Figure 1.
Spore ultrastructure of Orthotrichum acuminatum.
A–B: SEM, C–E: TEM. A) Ellipsoidal spore ornamented with perine elements (verrucae and baculi). B) Detail showing primary elements (verrucae and baculi) covered with abundant papillose secondary processes dispersed across their surface. C) Bicellular spore. Note the loosely attached perine verrucae surrounding the spore. Ample areas of the spore proximal surface appear almost naked, with little sculpturing material (square brackets). Exine very thin, formed by electron-translucent, compact material. Cytoplasm dense, granular; plastids densely disposed with well developed, packed thylakoids. Note the presence of undissolved, lipidic droplets (most of them electrondense and partially dissolved) filling only a small fraction of the cytoplasm D) Unicellular spore. The inner surface of the intine appears typically undulated. Starch grains are frequent within the plastids. Note the scattered presence of undissolved, more electrontranslucent, lipidic droplets. E) Detail of the spore wall showing perine with sparse primary elements, connected by a thin basal layer and exine separating into parallel lamellae, the inner ones intermingled with intinous material (a common phenomenon in particular areas of these spores). Intine two-layered, the external layer amorphous, with granular, electrontranslucent material; the innermost more electrondense and rather fibrous. Abbreviations: bPe: basal layer of perine material; Chl: chloroplasts; CW: cell wall; dL: partially dissolved, electrondense lipidic droplets; dPe: detached perine elements; E: exine; I: intine; Ie: external layer of the intine; Ii: internal layer of the intine; N: nucleus; Pe: perine elements; sPe: perine secondary processes; S: starch grains; uL: undissolved, electron translucent lipid droplets.
Figure 2.
Spore ultrastructure of Orthotrichum affine (type I).
A–B: SEM, C–D: TEM. A) Subspherical spore ornamented with irregular primary elements forming verrucae B) Detail of the spore showing primary elements covered with abundant, irregular secondary processes C) Verrucae are ornamented with abundant secondary processes. Perine elements appear connected by a relatively thick basal layer of electrondense material. Exine electrontranslucent, clearly polarized, proximally thin and compact, distally enthickened and locally separating into parallel lamellae. Plastids with well-developed thylakoids, fusiform, loosely disposed in the cytoplasm. Small starch grains present within the plastids. D) Wall structure of a spore in detail. Distal part of the spore with thick exine. Intine two-layered, outer layer granular, inner layer fibrillar, undulate, and more electrondense. Abbreviations: bPe: basal layer of perine material; Chl: chloroplasts; dL: partially dissolved, electrondense lipidic droplets; dPe: detached perine elements; E: exine; I: intine; Pe: perine elements; sPe: perine secondary processes; S: starch grains.
Figure 3.
Spore ultrastructure of Orthotrichum affine (type II).
A–B: SEM, C–D: TEM. A) Subesphericall spore. Smooth perine elements cover the spore surface; some primary elements appear fused forming extensive bands throughout the spore (a feature common in type II morphotipes of this species). B) Detail of spore ornamentation showing smooth perine elements without secondary processes. C) General view of a spore, note the smooth perine and the fused primary elements in cross section. Exine thin, of uniform thickness, without polarization. Intine electrontranslucent, bilayered. Plastids well developed. Lipidic droplets abundant, most of them medium-electrondense and undissolved. D) Detail of a spore, note the continuous basal layer of perine connecting the primary elements and the bilayered structure of the intine, the outer layer compact, the inner layer thinner, fibrillar, lamellated. Abbreviations: bPe: basal layer of perine material; Chl: chloroplasts; dL: partially dissolved, electrondense lipidic droplets; dPe: detached perine elements; E: exine; fPe: fused perine elements; I: intine; Ie: external layer of the intine; Ii: internal layer of the intine; N: nucleus; Pe: perine elements; pg: plastoglobuli; sPe: perine secondary processes; S: starch grains, uL: undissolved, electron translucent lipid droplets.
Figure 4.
Spore ultrastructure of Orthotrichum ibericum.
A–B: SEM, C–E: TEM. A) A subellipsoidal spore (usually slightly flattened), irregularly ornamented with perine elements, leaving large naked areas. B) Detail of the sporoderm showing perine primary elements (verrucae and baculi) covered with secondary processes (scattered papillae). C) A bicellular spore showing a sporoderm with sparse perine elements and polarized intine (proximally much thicker), and a granular cytoplasm with loosely packed chloroplasts and lipidic droplets (usually sparse in this species), some electrondense and partially dissolved, more often medium-electrondense, undissolved. D) A spore showing the sporoderm with two continuous intine layers and an occasional, internal, electrontranslucent, granular layer locally present; and exine, electrontranslucent and extensively separating into parallel lamellae. In the cytoplasm the chloroplasts appear with abundant plastoglobuli. E) Detail showing the sporoderm with a very thin basal layer connecting perine elements; the exine extensively separating into parallel lamellae (asterisks); and the intine stratification: an outermost layer amorphous, an inner granular layer, and a discontinuous granular, electrontranslucent, innermost layer. Abbreviations: bPe: basal layer of perine material; Chl: chloroplasts; CW: cell wall; dL: partially dissolved, electrondense lipidic droplets; E: exine; I: intine; Ie: external layer of the intine; Ig: innermost discontinuous intine layer; Ii: internal continuous layer of the intine; N: nucleus; Pe: perine elements; sPe: perine secondary processes; pg: plastoglobuli; S: starch grains; uL: undissolved, electron translucent lipid droplets.
Figure 5.
Spore ultrastructure of Orthotrichum lyellii.
A) Subspherical spore (usually subespherical to subellipsoidal in the species) with small sized verrucae scattered throughout the spore surface. B) Detail of the perine elements with abundant granular secondary processes over the surface of verrucae. C) Detail of the sporoderm structure showing electrondense perine and a very thin basal layer of electrondense material joining verrucae (frequent in the species). Note also the aggregations of detached secondary elements. The spore shows a thick electrontranslucent exine locally separated into parallel lamellae, layers of exine lamellae alternating electron translucent and opaque material. Intine electrontranslucent, one layered, fibrillar, variable in thickness, inner surface of the intine undulate. D) Granular cytoplasm bearing chloroplasts with well developed thylakoids. Lipid droplets abundant, of two different types, some medium-electrondense undissolved, most electrondense and partially or almost totally dissolved. E) Detail of the cytoplasm, note the starch granules within the chloroplast (a sporadic feature in the spores of this species. F) Detail of sporoderm that shows a large gap filled with electrontranslucent material between intine and exine that ocasionally appears in some of the spores. Abbreviations: bPe: basal layer of perine material; dPe: Chl: chloroplasts; CW: cell wall; dL: partially dissolved, electrondense lipidic droplets; dPe: detached perine elements; E: exine; I: intine; Ie: external layer of the intine; Ii: internal layer of the intine; N: nucleus; Pe: perine elements; sPe: perine secondary processes; S: starch grains; uL: undissolved, electron translucent lipid droplets.
Figure 6.
Spore ultrastructure of Orthotrichum speciosum.
A) Subspherical spore. Verrucae irregularly scattered, sometimes fused into heterogeneous units, variable in shape (spike-like to rounded) and size. B) Detail of the perine, granular secondary processes abundant throughout the basal layer and the verrucae. C) Detail of the sporoderm. Perine electrondense, elements connected by a electrondense basal layer. Granular secondary processes abundant throughout the basal layer and the verrucae. Exine thin, electrontranslucent, locally separating into parallel lamellae, with occasional conspicuous gaps filled with electrondense material (asterisks). Intine bilayered, outer layer fibrillar-granular, inner layer fibrillar, undulate. D) General view of a spore. Cytoplasm granular. Chloroplasts with well developed thylakoids. Lipid droplets abundant, of two different types. Some medium-electrondense, electrondense droplets more abundant. E) Chloroplasts with numerous plastoglobuli. Contact between exine and intine with expanded and labyrinth-like intrusions. Abbreviations: bPe: basal layer of perine material; Chl: chloroplasts; dL: partially dissolved, electrondense lipidic droplets; dPe: detached perine elements; E: exine; I: intine; Pe: perine elements; sPe: perine secondary processes; S: starch grains; uL: undissolved, electron translucent lipid droplets.
Figure 7.
Spore ultrastructure of Orthotrichum striatum.
A–B: SEM, C–E: TEM. A) A subellipsoidal spore, ornamented with dense, irreglarly fused, perine elements. B) Perine primary elements (verrucae), sometimes fusing into a plate, and covered with abundant secondary processes. C) Detail showing the sporoderm stratification: fused perine verrucae; a thick exine separating into parallel lamellae (in this species this happens in extense areas of the sporoderm); and an intine with two continuous layers, the outermost granular and the innermost fibrillar. D) Spore showing a sporoderm irregular in thickness; and a cytoplasm filled with copious lipidic droplets (some partially dissolved, most undissolved) and chloroplasts with abundant plastoglobuli. E) Detail showing sporoderm with perine verrucae connected by an electrondense basal layer, exine separating into parallel lamellae (asterisks) and intine with an inner thickening of granular material, additional to its two continuous layers. In the cytoplasm, electrondense, partially dissolved lipidic droplets, and chloroplasts with well developed thylakoids and plastoglobuli, are observed.
Figure 8.
Spore ultrastructure of Orthotrichum tortidontium.
A–B: SEM, C–E: TEM. A) Spore subellipsoidal. Verrucae large, irregular in shape and size. B) Primary elements irregularly fused, occasionally forming large bands. Secondary processes scarce, irregularly present on the verrucae. C) Perine electrondense, elements connected by an electrondense basal layer. Exine thick, electrontranslucent, locally separating into parallel lamellae (asterisk). Intine electrontranslucent, thick, two layered. D) Cytoplasm granular. Chloroplasts with well developed thylakoids, often with starch. Abundant lipid droplets of two different types, some electrontranslucent, undisolved, the others electrondense and partially or almost totally dissolved. E) Detail of sporoderm structure showing two layered intine, outermost layer granular, innermost layer granular-fibrillar. Abbreviations: bPe: basal layer of perine material; Chl: chloroplasts; CW: cell wall; dL: partially dissolved, electrondense lipidic droplets; dPe: detached perine elements; E: exine; fPe: fused perine elements; I: intine; Ie: external layer of the intine; Ii: internal layer of the intine; N: nucleus; Pe: perine elements; sPe: perine secondary processes; S: starch grains; uL: undissolved, electron translucent lipid.
Table 1.
Main spore features of each species.