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Developmental reaction norms for water stressed seedlings of succulent cacti.

Rosas U, Zhou RW, Castillo G, Collazo-Ortega M - PLoS ONE (2012)

Bottom Line: The anatomy was quantified as number and area of xylem vessels.These tissues were located inside the epidermis, resembling a web of collapsible-cell groups surrounding turgid cells, vascular bundles, and spanned across the pith.Occasionally the groups formed a continuum stretching from the epidermis towards the vasculature.

View Article: PubMed Central - PubMed

Affiliation: Center for Genomics and Systems Biology, New York University, New York City, New York, United States of America. ur6@nyu.edu

ABSTRACT
Succulent cacti are remarkable plants with capabilities to withstand long periods of drought. However, their adult success is contingent on the early seedling stages, when plants are highly susceptible to the environment. To better understand their early coping strategies in a challenging environment, two developmental aspects (anatomy and morphology) in Polaskia chichipe and Echinocactus platyacanthus were studied in the context of developmental reaction norms under drought conditions. The morphology was evaluated using landmark based morphometrics and Principal Component Analysis, which gave three main trends of the variation in each species. The anatomy was quantified as number and area of xylem vessels. The quantitative relationship between morphology and anatomy in early stages of development, as a response to drought was revealed in these two species. Qualitatively, collapsible cells and collapsible parenchyma tissue were observed in seedlings of both species, more often in those subjected to water stress. These tissues were located inside the epidermis, resembling a web of collapsible-cell groups surrounding turgid cells, vascular bundles, and spanned across the pith. Occasionally the groups formed a continuum stretching from the epidermis towards the vasculature. Integrating the morphology and the anatomy in a developmental context as a response to environmental conditions provides a better understanding of the organism's dynamics, adaptation, and plasticity.

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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.
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pone-0033936-g004: 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.

Mentions: In adult cacti, most of the tissue is constituted by water storage parenchyma with cellular spaces that are mostly occupied by the vacuole. In some parenchyma regions, however, turgid cells are adjacent to collapsed cells, which have been named the collapsible tissue [27], [28]. This is because the cell walls in the collapsible tissue have properties that allow the cells to expand and shrink to store water, presumably as a response to the water availability conditions. This phenomenon has been reported in seedlings of another cactus [18], and was observed in seedlings of P. chichipe and E. platyacanthus. In the seedling stage, the parenchyma cells are very similar between these two species, thus for simplicity only the latter is shown. The collapsible tissue was observed more often in seedlings that were subjected to the water stress treatment (Figures 4A and 4B). Groups of collapsed cells were located inside the epidermis, resembling webs surrounding turgid cells (Figure 4B and 4E), around the vascular bundles, spanning across the pith (Figure 4C and 4F) and in the cortex (Figure 4D).


Developmental reaction norms for water stressed seedlings of succulent cacti.

Rosas U, Zhou RW, Castillo G, Collazo-Ortega M - PLoS ONE (2012)

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.
© Copyright Policy
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC3316504&req=5

pone-0033936-g004: 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.
Mentions: In adult cacti, most of the tissue is constituted by water storage parenchyma with cellular spaces that are mostly occupied by the vacuole. In some parenchyma regions, however, turgid cells are adjacent to collapsed cells, which have been named the collapsible tissue [27], [28]. This is because the cell walls in the collapsible tissue have properties that allow the cells to expand and shrink to store water, presumably as a response to the water availability conditions. This phenomenon has been reported in seedlings of another cactus [18], and was observed in seedlings of P. chichipe and E. platyacanthus. In the seedling stage, the parenchyma cells are very similar between these two species, thus for simplicity only the latter is shown. The collapsible tissue was observed more often in seedlings that were subjected to the water stress treatment (Figures 4A and 4B). Groups of collapsed cells were located inside the epidermis, resembling webs surrounding turgid cells (Figure 4B and 4E), around the vascular bundles, spanning across the pith (Figure 4C and 4F) and in the cortex (Figure 4D).

Bottom Line: The anatomy was quantified as number and area of xylem vessels.These tissues were located inside the epidermis, resembling a web of collapsible-cell groups surrounding turgid cells, vascular bundles, and spanned across the pith.Occasionally the groups formed a continuum stretching from the epidermis towards the vasculature.

View Article: PubMed Central - PubMed

Affiliation: Center for Genomics and Systems Biology, New York University, New York City, New York, United States of America. ur6@nyu.edu

ABSTRACT
Succulent cacti are remarkable plants with capabilities to withstand long periods of drought. However, their adult success is contingent on the early seedling stages, when plants are highly susceptible to the environment. To better understand their early coping strategies in a challenging environment, two developmental aspects (anatomy and morphology) in Polaskia chichipe and Echinocactus platyacanthus were studied in the context of developmental reaction norms under drought conditions. The morphology was evaluated using landmark based morphometrics and Principal Component Analysis, which gave three main trends of the variation in each species. The anatomy was quantified as number and area of xylem vessels. The quantitative relationship between morphology and anatomy in early stages of development, as a response to drought was revealed in these two species. Qualitatively, collapsible cells and collapsible parenchyma tissue were observed in seedlings of both species, more often in those subjected to water stress. These tissues were located inside the epidermis, resembling a web of collapsible-cell groups surrounding turgid cells, vascular bundles, and spanned across the pith. Occasionally the groups formed a continuum stretching from the epidermis towards the vasculature. Integrating the morphology and the anatomy in a developmental context as a response to environmental conditions provides a better understanding of the organism's dynamics, adaptation, and plasticity.

Show MeSH
Related in: MedlinePlus