Kingdom Plantae: Definition and Characteristics

• Ancestors of land plants are likely ancestral green algae.

Charophytes (Stoneworts)

• Crucial evolutionary link in the phylogenetic tree.
• Critical developmental step from algae.
• Possible insight to the link of aquatic plants to land plants.

Gymnosperms (Conifers)

• Strong stems and roots
• Seeds are made inside cones.

Angiosperms (Flowering plants)

• Strong stems, roots, and leaves.
• Flowers, that make seeds.

Monocotyledons

• Possess leaves with parallel veins.

Dicotyledons

• Possess leaves with a network of veins.

Kingdom Plantae

• Eukaryotic, multicellular, and autotrophic organisms.
• Organisms range in size from tiny mosses to giant trees.
• Plant cell has a rigid cell wall.
• Has chloroplast and chlorophyll pigment, required for photosynthesis.

Characteristics of Kingdom Plantae

• Non-motile organisms.
• Autotrophs, make their own food
• Asexual reproduction by vegetative propagation or sexual reproduction.
• Multicellular eukaryotes.
• Plant cell contains an outer cell wall and a large central vacuole.
• Photosynthetic pigments include chlorophyll, present in plastids.
• Different organelles for anchorage, reproduction, support, and photosynthesis.

Classification of Kingdom Plantae

• Uses presence/absence of a well-differentiated plant body (roots, stem, leaves)
• Classification by vascular system indicates the presence/absence for transportation of water and substances.
• Presence/absence of flowers and seeds determines seed formation.

Subgroups

• Thallophytes
• Bryophytes
• Pteridophytes
• Gymnosperms
• Angiosperms

Thallophyta (Not included in plantae → Protista)

• Includes lichen, algae, fungus, bacteria, slime moulds and bryophytes but does not include plants
• Polyphyletic non-mobile organisms that are grouped together by similar characteristics but not from a common ancestor

Bryophyta (Non-Vascular)

• Common examples are Marchantia, Funaria, Sphagnum, Antheoceros, etc.
• Division refers to embryophytes, which are in literal terms, land plants, especially in non-vascular ones
• Divisions are:
  • Mosses - class Bryopsida (Bryophyta)
  • Liverworts - class Marchantiopsida (Marchantiophyta)
  • Hornworts - class Anthocerotopsida (Anthocerotophyta)
• Non-vascular tissue
• Lacks lignin
• Believed to evolve from charophytes, considered to be the first true plants to evolve.
• Rhizoids, Marchantia
• Sphagnum (a moss) provide peat = used as fuel.
• Significant in plant succession.
• Amphibians of Plantae.
• Plant body has root-like, stem-like, and leaf-like structures.
• Present in moist and shady places.
• Rep. by mosses.
• Includes hornworts and liverworts.

Vascular (Seedless)

• Has xylem and phloem.
• Tracheophytes.
• Has true stems, leaves, and roots.
• Lower vascular plants, cryptogams.

Pteridophyta

• Well-differentiated plant body into root, stem and leaves.
• Much evolved.
• True plants that adapted.
• Common examples are Selaginella, Equisetum, Pteris, etc.
• Spore-dispersing vascular plants, develop in sporangia.
• Older groups of plants present in Plantae.
• Seedless, vascular plants that show true alternation.
• Homosporous or heterosporous.
• Used for medicinal value, i.e. Rattlesnake fern, Ostrich fern, Bracken fern.
• Used as soil-binders

Four Main Classes of Pteridophyta

• Psilopsida/Psilotophyta: Most primitive and ruthless, rootless with rhizoids (ex. Fossil genera; Rhynia and Horneophyton; Psilotum
• Lycopsida/Lycophyta: microphyllous leaves, homosporous (Selaginella Lycopodium) or heterosporous, sporophylls form strobili or cones
• Sphenopsida/Sphenophyta: All are fossils except Equisetum; sporangia forming strobili or cones; homosporous
• Pteropsida/Pterophyta: most widely distributed vascular cryptogams; Leaves macrophyllus called as fronds; homosporous (Pteris) or heterosporous (Marselia)

Vascular (Seeded)

• Stems = branch laterally.
• Vascular tissue = Arranged in strands (bundles) around the pith (eustele).
• Seeds represent important evolutionary innovation within the kingdom.
  • Seed contains and protects embryonic plant.

Gymnosperms

• Gymnos = naked; sperma = seeds.
• Vascular plants that possessed "exposed” seeds.
• Ovules are not enclosed by ovary wall.
• Seeds develop post-fertilization are not covered (naked).
• Include medium-sized trees or tall trees and shrubs.
• Sequoia (Giant redwood) = tallest tree species.
• Roots are generally tap roots, some have mycorrhiza; (Eg. Pinus).
• Cycas, small specialized roots (coralloid roots) are associated with N2- fixing cyanobacteria.
• Stems are unbranched (Cycas) or branched (Pinus, Cedrus).
• Leaves are simple or compound.

Four Divisions of Gymnosperms

• Cycadophyta: ancient seed plants; palmlike in general appearance; sexes are separate; many species produce conspicuous cones (stobili); symbiont cyanobacterium (Nostoc) in root; (ex. Cycas ("Sago Palm"), Zamia)
• Ginkgophyta: represented by Ginkgo biloba (maidenhair tree, monotypic); formerly restricted to southeastern China, now is likely extinct in the wild; multibranched
• Gnetophyta: Comprises of three genera
  • Ephedra: In dry regions in tropical and temperate North and South America, from the Mediterranean Sea to China
  • Gnetum: Occur as woody shrubs, vines, or broad-leaved trees
  • Welwitschia: Restricted to extreme deserts, enormous underground stem and a pair of long strap-shaped leaves
• Pinophyta: Coniferophyta, Podocarpus (Yew pines), Araucaria, Juniperus (Juniper), Pinus

Angiosperms

• Evolved from gymnosperms.
• Reproduce by means of flowers.
• Modified shoots bearing series leaf-like modified appendages containing ovules.
• Vascular plants that possess special characteristics such as flowers and fruits.
• Widely distributed in size; Wolffia = 0.1cm, Eucalyptus trees = around 100m tall.
• Divided to monocotyledons and dicotyledons.
• Examples are found like Mango, Rose, Tomato, Onion, Wheat, Maize, etc.
  • Monocots: Oryza, Triticum, Zea, Cyperus, Bambusa, Paspalum, Banana, Sugarcane, Lilies, etc.
  • Eudicots: Bougainvillea, Acacia, Lantana, Grapes, Sunflowers, Tomatoes, etc.