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Land Plants (Exam 2) - Coggle Diagram

- - - - plants have linear growth (2D)
        
        cells elongate in one direction
        
        seen in protonema of bryophytes
    - - plants switch to 3D growth later
      - requires cytokinesis to occur in multiple planes
  - - - isodamous
        
        equal branching where all branches are the same size
      - anisotomas
        
        unequal branching where one branch is dominant
  - - - trait that appears similar in different taxa but does not arise from a common ancestor
    - - newly derived trait not found in older lineages
    - - shared derived trait that indicates a common ancestor
    - - ancestral trait found in older lineages
- - - - vascular tissue in plants
      - responsible for transport of photosynthates (sugars) and other nutrients
      - works closely with xylem
    - - sieve cells
        
        found in gymnosperms
        
        primary conducting cells in phloem
        
        with albuminous cells
        
        specialized parenchyma cells that help in transport and signaling
      - sieve tube elements
        
        found in angiosperms
        
        have sieve plates at their ends
        
        allows for efficient nutrient transport
        
        have a lot of pores thqt move cytoplasm and nutrients between cells
        
        alive at maturity
        
        have very few organelles
        
        comes with companion cells
        
        have organelles like a nucleus and mitochondira
        
        supports the metabolic needs of the sieve tube
    - - nuclear breakdown
        
        nucleus breaks down as sieve tube elements mature
      - formation of sieve plates
        
        primary cell wall is digested to create larger pores
      - thickening of cell wall
        
        happens near the sieve plates
    - - p proteins
        
        help seal sieve plates during injury
      - flouresomes
        
        found in legumes
        
        help sieve pores during stress
  - - - simplest
      - found in early land plants, like lycophytes
      - solid cylinder of vascular tissue with a ring of phloem surrounding a core of xylem
    - - more complex
      - ring of phloem and a ring of xylem with ground tissue (pit) in between
    - - flowering plants (spermatophytes)
      - separated strands of xylem and phloem
      - vascular bundles with ground tissue separating them
    - - monocots
        
        vascular bundles are scattered throughout the stem
        
        no pith
        
        surrounded by sclerenchyma tissue
      - eudicots
        
        vascular bundles are arranged in a U shape
        
        central pith and ground tissue separating the vascular bundles
  - - - tracheids
        
        evolved later
        
        thickened secondary cells reinforced with lignin
        
        efficient water transport and structural support
      - vessel elements
        
        in angiosperms
        
        shorter and wider than tracheids
        
        greater water conductivity
        
        unique wall structure that is different than their lateral walls
      - hydroids
        
        found in gametophyte stages of mosses
        
        lack plasmodesmata in their lateral walls
        
        assist in refilling after cavitation
    - - lignin
        
        complex organic polymer
        
        waterproofing and structural support
        
        crucial for tall plants
        
        allows them to maintain rigid
      - secondary cell wall
        
        formed during maturation of xylem cells
        
        walls are thickened to enhance strength and prevent collapse under pressure
  - - - crucial for secondary growth
      - produces secondary xylem (wood) and secondary phloem (inner bark)
      - consists of 2 stem cells
        
        ray initials
        
        connect the pith to the cortex
        
        fusiform initials
        
        give rise to xylem and phloem
    - - anticlinal divison
        
        increases the number of vascular camibum cells
        
        allows cambium to expand outward
      - periclinal division
        
        produces new xylem on the inside and phloem on the outside
      - grows in girth through formation of growth rings
        
        study of the rings is known as dendrochryonology
    - - evolution of wood was because of the need for effective spore dispersal and competition for light
      - resulted in taller vascular plants
    - - softwood
        
        mainly tracheids
        
        found in gymnosperms (e.g. pines)
      - hardwood
        
        contains vessel elements and fibers
        
        structural support and efficient water transport
  - - - crucial for transport of water, nutrients, and food
      - known as tracheophytes
    - - tracheids
        
        long, narrow cells that conduct water and provide structural support
      - vessel elements
        
        shorter, wider cells that allow for better water transport
      - sieve cells and sieve tube elements
        
        transport of nutrients
      - companion cells
        
        help sieve tube elements
    - - pteridophytes
        
        ferns
      - spermatophytes
        
        seed plants
      - lycophytes
        
        earliest vascular plants
    - - secondary cell walls
        
        provide extra support and are crucial for the function of tracheids
      - annular thickenings
        
        found in fossilized cells, shows presence of vascular tissue in early plants
- - - - evidence
        
        earliest fossil evidence of stomata dates back to the early devonian period
        
        found in the sporangia of the sporophyte
        
        including rhyniophytes and some early vascular plants
      - one of the earliest features of land plants
        
        appears shortly after the evolution of land plants
        
        present in all land plants except for liverworts, who have lost this trait
  - - - guard cells
        
        controls opening and closing
        
        actively pumps ions, primarily potassium, across membrane
        
        process is energy-dependent
        
        involves ATP generated during photosynthesis
      - turgor pressure
        
        increased when potassium ions are pumped into the guard cells
        
        causes stomata to open
      - open and closing is an active metabolic process
    - - water stress
        
        stomata closes under dry conditions
        
        mediated by ABA that signals guar cells to reduce pore size
      - vapor pressure deficit (VPD)
        
        angiosperms adjust stomata based on the air dryness
        
        high VPD leads to quicker stomata closure to minimize water loss
      - light
        
        stomata open in the presence of light due to the photosynthetic activity of chloroplast
        
        generates ATP for potassium pumping
    - - measure of the amount of water lost relative to the amount of carbon gained
      - cavitation risk
        
        stomata play a role in preventing cavitation in xylem
        
        can occur when air bubbles form in vascular tissue
        
        closing stomata during high cavitation risk helps maintain plant hydration
  - - - surrounds stoma
      - regulate opening and closing
      - rich in chloroplast
    - - stomata allow oxygen to exit the leaf and carbon dioxide to enter
        
        essential for photosynthesis
    - - shape
      - frequency
- - - - one of the essential tissues
      - type of ground tissue
      - made up of specialized parenchyma cells that contain chloroplasts
    - - type of ground tissue
      - consists of modified parenchyma cells
        
        large air spaces between the cells
        
        spaces created by cell digestion
        
        cavities facilitate gas exhance
        
        also contributes to bouyancy
    - - provides flexible support
      - primary cell walls are thickened
        
        gives support while still allowing growth
      - typically found in bundle sheaths
      - e.g. fibrous strands in celery
    - - found in the veins of the leaf
      - consists of xylem and phloem
        
        xylem helps water transport from roots to shoots
        
        adaxial
        
        phloem moves photosynthates
        
        abaxial
    - - outermost layer of dermal tissue
      - made up of epidermal cells and guard cells
        
        guard cells are specialized epidermal cells that regulate the opening and closing of tiny pores within the leaf
      - usually covered by a waxy cuticle
        
        helps reduce water loss through evaportaion
      - protects inner tissues from environmental stress
  - - - mesophyll types
        
        chlorenchyma
        
        specialized for photosynthesis
        
        bundle sheath cells
        
        provide support for vascular tissue
      - stomata
        
        openings in the epidermis that allow gas exchange
      - vascular tissue
        
        essential for nutrient transport and structural support
    - - lycophylls
        
        simple structure
        
        single vascular trace
      - euphylls
        
        more complex
        
        multiple vascular traces
        
        specialized mesophyll layers
    - - monocot leaves
        
        e.g. corn leaf (zea mays)
        
        epidermis
        
        covered in a protective cuticle
        
        vascular system
        
        central mid vein
        
        several side veins
        
        bouleform cells
        
        regulates turgor pressue
        
        responds to environmental conditions
        
        e.g. drought
      - eudicot leaves
        
        epidermis
        
        made up of upper and lower layer
        
        both covered in cuticle
        
        mesophyll
        
        has choloroplast-rich cells for efficient light absorption
        
        palisade mesophyll
        
        upper layer filled with tightly packed parenchyma cells
        
        enhances light capture
        
        air spaces
        
        facilitate internal gas exhange near stomata
      - aka true leaves, more complex
    - - leaves with a single vascular trace
      - structure
        
        vascular bundle
        
        contains xylem and phloem
        
        surrounded by mesophyll and epidermis
        
        epidermis
        
        made of guard cells and chloroplasts within mesophyll cells
        
        manages gas exchange and photosynthesis
        
        cross section
        
        vascular bundle leads back to the stem
        
        ensures nutrient transport
  - - - anatian theory
        
        explains the evolution of lycophylls through epidermal growths
      - zimmerman-tilum theory
        
        describes euphyll evolution through processes like overtopping, planation, and webbing
    - - microphylls
        
        formed from two dividing epidermal cells
      - fern fronds
        
        come from a single apical cell
        
        characteristic fiddlehead arrangement
      - liverworts and mosses
        
        developed from a single layer
        
        mosses may have an extra layer in the mid vein
    - - phyllad evolution
        
        high global temperature and low stomatal density hindered leaf formation
        
        as stomatal density increased, leaves evolved to optimize water usage and photosynthesis
      - stomatal function
        
        stomata allow for evaporative cooling
        
        essential for leaf health
    - - lycophytes
        
        earliest evidence of leaves, known as microphylls
        
        developed from the mitosis of a single cell
        
        typically one cell layer thick
      - euphyllophytes
        
        evolved later with true leaves
        
        leaf development involves a pooled set of cells from the apical meristem
- - - - primary roots
        
        main root
        
        emerges from seed during germination
        
        dominant in eudicots
        
        ephemeral in monocots
      - lateral roots
        
        adventitious roots
        
        originate from the shoot body and grown downward
        
        seminal roots
        
        emerge from the mesocotyl of the seed
    - - anchoring
        
        stabilize the plant
      - absorption
        
        absorb water and minerals essential for growth
    - - apical meristem
        
        located behind root cap
        
        rapid cell cell division and growth
        
        quiescent center maintains structure of dividing cells
      - zones of development
        
        zone of elongation
        
        cells begin to vacuolize and elongate
        
        zone of differentiation
        
        cells mature and develop specific function
        
        zone of division
        
        rapid cell division
      - root cap
        
        protects the meristematic region
        
        helps soil penetration by reducing friction
    - - root hairs
        
        single cells
        
        increase surface area for absorption of water and minerals through osmosis
      - cortex
        
        fills the root
        
        bounded by the endodermis and epidermis
        
        storage and transport of nutrients
      - endodermis
        
        filtering layer
        
        prevents apoplastic water movement
        
        ensures water passes through cell membranes to reach vascular tissue
    - - apoplastic movement
        
        water moves around cells through intercellular spaces and cell walls
        
        efficient but pathogens can enter
      - symplastic movemet
        
        water must pass through cell membranes
        
        filter against contaminents
        
        casparian strip in the endodermis enforces this
  - - - selaginella
      - no root cap or root hairs
      - has an epidermis, hypodermis, cortex, endodermis, and vascular tissue
    - - pith ground tissue in the center of the stele
      - surrounded by an endodermis and cortex
      - vascular tissue includes xylem and phloem with a thick casparian strip in the endodermis
    - - no pith in stele; consists of xylem and phloem
      - surrounded by a thick cortex and epidermis
      - endodermis with a prominent casparian stirp
    - - cortex
        
        storage tissue
        
        made of parenchyma cells
      - endodermis
        
        innermost layer of the cortex
        
        regulates water and nutrient flow
      - epidermis
        
        outer layer protecting the root
      - stele
        
        xylem
        
        transports water and minerals from roots to other parts
        
        phloem
        
        transports sugars and nutrients produced by photosynthesis
        
        central part containing vascular tissue
  - - - rhizoids
        
        early root-like structure
        
        mineral absorption through capillary action and osmosis
      - true roots
        
        bifurcation
        
        root caps in certain lineages
        
        evolved from shoots that adapted to grow downwards
    - - pro roots
        
        early form of roots
        
        lacked root hairs and chlorophyll
      - rhizomorphs
        
        found in extinct tress
        
        dichotomous rooting system
    - - earliest land plants likely evolved in flood-prone areas
      - rhizoids developed for anchorage
    - - apical meristem
        
        region of growth at the root tip
        
        crucial for root development and diversity
      - root hairs
        
        enhances nutrient absorption
- - - - cohesion is the attraction between water molecules
        
        helps maintain an unbroken column of water in the xylem
      - adhesion is the attraction of water molecules to the walls of the xylem vessels
        
        helps in countering the effects of gravity
    - - water enters the plant through root hairs via osmosis
        
        moving from a hypotonic soil solution into the the root cells
      - the endodermis, with its casparian strip, filters water as it moves into the vascular tissue
    - - water potential in the soil is typically higher (less negative) than the atmosphere
      - as water evaporates, it creates a gradient that pulls water from the soil, through the roots, and up to the leaves
    - - created when water is lost from the leaves
      - essential for pulling water upward against gravity
      - negative pressure in the xylem is crucial for maintaining this flow
    - - when stomata are open, water evaporates
        
        creates a water potential gradient
        
        facilitates water movement from the roots through the xylem
    - - osmosis
        
        movement of water from the soil into root hairs due to a concentration gradient
      - capillary action
        
        combined effects of cohesion and adhesion help water move through narrow xylem vessels
      - transpiration
        
        evaporation of water from the stomata, creating a negative pressure that pulls water upward
    - - water moves from area s of high moisture (soil) to low moisture (atmosphere) due to differences in water potential
      - driven by transpiration
        
        water evaporates from the stomata
        
        creates a negative pressure that pulls water upward through the plant
  - - - loading of sucrose
        
        active transport
        
        sucrose is loaded into sieve tube elements with the help of companion cells
        
        sucrose - form sugar is transported
        
        process requires energy (ATP)
      - osmotic pressure and turgor pressure
        
        water potential is decreased as sucrose is loaded into the sieve tubes
        
        causes water to enter from the xylem due to osmotic pressure
        
        influx of water creates turgor pressure, which helps push the photosynthate through the phloem
      - photosynthate movement
        
        photosynthate moves from sources to sinks
        
        sources
        
        areas of production
        
        primarily leaves (during growing seasons)
        
        roots (especially in early spring)
        
        sinks
        
        areas of consumption or storage
        
        fruits
        
        actively growing regions like apical meristems
      - bulk flow mechanism
        
        the movement of photosynthates occurs via bulk flow driven by pressure differences
        
        water follows sucrose as it's unloaded at the sink
        
        reduces pressure in the phloem
    - - loading
        
        sucrose is actively transported into sieve tube elements from sources
      - water influx
        
        water enters the sieve tubes from the xylem
        
        increases turgor pressure
      - bulk flow
        
        pressure difference drives the movement of photosynthate towards sinks
      - unloading
        
        at the sink, sucrose is unloaded and water follows
        
        reduces pressure in the phloem
  - - - evaporation of water from the stomata to the leaves
      - major driver of the water cycle
      - moves water from the soil to the atmosphere
        
        contributes to rainfall
    - - potential energy of water in a system compared to pure water
      - measured in megapascals (MPa)
      - influences direction of water movement
      - components
        
        osmotic potential
        
        effect of solutes on water potential
        
        always negative
        
        matrix potential
        
        water's adhesion to non-dissolved structure
        
        significant in dry soils
        
        pressure potential
        
        pressure exerted by water in the cell
        
        usually positive in turgid cells
    - - cohesion-tension theory
        
        explains how water moves through the xylem due to the cohesive properties of water molecules and the tension created by transpiration
      - pressure flow hypothesis
        
        describes how photosynthates move through the phloem from sources to sinks
    - - method to measure water potential
      - apply pressure to a cut leaf until water is expelled, indicating the water potential of the leaf
- - - - gives info on timing of evolutionary events
      - evolved from algae
    - - proves that terrestrialization occurred around 470 mya
        
        mid-ordovician
      - supports timeline of plant evolution onto land
  - - - key innovations
        
        vascular tissue
        
        needed for water and nutrient conduction
        
        allows plants to grow larger
        
        helps plants live away from water sources
        
        stomata
        
        needed to survive on land
        
        structure for gas exchange
        
        similar to human respiration
        
        enables plants to take in CO2 and release O2
        
        vital for photosynthesis
        
        sporophytes
        
        transition to a dominant sporophyte stage
      - life cycle
        
        alternation of generations
        
        gametophyte stage
        
        four haploid spores are formed at the end of meiosis, develops into gametophytes
        
        sporophyte stage
        
        diploid seed that produces spores through meiosis
      - seed plants
        
        gymnosperms
        
        naked seed
        
        pine and spruces
        
        angiosperms
        
        hidden seed
        
        evolved later
        
        more familiar today
        
        first seeds were likely from seed ferns
        
        likley extinct