Plant Kingdom Notes

What Are Plants?

  • Basic Characteristics:

    • Multicellular organisms.

    • Terrestrial, meaning they live on land.

    • Eukaryotic cells, which contain a nucleus.

    • Autotrophs, capable of photosynthesis to produce their own food.

    • Cell walls composed of cellulose.

Overview of the Plant Kingdom

  • Major Groups of Plants: Four main categories:

    1. Bryophytes:

    • Include mosses and relatives.

    1. Seedless Vascular Plants:

    • Include ferns and relatives.

    1. Gymnosperms:

    • Cone-bearing plants, such as pines.

    1. Angiosperms:

    • Flowering plants and comprise the largest group (90% of all plants).

Plant Classification

  • Based on Two Major Characteristics:

    1. Mode of Reproduction:

    • All plants undergo alternation of generations.

    • Dominant Generation Types:

      • Gametophyte (haploid) is dominant in some plants.

      • Sporophyte (diploid) is dominant in others.

    • Fertilization and Sperm Dispersal:

      • Sperm can be dispersed either inside or outside the plant.

    • Offspring dispersal methods:

      • Spores or seeds.

    1. Adaptations for Terrestrial Life:

    • Includes features to prevent water loss:

      • Waxy cuticle, stomata, and specialized vascular tissues (xylem and phloem).

    • Growth forms include primary (length) and secondary (width) growth.

Alternation of Generations

  • Key Vocabulary:

    • Diploid (2N): Organisms with two sets of chromosomes.

    • Haploid (1N): Organisms with one set of chromosomes.

    • Gametes: Reproductive cells (haploid sperm or egg).

    • Fertilization: Sperm (1N) and egg (1N) fuse to create a zygote (2N).

    • Spores: Single haploid cells that develop into new plants.

  • Animals lack alternation of generations; only diploid (2N) phases are multicellular.

  • Plant Lifecycle Includes:

    • Both haploid (gametophyte) and diploid (sporophyte) phases are multicellular.

    • Generations:

    • Gametophyte:

      • Multicellular haploid (1N), grows from spores, produces gametes.

    • Sporophyte:

      • Multicellular diploid (2N), grows from zygote, produces spores.

Spores vs. Seeds

  • Spores:

    • Haploid, unicellular, grow into gametophytes, provide no nutrients to the baby plant.

  • Seeds:

    • Diploid, multicellular, grow into sporophytes, provide substantial nutrients to the developing plant.

Bryophytes

  • Types of Bryophytes:

    1. Mosses

    2. Liverworts

    3. Hornworts

  • Bryophyte Characteristics:

    • Dominant Generation: Gametophyte.

    • Reproduction needs wet environments; sperm swims from one gametophyte to another.

    • Sporophyte grows on top of the gametophyte and is supported by it.

    • Offspring dispersed via spores.

    • Adaptations for land include:

    • Waxy cuticle and absence of true roots, stems, and leaves.

Seedless Vascular Plants

  • Types:

    1. Ferns

    2. Horsetails

    3. Clubmosses

  • Characteristics:

    • Dominant Generation: Sporophyte.

    • Larger sporophyte replaces the gametophyte after fertilization.

    • Requires wet environments for sperm mobility and reproduction via spores.

    • Adaptations include waxy cuticle, stomata, true roots, and vascular tissues.

Vascular Tissue

  • Xylem:

    • Transports water from roots to leaves in one direction (up).

    • Comprised of dead cells; includes tracheids (narrow) and vessel members (found only in angiosperms).

  • Phloem:

    • Transports nutrients and food from leaves to various parts of the plant in both directions.

    • Composed of both living and dead cells, allowing for nutrient transport in summer and winter.

Gymnosperms

  • Types:

    1. Conifers

    2. Cycads

    3. Ginkgo

    4. Gnetophytes

  • Characteristics:

    • Dominant Generation: Sporophyte.

    • Male gametophyte is pollen grain produced by male cones.

    • Female gametophyte is attached to the female cone; fertilization occurs internally.

    • Reproduction by "naked seeds" and no fruit protection.

    • Adaptations similar to vascular plants, with true roots, stems, and leaves.

Angiosperms

  • Types:

    1. Monocots

    2. Dicots

  • Characteristics:

    • Dominant Generation: Sporophyte.

    • Male gametophyte is pollen grain from flower stamen.

    • Female gametophyte is found inside the ovule of a flower; fertilization involves a pollen tube growing to the egg.

    • Offspring dispersed as "covered seeds" protected within fruit (ovaries).

  • Adaptations for land involve a waxy cuticle, stomata, and vascular tissue, with primary and secondary growth.

  • Comparison of Monocots vs. Dicots:

    • Monocots: One cotyledon, parallel leaf veins, floral parts in threes.

    • Dicots: Two cotyledons, net-like leaf veins, floral parts in fours or fives.

Summary of Plant Groups

  • Bryophytes: Dominant Gametophyte, no vascular tissue, reproduce via spores.

  • Seedless Vascular Plants: Dominant Sporophyte, vascular tissue present, reproduce via spores.

  • Gymnosperms: Dominant Sporophyte, vascular tissue, reproduce via naked seeds.

  • Angiosperms: Dominant Sporophyte, vascular tissue includes vessel members, reproduce via covered seeds (fruit), and include flowers for reproduction.