Gymnospermae

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Gymnospermae (裸子植物)

Mount Usu / Sarobetsu post-mined peatland
From left: Crater basin in 1986 and 2006. Cottongrass / Daylily

HOME > Plant taxonomy (植物分類学) > Plant list (植物リスト) > Gymnospermae

[Engler's syllabus (エングラー体系), Angiospermae (被子植物)]

Gymnospermae (Gr. gymnos = naked + Gr. sperma = seed) and the informal term "gymnosperm"

General characteristics

vegetable organ = vegetative type (or sporophyte) → remarkable, asexual
vegetable organ = gametophyte → degenerative, parasitical, sexual

♀
sporophyte = primarily endoderm
gametophyte ⇒ ovule
♂
macrophyll → macrosporogphyll (果葉) → macrosporangium ← n | 2n → ovule → macrospore
microphyll → microsporophyll (粉葉) → microsporangium ← n | 2n → anther cell or pollen sac → microspore

Life cycle

Table. Comparison of characteristics between Cycadopsida and Coniferopsida
	Cycadopsida	Coniferopsida
Leaf	Large, complex, fern-frond-like compound	Simple, often scale-like or needle-like
Leaf trace	Numerous	One to a few, simple
Leaf base	Persistent, forming an "armor" on the stem	Not persistent
Stem	Not differentiated into long and spur shoots	Having long and spur shoots
Wood	Pith and cortex extension, as compared with xylem and phloem. Xylem loosely arranged with broad parenchymatous rays (monoxylix)	Pith and cortex restricted, xylem composing bulk of stem. Xylem compact, composed mostly of tracheids, rays narrow (pycnoxylic)
Ovule (+ seed)	Ovlues borne singly on leaves, in simple strobili, on a megasporophyll (Cycas), or on an conical axis. Seed is radical symmetry.	Ovlues often borne in compound strobili or ovlues borne singly. Seed is bilateral symmetry

I. Class Cycadopsida Brongn. ソテツ綱

1869 Hrase S (平瀬作五郎): discovered sperms from Ginkgo biloba
1869 Ikeno S (池野成一郎): discovered sperms from Cycas revoluta

→ kinship with Pteridophyta

↓ Potonie (Cycadofilices ソテツシダ類): capsule (杯状体)_sulpynx
↓ Mudullose: capsule – fusion with integument__________↓
Cycas: basicall same with Mudullose_________________shrinkage

Subclass Pteridospermidae (シダ状種子植物*)

Devonian- Jurassic

Subclass Cycadidae (ソテツ)

Cycas and confiers – development of microspore

microspore → prothalial cell
→ prothalial cell → tube cell
→ generative cell

| pollen (n)
|
| → stalk cell
| → body cell → sperm
(♀) free nuclear division → archegonium = same with Ginkgo
The maturation of seeds needs longer time

Ex. June ♀ macrospore cell → pollination / miosis: tissues developed one year later → fertilization in the next year

Order Bennettitales *: Triassic
Order Cycadales (ソテツ): Upper Triassic-present
Cycadaceae Pers. (ソテツ)
Leaf emergence: curly in the early stage like Osmunda japonica Identification by vegetative organs is difficult
Microscopic structures of organs are about the same with those of Ginkyo
The development of secondary xylem is not well
Cycas L. (one genus)
C. circinalis L. (インドソテツ)
C. revoluta Thunb. (ソテツ)
C. rumphii Miq. (ナンヨウソテツ)
C. taitungensis C. F. Shen, K. D. Hill, C. H. Tsou et C. J. Chen (タイワンソテツ)

Fig. Cycas and its allies. inside of seed: cotyledone that has already formed, enclosed by endosperm (内胚乳). endosperm = haploid. Cross section: p = pith, v = vascular bundle, lt = leaf trace
Zamiaceae Horan. (ザミア), sago-cycas family
when separated from Cycadaceae
Subfam Encephalartoideae
Tribe Diooeae: Dioon Lindl. (サゴソテツ)
Tribe Encephalarteae: Encephalartos Lehm.,Macrozamia Miq., Lepidozamia Lehm.
Subfam Zamioideae
Tribe Ceratozamieae: Ceratozamia Brongn. (ツノザミア)
Tribe Zamieae: Microcycas (Miq.) A. DC. (オニソテツ), Chigua D. W. Stev., Zamia L. (フロリダソテツ)

Also Bowenia is classified into Zamiaceae (see Cycadaceae)

Nilssoniaceae*

Subclass Pentoxylidae*

One family and one order
Order Pentoxylales
Pentoxylaceae
→ phylogenetical reation is unknown, probably shrub

Subclass Ginkgopsida

Order Ginkgoales Trichopityaceae *
Lower Permian in France
Ginkgoaceae (イチョウ)

(♂)  p.c. = prothalial cell
microspore → 1st → 2nd
      ┃              p.c.     p.c.
      ┗━━━> 1st → 2nd → tube cell
                        p.c.     p.c. → generative cell

| pollen (n)
|
| → stalk cell
| → body cell → sperm
(♀) free nuclear division → archegonium
Ginkgo biloba, one species in one genus in one family in the present

Fossil: 17 or more species → diverse (after Upper Paleozoic)

*: extinct (fossil records)

II. Class Coniferopsida 球果植物綱 (針葉樹綱)

Evolution of flower → one scale = one flower →
The whole of pine cone = inflorescence
Species non-producing cones in Coniferopsida

1. devolution → 1 seed (e.g., Podocarpus)
2. unknown: Taxus → many characteristics differ from the other coniferous species

→ Taxopsida (establishing independent version of class)
Fossil record: differentiated in the vicinity of the Permian

Araucariaceae → Pinaceae → Taxodiaceae → Cupressaceae

× Podocarpaceae forming epimatium → different phylogeny

Order Cordaitales*

upper Devonian - the Permian* (flourished in the Carboniferous)

Order Coniferales (球果植物目) = Pinales (マツ目)

Walchiaceae (Lebachiaceae)*
Voltziaceae*
Palissyaceae*
Araucariaceae (ナンヨウスギ)
Sciadopityaceae
Pinaceae (マツ, conifer)
Cupressaceae (ヒノキ): Actinostrobus Miq. (WA)

Order Taxales (= Class Taxopsida) (イチイ)

Podocarpaceae マキ
Cephalotaxaceae イヌガヤ
Taxaceae イチイ

III. Class Gnetopsida (Chlamydospermopsida, グネツム綱)

Growth

Leaf = finite or determinate growth (exception: Lygodium japonicum, Diplopterygium glaucum – growth point on apex)
Stem = indeterminate growth (exception: Welwitschia – growth point on leaf base)
Vessel present + xylem fiber present
Companion cell developed in a few species (Gnetum) → close to Angiospermae
Lignin structure close to Angiospermae
Ovule (♀): enveloped by a structure like a perianth or floral envelope s.s., connate scales)
Microsporangium (♂): the number of microsporangia present in an androphore or a microsporangiophore are constant on each species

female flower connoted vestigial or immature ♂ – Welwitschia, Gentum

Order Ephedrales (= Ephedraceae)

(♂) The microsporangiate strobili have rounded apices, while those of the ovulate strobilis are acute. The strobili of E. antisyphilitica are already visible and well developed in the vicinity of abilene and elsewhere in texas, at the nodes among the fasciculate, photosynthetic axis (Bold et al. 1980).

Microspore

→ prothalial cell
→ prothalial     → tube nucleus
1°       nucleus → generative
                        2°          nucleus

│ → pollen (n): 4 cells = spores
│
│ → stalk nucleus
│ → body nucleus → sperm (n)
│ → sperm (n)

Ephedra (マオウ): 40 spp., xerophytic, 3-5 m in height

Order Welwitschiales (= Welwitschiaceae サバクオモト)

often merged into Gnetales

Microspore

→ prothalial cell
→ prothalial cell → tube cell
→ generative cell

│ → pollen (n): three cells = spores
│
│ → sperm (n)
│ → sperm (n)

No stalk cell stage
Pollen formation of Welwitchia is earlier than that of Gnetum because the karyokinesis makes a time

Fig. Disjunct distribution area of Welwitschia and its relation to annual rainfall. (a) is a satellite map of southwestern Africa from 12.5&de; to 24°S latitude. The black dots represent 991 Welwitschia locations confirmed by or newly recorded during this project. Large populations with a quasi-continuous presence are shown in gray. Isolated range fragments are named in yellow. White numbers and names designate the locations of populations sampled for SSR analysis. The isolation of range fragments is indicated by their distance in km. The white bar designates a major geographic gene-flow barrier; within Welwitschia, the broken lines designate geographic gene-flow barriers within subspecies. The black line marks the border between Angola and Namibia. (b) shows Welwitschia locations and range fragments (as in a) against a color ramp, which illustrates the arid zone in yellow, orange, and red. The blue lines are isohyets of mean annual rainfall in 100-mm increments. The horizontal black line marks the border between Angola and Namibia. (Jürgens et al. 2021) Welwitschia Hook. f. = W. mirabilis Hook. f.

Synonyms: Tumboa bainesii Hook. f., Welwitschia bainesii (Hook. f.) Carrière, nom. inval., Tumboa strobilifera Welw. ex Hook. f.

ssp. mirabilis, male flower = red brown
ssp. namibiana Leuenb., male flower = grey brown

Order Gnetales (= Gnetaceae)

ca. 50 spp. Gnetum L. (G. gnemon, the type)

Fig. Distribution of genus Gnetum
Gnetum

Fig. Gnetum gnemon L., Gnemon tree
♀ flower = female gametophyte = the structure is clearly Gymnospermae (archaegonium, not developed)