Organismal Biology: Plant Organ System

Organismal Biology: Plant Organ System

• Plant bodies are made up of trillions of cells organized into tissues, organs, and organ systems, allowing specialized functions and division of labor.
• Organs work together in systems, forming a complete living organism.
• Flowering plants generally consist of a root and shoot system.

Root System

• The root system comprises the roots.
• Roots grow extensively underground, branching to anchor the plant, absorb water and minerals, supporting metabolic processes.
• Root hairs increase the absorptive surface area of the root.
• Root systems are classified as taproot (one main root), fibrous (multiple roots of similar size), and adventitious (roots arising from parts other than the root).
• Vascular tissues (xylem and phloem) transport substances differently in monocots (ring-shaped arrangement) and dicots (star-shaped xylem).

Shoot System

• The shoot system consists of the stem, branches, and leaves.
• The stem is the main axis, supporting the leaves and exposing them to sunlight.
• Stem characteristics include nodes (bud attachment points), internodes (section between nodes), buds (embryonic stems), and branch types.
• Stems, like roots, have vascular tissues for transport.

Leaves

• Leaves are primarily the food factory of the plant.
• Leaf parts include the blade (expanded green part), petiole (leaf stalk), and stipule.
• Leaf veins (vascular bundles) in monocots are parallel, while dicots have net-like (pinnate or palmate) venation.

Reproductive Organs (Flowers)

• Flowers are specialized reproductive structures of angiosperms.
• Parts of a flower include petals (corolla), sepals (calyx), pistils (female organs), and stamens (male organs).
• The stigma traps pollen. The style supports the stigma. The ovary contains ovules with egg cells. Pollen contains sperm cells.
• Flower structures may vary in arrangement and symmetry.

Fruit

• Fruit is the mature ovary.
• Different fruit types exist (drupe, berry, aggregate).
• Fruits contain the seed.

Seed Structure

• Seeds enclose a plant embryo, surrounded by protective seed coats, and endosperm (food storage).
• The three primary parts of a seed include the embryo, endosperm, and seed coat.