Plant taxonomy

1. Pablo León Cruz www.biogeosfera.es
KINGDOM PLANTAE: PLANT TAXONOMY

2. The evolution of plants
The plants that we know today emerged about 500 million years
ago through the process of evolution. The most primitive plants
inhabited aquatic environments and gradually colonized the
terrestrial environment.
For this to occur, it was necessary to develop new organs and
tissues:
 Epidermal tissues to prevent dehydration.
 Supportive tissues to grow upright.
 Conductive tissues to transport substances.
 Flowers to produce pollen and promote fertilization.

3. The evolution of plants
 Algae: Aquatic organisms that lack differentiated tissues.
 Bryophytes: Very simple and small with epidermal tissue
but no conductive or supporting tissues.
 Pteridophytes: Have epidermal and conductive tissues.
They have roots, stems and leaves, but no flowers.
 Gymnosperms: Have epidermal, conductive and supporting
tissues. Woody plants with inflorescence and naked seeds.
 Angiosperms: The largest group. They have epidermal,
conductive and supportive tissues. They have flowers and
fruits.
Algaes Bryophytes Pteridophytes Gymnosperms Angiosperms

4. The evolution of plants

5. The evolution of plants
Epidermal
tissues
Conductive
tissues
Supportive
tissues
Bryophytes
Pteridophytes
Gymnosperms
Angiosperms

6. Bryophytes
Characteristics of bryophytes
 Small plants with very simple structures.
 Non-vascular plants, that is, not having specialized organs for
transporting water.
 Have false roots (rhizoids), false stems (cauloids) and false leaves
(phyllodes).
 Only have epidermal tissue, but no conductive or supportive tissues.
 Don’t have flowers and breed by spores.
 Have alternating reproduction, with gametophyte and sporophyte.
 Live in the shade in very humid places.
 Grow on walls, tree trunks, rocks and on the ground.
 There are three types of bryophytes: mosses, liverworts and hornworts.

7. Bryophytes
Parts of a moss
Stalk
Phyllodes
Rhizoids
Capsule
Spores
Cauloids
gametophyte
SporophyteGametophyte

8. Bryophytes

9. Bryophytes
Mosses

10. Bryophytes
Hornworts
Liverworts

11. Pteridophytes
Characteristics of pteridophytes
 Medium-sized plants.
 Vascular plants: have roots, stems and leaves.
 Mainly comprised of epidermal and conductive tissues.
 Their leaves are called fronds.
 They don’t have flowers and breed by spores.
 Alternating reproduction of gametophyte and sporophyte.
 Inhabit cool, humid and shaded terrestrial environments, although some
species can live in dry environments.
 Grow on walls, tree trunks, rocks and on the ground.
 Originated in the Devonian period. During the Carboniferous period they
formed large forests that gave rise to current coal deposits.
 There are three primary groups: Lycopods, ferns and horsetails.

12. Pteridophytes
Parts of a fern
Rhizome Roots
Sorus
Spores
Frond

13. Pteridophytes
Lycopods Horsetails

14. Pteridophytes
Different types of ferns

15. Pteridophytes
The pteridophyte forests of the Carboniferous period
The Carboniferous plants formed huge swamp forests
where a large number of pteridophytes grew. When
they died, the plants sank down into the water,
gradually decomposed and, when covered with
several layers of soil and underneath great pressure
for millions of years, they formed the coal deposits
we know today.

16. Gymnosperms
Characteristics of gymnosperms
 Medium to large-sized plants.
 Vascular plants: they have roots, stems and leaves.
 Have epidermal, conductive and supporting tissues.
 Possess unisexual inflorescence: male and female.
 Evergreens with needle-shaped leaves.
 Pollination is by anemophily (by wind).
 The seeds are not protected by a fruit (naked) and are found in the cone.
 The most well-known gymnosperms are conifers: pines, fir trees, cedars,
cypresses, junipers… but there are also other gymnosperms such as
gingkoes, yews and sago palms.

17. Gymnosperms
The inflorescences of gymnosperms

18. Gymnosperms
The inflorescences of gymnosperms

19. Gymnosperms
Pine (Genus Pinus)

20. Gymnosperms
Cypress (Genus Cupressus)

21. Gymnosperms
Cedar (Genus Cedrus)

22. Gymnosperms
Fir (Genus Abies)

23. Gymnosperms
Other gymnosperms you should know…
Yew (Taxus baccata) Ginkgo (Ginkgo biloba)
Sago palm (Cycas revoluta) Melinjo (Gnetum gnemon)

24. Angiosperms
Characteristics of the angiosperms
 Very large, such as herbs, shrubs and trees.
 Vascular plants: they have roots, stems and leaves.
 Epidermal, conductive and structural tissues.
 Possess very striking flowers that are typically hermaphroditic.
 Pollination is usually zoogamous, especially by insects (entomophily).
 The seeds are protected by a fleshy or dried fruit.
 There are about 257,000 species, making them the largest group of plants.
 The diversity of angiosperms is much higher in tropical areas and
decreases towards colder climates.
 They can be monocotyledonous (monocots) or dicotyledonous (dicots).

25. Angiosperms
Monocotyledonous (Monocots)
 There is no primary root.
 The stems don’t have branches.
 The leaves do not have a petiole.
 The venation of the leaf is parallel.
 The conductive tissues are randomly distributed.
 The flower structures are usually in sets of three.
 The embryo emits a single cotyledon when it begins to grow.
 Examples: Palm trees, orchids, grasses, bulbous plants…
Dicotyledonous (Dicots)
 They have a main branching root.
 The stems are typically branched.
 The leaves have a petiole.
 The venation of the leaves can be very varied.
 The conductive tissues are arranged in concentric rings.
 The flower structures are usually in sets of four or five.
 The embryo emits two cotyledons when it begins to grow.
 Examples: Trees (oak, olive, beech), shrubs (rose, camellia), legumes…

26. Angiosperms
Comparing monocots and dicots

27. Angiosperms
Monocots

28. Angiosperms
Dicots

29. Angiosperms
Angiosperms are found all over the world

30. Angiosperms
Angiosperms are found all over the world

31. Angiosperms
Angiosperms are found all over the world

32. Angiosperms
Angiosperms are found all over the world