Angiosperms

Flowering Plants

Ecology & Form

  • Ancestral extant angiosperms (e.g. Amborella, Austrobaileyales, and Chloranthaceae) share ecophysiological traits associated with shady, disturbed, and wet habitats (Feild et al. 2004)

    • These features include low and easily light-saturated photosynthetic rates, leaf anatomy related to the capture of understory light, small seed size, and clonal reproduction

  • Some researchers have hypothesized that the earliest angiosperms were woody plants that grew in dimly lit, disturbed forest understory habitats and/or shady streamside settings

  • Evidence of the oldest known fossil angiosperms (e.g. Montsechia and Archaefructus) seems to indicate that flowering plants originated as herbaceous aquatic plants

Biology

Sporophyte (diploid) phase

Stems

  • Great variety of forms: herbs, vines, shrubs, trees

  • Xylem with vessel elements

  • Phloem cells with sieve elements

  • Stems exhibit a eustelic (eudicots) or atactostelic (monocots) pattern of vascular tissue

    • Maturation is usually endarch in stems

Leaves

  • Parallel or netted (reticulate) venation

  • Intercostal veins present, unlike most other living plant groups

    • These are veins in between larger veins that connect the smaller portions of leaf lamina

Roots

Reproductive structures

  • Flowers (determinate stem with modified leaves)

  • Carpal (megasporophyll) encloses ovules and become fruit after fertilization

  • Ovules that become seeds after fertilization

    • Double seed coat (integument) around ovule

Gametophyte (haploid) phase

  • Simple gametophyte; not free-living

    • Female ♀ gametophyte is reduced to 4-7 cells in ovule

      • no archegonium

    • Male ♂ gametophyte is just a few nuclei in pollen

      • Pollen wall morphology is columellar-tectate structure

      • Outer layer of the pollen wall (exine) is differentiated into two layers separated by columns


Geologic Range

Classification

└Embryophytes

└Tracheophytes

└Euphyllophytes

└Lignophytes

└Spermatophytes

└Angiosperms

Angiosperms

├Amborellaceae

├Nymphaeales

├Austrobaileyales

├Magnoliids

├Canellales

├Piperales

└Magnoliales

├Chloranthales

├Monocots

├Ceratophyllales

├Eudicots

├Ranunculales

├Rosids

├Caryophyllales

└Asterids

Diversity

Florigerminis jurassica †

  • Cui et al. 2022

  • late Middle Jurassic of the Daohugou Formation, Inner Mongolia, China

    • However, Wang et al. (2005) challenged the dating and claimed that the Daohugou Formation was of Early Cretaceous age

    • If the Jurassic age of the formation, and the analysis of the morphology of this fossil are correct, then Florigerminis is the earliest known flowering plant, although the Jurassic origin of angiosperms is disputed

  • Fossil includes not only a leafy, woody branch but also physically connected fruit and flower bud.

  • There is a flower bud located in-between a blooming flower and mature fruit

  • Leaves abscised, helically arranged, with decurrent petioles.

  • Flower–fruit pairs helically clustered on the distal portion of the branch.

  • Flower bud terminated on the branch, paired, with a straight pedicel, oval-shaped, with several tepals suggested by their sculpture.

  • Multiple tepals smooth-margined, tightly enwrapping the center.

  • Fruit born on a slender curving pedicel, oval-shaped, with four persistent decussately arranged foliar parts and an apical invagination.

  • Endocarp elongated oval, with a pointed tip.

Above: Figure 2, Cui et al. 2022 (a) Holotype of Florigerminis jurassica, showing the physically connected parts. Two (one missing to the left) fruits and a flower bud are on the branch terminal. Arrows point to the nodes on the branch. PB21737. The scale bar is 10 mm. (b) Close-up of the branch terminal showing a physical connection between two fruit pedicels (1 and 2) and a pedicel of flower bud (3). The scale bar is 2 mm. (c) Close-up of the fruit in (a). Note the mesocarp (m), endocarp (e), three persistent foliar parts visible (arrows), and connected pedicel (lower right). The scale bar is 2 mm. (d) Longitudinal fine striations on the branch surface. The scale bar is 0.25 mm. (e) The flower bud in (b). Note a foliar part at the bottom (arrow). The scale bar is 1 mm. (f ) Close-up of (e) showing overlapping distinct tepals (1–4). The scale bar is 0.2 mm. (g) Close-up of (e) showing distinct overlapping tepals in the top portion of the flower bud. The scale bar is 0.5 mm.

Dilcherifructus mexicana †

  • Wang 2021

  • Middle Jurassic of Mexico

  • Possible fruit with an early origin for angiosperms

  • Fruit with depressions at both top and base, with a style in apical depression

  • Exocarpic epidermal cells polygonal or rectangular in shape, with straight cell walls

  • Stomata anomocytic, level with neighboring cells.

  • Single seed enclosed by a pericarp

Above: Dilcherifructus mexicana (Fig. 1, Wang 2021)

Montsechia vidalii †

  • Gomez et al. 2015

  • Barremian from Spain (~130 Ma)

  • An early aquatic flowering plant which possessed no obvious flower parts, such as petals or nectar-producing structures for attracting insects

  • The fruit contains a single seed, which is borne upside down.

  • Montsechia is possibly related to the living Ceratophyllum

  • This fossil is the earliest definitive evidence of angiosperm fossil leaves and flowers

Above: Montsechia vidalii

Right: Montsechia vidalii bearing fruits (Fig. 8, Gomez et al. 2015)

Archaefructus †

  • Sun et al. 2002

  • Barremian (~124.6 Ma)

  • One of the earliest known genera of flowering plants

  • Herbaceous and aquatic plant

  • carpels and stamens, sometimes produced on elongate stem

  • Staminate (male) flowers proximal and pistillate (female) flowers distal

  • Archaefructus may not be basal within angiosperms, but close to the Nymphaeales or the basal eudicots.

A. eoflora †

  • Qiang et al. 2004

  • Barremian from Beipiao, Western Liaoning, China

  • Unlike other species, A. eoflora lacks an extended section of male flowers

  • Male flowers are located closely proximal to carpellate flowers

A. liaoningensis †

A. sinensis †

Above: Archaefructus liaoningensis

Above: Archaefructus eoflora (Plate I, Qiang et al. 2004)

Additional Resources