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Vegetative characters, growth habit and microsporangiate strobilus of lycopsid Minostrobus chaohuensis.

Meng MC, Wang DM, Yao JX - PLoS ONE (2015)

Bottom Line: Based on comparisons with other isoetaleans, the usage of the terms "leaf cushion" and "leaf base" is discussed, and Minostrobus chaohuensis is considered as a tree-like lycopsid.It suggests that arborescent isoetaleans with monosporangiate strobili had appeared and diversified in the Late Devonian.The multi-dichotomous branching system of Minostrobus provides new data on the evolution of growth architecture in rhizomorphic lycopsids.

View Article: PubMed Central - PubMed

Affiliation: Ministry of Land and Resources Key Laboratory of Stratigraphy and Paleontology, Institute of Geology, Chinese Academy of Geological Sciences, Beijing, China.

ABSTRACT
Late Devonian Minostrobus chaohuensis is one of the earliest monosporangiate-strobilate isoetaleans. Based on new material of this plant, the vegetative axis and microsporangiate strobilus are studied in detail, and the whole plant knowledge is summarized. The vegetative axis is isotomously branched. The stem is up to 55 mm in diameter with helically arranged leaf cushions. Stems and thick branches bear long fusiform leaf cushions and interareas with vertical linear ornamentations. A ligule pit, oblanceolate leaf scar, and vascular bundle scar appear on the leaf cushion. Distal axes have persistent lanceolate leaves and rhombic leaf bases. The microsporangiate strobilus is cylindrical in shape, possesses sporophyll with alate pedicel and long triangular lamina, uniseriate sporangial wall, subarchesporial pad inside the sporangium, and microspore with cingulum. Based on comparisons with other isoetaleans, the usage of the terms "leaf cushion" and "leaf base" is discussed, and Minostrobus chaohuensis is considered as a tree-like lycopsid. It suggests that arborescent isoetaleans with monosporangiate strobili had appeared and diversified in the Late Devonian. The multi-dichotomous branching system of Minostrobus provides new data on the evolution of growth architecture in rhizomorphic lycopsids.

No MeSH data available.


Related in: MedlinePlus

Compressions of leafy axes and leaves (A-D, G, H), limonite permineralized strobili (E, F, I-K) of Minostrobus chaohuensis.(A) Dichotomous vegetative axes with persistent leaves. Rectangle indicating portion enlarged in Fig. 3H. PKUB12124. Scale bar = 10 mm. (B) Distal part of vegetative axis with persistent leaves. Rectangle indicating portion enlarged in Fig. 3C. PKUB12139. Scale bar = 10 mm. (C) Enlargement of Fig. 3B (rectangle), showing the lanceolate leaf in face view. PKUB12139. Scale bar = 2 mm. (D) Lanceolate vegetative leaf in face view. PKUB12159. Scale bar = 2 mm. (E) Limonite permineralized megasporangiate strobilus. Rectangle indicating portion enlarged in Fig. 3J. PKUB12188. Scale bar = 5 mm. (F) Limonite permineralized microsporangiate strobilus. Arrow indicating portion enlarged in Fig. 3I. Rectangle indicating portion enlarged in Fig. 3K. PKUB12189. Scale bar = 10 mm. (G) Detached vegetative leaves in the matrix. PKUB12160. Scale bar = 2 mm. (H) Enlargement of Fig. 3A (rectangle), showing vegetative leaves in lateral view and rhombus leaf bases. PKUB12124. Scale bar = 5 mm. (I) Enlargement of Fig. 3F (arrow), showing laminae of microsporophyll. PKUB12189. Scale bar = 2 mm. (J) Enlargement of Fig. 3E (rectangle). Arrow indicating megaspores. PKUB12188. Scale bar = 2 mm. (K) Enlargement of Fig. 3F (rectangle), showing strobilar axis and microsporangia on the adaxial surface of sporophyll pedicel. PKUB12189. Scale bar = 2 mm.
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pone.0122167.g003: Compressions of leafy axes and leaves (A-D, G, H), limonite permineralized strobili (E, F, I-K) of Minostrobus chaohuensis.(A) Dichotomous vegetative axes with persistent leaves. Rectangle indicating portion enlarged in Fig. 3H. PKUB12124. Scale bar = 10 mm. (B) Distal part of vegetative axis with persistent leaves. Rectangle indicating portion enlarged in Fig. 3C. PKUB12139. Scale bar = 10 mm. (C) Enlargement of Fig. 3B (rectangle), showing the lanceolate leaf in face view. PKUB12139. Scale bar = 2 mm. (D) Lanceolate vegetative leaf in face view. PKUB12159. Scale bar = 2 mm. (E) Limonite permineralized megasporangiate strobilus. Rectangle indicating portion enlarged in Fig. 3J. PKUB12188. Scale bar = 5 mm. (F) Limonite permineralized microsporangiate strobilus. Arrow indicating portion enlarged in Fig. 3I. Rectangle indicating portion enlarged in Fig. 3K. PKUB12189. Scale bar = 10 mm. (G) Detached vegetative leaves in the matrix. PKUB12160. Scale bar = 2 mm. (H) Enlargement of Fig. 3A (rectangle), showing vegetative leaves in lateral view and rhombus leaf bases. PKUB12124. Scale bar = 5 mm. (I) Enlargement of Fig. 3F (arrow), showing laminae of microsporophyll. PKUB12189. Scale bar = 2 mm. (J) Enlargement of Fig. 3E (rectangle). Arrow indicating megaspores. PKUB12188. Scale bar = 2 mm. (K) Enlargement of Fig. 3F (rectangle), showing strobilar axis and microsporangia on the adaxial surface of sporophyll pedicel. PKUB12189. Scale bar = 2 mm.

Mentions: The stems are 25–55 mm wide (Fig. 1A–C), and branch isotomously at the top (Fig. 1C). Long fusiform leaf cushions are 6.0–9.0 mm long and 1.0–1.6 mm wide (Fig. 1B, F, G, I, J), helically arranged on stems and branches that are at least 8.0 mm wide. Parastichies cross at nearly right angles, whereas orthostichy and horizontal rows are absent (Fig. 1A–G). Evident interareas with vertical linear ornamentations among the leaf cushions exist on axes thicker than 10 mm (Fig. 1B, F, H), and their area is in proportion to the width of axes (Fig. 1A, C, F). An oblanceolate leaf scar is located at the middle part of the leaf cushion, occupying half the length and almost all the width of the cushion (Figs. 1B, G, I, J and 2). An evident and depressed ligule pit (Lp) appears on the top of the leaf scar, and an oval or linear vascular bundle scar (Vs) exists on the upper part of the leaf scar (Figs. 1B, G, K and 2). In some specimens, the leaf cushion can’t be recognized but the oblanceolate leaf scar and depressed ligule pit (Lp) were observed (Fig. 1B, D, L). Distal axes are 2.0–3.0 mm wide, with persistent vegetative leaves arranged helically (Fig. 3A, B, H). The leaf is inserted at acute angle onto the axis, with a decurrent base and a linear profile in lateral view (Fig. 3A, B, H). From face view, however, the leaf is lanceolate in outline, 5.0–7.0 mm long and about 1.5 mm wide at the base (Fig. 3B–D, G). Leaf bases were exposed when the leaves broke off, and they are rhombic in shape, adjacent with each other, and about 2.5 mm long and 1.3 mm wide (Fig. 3H).


Vegetative characters, growth habit and microsporangiate strobilus of lycopsid Minostrobus chaohuensis.

Meng MC, Wang DM, Yao JX - PLoS ONE (2015)

Compressions of leafy axes and leaves (A-D, G, H), limonite permineralized strobili (E, F, I-K) of Minostrobus chaohuensis.(A) Dichotomous vegetative axes with persistent leaves. Rectangle indicating portion enlarged in Fig. 3H. PKUB12124. Scale bar = 10 mm. (B) Distal part of vegetative axis with persistent leaves. Rectangle indicating portion enlarged in Fig. 3C. PKUB12139. Scale bar = 10 mm. (C) Enlargement of Fig. 3B (rectangle), showing the lanceolate leaf in face view. PKUB12139. Scale bar = 2 mm. (D) Lanceolate vegetative leaf in face view. PKUB12159. Scale bar = 2 mm. (E) Limonite permineralized megasporangiate strobilus. Rectangle indicating portion enlarged in Fig. 3J. PKUB12188. Scale bar = 5 mm. (F) Limonite permineralized microsporangiate strobilus. Arrow indicating portion enlarged in Fig. 3I. Rectangle indicating portion enlarged in Fig. 3K. PKUB12189. Scale bar = 10 mm. (G) Detached vegetative leaves in the matrix. PKUB12160. Scale bar = 2 mm. (H) Enlargement of Fig. 3A (rectangle), showing vegetative leaves in lateral view and rhombus leaf bases. PKUB12124. Scale bar = 5 mm. (I) Enlargement of Fig. 3F (arrow), showing laminae of microsporophyll. PKUB12189. Scale bar = 2 mm. (J) Enlargement of Fig. 3E (rectangle). Arrow indicating megaspores. PKUB12188. Scale bar = 2 mm. (K) Enlargement of Fig. 3F (rectangle), showing strobilar axis and microsporangia on the adaxial surface of sporophyll pedicel. PKUB12189. Scale bar = 2 mm.
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pone.0122167.g003: Compressions of leafy axes and leaves (A-D, G, H), limonite permineralized strobili (E, F, I-K) of Minostrobus chaohuensis.(A) Dichotomous vegetative axes with persistent leaves. Rectangle indicating portion enlarged in Fig. 3H. PKUB12124. Scale bar = 10 mm. (B) Distal part of vegetative axis with persistent leaves. Rectangle indicating portion enlarged in Fig. 3C. PKUB12139. Scale bar = 10 mm. (C) Enlargement of Fig. 3B (rectangle), showing the lanceolate leaf in face view. PKUB12139. Scale bar = 2 mm. (D) Lanceolate vegetative leaf in face view. PKUB12159. Scale bar = 2 mm. (E) Limonite permineralized megasporangiate strobilus. Rectangle indicating portion enlarged in Fig. 3J. PKUB12188. Scale bar = 5 mm. (F) Limonite permineralized microsporangiate strobilus. Arrow indicating portion enlarged in Fig. 3I. Rectangle indicating portion enlarged in Fig. 3K. PKUB12189. Scale bar = 10 mm. (G) Detached vegetative leaves in the matrix. PKUB12160. Scale bar = 2 mm. (H) Enlargement of Fig. 3A (rectangle), showing vegetative leaves in lateral view and rhombus leaf bases. PKUB12124. Scale bar = 5 mm. (I) Enlargement of Fig. 3F (arrow), showing laminae of microsporophyll. PKUB12189. Scale bar = 2 mm. (J) Enlargement of Fig. 3E (rectangle). Arrow indicating megaspores. PKUB12188. Scale bar = 2 mm. (K) Enlargement of Fig. 3F (rectangle), showing strobilar axis and microsporangia on the adaxial surface of sporophyll pedicel. PKUB12189. Scale bar = 2 mm.
Mentions: The stems are 25–55 mm wide (Fig. 1A–C), and branch isotomously at the top (Fig. 1C). Long fusiform leaf cushions are 6.0–9.0 mm long and 1.0–1.6 mm wide (Fig. 1B, F, G, I, J), helically arranged on stems and branches that are at least 8.0 mm wide. Parastichies cross at nearly right angles, whereas orthostichy and horizontal rows are absent (Fig. 1A–G). Evident interareas with vertical linear ornamentations among the leaf cushions exist on axes thicker than 10 mm (Fig. 1B, F, H), and their area is in proportion to the width of axes (Fig. 1A, C, F). An oblanceolate leaf scar is located at the middle part of the leaf cushion, occupying half the length and almost all the width of the cushion (Figs. 1B, G, I, J and 2). An evident and depressed ligule pit (Lp) appears on the top of the leaf scar, and an oval or linear vascular bundle scar (Vs) exists on the upper part of the leaf scar (Figs. 1B, G, K and 2). In some specimens, the leaf cushion can’t be recognized but the oblanceolate leaf scar and depressed ligule pit (Lp) were observed (Fig. 1B, D, L). Distal axes are 2.0–3.0 mm wide, with persistent vegetative leaves arranged helically (Fig. 3A, B, H). The leaf is inserted at acute angle onto the axis, with a decurrent base and a linear profile in lateral view (Fig. 3A, B, H). From face view, however, the leaf is lanceolate in outline, 5.0–7.0 mm long and about 1.5 mm wide at the base (Fig. 3B–D, G). Leaf bases were exposed when the leaves broke off, and they are rhombic in shape, adjacent with each other, and about 2.5 mm long and 1.3 mm wide (Fig. 3H).

Bottom Line: Based on comparisons with other isoetaleans, the usage of the terms "leaf cushion" and "leaf base" is discussed, and Minostrobus chaohuensis is considered as a tree-like lycopsid.It suggests that arborescent isoetaleans with monosporangiate strobili had appeared and diversified in the Late Devonian.The multi-dichotomous branching system of Minostrobus provides new data on the evolution of growth architecture in rhizomorphic lycopsids.

View Article: PubMed Central - PubMed

Affiliation: Ministry of Land and Resources Key Laboratory of Stratigraphy and Paleontology, Institute of Geology, Chinese Academy of Geological Sciences, Beijing, China.

ABSTRACT
Late Devonian Minostrobus chaohuensis is one of the earliest monosporangiate-strobilate isoetaleans. Based on new material of this plant, the vegetative axis and microsporangiate strobilus are studied in detail, and the whole plant knowledge is summarized. The vegetative axis is isotomously branched. The stem is up to 55 mm in diameter with helically arranged leaf cushions. Stems and thick branches bear long fusiform leaf cushions and interareas with vertical linear ornamentations. A ligule pit, oblanceolate leaf scar, and vascular bundle scar appear on the leaf cushion. Distal axes have persistent lanceolate leaves and rhombic leaf bases. The microsporangiate strobilus is cylindrical in shape, possesses sporophyll with alate pedicel and long triangular lamina, uniseriate sporangial wall, subarchesporial pad inside the sporangium, and microspore with cingulum. Based on comparisons with other isoetaleans, the usage of the terms "leaf cushion" and "leaf base" is discussed, and Minostrobus chaohuensis is considered as a tree-like lycopsid. It suggests that arborescent isoetaleans with monosporangiate strobili had appeared and diversified in the Late Devonian. The multi-dichotomous branching system of Minostrobus provides new data on the evolution of growth architecture in rhizomorphic lycopsids.

No MeSH data available.


Related in: MedlinePlus