Botany: Gymnosperms and Angiosperms

• Parenchyma can differentiate into various cell types

Ecological and Economic Importance of Plants

• Plants are essential for human needs and luxuries
• Plants, as phototrophs, use sunlight to produce sugars that serve as food for consumers and decomposers
• Plants produce oxygen and consume carbon dioxide
• Roots maintain soil structure and prevent erosion
• Plants provide raw materials for industry, including clothing, building materials, rubber, soap, and paper
• Plants are used in medicine, such as chemotherapy drugs
• Plants are a vital source of food in agriculture, providing grains, fruits, and vegetables

Traits Separating Plants from Charophytes

• Land plants evolved within the Archaeplastida, including red algae (Rhodophyta), Chlorophyta, and Charaphyta
• Plants likely evolved from a green algal ancestor, supported by molecular evidence
• Both plants and their ancestors have cellulose walls, chlorophyll a/b, and produce starch for short-term energy storage
• Sporopollenin protects spores and pollen from desiccation
• Plants have multicellular gametangia, with antheridia producing sperm and archegonia producing eggs

Plant Adaptations for Terrestrial Life

• Plants evolved key adaptations to thrive in terrestrial environments, overcoming challenges like water loss, structural support, reproduction without water, and nutrient transport
• Cuticle: A waxy layer on leaves and stems that prevents water loss
• Stomata: Pores that allow gas exchange while minimizing water loss, regulated by guard cells
• Sporopollenin: A durable polymer in spores and pollen that prevents desiccation
• Lignin: A complex polymer in cell walls providing rigidity, enabling plants to grow taller
• Vascular Tissue (Xylem & Phloem): Xylem transports water and minerals from roots to leaves, while phloem transports sugars and nutrients
• Apical Meristems: Regions at the tips of roots and shoots where active cell division allows vertical growth
• Multicellular Gametangia: Archegonium produces eggs, and antheridium produces sperm
• Embryo Protection: Embryos develop within the parent plant (Embryophyte)
• Pollen: Male gametophyte that allows sperm to reach eggs without water
• Seeds: Protect the developing embryo and aid in dispersal
• Roots: Absorb water and minerals from soil
• Rhizoids: Present in nonvascular plants (bryophytes) for anchorage
• Mycorrhizae: Fungal symbiosis that enhances nutrient and water absorption
• Flowers (Angiosperms): Attract pollinators for efficient reproduction
• Fruits (Angiosperms): Protect and aid in seed dispersal

Plant Groups and Synapomorphies

• Green Algae (Charophytes)
• Nonvascular Plants (Bryophytes) have Cuticles, Stomata, and Protected Embryos
• Seedless Vascular Plants possess Vascular Tissue and Lignin
• Gymnosperms have Pollen and Seeds
• Angiosperms feature Flowers and Fruits

Key Plant Traits

• Chloroplasts & Cellulose Cell Walls: Evolved in the common ancestor of green algae and land plants
• Cuticle & Stomata: First appeared in nonvascular plants
• Vascular Tissue (Xylem & Phloem): Evolved in seedless vascular plants
• Lignin: Strengthened vascular tissue, allowing larger plants
• Seeds & Pollen: Allowed gymnosperms to reproduce independently of water
• Flowers & Fruits: Key innovations in angiosperms

Nonvascular Plants (Bryophytes)

• Lack vascular tissue (xylem & phloem), limiting their size and requiring moist environments
• Gametophyte is the dominant stage, with the sporophyte dependent on it
• Require water for reproduction due to flagellated sperm
• Possess rhizoids instead of true roots
• Reproductive structures include sporangia (producing haploid spores via meiosis), archegonia (producing eggs), and antheridia (producing sperm)
• Representative species include liverworts (Marchantia), hornworts (Anthoceros), and mosses (Sphagnum)
• Liverworts have gemmae cups for asexual reproduction
• Hornworts have symbiotic cyanobacteria for nitrogen fixation
• Mosses form peat bogs, acting as carbon sinks

Seedless Vascular Plants (Tracheophytes)

• Have vascular tissue, enabling them to grow larger than bryophytes
• Sporophyte is dominant, while the gametophyte is independent but small
• Lignin strengthens cell walls
• Require water for reproduction due to flagellated sperm
• Reproduce using sori (clusters of sporangia on fern fronds) or strobili (cone-like structures)
• Homosporous plants produce one type of spore, while heterosporous plants produce megaspores and microspores
• Ferns (Polypodium) have megaphylls (large leaves)
• Horsetails (Equisetum) contain silica in stems
• Whisk ferns (Psilotum) lack true roots and leaves
• Club mosses (Selaginella) can be heterosporous

Roots - Structure and Functions

• Absorb water and minerals from the soil
• Anchor the plant and provide structural support
• Store food and nutrients
• Form mutualistic relationships with mycorrhizal fungi for nutrient uptake
• Taproot System: Single, large root with smaller branches
• Fibrous Root System: Many thin roots of equal size
• Adventitious Roots: Grow from stems or leaves instead of roots
• Specialized Roots: Pneumatophores (aerial roots for oxygen absorption) and rhizomes (underground stems that store nutrients)

Stems- Structure and Functions

• Support leaves and flowers
• Transport water, minerals, and food via vascular tissue
• Store nutrients and aid vegetative reproduction
• Node: Point where leaves attach
• Internode: Region between nodes
• Vascular Bundle: Contains xylem (water transport) and phloem (sugar transport)
• Primary Growth: Increases stem length via apical meristem
• Secondary Growth: Increases stem thickness via vascular cambium
• Modified Stems: Tubers (underground storage), rhizomes (horizontal underground), stolons (horizontal above-ground for spreading), and thorns (protection)

Leaves- Structure and Functions

• Primary site of photosynthesis
• Regulate gas exchange through stomata
• Store nutrients and water
• Blade: Flat, expanded portion for light absorption
• Petiole: Stalk that connects the leaf to the stem
• Veins: Contain xylem (water transport) and phloem (nutrient transport)
• Cuticle: Waxy layer preventing water loss
• Epidermis: Outer protective layer
• Palisade Parenchyma: Densely packed cells with chloroplasts for photosynthesis
• Spongy Parenchyma: Loosely arranged for gas exchange
• Stomata (Guard Cells): Regulate gas exchange
• Leaf Types: Simple (one undivided blade) and compound (multiple leaflets)
• Modified Leaves: Spines (protection), tendrils (climbing support), and storage leaves (water retention)

Plant Tissue

• Meristematic Tissue (Growth Tissue): Responsible for plant growth
  • Apical Meristem enables primary growth (lengthening)
  • Lateral Meristem (Vascular & Cork Cambium) enables secondary growth (thickening) Intercalary Meristem in monocots allowing continuous growth after grazing
• Epidermal Tissue (Protective Outer Layer): Protects against water loss, herbivores, and pathogens and regulates gas exchange
  • Structures include cuticle (waxy layer minimizing water loss), stomata (regulate gas exchange and transpiration), trichomes (deter herbivores and reduce water loss), and root hairs (increase surface area for water/nutrient absorption)
• Ground Tissue (Support, Storage, Photosynthesis): Provides structural support as well as stores nutrients and water
  • Parenchyma is the most abundant, thin-walled cell
  • Collenchyma provides flexible support
  • Sclerenchyma contains thick, rigid cell walls with lignin for strong support
• Vascular Tissue (Transport System): Transports water, nutrients, and sugars
  • Xylem transports water and minerals, contains tracheids and vessel elements, and is strengthened by lignin
  • Phloem transports sugars and nutrients and contains sieve-tube elements supported by companion cells

Primary vs. Secondary Growth

• Primary Growth (Lengthening)
  • Occurs in all plants
  • Driven by the apical meristem
• Secondary Growth (Thickening)
  • Occurs in woody plants (gymnosperms and dicots)
  • Driven by the vascular cambium, producing secondary xylem (wood) and secondary phloem (inner bark)

Evolution of Pollen, Seeds, Flowers, and Fruits

• Plants transitioned onto land with the help of pollen, seeds, flowers, and fruits
• Pollen advantage: Removes the need for water in fertilization
  • Pollen grain: Male gametophyte enclosed in sporopollenin, containing two sperm cells and a pollen tube cell
  • Pollination by wind (gymnosperms) or animals (angiosperms)
• Seeds advantage: Protects the developing embryo and allows long-distance dispersal
  • Seeds contain a seed coat, endosperm, and embryo -Spores are single-celled, lack food storage, and are short-lived
• Flowers advantage: Heightened pollination efficiency
  • Flowers contain sepals, petals, and stamen (anther + filament)
  • Carpel contains stigma, style, and ovary
• Fruits advantage: Protects seeds and aids in dispersal by animals, wind, or water.
  • Fleshy fruits dispersed through feces after eaten by animals
  • Dry fruits are dispersed by wind or animals
  • Explosive fruits burst open to release seeds

Gymnosperm Key Features

• Gymnosperms produces seeds without fruits, therefore relies on wind pollination
• Cycadophyta (Cycads)
  • Palm-like appearance with large cones
  • Diecious and beetle-pollinated
• Ginkgophyta (Ginkgo biloba)
  • Only one species alive today
  • Deciduous
  • Smells bad when mature
  • Resists pollution
• Coniferophyta (Conifers)
  • The biggest group of Gymnosperms
  • Evergreen and needle-like leaves
  • Has woody cones
• Gnetophyta (Gnetophytes)
  • Has angiosperm-like features
  • Includes ephedra, gnetum, and welwitschia

Conifer Life Cycle

• Conifers reproduce through cones (strobili) and display alternation of generations with a dominant sporophyte and diminished gametophyte
  • Male Staminate cones produce microsporangia, and the female Ovulate cones produce megaspores
  • Pollen tubes grow towards an egg within a year after wind dispersal.
  • Fertilized ovule -> seed w/ embryo, female gametophyte tissue, and seed coat
  • Dispersal is through wind, gravity, or animals

Key Terms

• Male gametophyte (Pollen Grain)
• Pollination: transfer of pollen to egg
• Ovule: female structure that can develop in a seed
• Seed: an embryo packaged with nutrients and a protective coat.
• Male cone that produces pollen: Staminate cone
• Female cone that contains ovules: Ovulate cone
• Flowering part of plant: Flower
• Fruit: Aids in dispersal

Angiosperm Key Features

• Angiosperms are one of the diverse plant groups that contain flowers and fruits
• Flowers attract pollinators
• Seed Dispersal occurs through mature ovaries which protect the seeds
• Double Fertilization: a unique process where one sperm fertilizes the egg and the other forms a triploid endosperm
• Small male and female gametophytes are dependent on the sporophyte
• Coevolution occurs by evolving specific pollinators to attract

Monocots vs. Dicots

• Monocots have one seed while dicots have two seeds
• Monocots contain parallel veins and dicots contain net veins
• Monocots have flower parts in multiples of 3; Dicots exist in multiples of 4 or 5
• A Monocot contains scattered vascular bundles while a Dicot contains bundles arranged in a ring

Life Cycle

• Pollen is transferred to stigma
• Pollen travels downs the style to the ovule to create an embryo and storage
• Embryo and storage develops into a fully grown sporophyte

Double Fertilization & Endosperm

• Sperm cells fertilize the female gametophyte (double fertilization)
• Seed development contains the zygote (develops into an embryo)
• Endosperm provides nutrients to the embryo
• Ex) White part of popcorn is the result of the endosperm

Double Fertilization

• Lands on stigma
• Creates zygote (2n)
• Forms a triploid endosperm (3n)

More Key Terms

• Anther: Part of the stamen that produces pollen
• Coevolution: Mutual evolutionary influence between plants and pollinators
• Cotyledon: Seed leaf; monocots vs. dicots
• Dicot: Contains two seed leaves
• Ovule: the female area that helps with sperm
• Monocot: Contains on seed leave
• Flower: helps with pollen
• Fruit: helps with seed dispersal
• Final Summary of Angiosperms: Most advanced plants that use flowers, fruits, and double fertilization.
• Double Fertilization occurs when pollen is transferred to the stigma

Cohesion-Tension Theory of Water Movement

• Transpiration: Water loss in plants that can lead to pressure
• Cohesion: Hydrogen bonding that leads to pulled h2o molecules
• Adhesion: H20 clings to prevent backflow
• The adaption for this process occurs through thick leaves that reduce airflow for waterloss

Translocation

• Use of photosynthetic tissue
• Growing tissues such as roots and fruits
• Process
  • 1. Sucrose turns into phloem
  • 2. Sugars sink
  • 3. Water backflows

Fungi Charateristics

• Absorption of nutrients via extracellular digestion
• Cell walls are made of Chitin
• Asexual/sexual reproduction

Types of Fungi

• Important for the role of decomposing material
• Symbiotic through mycorrhizae + lichens
• Used in the creation of antibiotics

Explore gymnosperm and angiosperm reproduction, adaptations, and ecological roles. Understand plant evolution, from early adaptations to flowering plants. Focus on key structures like pollen tubes and fruits.