G-fibers and Florin ring-like structures in Dioon (Zamiaceae)

Abstract

Cuticle information and epidermal characters have great potential in systematic studies. However, micromorphology and anatomical studies on cycads are relatively scarce in comparison to similar studies on other gymnosperms. In this study leaflet anatomy and cuticles in the genus Dioon have been investigated with bright field microscopy, epifluorescence, and scanning electron microscopy. Structures hitherto not completely studied for the genus are reported such as lignified hypodermis, girder sclerenchyma, especially G-fibers, and Florin ring-like structures associated with the stomatal apparatus. Key words: anatomy, cuticles, cycads, Cycadales, leaflets. Fibras-G y estructuras de anillo tipo Florin en Dioon (Zamiaceae) ResumenLa información de cutículas y caracteres epidérmicas tienen gran potencial para estudios sistemáticos. Sin embargo, la micromorfología y estudios anatómicos en las cícadas son relativamente escasos en comparación de estudios similares con otras gimnospermas. En este estudio se investigó la anatomía de foliolos y cutículas del género Dioon con técnicas de microscopia de campo claro, epifluorescencia y de microscopía electrónica de barrido y se reportan estructuras no completamente estudiadas antes para el género. Se observó hipodermis lignificada, presencia de esclerénquima de trabe y particularmente fibras gelatinosas y estructuras semejantes a anillos de Florin asociados con los aparatos estomáticos.

Aridification as a driver of biodiversity: a case study for the cycad genus Dioon (Zamiaceae)

“…We show for example that the Spinulosum clade, which comprises species that inhabit mesic habitats, show the thinnest cuticles in the genus. In contrast, the thickest cuticles are found in species from arid habitats of the Dioon major clade, where thick cuticles can be advantageous against water stress (Caldwell et al, 2007) or mechanical stress (Vovides and Galicia, 2016), and as protection from ultraviolet radiation in deserts and at high altitudes (Körner, 2007;Barone-Lumaga et al, 2015). In the same manner, stomatal chamber architecture shows significant correlations in both cross-species and PIC analyses, suggesting direct functional associations between stomata and habitat differentiations.…”

“…In Dioon, the stomata are arranged in parallel bands (Vovides and Galicia;2016). The widths of these bands positively correlate with annual precipitation (Fig.…”

“…The following TS measurements were taken on ten randomly chosen replicates of each cell or tissue type for each of the leaflets sampled per taxon: thickness of adaxial epidermis, abaxial epidermis and cuticle at leaflet margin (measurement taken from the top anticlinal limit of the epidermal cell where cuticle is thinnest); TS dimensions of adaxial and abaxial epidermal cells; number of layers of girder sclerenchyma associated with the vascular bundles and sclerenchyma layers at leaflet margin; depth and width of epistomatal chamber (depth measurement taken from the top surface of the guard cells to the top of the uppermost encircling cell (Florin ring sensu Vovides and Galicia, 2016) width measurement taken at the cuticle level of the epistomatal pore); and number of perivascular and intervascular G-fibres and number of mucilaginous canals. Observations and measurements were done with a calibrated microscope; digital photomicrographs were taken using a Zeiss Fomi III photomicroscope (Zeiss, Oberkochen, Germany) fitted with a Canon ® digital camera.…”

“…We confirm the presence of Florin rings associated with stomata in all the Dioon species. Florin rings are thick cutin layers overlying the uppermost cells surrounding the stomata (Vovides and Galicia, 2016). These Florin rings can be categorized into two types (Fig.…”

Population Differentiation and Demographic History of the Cycas taiwaniana Complex (Cycadaceae) Endemic to South China as Indicated by DNA Sequences and Microsatellite Markers

“…However, molecular phylogenetic analyses indicated that the extant cycads underwent a synchronous global re-diversification and are not much more than 12 million years old (Nagalingum et al, 2011). In recent years, researchers have studied cycad phylogeny Wei et al, 2015), conservation (Feng et al, 2014;Feng et al, 2016;Feng et al, 2017;Gregory and Lopez-Gallego, 2018;Tang et al, 2018a;Zheng et al, 2017), biogeography (Gutiérrez-Ortega et al, 2017Meerow et al, 2018;Cabrera-Toledo et al, 2019), pollination biology (Tang et al, 2018b;Santiago-Jimnez et al, 2019), and physiology (Vovides and Galicia, 2016). Cycads comprise two families (Cycadaceae and Zamiaceae), with 10 genera and 355 accepted species (Calonje et al, 2019).…”