Plant Diversity, Structure, and Development: Study Guide (Chapters 29, 30, 35)

Plant Diversity and Evolution

Charophytes and Land Plants: Similarities and Differences

• Charophytes are the closest algal relatives of land plants.

• Four shared traits between charophytes and land plants:

  • Rings of cellulose-synthesizing proteins in the plasma membrane

  • Structure of flagellated sperm

  • Formation of a phragmoplast during cell division

  • Similar peroxisome enzymes

• Seven traits unique to land plants (not found in charophytes):

  • Alternation of generations

  • Multicellular, dependent embryos

  • Walled spores produced in sporangia

  • Multicellular gametangia

  • Apical meristems

  • Cuticle (waxy covering)

  • Stomata (pores for gas exchange)

Alternation of Generations

• Land plants exhibit alternation of generations, a life cycle with two multicellular stages:

  • Sporophyte (diploid, 2n): Produces haploid spores by meiosis.

  • Gametophyte (haploid, n): Produces gametes by mitosis.

• Fertilization produces a diploid zygote, which develops into the sporophyte.

• Key structures:

  • Archegonia: Female gametangia, produce eggs.

  • Antheridia: Male gametangia, produce sperm.

• Know which stages are haploid (gametophyte, gametes, spores) and which are diploid (sporophyte, zygote).

Major Plant Groups and Life Cycles

• Bryophytes (mosses, liverworts, hornworts):

  • Dominant generation: Gametophyte

  • Sporophyte is dependent on gametophyte

  • Key structures: Protonema (early gametophyte), Gametangia (archegonia and antheridia), Sporophyte (seta, capsule, foot)

• Lycophytes (club mosses, spike mosses, quillworts) and Monilophytes (ferns, horsetails, whisk ferns):

  • Dominant generation: Sporophyte

  • Vascular tissue present

  • Gametophyte is reduced and independent (in ferns)

• Comparison of dominant generations and key features is summarized below:

Group	Dominant Generation	Vascular Tissue	Key Features
Bryophytes	Gametophyte	No	Protonema, dependent sporophyte
Lycophytes/Monilophytes	Sporophyte	Yes	Roots, leaves, independent gametophyte (in ferns)

Vascular Tissue: Xylem vs. Phloem

• Xylem: Conducts water and minerals from roots to shoots; contains tracheids and vessel elements.

• Phloem: Transports sugars, amino acids, and other organic products; contains sieve-tube elements and companion cells.

Roots, Leaves, and Adaptations

• Roots: Anchor plant, absorb water and nutrients.

• Leaves: Main photosynthetic organ; types include microphylls (single vein) and megaphylls (branched veins).

• Sporophylls: Modified leaves that bear sporangia.

• Homosporous plants: Produce one type of spore.

• Heterosporous plants: Produce megaspores (female) and microspores (male).

Seed Plants: Gymnosperms and Angiosperms

Seed Plant Innovations

• Five derived traits of seed plants:

  • Reduced gametophytes

  • Heterospory

  • Ovules

  • Pollen

  • Seeds

• Reduced gametophyte: Gametophytes develop within the tissues of the sporophyte, protected from environmental stress.

• Seed: Fertilized ovule containing embryo, food supply, and protective coat.

• Ovule: Structure containing megasporangium, megaspore, and integuments.

• Pollen: Male gametophyte enclosed within a pollen wall; allows fertilization without water.

Gymnosperms

• "Naked seeds" not enclosed in ovaries.

• Major groups: Cycads, Ginkgo, Gnetophytes, Conifers.

• Life cycle features:

  • Dominant sporophyte

  • Seeds develop on scales of cones

  • Pollen delivered by wind

Angiosperms

• Seeds enclosed in fruits (mature ovaries).

• Key structures:

  • Flower: Reproductive organ with sepals, petals, stamens (male), carpels (female).

  • Fruit: Mature ovary containing seeds; aids in seed dispersal.

  • Double fertilization: One sperm fertilizes egg (forms zygote, 2n), another sperm fuses with two nuclei to form endosperm (3n).

• Parts of angiosperm that are diploid: Sporophyte tissues, zygote.

• Parts that are triploid: Endosperm (nutritive tissue in seed).

• Groups: Monocots (one cotyledon) vs. Eudicots (two cotyledons).

• Comparison of monocots and eudicots:

Feature	Monocots	Eudicots
Cotyledons	1	2
Leaf venation	Parallel	Netlike
Vascular bundles	Scattered	Ring
Root system	Fibrous	Taproot
Floral organs	Multiples of 3	Multiples of 4 or 5

Plant Structure, Growth, and Development

Plant Organs and Organ Systems

• Three basic organs: Roots, stems, leaves.

• Organ systems: Root system (below ground), shoot system (above ground).

Roots: Types and Adaptations

• Taproot: Main vertical root with lateral roots (common in eudicots).

• Lateral roots: Branch from taproot, increase absorption.

• Root adaptations: Prop roots, storage roots, aerial roots, buttress roots, pneumatophores.

Stems: Structure and Adaptations

• Parts: Nodes (where leaves attach), internodes (stem segments between nodes), axillary buds, apical bud.

• Stem adaptations: Rhizomes, stolons, tubers.

Leaves: Structure and Adaptations

• Parts: Blade, petiole, veins.

• Leaf adaptations: Tendrils, spines, storage leaves, reproductive leaves, bracts.

• Simple leaf: Single, undivided blade.

• Compound leaf: Blade divided into leaflets.

Plant Tissues

• Dermal tissue: Outer protective covering; includes epidermis, cuticle, periderm (in woody plants).

• Vascular tissue: Conducts water, minerals, and food; xylem and phloem.

• Ground tissue: Fills space between dermal and vascular; functions in photosynthesis, storage, support.

• Specialized structures: Trichomes (dermal), fibers (vascular), parenchyma, collenchyma, sclerenchyma (ground).

Common Plant Cell Types

Cell Type	Main Function	Characteristics
Parenchyma	Photosynthesis, storage	Thin, flexible walls; alive at maturity
Collenchyma	Support for young parts	Unevenly thickened walls; alive at maturity
Sclerenchyma	Rigid support	Thick, lignified walls; dead at maturity
Tracheids/Vessel elements	Water transport (xylem)	Dead at maturity; lignified
Sieve-tube elements	Sugar transport (phloem)	Alive; lack nucleus; companion cells assist

Meristems and Plant Growth

• Meristems: Regions of undifferentiated cells that divide for growth.

• Apical meristems: At tips of roots and shoots; cause primary growth (lengthening).

• Lateral meristems: Vascular cambium (produces secondary xylem and phloem), cork cambium (produces periderm); cause secondary growth (thickening).

• Indeterminate growth: Growth throughout life (most plants).

• Determinate growth: Growth stops after reaching a certain size (some organs, e.g., leaves, flowers).

Primary vs. Secondary Growth

• Primary growth: Increases length; occurs at apical meristems.

• Secondary growth: Increases thickness; occurs at lateral meristems (mainly in woody plants).

• Vascular cambium produces secondary xylem (wood) and secondary phloem.

• Cork cambium produces cork (part of bark).

Monocot vs. Eudicot Anatomy

• Root cross-section:

  • Monocots: Vascular tissue in a ring.

  • Eudicots: Vascular tissue in a central star shape.

• Stem cross-section:

  • Monocots: Vascular bundles scattered.

  • Eudicots: Vascular bundles in a ring.

Tree Trunk Anatomy and Bark

• Bark: All tissues external to vascular cambium (includes secondary phloem and periderm).

• Tree trunk (from outside in): Periderm (cork), cortex, secondary phloem, vascular cambium, secondary xylem (wood), pith.

Summary Table: Plant Life Cycle Dominance and Key Features

Group	Dominant Generation	Vascular Tissue	Seeds	Flowers
Bryophytes	Gametophyte	No	No	No
Lycophytes/Monilophytes	Sporophyte	Yes	No	No
Gymnosperms	Sporophyte	Yes	Yes	No
Angiosperms	Sporophyte	Yes	Yes	Yes

Additional info:

• Figures referenced (e.g., 29.3, 30.2, 30.3, 35.10, 35.22) typically illustrate life cycles, plant anatomy, and tissue organization. Review textbook figures for visual reinforcement.

• For exam preparation, practice drawing and labeling plant life cycles and anatomical diagrams.