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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
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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
- Traits that unite plants
- 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
Alternation of Generations
- Has two living forms: Haploid (1N) and Diploid (2N)
- Alternates between Sexual and Asexual reproduction
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Plant Characteristics
- Photoautotrphs: receive energy from the sun and carbon from CO2
- Chlorophyll: specialized organs that generate sugars from sunlight, CO2 and water
- Immobile
- Rooted producers
- Unlimited growth
Plant Cell Walls
- Rigid cell walls
- Cellulose, Hemicellulose: rigid carbohydrates around outside of plant cell
- Pectin: glues adjacent cells together
- Provides structural support and protection
- Prevents mobility
- Plasmodermata: channels that run through cells
- Allows transport of materials throughout the plant
Example: Plant Characteristics
List characteristics that ALL plants have in common.
Have cell walls made of cellulose
Use photosynthesis - are photo-autotrophs
Are multicellular eukaryotes
Undergo alternation of generations - they have a multicellular diploid and haploid life stage!
Example: Alternation of Generations
Using a diagram, demonstrate how plants utilize the cell division processes of mitosis and meiosis at different life stages.
Practice Plant Cell Biology
Which of the following is used to glue adjacent plant cells together?
Practice: Transition to Land
Which of the following does NOT represent a benefit of the transition to land in plants?
Practice: Xylem
Which of the following best describes plant xylem?