Integrated Science — Living Things and Their Environment

Subtopic: Reproduction in Plants (Age 14 — Kenya)

Learning objectives:

• Define reproduction in plants and explain why it is important.
• Describe and give examples of sexual and asexual reproduction in plants.
• Explain pollination, fertilisation, seed and fruit formation, and germination.
• Carry out simple investigations (e.g. seed germination, vegetative propagation).

Key terms

Reproduction, sexual reproduction, asexual reproduction, pollination, self-pollination, cross-pollination, fertilisation, seed, fruit, germination, spore, vegetative propagation.

1. What is plant reproduction?

Reproduction is the process by which plants make new plants. It ensures their survival and helps produce seeds, fruits and more plants for food, forestry and farming.

2. Two main methods

1. Sexual reproduction — involves flowers (in flowering plants). Male cells (pollen) join with female cells (ovules) to form seeds. Example: maize, beans, mango.
2. Asexual reproduction — new plants form from parts of a parent plant without seeds. Examples: potato tubers, sweet potato vines, cassava cuttings, grafting.

3. Structure of a typical flower (simple)

Main parts: petal (attracts pollinators), sepal (protects bud), stamen (male: anther + filament), pistil/ carpel (female: stigma + style + ovary containing ovules).

4. Pollination and fertilisation

Pollination is the transfer of pollen from an anther to a stigma. Fertilisation is when the male cell in the pollen joins an ovule in the ovary to form a seed.

Types of pollination:

• Self-pollination — pollen from the same flower or another flower on the same plant (e.g., some beans).
• Cross-pollination — pollen from one plant pollinates a flower on another plant (e.g., maize, many fruit trees).

Agents of pollination: insects (bees, butterflies), wind (e.g., maize), water, birds, and mammals. (Use emojis as reminders: 🐝 wind:💨 water:💧 animals:🐦)

5. After fertilisation

• Ovule becomes a seed (contains embryo + food store + seed coat).
• Ovary becomes a fruit (protects seed; helps in seed dispersal).

6. Germination (how a seed grows)

Germination is the process when a seed starts to grow into a young plant (seedling). Conditions needed:

• Water — to soften the seed coat and start chemical reactions.
• Suitable temperature — enzymes work best at particular temperatures.
• Oxygen — for respiration of growing embryo.
• Light — some seeds need light, others need darkness.

7. Asexual reproduction (vegetative propagation and others)

Asexual methods produce plants genetically identical to the parent (useful in agriculture for maintaining desired traits).

• Cuttings — stem or leaf cuts planted to form new plants (e.g., cassava cuttings, sweet potato vines).
• Tubers — potato tubers produce new plants from "eyes".
• Runners — strawberry runners grow into new plants.
• Grafting and budding — join parts of two plants (used in fruit tree propagation).
• Spores — non-flowering plants like ferns and mosses produce spores instead of seeds.

8. Seed dispersal — ways seeds move away from the parent

Methods help reduce competition and spread to new areas:

• Wind (anemochory) — e.g., cotton, maize pollen, seeds with wings (💨).
• Water (hydrochory) — e.g., coconut (💧).
• Animals (zoochory) — seeds eaten and passed out, or hooked seeds cling to fur (🐾).
• Explosion (ballistic) — pods burst to scatter seeds.

9. Importance of reproduction in plants

• Provides food (seeds, fruits, vegetables).
• Makes new plants for timber, medicine and conservation.
• Maintains species and biodiversity.
• Allows farmers to improve crops by selecting good varieties.

10. Simple practical activities (class or at home)

1. Germination test:
   • Materials: bean seeds, moist cotton/wet towel, small plate or transparent jar.
   • Method: place seeds on moist cotton, keep at room temperature, observe daily for root/shoot over 7–10 days.
   • Record: time to first root, time to shoot, count germinated seeds.
2. Vegetative propagation:
   • Take a stem cutting from a plant (e.g., coleus), plant in soil or water, watch root formation.
   • Observe how new plant develops and compare to parent.
3. Pollination observation:
   • Visit school garden, observe flowers and pollinators (bees, butterflies), note which plants are insect- or wind-pollinated.

11. Useful tips for exams

• Learn parts of a flower and their functions.
• Be able to tell differences between self- and cross-pollination with examples.
• Memorise conditions for germination and give examples of asexual methods.

12. Short questions (with answers)

1. Q: Define pollination.
   A: The transfer of pollen from anther to stigma.
2. Q: Give two agents of pollination.
   A: Insects (bees) and wind.
3. Q: Name two methods of asexual reproduction and give one Kenyan crop example.
   A: Cuttings (cassava), tubers (Irish potato).
4. Q: What conditions are needed for seed germination?
   A: Water, suitable temperature, oxygen (and sometimes light).

Prepared for Kenyan learners — Integrated Science (Age 14)