The development and structure of the guard cell walls in stomata of Funaria (Bryophyta)

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Funaria hygrometrica – Capsules

Funaria hygrometrica moss –


Structure and development of walls in Funaria stomata.

by Sack F. D., Paolillo D. J. (1983)

Fred D. Sack, D. J. Paolillo Jr.

in Am. J. Bot. 70, 1019–1030 –


The development and structure of the guard cell walls of Funaria hygrometrica Hedw. (Musci) were studied with the light and electron microscopes.
The stoma consists of only one, binucleate guard cell as the pore wall does not extend to the ends of the cell. The guard cell wall is thinnest in the dorsal wall near the outer wall but during movement is most likely to flex at thin areas of the outer and ventral walls.
The mature wall contains a mottled layer sandwiched between two, more fibrillar layers. The internal wall layer has sublayers with fibrils in axial and radial orientations with respect to the pore.
During substomatal cavity formation, the middle lamella is stretched into an electron dense network and into strands and sheets.
After stomatal pore formation, the subsidiary cell walls close to the guard cell become strikingly thickened.
The functional implications of these results are discussed.
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Protoplasmic changes during stomatal development in Bryophyta


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Funaria hygrometrica

Protoplasmic changes during stomatal development in Funaria.

by Sack F. D., Paolillo D. J. (1983)

Fred D. Sack, D. J. Paolillo Jr.

in Canadian Journal of Botany, 61: 251526 – –


Key protoplasmic features of stomatal development in Funaria hygrometrica Hedw. (Musci) were characterized using light and electron microscopy.

Endoplasmic reticulum (ER) cisternae are initially rough and often arranged in parallel arrays. During pore formation, the cytoplasm becomes packed with tubular, smooth ER.

Older but still functional stomata contain small amounts of primarily cisternal ER. Lipid bodies decrease in electron density when tubular ER appears.

Preliminary observations indicate that two large vacuoles occupy the polar regions of open, but not closed, stomata.

Intact plasmodesmata occur in developing but not mature walls. Plastid structure, microtubule distribution, and other protoplasmic features are essentially similar to those described in the stomata of other genera.


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The morphology of the stomatal pore cuticle and peristomatal transpiration in Bryophyta



Stomatal pore and cuticle formation in Funaria.

by Sack F. D., Paolillo D. J. Jr. (1983)

Fred D. Sack, D. J. Paolillo Jr.

Boyce Thompson Institute for Plant Research and the Section of Plant Biology, Cornell University, Ithaca, USA

in Protoplasma 116 : 1 – 13 –


Cuticle and pore development in the guard cells of Funaria were investigated with the electron microscope.

Pore cuticle formation is simultaneous with the creation of the pore itself. The morphology of the pore cuticle is unlike that of any cuticle described in the literature. It has many lamellae which are penetrated by electron dense fibrils.

Three different cuticular morphologies exist from the pore to the subsidiary cell walls. The cuticles on the pore and outer walls contain fibrils that sometimes reach to the surface.

The subsidiary cell cuticle lacks fibrils altogether. It is hypothesized that (1) cuticularization of the middle lamella contributes to ventral wall separation and (2) differences in extent of cuticular fibrils are related to greater water loss from stomata than from subsidiary cells (peristomatal transpiration).

Functions and physiology of Bryophyta stomata



The occurrence, structure and functions of the stomata in British bryophytes. II. Functions and physiology.

by Paton J. A., Pearce J. V. (1957)

in Transactions of the British Bryological Society, 3: 242–259 –

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The one-celled condition in stomata of Funaria (Musci)


Incomplete cytokinesis in Funaria stomata

by Sack F. D., Paolillo D. J. (1985)

in Am J Bot 1985, 72:1325-1333. –

Publisher Full Text –


The development of the one-celled condition in Funaria (Musci) stomata was investigated using light and electron microscopy. The guard cell parent cell is unusual in that it undergoes karyokinesis but incomplete cytokinesis. The septal wall, and the cell plate from which it forms, have incurved edges in contact with the polar cytoplasm.
No evidence was found to support Haberlandt’s claim that the stomate is initially two celled but undergoes wall resorption. Preprophase microtubule bands appear to be present in nonstomatal epidermal cells with normal cytokinesis, but the possibility is raised that they are absent in guard cell parent cells.

400 million years of stomata


Regulatory mechanism controlling stomatal behavior conserved across 400 million years of land plant evolution

by Chater C., Kamisugi Y., Movahedi M., Fleming A., Cuming C., Gray J. E.,  Beerling D. J.  (2011)

in Current Biology 21 : 1025 – 1029 –  – doi: 10.1016/j.cub.2011.04.032. –


Stomatal pores evolved more than 410 million years ago [1, 2] and allowed vascular plants to regulate transpirational water loss during the uptake of CO(2) for photosynthesis [3].

Here, we show that stomata on the sporophytes of the moss Physcomitrella patens [2] respond to environmental signals in a similar way to those of flowering plants [4] and that a homolog of a key signaling component in the vascular plant drought hormone abscisic acid (ABA) response [5] is involved in stomatal control in mosses.

Cross-species complementation experiments reveal that the stomatal ABA response of a flowering plant (Arabidopsis thaliana) mutant, lacking the ABA-regulatory protein kinase OPEN STOMATA 1 (OST1) [6], is rescued by substitution with the moss P. patens homolog, PpOST1-1, which evolved more than 400 million years earlier.

We further demonstrate through the targeted knockout of the PpOST1-1 gene in P. patens that its role in guard cell closure is conserved, with stomata of mutant mosses exhibiting a significantly attenuated ABA response.

Our analyses indicate that core regulatory components involved in guard cell ABA signaling of flowering plants are operational in mosses and likely originated in the last common ancestor of these lineages more than 400 million years ago [7], prior to the evolution of ferns [8, 9].

Stomatal control and gene signalling networks in bryophytes and lycophytes


Early evolutionary acquisition of stomatal control and development gene signalling networks.

by Chater C., Gray J. E., Beerling D. J. (2013)

Department of Molecular Biology and Biotechnology, University of Sheffield, Sheffield S10 2TN, UK.

in Current Opinion in Plant Biology 16 : 638 – 646  – doi: 10.1016/j.pbi.2013.06.013. –


Fossil stomata of early vascular land plants date back over 418 million years and exhibit properties suggesting that they were operational, including differentially thickened guard cells and sub-stomatal chambers.

Molecular studies on basal land plant groups (bryophytes and lycophytes) provide insight into the core genes involved in sensing and translating changes in the drought hormone abscisic acid (ABA), light and concentration of CO2 into changes in stomatal aperture.

These studies indicate that early land plants probably possessed the genetic tool kits for stomata to actively respond to environmental/endogenous cues. With these ancestral molecular genetic tool kits in place, stomatal regulation of plant carbon and water relations may have became progressively more effective as hydraulic systems evolved in seed plant lineages.

Gene expression and cross-species gene complementation studies suggest that the pathway regulating stomatal fate may also have been conserved across land plant evolution.

This emerging area offers a fascinating glimpse into the potential genetic tool kits used by the earliest vascular land plants to build and operate the stomata preserved in the fossil record.