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Questions and Answers

Which factor primarily stimulates seed production in trees after hot dry years?

Decrease in photosynthesis

Enhanced soil nutrients

Reduction in competition

Increased photosynthesis (correct)

How do conifers primarily disperse their seeds?

By soil

By gravity

By wind (correct)

By water

What is required for a seed to germinate if the embryo is fully developed?

The seed must undergo after ripening processes. (correct)

The seed must be surrounded by fertile soil.

The seed must be planted in direct sunlight.

Moisture must reach the seed.

Which term describes the percentage of seeds in a sample that actually germinate?

Germinative capacity Signup and view all the answers

Which type of seed is defined as having the potential capacity to germinate?

Viable seeds Signup and view all the answers

What is the effect of fire injury on seed production?

It stimulates seed production Signup and view all the answers

Which characteristic is true of recalcitrant seeds?

They cannot survive drying below a high moisture content. Signup and view all the answers

What percentage of Acacia arabica seeds develops into seedlings by the end of the first growing season?

26% Signup and view all the answers

What impact does the size of a seed have on its natural regeneration?

Smaller seeds are easily washed away by rain. Signup and view all the answers

Which internal factor is not essential for seed germination?

Temperature control Signup and view all the answers

Which external factor is likely to enhance seed production in plants?

Insect attack Signup and view all the answers

Which type of seeds typically have a longer viability when stored properly?

Orthodox seeds Signup and view all the answers

Which method of forest regeneration involves planting seedlings?

Natural Regeneration supplemented by Planting Signup and view all the answers

What is the primary definition of regeneration in the context of forests?

The renewal of forest crops by natural or artificial means Signup and view all the answers

Which of the following factors does NOT influence seed production in trees?

Soil type Signup and view all the answers

Which type of regeneration involves the use of self-sown seeds?

Natural regeneration from seed Signup and view all the answers

What is the ideal age range of trees for optimal seed production?

Middle-aged trees Signup and view all the answers

What does the term 'seedling year' refer to?

A year with abundant first-year seedlings Signup and view all the answers

What climatic condition generally favors increased seed production?

Warmer climates Signup and view all the answers

Which of the following is NOT a method of natural regeneration?

Natural Regeneration by Artificial Seeding Signup and view all the answers

Which species seeds annually and abundantly?

Teak Signup and view all the answers

Study Notes

Forest Regeneration

Forest regeneration is the renewal of a forest, naturally or artificially.
Regeneration methods include natural regeneration, artificial regeneration, and a combination of both.

Natural Regeneration

Natural regeneration uses self-sown seeds, coppice, or root suckers.
It's also known as reforestation via natural seeding.
A seedling crop originates from naturally occurring seeds in situ.

Natural Regeneration: From Seed

Successful seed regeneration depends on seed production, dispersal, germination, and seedling establishment.
Seeds are cultured ovules containing embryos.
Seed production varies by species, tree age, crown size, and climate.

Factors Affecting Seed Production

Species: Some species (e.g., teak, babul, khair) seed annually, while others (e.g., deodar, fir, spruce) seed intermittently.
Age: Middle-aged trees produce the best seeds; young and old trees produce poor quality seeds in small quantities.
Crown Size: Larger crowns generally produce more seeds due to increased solar energy capture for photosynthesis.
Climate: Warmer climates favor greater seed production; lower altitudes usually produce more seeds than higher altitudes.
Hot, dry years often lead to good seed years due to increased photosynthesis.
External factors such as fire, insect attacks, and girdling can also influence seed production. Fire and insect attacks can sometimes stimulate seed production.

Seed Dispersal

Seeds are dispersed by wind (e.g., conifers, Acer, Rhododendron), water (e.g., mangroves, Dalbergia, teak), gravity (e.g., oak, Juglans regia), birds (e.g., Prunus, mulberry), and animals (e.g., Acacia arabica).

Seed Germination

Germination is the process of a seed sprouting and growing into a seedling.

Relevant Terminology

Germinative capacity: Percentage of seeds in a sample that germinate.
Germinative energy: Percentage of seeds germinated before the germination rate peaks.
Plant percent: Percentage of seeds developing into seedlings by the end of the first growing season.
Seedling year: A year with abundant first-year seedlings of a given species.
Example data:
- Acacia arbica: 50% germinative capacity, 26% plant percent
- Shorea robusta: 80% germinative capacity, 66% plant percent

Factors Affecting Germination

Internal Factors:
- Permeability to water: A hard seed coat can prevent water uptake and germination.
- Permeability to oxygen: Oxygen is essential for germination. Factors inhibiting moisture also inhibit oxygen access.
- Embryo development: The embryo must be fully developed for germination. Some species (e.g., Fraxinus floribunda) have seeds that remain dormant for a year after falling.
- After-ripening processes: Some fully developed embryos need additional processes before they can germinate (e.g., Juniperus macropoda).
- Viability: The ability of a seed to germinate. Recalcitrant seeds have low viability and cannot be stored long-term; Orthodox seeds dry well, have long viability, and long-term storage is possible.
- Seed size: Small seeds might wash away, while large seeds may not get properly covered with soil. Thicker seeds generally germinate better
External factors: (not detailed in provided text)

Seed Viability Types

Recalcitrant Seeds: Cannot survive drying below 20-50% moisture and cannot be stored at low temperatures for long periods (e.g., Shorea robusta, Dipterocarpus, Azadirachta indica).
Orthodox Seeds: Withstand drying to 5% moisture and can be stored at low temperatures for long periods (e.g., Pinus, Picea, Eucalyptus, Prosopis, Albizia).