Lecture Notes: Trees

Definition and Characteristics

• Trees are perennial plants with elongated stems/trunks supporting branches and leaves.
• Definitions vary: some include only woody plants with secondary growth, others include palms, tree ferns, bananas, and bamboos.
• Not a monophyletic group but evolved independently to compete for sunlight.
• Types: mostly angiosperms (hardwoods) and gymnosperms (softwoods).
• Estimated 3 trillion mature trees globally.

Structure

Trunk and Branches

• Trunk provides strength with woody and vascular tissue for material transport.
• Bark protects the trunk; roots anchor the tree and absorb nutrients.
• Leaves on shoots capture light for photosynthesis.

Roots

• Anchor the tree, absorb moisture, and assist in reproduction.
• Mycorrhizal fungi form mutualistic relationships, aiding in nutrient absorption.
• Some trees have aerial roots or pneumatophores for stability or oxygen uptake.

Growth

• Trees grow through primary (height) and secondary (thickness) growth.
• Growth involves forming buds that expand when conditions improve.

Reproduction

• Generally through seeds; angiosperms have seeds in fruits, conifers in cones.
• Pollination can be through wind or animals.

Ecological Role

• Reduce soil erosion and climate moderation by storing carbon and providing habitats.
• Tropical rainforests are highly biodiverse.

Uses

Wood and Timber

• Used in construction, furniture, paper, and as fuel.
• Engineered wood products are also popular.

Food and Medicine

• Trees produce many fruits, nuts, and spices.
• Important source of drugs like quinine and aspirin.

Ornamental and Cultural Significance

• Trees are used in landscaping for aesthetics and cultural rituals.
• Sacred groves and mythologies across cultures link human life with trees.

Conservation and Challenges

• Deforestation for agriculture reduces tree populations.
• Conservation efforts are critical, with many tree species threatened.

Unique Features

• Trees like the coast redwood and giant sequoia are notable for their size and longevity.
• Specific trees hold cultural significance, such as the banyan in India or the sacred oak in Celtic lore.

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These notes consolidate the essential information from a detailed transcript discussion on trees, covering definitions, structure, ecological roles, uses, and conservation. Remember to review these notes for a comprehensive understanding of the topic.