Fungi Characteristics and Structure

• Fungi are classified into five phyla: Basidiomycota, Ascomycota, Glomeromycota, Zygomycota, and Chytridiomycota.
• Single-celled fungi are known as yeast.

Fungi Characteristics

• Fungi possess chitin in their cell walls.
• Fungi do not perform photosynthesis.
• Fungi are heterotrophic organisms.
• Fungi store energy in the form of glycogen.
• Fungi absorb nutrients across their cell surfaces.

Fungi Structures

• Hyphae are long, branching filaments that make up the structure of fungi.
• A mycelium is a mass of hyphae found within a substrate or underground.
• The reproductive structure, or "fruiting body", of fungi is a hypha located above ground.

Fungi Symbiotic Relationships

• Mycorrhiza is a symbiotic relationship between a plant and a fungus.
• Ectomycorrhizal fungi (EMF) grow a sheath around plant roots to facilitate nutrient transfer and are typically Basidiomycota and Ascomycota.
• Arbuscular mycorrhizal fungi (AMF) have hyphae that grow directly into plant roots for nutrient transfer and are typically Glomeromycota.
• Endophytes live inside plant tissue, increasing drought resistance and providing toxins against herbivores, while the plant provides sugars to the fungus.
• Lichens are a symbiotic relationship between algae and fungi.

Types of Fungi

• Saprophytes digest dead plant matter.
• Microsporidia are spore-forming unicellular parasites that infect insects, fish, and crustaceans.
• Chytrids are mostly aquatic/unicellular fungi, the simplest and most primitive true fungi, and the only fungi with flagella.
• Zygomycetes are mostly saprobes with coenocytic hyphae.
• Zygomycetes reproduce asexually via sporangiospores and sexually via hyphae fusion to produce zygospores.
• Glomeromycota are associated with the roots of trees.
• Basidiomycota have club-shaped fruiting bodies, with most edible mushrooms belonging to this phylum, and a dominant dikaryotic phase.
• Ascomycota feature an ascus, or sac structure, that contains haploid ascospores.
• Ascomycota hyphae have perforated septa, and asexual reproduction is most common.
• Conidiospores are haploid spores used for asexual reproduction in Ascomycota.
• Sexual reproduction in Ascomycota involves male (antheridium) and female (ascogonium) parts.

Plant Classification

• Early plant ancestors are aquatic green algae.
• Plants overcame desiccation and gravity to adapt to land.
• Bryophytes are nonvascular plants, including mosses, liverworts, and hornworts.
• Vascular seedless plants include ferns and horsetails
• Vascular tissue transports water and nutrients throughout the plant.
• Gymnosperms include conifers, cycads, gnetophytes, and ginkgo, and require pollination for fertilization.
• Angiosperms are the most modern plants, characterized by flowers and seeds.

Plant Structure: Systems

• The shoot system is above ground and primarily absorbs light; it includes vegetative (non-reproductive) parts.
• The root system is below ground, supporting the plant and absorbing water and nutrients.

Plant Structure: Meristematic vs. Non-Meristematic Tissue

• Meristematic tissue is capable of cell division and differentiation, while non-meristematic tissue is not.
• Apical meristems are at the tips of stems/roots and facilitate growth in length (primary growth).
• Lateral meristems enable growth in the thickness of maturing plants (secondary growth).
• Intercalary meristems, found only in monocots, enable leaf elongation from the leaf base.
• Dermal tissue covers and protects the plant.
• Vascular tissue, consisting of xylem and phloem, transports water and nutrients.
• Ground tissue is responsible for photosynthesis, sugar/water storage, and structural support for vascular tissue.

Plant Structure: Phloem

• Phloem transports organic compounds.
• All phloem cells are alive at maturity.

Plant Structure: Xylem

• Xylem transports water.
• Xylem conducting cells are dead at maturity.

Plant Structure: Stems

• Stems support the plant and can be above or below ground.
• Stem anatomy includes nodes, internodes, axillary buds, and petioles.

Plant Structure: Cells

• Parenchyma cells are the most common, performing metabolic functions and repair.
• Collenchyma cells are elongated with thick cell walls, providing structural support and are alive at maturity.
• Sclerenchyma cells contain lignin, are dead at maturity, and include sclereids and fibers.
• Bark consists of cork cells, providing protection to the stem.
• Trichomes are hairlike structures on the surface, reducing water loss and deterring herbivores.

Plant Structure: Vascular Bundles

• Monocots have scattered vascular bundles, while eudicots have vascular bundles arranged in a ring.

Plant Structure: Primary vs. Secondary Growth

• Primary growth is an increase in length, facilitated by cell division at the apical meristem.
• Secondary growth is an increase in width, facilitated by cell division at the lateral meristem, and is rare in monocots.

Plant Structure: Root Systems

• A taproot system has one main root with smaller lateral roots, while a fibrous root system has many roots of similar size.
• Root hairs are extensions of epidermal cells that increase the surface area of the root for absorption.
• Dicots have a vascular cylinder, and eudicots have the xylem in an X shape in the center of the root.

Plant Structure: Leaves

• A sessile leaf is attached directly to the stem without a petiole.
• Leaf veins can be parallel (monocots) or net-like (eudicots).
• The mesophyll is the inner layer of the leaf, containing chloroplasts.
• Palisade parenchyma is column-shaped and tightly packed for efficient light capture.
• Spongy parenchyma has an irregular shape and is loosely packed, allowing for gas exchange.
• The cohesion-tension theory explains water movement in plants.

Plant Reproduction

• Sexual reproduction involves the fusion of egg and sperm.
• Asexual reproduction clones the organism, creating an exact replica.
• Vegetative reproduction is a form of asexual reproduction where a new plant grows from an existing plant via runners.
• The sporophyte is the diploid generation, undergoing mitosis and meiosis to produce spores.
• The gametophyte is the haploid generation for reproduction, a product of meiosis that does not undergo meiosis itself.

Plant Reproduction: Nonvascular vs. Vascular Plants

• Nonvascular plants require a film of water for sperm to swim to the egg on the female moss plant.
• vascular plants do not require a film of water for sperm transport.
• In nonvascular plants, the sporophyte depends on the gametophyte for support and nutrition, with the gametophyte being the dominant generation.
• As plants evolve, the sporophyte generation becomes larger.

Plant Reproduction: Flowers

• Flowers can have male and female parts, with male parts including stamen (anther and filament) and female parts including pistil (stigma, style, and ovary).
• Complete flowers have sepals, petals, stamens, and pistils, while incomplete flowers lack one or more of these parts.
• Perfect flowers have both stamens and pistils, while imperfect flowers have only stamens or only pistils.
• Pollination mechanisms include wind, water, and animal pollination.
• Fruits are classified into four types: simple, aggregate, multiple, and accessory.
• Seeds are dispersed by wind, water, or animals.
• Seed germination requires water, oxygen, and the right temperature.