Terrestrial Plants: Adaptations and Life Cycle

Chapter 25: Terrestrial Plants

• Terrestrial plants thrive due to abundant sunlight and CO2, with fewer resource competitors and predators
• They face desiccation, UV radiation, and the need for structural support
• Reproduction and zygote survival depend on water

Adaptations

• Sporopollenin protects spores from desiccation
• Alternation of generations involves sexual (gametophyte) and asexual (sporophyte) phases
• Apical meristems in roots and shoots facilitate upward growth
• Waxy cuticles on leaves and stems prevent desiccation
• Lignin in vascular tissues provides structural support and prevents water loss

Alternation of Generations

• This describes the life cycle with multicellular diploid and haploid stages
• Sporophytes are diploid (2n), containing two sets of chromosomes
• Gametophytes are haploid (n), containing one set of chromosomes
• Sporophytes produce spores through meiosis
• Gametophytes produce gametes (eggs and sperm) through mitosis

Apical Meristems

• These are undifferentiated cells capable of becoming any cell type
• In seedless plants, they're located at shoot and root tips
• Shoot tips enable upward growth for sunlight
• Root tips enable downward growth for water and minerals
• Think "Shoot-UP" and "Root-DOWN"

Waxy Cuticle

• Prevents desiccation and water loss
• Located on the epidermis

Sporopollenin

• Thick walls resist desiccation and degradation
• Located in the outer layer of spores and pollen grains

Seedless Nonvascular Plants (Bryophytes)

• They lack vascular tissue, relying on diffusion and osmosis for water transport
• The gametophyte (haploid) stage is dominant, producing haploid gametes via mitosis
• The sporophyte is dependent on the gametophyte, diploid, and produces spores via meiosis
• Examples include hornworts, liverworts, and mosses
• They have thallus and rhizoids instead of true leaves, stems, and roots
• Fertilization is water-dependent
• Antheridia produce sperm via mitosis
• Archegonia produce eggs via mitosis
• Zygotes are diploid
• Haploid spores are produced

Seedless Vascular Plants (Lycophytes and Monilophytes)

• The sporophyte is dominant, diploid, and produces haploid spores via meiosis
• Features include roots, microphylls or megaphylls, and sporophylls
• Sporophylls are spore-producing leaves
• They have vascular tissue
• Fertilization is water-dependent
• Sporangia on sporophytes produce haploid spores through meiosis
• Megasporangia produce megaspores that develop into female gametophytes
• Microsporangia produce microspores that develop into male gametophytes

Chapter 26: Seed Plant Adaptations

• The sporophyte stage is dominant
• Fertilization is not water-dependent
• They are heterosporous, producing different spore types by size and sex
• Seeds (female gametophyte) and pollen (male gametophyte) are adaptations for terrestrial living

Gymnosperms

• They are sister taxa to angiosperms
• Gymnosperms have naked seeds, lacking fruits
• They can be monoecious or dioecious
• Monecious plants have both eggs and sperm on the same plant
• Dioecious plants have eggs and sperm on separate plants
• They rely on wind pollination
• Tracheids in xylem facilitate water movement with lignin

Gymnosperm Life Cycle

• It is heterosporous
• Male pollen cones and female ovulate cones are present
• Microsporangia produce male microspores, which become male gametophytes that produce pollen
• Megasporangia produce female megaspores, which become female gametophytes that produce eggs
• Pollen contains a generative cell (produces sperm) and a pollen tube cell (grows into the pollen tube)
• Seeds contain three generations of tissue: parent sporophyte, gametophyte, and new sporophyte

Angiosperms

• They have fruits for pollination and flowers for protection and nutrition
• They can be monoecious or dioecious
• Pollination occurs via wind, insects, and animals
• They have xylem with vessel cells for efficient water movement
• Flower structures include carpels (female) and stamens (male)
• Ovaries contain ovules (megasporangium) and anthers contain microsporangium

Angiosperm Life Cycle

• It is heterosporous
• Microsporangia produce male microspores that become male gametophytes producing pollen
• Megasporangia produce female megaspores that become female gametophytes producing eggs
• Eggs undergo mitosis three times, forming 7 cells and 8 nuclei
• Double fertilization involves one sperm fertilizing the egg and another fertilizing polar nuclei
• Fruit aids seed dispersal
• Angiosperms can have fleshy or dry fruits
• They exhibit coevolution with insects and animals, contributing to plant biodiversity

Monocots

• One cotyledon
• Flower parts in multiples of 3 or 6
• Parallel leaf veins
• Many fibrous roots
• Scattered vascular bundles
• No woody tissue
• Cannot have a secondary system

Dicots

• Two cotyledons
• One main root with small fibrous roots
• Vascular bundles in a ring or X pattern
• Net-like leaf veins
• Woody veins
• Flower parts in multiples of 4 or 5
• Can have a secondary system

Chapter 30: Plant Organ Systems

• The shoot system grows above ground for photosynthesis
• The root system grows below ground for water/nutrient absorption and support
• Meristematic tissue contains actively dividing, undifferentiated cells for vertical (apical), lateral growth and intercalary growth
• Nonmeristematic tissue is differentiated
• Nonmeristematic tissue includes dermal, ground (photosynthesis, support, and storage), and vascular tissues
• Stem anatomy includes dermal tissue (epidermis), vascular tissue (xylem and phloem), and ground tissue (photosynthesis, storage, and support)
• Monocots have scattered vascular bundles, while eudicots have vascular bundles in a ring formation

Stem, Root, and Leaf Modifications

• Stem modifications include tubers, bulbs, rhizomes, corms, and stolens for storage and growth
• Root anatomy includes dermal, vascular (arranged differently in monocots and eudicots), which are arranged in X shapes and ground tissues
• Root modifications include carrots or beets for underground storage and ariel roots for anchoring
• Leaf anatomy includes dermal tissue (stomata), ground tissue (mesophyll: palisade and spongy), and vascular tissue (xylem and phloem) in bundles
• Leaf arrangement can be alternate, opposite, or whorled
• Leaf form can be simple or compound

Primary vs. Secondary Growth

• Primary growth refers to stem's vertical growth in height
• Secondary growth measures stem's growth in thickness

Chapter 32: Plant Reproduction

• Gymnosperms rely solely on wind pollination
• Angiosperms utilize wind, insect, bird, and mammal pollination
• Self-pollination involves pollen transfer within the same plant
• Cross-pollination involves pollen transfer between different plants
• Asexual reproduction results in genetically identical offspring
• Examples of asexual reproduction include bulbs, tubers, corms, and rhizomes/stolons