Plant Structure and Function Notes

Characteristics of Plants

  • Plants are multicellular eukaryotes.
  • Most can produce glucose through photosynthesis.
  • Plant cells feature thick cell walls made of cellulose.
  • Stems and leaves have a waxy cuticle for waterproofing.

Evolution of Plants

  • All plants likely evolved from filamentous green algae.
  • Green algae and plants share cell wall composition (cellulose) and chlorophyll types for photosynthesis.
  • Both groups store food as starch.

Plant Adaptations

  • Water Absorption: Roots are specialized to absorb water and minerals from the soil.
  • Water Loss Prevention: The cuticle helps retain moisture by creating a barrier against evaporation.

Photosynthesis in Leaves

  • Leaves are where gas exchange and photosynthesis occur.
  • Each species of plant has unique leaf structures.

Root Functions

  • Roots absorb water and minerals and anchor the plant.
  • Some roots, like radishes, store starch.

Transporting Materials in Plants

  • Roots collect water which is transported to leaves through stems, while sugars move to roots.
  • Vascular Tissues:
    • Xylem: Transports water and dissolved minerals.
    • Phloem: Transports sugars throughout the plant.

Vascular vs. Nonvascular Plants

  • Nonvascular Plants: (e.g., mosses, liverworts)
    • Lack vascular tissues, are usually a few cells thick.
    • Nutrient and water transport happens via diffusion and osmosis.
  • Vascular Plants:
    • Have vascular tissues and can grow larger, living farther from water sources.

Reproductive Strategies

  • Seeds: An adaptation that protects the embryo, contains food, and has a protective coat.
  • Spores vs Seeds: Seed plants have an advantage in dry environments.

Seed Plant Diversity

  • Gymnosperms: Seeds develop on cone scales.
  • Angiosperms: Flowering plants with seeds enclosed in fruit, aiding in dispersal.

Plant Body Plan

  • Composed of cells, tissues, and organs; includes apical meristems.

Plant Cell Types

  • Composed of central vacuole, chloroplast, and cell wall.

Plant Tissues Overview

  • Tissue Types:
    • Dermal: Protects and retains moisture.
    • Ground: Involved in photosynthesis, storage, and support.
    • Vascular: Includes xylem and phloem to transport materials.
    • Meristematic: Actively dividing cells for growth.

Leaf Structure and Function

  • Primary function is photosynthesis. Leaves possess stomata for gas exchange.
    • Stomata: Openings controlled by guard cells to regulate water vapor loss.

Flower Structure and Function

  • Flowers facilitate sexual reproduction with parts including sepals, petals, stamen, and pistils.
  • Pollination: Transfer of pollen, with fertilization following.

Seed Dispersal and Germination

  • Dispersal reduces competition for resources. Seeds can remain dormant until favorable conditions for germination are met.

Plant Hormones

  • Hormones like auxins, gibberellins, and ethylene regulate growth and development.

Plant Responses to Environment

  • Tropisms: Plant responses to stimuli.
    • Phototropism: growth toward light.
    • Gravitropism: growth in response to gravity.