Wize University Biology Textbook > Seedless Plants
Overview of Plants
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Plant Kingdom
Plants are vital to all terrestrial systems since they produce all of the energy in the ecosystem
General features
- Most plants live on land, few are aquatic
- Are Multicellular Eukaryotes
- Use Photosynthesis
- Cell walls made of cellulose
- Undergoes alternation of generations
Exam Tip
Cell walls made of cellulose is the most distinguishing feature of plants!
Main Groups
- Non-vascular plants: no vascular bundle Example: Mosses
- Seedless Vascular plants Example: Ferns
- Gymnosperms: has seeds but no flowers Example: Conifers and pines
- Angiosperms: flowering plants Example: Roses
Transition to life on land (~500 MYA)
- Benefits
- Lots of space
- Direct sunlight (unlike under water)
- Lots of mineral nutrients
- Few herbivores / pathogens
- Challenges
- Less water
- Gravity
- How did they succeed?
- Adapted through natural selection
- Took millions of years
Charophytes
- Charophytes are sister to Plantae (which contains all land plants)
- Synapomorphies with land plants (shared characteristics)
- Rings of protein in plasma membranes (synthesize cellulose)
- Flagellated sperm
- Phragmoplast: Cell plate between dividing cells (becomes new cell wall)
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Adaptations to Life on Land
This was one of the most significant transitions in all of the history of life on earth!
- Sporopollenin: tough polymer
- protects zygotes and spores from drying out
Unique plant traits (synapomorphies)
- Traits that unite plants (not charophytes)
- Water conservation
- Waxy cuticle: on epidermis, protect from water-loss and bacteria
- Stomata: cells that can open / close for gas exchange
- Multicellular and Dependent embryos
- Zygotes kept in tissue of female plant
- Placental cells: give zygote nutrients from parent
- Protect zygote from drying out
- Vascular tissues: contain lignin for strength
- Xylem: Dead - carries water and minerals from roots
- Phloem: Live - carries nutrients
- Compartmentalized Nutrients
- Nutrients from two sources
- Roots: water and minerals
- Shoots: light and gases
- early plants did not have roots - required mycorrhizae fungus
- Elongation and branching: increase surface area to absorb nutrients
- Apical Meristem: undifferentiated cells (like stem cells in humans)
- Can become any tissue
Wize Tip
These structures and functions of land plants are explained in greater detail in the Plant Physiology section of this textbook
Alternation of Generations
- Has two living forms: Haploid (1N) and Diploid (2N)
- Alternates between Sexual and Asexual reproduction
Practice: Transition to Land
Which of the following does NOT represent a benefit of the transition to land in plants?
Practice: Seedless Plants
Which of the following is true about Charophytes?
Practice: Sporopollenin
Mark the following statement True or False:
Sporopollenin is a tough polymer that evolved to protect the sperm and zygotes for life on land.
Practice: Xylem
Which of the following best describes plant xylem?
Practice: Undifferentiated Plant Cells
Which term about plants best fits the following description:
Undifferentiated cells that have the ability to become any type of cell in the plant.