Plant Kingdom: Taxonomy and Classification
🟢 Lite — Quick Review (1h–1d)
Rapid summary for last-minute revision before your exam.
Plant Kingdom — Key Facts for Sri Lanka A/L Examination
Five Kingdom Classification (Whittaker, 1969):
| Kingdom | Cell Type | Nutrition | Examples |
|---|---|---|---|
| Monera | Prokaryotic | Autotrophic/Heterotrophic | Bacteria, Cyanobacteria |
| Protista | Eukaryotic | Autotrophic/Heterotrophic | Amoeba, Euglena |
| Fungi | Eukaryotic | Heterotrophic (absorption) | Mushrooms, Yeast |
| Plantae | Eukaryotic | Autotrophic (photosynthesis) | Mosses, Ferns, Trees |
| Animalia | Eukaryotic | Heterotrophic (ingestion) | Animals |
Plant Divisions (Major Groups):
| Division | Common Name | Features | Examples |
|---|---|---|---|
| Bryophyta | Mosses | No vascular tissue, land plants | Funaria, Polytrichum |
| Pteridophyta | Ferns | Vascular, spores, no seeds | Dryopteris, Pteris |
| Gymnospermae | Conifers | Vascular, naked seeds, no fruits | Pinus, Cycas |
| Angiospermae | Flowering plants | Vascular, enclosed seeds, fruits | All flowering plants |
⚡ A/L Exam Tip: Remember - Bryophytes need water for reproduction (flagellated sperm), Pteridophytes have vascular tissue but still need water!
🟡 Standard — Regular Study (2d–2mo)
Standard content for students with a few days to months.
Plant Kingdom — Detailed Study Guide
Bryophytes (Mosses and Liverworts)
Characteristics:
- First true land plants
- No vascular tissue (no xylem/phloem)
- No true roots (rhizoids instead)
- Require water for fertilization
- Dominant gametophyte generation
- Alternation of generations
Structure:
- Gametophyte: Green, leaf-like structures
- Sporophyte: Dependent on gametophyte
- Rhizoids: Anchor to substrate, absorb water/minerals
Examples in Sri Lanka:
- Funaria hygrometrica: Common cord moss
- Marchantia polymorpha: Liverwort
Life Cycle:
- Spores germinate → protonema → gametophyte
- Gametophyte produces gametes (antheridia and archegonia)
- Sperm swims to egg (needs water)
- Fertilization → zygote
- Zygote develops into sporophyte
- Sporophyte produces spores (meiosis)
Pteridophytes (Ferns)
Characteristics:
- First vascular plants
- Have xylem and phloem
- Dominant sporophyte generation
- Still need water for reproduction
- Leaves called fronds (circinate vernation)
- Spores produced in sporangia (sori)
Structure:
- Rhizome: Horizontal underground stem
- Fronds: Large compound leaves
- Prothallus: Heart-shaped gametophyte (independent)
Examples in Sri Lanka:
- Dryopteris: Common fern
- Pteris: Brake fern
- Azolla: Water fern (used as biofertilizer)
Life Cycle:
- Sporophyte (dominant) produces spores in sporangia
- Spores germinate → prothallus (gametophyte)
- Prothallus produces antheridia and archegonia
- Sperm swims to egg (needs water)
- Fertilization → zygote → new sporophyte
⚡ A/L PYQ: “What is meant by circinate vernation?” Answer: The young fronds of ferns are coiled like a watch spring, which uncoil as they mature.
Gymnosperms (Naked Seed Plants)
Characteristics:
- Vascular plants with seeds
- Seeds not enclosed in fruits (naked)
- Mostly trees and shrubs
- Usually evergreen, needle-like leaves (reduce transpiration)
- No flowers (no fruits)
- Male and female cones separate
Examples:
| Plant | Type | Notable Feature |
|---|---|---|
| Pinus | Conifer | Needles, woody cones |
| Cycas | Cycad | Palm-like, compound leaves |
| Ginkgo | Ginkgo | Fan-shaped leaves, deciduous |
| Podocarpus | Conifer | Resembles Podocarpus in Sri Lanka highlands |
Pinus Structure:
- Needles: 1-5 per sheath, long and slender
- Monoecious: Male and female cones on same tree
- Male cones: Produce pollen grains
- Female cones: Ovules on cone scales
Angiosperms (Flowering Plants)
Two Main Classes:
| Feature | Monocotyledons | Dicotyledons |
|---|---|---|
| Cotyledons | 1 | 2 |
| Leaf venation | Parallel | Reticulate |
| Flower parts | Usually multiples of 3 | Usually multiples of 4 or 5 |
| Vascular bundles | Scattered | Ring arrangement |
| Roots | Fibrous (adventitious) | Tap root system |
| Stem | Usually herbaceous | Woody or herbaceous |
Sri Lankan Examples:
- Monocots: Rice, coconut, banana, orchids, grasses
- Dicots: Mango, jackfruit, rubber, tea
🔴 Extended — Deep Study (3mo+)
Comprehensive coverage for students on a longer study timeline.
Plant Kingdom — Complete Notes for A/L Sri Lanka
Plant Tissue Systems
Meristematic Tissue (actively dividing):
| Type | Location | Function |
|---|---|---|
| Apical meristem | Root/shoot tips | Primary growth (length) |
| Lateral meristem | Sides of stems/roots | Secondary growth (width) |
| Intercalary meristem | Between nodes | Growth in grasses |
Permanent Tissue:
| Tissue | Function | Types |
|---|---|---|
| Parenchyma | Storage, photosynthesis | Chlorenchyma, aerenchyma |
| Collenchyma | Support (flexible) | Angular, lamellar, lacunar |
| Sclerenchyma | Support (rigid) | Fibers, sclereids |
Vascular Tissue:
- Xylem: Water conduction, support
- Tracheids, vessels, parenchyma, fibers
- Phloem: Food conduction
- Sieve tubes, companion cells, parenchyma, fibers
Alternation of Generations
Haplo-Diplontic Life Cycle (Plants):
| Generation | Ploidy | Description |
|---|---|---|
| Gametophyte | n | Produces gametes |
| Sporophyte | 2n | Produces spores |
Comparison:
| Plant Group | Dominant Generation | Gametophyte Size |
|---|---|---|
| Bryophytes | Gametophyte | Large |
| Pteridophytes | Sporophyte | Small (prothallus) |
| Gymnosperms | Sporophyte | Very small (pollen grain) |
| Angiosperms | Sporophyte | Reduced (pollen grain, embryo sac) |
⚡ Key for Exam: In bryophytes, the green moss plant IS the gametophyte. In ferns, the large frond-bearing plant IS the sporophyte.
Plant Responses and Growth Regulators
Plant Hormones:
| Hormone | Primary Function |
|---|---|
| Auxin | Cell elongation, phototropism, gravitropism |
| Gibberellin | Stem elongation, seed germination |
| Cytokinin | Cell division, delay senescence |
| Ethylene | Fruit ripening, abscission |
| Abscisic acid | Stress response, seed dormancy |
Tropisms:
| Tropism | Stimulus | Response |
|---|---|---|
| Phototropism | Light | Grow toward light |
| Gravitropism | Gravity | Grow up/down |
| Thigmotropism | Touch | Coiling response |
GCE A/L Sri Lanka Past Paper Tips
Common Diagram Questions:
- Draw and label life cycle of a moss (8 marks)
- Draw and label fern prothallus (6 marks)
- Draw TS of pine needle/leaf (5 marks)
- Draw external features of a dicotyledonous plant (10 marks)
- Compare monocot and dicot stem vascular bundles (5 marks)
Short Answer Questions:
- State two differences between gymnosperms and angiosperms
- Explain why bryophytes are called “amphibians of plant kingdom”
- Describe the process of spore dispersal in ferns
Structured Questions:
- “With reference to a named bryophyte, describe the alternation of generations in non-vascular plants” (15 marks)
- “Describe the structure and function of vascular tissues in plants” (12 marks)
⚡ A/L Strategy: For life cycle questions, always include both gametophyte and sporophyte generations with correct ploidy levels and where fertilization occurs.
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