Plant Structure, Growth, and Reproduction Notes

Types of Plants

  • Gymnosperms: Plants that bear seeds on cones.
  • Angiosperms: Flowering plants that bear seeds in fruits. Most plants are angiosperms.
    • Classified into two main groups:
    • Monocots
    • Dicots

Monocots

  • Characteristics include:
    • One cotyledon: First leaf of a plant embryo.
    • Parallel leaf venation: Leaf veins run parallel to each other.
    • Scattered vascular bundles: Vascular tissue not arranged in a ring.
    • Flower parts in threes: Multiples of three, such as lilies and orchids.
    • Fibrous roots: Root system consisting of numerous thin roots.

Dicots

  • Eudicots: True dicots that diverged from a common ancestor about 125 million years ago, making them constitutive of most plants.
  • Characteristics include:
    • Two cotyledons.
    • Branched leaf venation: Leaf veins that branch out.
    • Ring of vascular bundles: Vascular tissue arranged in a circle.
    • Flower parts in fours or fives: Examples include roses and hibiscus.
    • Taproot system: A primary root that grows deeper into the soil.

Typical Plant Body: Roots, Stems, and Leaves

  • Two organ systems:
    1. Root system
    2. Shoot system
  • Root system functions:
    • Anchoring the plant in the soil.
    • Absorbing and transporting water and minerals.
    • Storing carbohydrates.
    • Root hairs: Increase surface area for absorption.
  • Shoot system consists of:
    • Stems: Contains nodes (points where leaves attach) and internodes (sections between nodes).
    • Leaves: Main photosynthetic organs; green stems can also perform photosynthesis.

Tissue Systems of Plants

  • Composed of three main types of tissues:
    • Dermal Tissue: Protective outer covering; consists of epidermis.
    • Cuticle: A waxy layer that reduces water loss.
    • Vascular Tissue: Provides support and long-distance transport;
    • Comprised of xylem (water-conducting) and phloem (food-conducting).
    • Ground Tissue: Makes up most of the plant body, involved in food production and storage.

Plant Cell Structure

  • Unique structures include:
    • Chloroplasts: For photosynthesis.
    • Large vacuole: Storage and maintenance of cell turgor pressure.
    • Cell walls: Mainly composed of cellulose.
  • Five major types of plant cells:
    1. Parenchyma Cells: Most abundant, perform metabolic functions like photosynthesis.
    2. Collenchyma Cells: Provide flexible support in growing parts of the plant.
    3. Sclerenchyma Cells: Provide rigid support, dead at maturity.
    4. Water-Conducting Cells: Such as tracheids and vessel elements found in xylem.
    5. Food-Conducting Cells: Such as sieve-tube elements found in phloem.

Plant Growth

  • Characterized by indeterminate growth that continues throughout the plant's life.
  • Life cycle classifications:
    • Annuals: Complete life cycle in one year.
    • Biennials: Complete life cycle in two years.
    • Perennials: Live for many years.
  • Meristems:
    • Specialized tissues with undifferentiated cells that enable growth, found at the tips of roots and shoots.
    • Primary growth: Lengthening of shoots and roots through apical meristems.
    • Secondary growth: Thickening of stems and roots.

Flowers of Angiosperms

  • Contain four types of modified leaves known as floral organs:
    1. Sepals: Enclose and protect flower buds.
    2. Petals: Colorful and fragrant, attracting pollinators.
    3. Stamens: Male reproductive parts, consist of filament and anther (where pollen is produced).
    4. Carpels: Female reproductive parts, have a style and stigma; ovary contains ovules.
  • Pistil: Refers to a group of fused carpels or a single carpel.

Angiosperm Life Cycle Overview

  1. Fertilization occurs in an ovule within a flower.
  2. The ovary develops into a fruit.
  3. The ovule develops into a seed containing the embryo.
  4. The fruit aids in seed protection and dispersal.
  5. The seed germinates in a suitable habitat, developing into a seedling and ultimately a mature plant.