Stomata in cycads

Leaf micromorphology as a possible tool in cycads systematics

by Barone Lumaga M. R., Coiro M., Erdei B., Mickle J. (2012)


In Conference Botany 2012, Columbus, Ohio, USA, July 7–11, Abstract ID: 306 –



The genus Ceratozamia (Cycadales; Zamiaceae) was classically divided into two groups based on gross leaf morphology, but recent molecular phylogenetic analyses has identified three clades. On a larger scale, Ceratozamia appears closely related to Stangeria and to the neotropical genera Microcycas and Zamia. Whole leaf and isolated cuticle specimens from eight Ceratozamia species (C. euryphyllidia, C. hildae, C. kuesteriana, C. latifolia, C. matudae, C. mexicana, C. miqueliana, C. norstogii), Stangeria eriopus, Microcycas calocoma, and Zamia amblyphyllidia were examined using SEM for features of inner and external surfaces.

Samples were collected from the middle region of leaflets of mature leaves of greenhouse-grown plants. For external surfaces, samples were air dried or fixed in FAA (10:5:50) and critical-point dried. For the inner cuticle surface, isolated cuticles were obtained using 20% CrO3.

Characteristics in common to these species include hypostomy with the exception of S. eriopus showing stomata also on the adaxial side (near the midrib), occasional presence of hair scars, adaxial epidermal cells longitudinally elongated and arranged in rows, and smooth adaxial exterior cuticle (with the exception of S. eriopus showing irregular ridges).

Stomatal complexes are not contiguous and are oriented parallel to the leaflet axis (with the exception of S. eriopus showing randomly oriented stomata), and are of the diperigenous to tetraperiginous type in Ceratozamia species, M. calocoma and Z. amblyphyllidia, with S. eriopus showing stomata of polyperigenous type.

Lightly granulate epicuticular wax borders stomatal pits in M. calocoma and Z. paucijuga, and it is granulate in C. matudae and C. robusta.

Epicuticular wax occuring as granules to ridges borders the pits in C. euryphyllidia, C. miqueliana, C. norstogii and as reticulate ridges in C. hildae, C. kuesteriana, C. latifolia, C. mexicana.

The distribution of different kinds of epicuticular waxes in Ceratozamia species closely reflect the phylogenetic relationships that has emerged from molecular data. The presence of granulated wax in M. calocoma and Z. amblyphyllidia suggests that this character is ancestral in Ceratozamia.

The closeness of S. eriopus to the other taxa is not supported by cuticular micromorphology. The close correspondence between molecular and micromorphogical data in Ceratozamia confirms that micromorphology can provide useful data for rapidly and efficiently assessing systematics in other cycad taxa.

Stomata in the Cycads

North Carolina State University

Epidermal micromorphology and the diversification of the cycads

by Coiro M., Mickle J., Barone Lumaga M. R. (2015) – –

MARIO COIRO, Department of Biology, ETH Zurich, 8008 Zurich, Switzerland

James E. Mickle, North Carolina State University

Barone Lumaga Maria Rosaria (3)

1 ETH Zürich, Department Of Biology,
2 North Carolina State University, Department of Plant and Microbial Biology
3 Università di Napoli Federico II, Dipartimento di Biologia


Stomata of Populus (Salicaceae)


Stomata morphological traits in two different genotypes of Populus nigra L.

by Russo G., De Angelis P., Mickle J. E., Lumaga Baropne M. R. 

Giuseppe Russo, Paolo De Angelis, James E Mickle, Maria Rosaria Lumaga Barone,


in Italian Society of Silviculture and Forest Ecology


Giant stomata (GS), as the name implies, are distinct from normal-sized stomata primarily due to size. In a treatise on the anatomy of dicotyledons, Metcalfe & Chalk described large stomata of approximately 40 µm in relatively few families. Shiraishi et al. reported structures in Satsuma Mandarin (Citrus unshiu Marc) similar to large-sized stomata, surrounded by a number of normal-sized stomata on juvenile leaves immediately after full leaf expansion. The giant type stomata observed in C. unshiu were consistent with GS examined and characterized by Sitholey & Pandey and Stace in different taxa.

Electron microscopy studies on subfossil Holocene Salix herbacea L. (Salicaceae) samples in Sweden suggested the presence of GS. Finally, Pautov reported an eterostomatal organization in Populus tremula, with three stomatal types, i.e., paracitic, laterocitic, and intermediate anamo-paracytic.

Stomatal traits have been widely studied in Populus, as these traits are a useful criterion for clone discrimination in the genus. In particular, a series of clones have been explored that confirm general poplar micromorphologic features, including amphistomatic leaves, with evidence some stomatal traits change depending on environmental conditions, and in response to growing conditions. For example, in P. trichocarpa stomata were not found on the adaxial leaf surface when grown under field conditions, however low stomatal density was observed on the adaxial surface under glasshouse conditions.

Despite frequent studies on stomata in poplar, reports of giant stomata in Populus remain equivocal.

Recently, interest in several poplar morphological and physiological traits has increased, with the aim of evaluating new breeding strategies for industrial applications. Additional knowledge of poplar stomata might support industrial objectives, since stomatal density has been demonstrated to affect biomass production in different poplar clones.

Read the article: iForest

Stomata in Psilotum (Psilotaceae)



by Mickel J. E. (2012)

James E. Mickel

in Journal of the North Carolina Academy of Science, 128(3/4), 2012, pp. 95–99


Apical regions of developing aerial shoots of Psilotum nudum (L.) Beauv. were studied using both scanning electron microscopy (SEM) and light microscopy (LM) with the aim of improving our understanding of early stages in stomatal and epidermal ontogenesis.

SEM samples were fixed in gluteraldehyde, critical point dried, and coated with an Au-Pd alloy. LM samples were fixed in FAA and embedded in paraffin. LM sections were stained with 0.05% toluidine blue for protein.

SEM shows that P. nudum stomata develop from 20 mm-long domed meristemoid cells into guard cell mother cells (GMCs). A furrow dividing guard cells develops at 30 mm long, and wax deposition that will cover the entire cell begins at 70 mm long.

LM longitudinal sections of GMCs show a cytoplasmic protein net that organizes into radial fibers, similar to reports of actin fibers in stomata of angiosperms.

This study provides additional details of stomatal development in Psilotum and is the first report of an actin-like protein net in Psilotum.