Kingdom Plantae

• encompasses species that are:
  • multi-cellular
  • have eukaryotic cells
  • with cellulose walls
  • photosynthesise using c'phyll contained in c'plasts
• They also show distinct differentiation w/in cells in different parts of the plant eg. leaf cells specialised for p'syn

The two major plant groups are the Bryophytes and the Tracheophytes

• represented by mosses
• Structure:
  • lack true roots
  • lack stems and leaves
  • no vascular tissue (rely on turgor support)
  • cells organised into structure superficially similar to stems and roots
  • rhizoids water and minerals gained and lost over entire surface
    • anchor to ground
    • unable to penetrate substratum
    • no specific role in water uptake
  • leaf-like structures do not have cuticle or stomata
• As a result of not having true roots and vascular tissue, and limited ability to reduce water loss:
  • seldom reach significant size
  • restricted to damp habitats

• Mosses produce spores in a capsule at the end of a stalk
  • lifts the spore-producing cabsule above the ground, aiding dispersal by wind
  • capsule has stomata and a cuticle, so partially protected from desiccation

• Vascular plants
• have a vascular system of xylem (water and minerals) and phloem (sucrose and amino acids)

Two major sub-divisions: 

Ferns (pteridophytes)

Flowering plants (spermatophytes)

• Structure:
  • true roots
  • stems 
  • leaves (typically subdivided into leaflets- pinnae)
• possess vascular tissue- xylem (water and ion transport) and phloem (organic nutrient transport)
  • Support is by turgor w/in cells and by presence of xylem thickened by lignin (lignin creates secondary cell walls
  • vascular tissue important factor in allowing them to grow to considerable sizes
• Can colonise dried areas than mosses due to:
  • waterproof cuticle
  • stomata (allowing fine control) 

• In many ferms, the stem (rhizome) runs horizontally underground, with leaves the only part that extends above ground
• Disperse spores and germinate in damp conditions - spores not highly resistant to desiccation
  • an important factor in restricting ferns to relatively damp habitats

Stem- Rhizome

Leaf- Frond

Leaflet- Pinna (pl. Pinnae)

• Angiosperms have flowers as reproductive structures
• Produce seeds instead of spores
• Variable in form - include small herbaceous plants and large trees
• Structure: 
  • true roots
  • stems and leaves
  • waterproofed cuticle
  • stomata subject to fine control
  • vascular tissue highly developed
  • roots able to penetrate deep into ground to absorb water and minerals
• Adaptations to terrestrial habitats:
  • root systems more complex
  • xylem much more extensive + capable of providing more support

Note: Trees are usually over 95% xylem (wood). In older trees, most of this wood no longer transports water and has a purely supportive role.

This allows trees to reach great heights and obtain more light than other plants when growing in woodland.

• Seeds have tough outer coat which provides protection against desicattion
  • can be dispersed into hostile environments and remain dormant but viable, eventually germinating if conditions become suitable
  • many are highly adapted for disperal by wind, animal or explosive mechanism

• Diversity of flowering plants means diff adapted for virtually all habitats on Earth, and can be adapted for anything btwn v. moist environments (or in water- hydrophytes) to extremely dry (xerophytes)

Mosses- no vascular tissue, so do not grow tall

Ferns- reach a greater height than mosses, a competitive advantage

Ferns grow tall, but stem thickness does not increase proportionally

∴ fern  height : width ratio is much greater compared to trees

Woody angiosperms (trees)- reach greater height than ferns

They can increase stem thickness as height increases, as they have a layer of dividing cells (beside the cambium) between xylem and phloem in their vascular bundles 

Greater width allows trees to get taller still- having greater stability at heights

This is a competitive advantage, as it leads to more light, so greater rate of p'syn