BIO112 Lec5 Plant Reproduction and Development 2 2025

Plant Reproduction and Development - Overview

  • Focus on the processes involved in plant reproduction, including sporophyte and gametophyte development.

Key Terms and Concepts

Types of Cells

  • Sporophyte (2n): The mature diploid stage in the plant life cycle.

  • Gametes: Haploid (n) cells that fuse during fertilization.

  • Microspores: Result from meiosis and form pollen grains; male gametophytes.

  • Megaspores: Develop into female gametophytes within the ovule.

Stages of Plant Reproduction

  1. Meiosis

    • Microsporocytes (2n) in the anther undergo meiosis to produce microspores (n).

    • Megasporocytes (2n) in the ovule undergo meiosis to produce megaspores (n).

  2. Mitosis

    • Microspore develops into pollen grain containing a male gametophyte.

    • Megaspore divides to form the female gametophyte (embryo sac).

  3. Fertilization

    • Occurs when pollen lands on stigma, forming a pollen tube that carries sperm to the egg.

    • Results in the formation of both the zygote (2n) and endosperm (3n).

Structure of Flowers

  • Anther: Produces microspores.

  • Carpel: Contains ovule and is involved in the formation of female gametophytes.

  • Ovary: Develops into fruit containing seeds after fertilization.

  • Perianth: Includes petals (corolla) and sepals (calyx).

Pollination and Fertilization Process

  • Pollination: Transfer of pollen grains to stigma, leading to fertilization.

  • Double Fertilization: One sperm fertilizes the egg to form a zygote, the other fuses with polar nuclei to form the endosperm.

  • The ovule develops into a seed within the ovary which develops into a fruit.

Embryo Development

  1. Zygote Division: Zygote divides into basal and apical cells.

  2. Globular Stage: Development of a globular embryo stage.

  3. Differentiation: Cells differentiate into embryonic tissues (progenitor cells form the root and shoot systems).

  4. Emergence of Seed Structure: Includes cotyledons, radicle (root), and hypocotyl (stem).

Seed Structure and Variability

  • Cotyledons: Seed leaves; important in eudicots (e.g., beans).

  • Endosperm: Nutritional tissue; prominent in monocots (e.g., corn).

  • Seed maturation seen in dry seeds with variations in structures, such as the number of cotyledons and endosperm presence.

Meristematic Tissues

  • Apical Meristems: Sites of active cell division found at shoot and root tips where growth occurs.

  • Differentiation: Cells become specialized into vascular, ground, and epidermal tissues as the plant matures.