Section 2A Concise

Plant Structure, Growth and Development

• Hierarchical Organization (35.1)

  • Plants consist of organs, tissues, and cells.

• Basic Plant Organs

  • Root System: anchors the plant, absorbs minerals/water, stores carbohydrates.

  • Shoot System: relies on root system for water and minerals, contains stems and leaves.

• Types of Roots:

  • Taproot System: main vertical root (eudicots, gymnosperms).

  • Fibrous Root System: mat of slender roots (monocots).

  • Adventitious Roots: emerge from unusual sources (e.g., stems).

• Root Functions:

  • Increase surface area for absorption via root hairs.

  • Various adaptations: prop roots, storage roots, green roots, pneumatohores.

• Stems:

  • Raise leaves and reproductive structures, consist of nodes and internodes.

  • Apical and axillary buds control growth and branching.

  • Modified stems: rhizomes, bulbs, stolons, tubers.

• Leaves:

  • Main photosynthetic organs with flattened blades and petioles.

  • Leaf types: simple (undivided) and compound (multiple leaflets).

  • Specialized leaves for support, protection, storage, and reproduction.

• Tissue Systems:

  • Dermal: protective cover, includes epidermis and periderm in older plants.

  • Vascular: transports materials (xylem: water & minerals, phloem: sugars).

  • Ground: internal tissue for storage, photosynthesis, support.

• Meristems (35.2):

  • Allow for indeterminate growth, consists of apical and lateral meristems.

  • Primary growth: elongation of roots and shoots.

  • Secondary growth: increasing thickness, carried out by vascular cambium and cork cambium.

• Growth Cycle:

  • Primary and secondary growth occur simultaneously in woody plants.