next to collapsed cells. E–F: Schematic representation of B,C respectively: turgid cells in green, collapsed cells in grey, xylem cells in red, and phloem cells in blue. A–B: Bright field microscopy; C–D: Phase contrast microscopy. White arrows show a turgid cell, black arrows show groups of collapsible cells. Scale bar 100 µm. CO: cortex; PI: pith; VB: vascular bundle.