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PLANTS, PLANT GROUPS - Coggle Diagram

- - - - Important for symplastic transport.
      - Can have complex architecture - simple, H shaped or complex branched
- - - - oil bodies, peroxisomes, glyoxisomes: can swell or fuse
      - Glyoxisomes: Acetyl CoA production from fatty acid catabolism. Important cofactor in essential biochemical pathways which is sequestered in plant cells to be used when needed.
      - Microbodies are derived from the endomembrane system
    - - Plastids (and mitochondria) are semi-autonmous (have DNA, can divide independently) - not derived from end-membrane system - taken up into ancestral cell.
      - Pro-plastid: go through distinct development phases to produce specialised plastids.
      - Etioplast: chloroplast that hasn't been exposed to light - no colour
      - Amyloplasts: starch storage - different types:
        
        statoliths: help a plant sense changes in gravity, orientate cells.
      - Gerontoplast: derived from chloroplasts once leaves senesce. Many precursor compounds are made in chloroplasts before they are transported out into the cytosol of plant cells.
      - Chromoplast: contains different pigments - gives colour to petals.
      - Chloroplast: photosynthesis and lipid synthesis.
      - Leucoplast: Synthesis of fatty acids and amino acids.
      - Elaioplast: storage of lipids, oils
      - Proteinoplast: Sites of enzyme activity.
      - Diverse plastid types support the sessile, autotrophic life cycle of plants. e.g. attraction of pollinators
- - - - Anchoring the plant, growing
      - Absorbing water and minerals
      - Storing carbohydrates (sucrose into starch)
      - Primary root is the first organ to emerge from a germinating seed
    - - Role in transpiration-cohesion-tension mechanism of water transport - pump mineral ions into xylem vessels (lowers water potential in the vessels).
      - Creates root pressure, may result in guttation early in the morning - not dew!
      - Storage sink for sugars - balancing bulk flow across the two vascular tissue types. Positive pressure of water flow into the top end of the phloem
      - Cation exchange in the soil - influenced by soil pH, amount of colloidal organic matter (humus) in soil for increased exchange, soil conditioning (presence or earthworms and nematodes) to aerate the soil, and soil type (clay, sand, loam - clay less aerated than loam) will determine total exchange capacity of the soil
      - Creation of commensal structures with bacteria - rhizosphere = micro ecology of the soil. Depends on plant species, not all interactions will be beneficial.
      - Creation of commensal structures with fungi - Depends on plant species. Not all interactions are beneficial. Increase micronutrient and water absorption. Ectomycorrhizae - mantle-forming. Arbuscular mycorrhizae - penetrate into cells without damage.
    - - Most gymnosperms (pines) and edict angiosperms have a taproot system, which consists of A taproot, the main vertical root, and Lateral roots or branch roots, that arise from the taproot
      - Most monocots have a fibrous root system, which consists of Adventitious roots that arise from the stem or leaves, and lateral roots that arise from the adventitious roots
      - Both systems have large surface areas to allow for efficient uptake of water and minerals.
      - Root Adapatations
        
        Prop roots support tree above ground
        
        Buttress roots - in tropical rainforests, systems of trees can be very shallow due to competition for resources, so aerial roots from buttress structures support the tree
        
        'Strangling aerial roots' - seeds of the plant germinate in tall trees, send aerial roots down into the soil. Eventually, host tree dies through shading by invading plant leaves.
        
        Storage roots - sugar beet storage roots store water and sugar
        
        Pneumatophores - Mangroves produce these negatively geotropic respiratory roots to obtain oxygen which is lacking in thick estuarine mud. Also called rhizophores. Absorb oxygen.
        
        Assimilatory roots - water chestnuts roots have photosynthetic capacity to enhance carbohydrate production. Not needed for soil anchoring
        
        Floating roots
        
        Reproductive roots - Sweet potato gives rise to adventitious buds which will become new plantlets
        
        Sucking roots with haustoria - Non-green dodder plants (parasitic plants). Bind plant volatiles such as a-pinene. Create parasitic haustoria (interface zones) that release degradative enzymes that break down cellulose, pectin. To draw nutrients and water form plants, haustauria resemble haustoria of parasitic fungi. Usually catastrophic to tomato plants. Photosynthetic mistletoe is not destructive - infects but doesn't harm trees.
        
        (Also in steams and leaves) Some plants (hydrophytes) are adapted for wet conditions e.g. rice and soybean. Sensing of hypoxia (low O2) or anoxia (no O2) - up regulation of ethylene biosynthesis. Primary aerenchyma - schizogenous: present without stress. Lysigenous: present with water stress. Secondary aerenchyma- further anatomical modifications made to increase rapid rate of diffusion of dissolved gases.
        
        Schizogenous - splitting of cell walls of neighbouring cells. Air spaces develop between cells in extracellular spaces.
        Lysigenous - breaking down of cell walls to create bigger parenchyma cells. Air spaces between cells develop due to programmed cell death and lysis in parenchyma cells due to prolonged water logging.
- - - - Parenchyma Cells
        
        Are the least specialised - retain ability to divide and differentiate. A whole plant can be grown from a single parenchyma cell
        
        Perform the most metabolic functions
        
        Have thin, flexible primary cell walls.
        
        Lack secondary (lignified) walls
        
        Large central vacuole
        
        Contain chloroplasts in leaves, storage plastids in stems and roots
      - Collenchyma Cells
        
        Differentiated parenchyma cells.
        Grouped in living strands - help support young parts of the plant shoot.
        
        Have thicker and uneven cell walls that provide flexible support without restraining growth
        
        lack secondary cell walls
      - Sclerenchyma Cells .......................................
        
        Rigid with thick secondary walls strengthened with lignin
        
        Dead at functional maturity
        
        Two types
        
        Sclereids - Short and irregular in shape and have thick lignified secondary walls. Found in seed coats, nut shells and the texture to pear fruits
        
        Fibres - Long and slender and arranged in threads (hemp fibres for string and rope, flax fibres for weaving linen)
    - - Water conducting cells of the xylem
        
        At maturity, ground tissue cells die. Secondary cell walls needed so that the weight of water that is transported via several passive methods can be supported in plant tissue. Two types:
        
        Tracheids - Common to most plants (not bryophytes). Long, thin, tapered ends. Pitted walls for lateral movement of water
        
        Vessel Elements - 'higher plants' (angiosperms, gymnosperms) more robust lignified tissue. Perforated end walls primarily for upwards movement
      - Sucrose conducting cells of the phloem
        
        Sieve-tube Elements - Alive at functional maturity. No nucleus, ribosomes, vacuole oe cytoskeleton. Porous end sieve plates. Can conduct nutrients.
        
        Along each sieve-tube element is a non-conducting Companion Cell whose nucleus and ribosomes serve both cells. In some plants, companion cells load sucrose (main transport sugar in plants) into the sieve tube elements.
    - - Non-woody plants
        
        Epidermis - single layer, protective function
        
        Cuticle - waxy coating, prevents water loss
        
        Associated cells and structures
        
        Trichomes - diverse functions but mainly secretory
        
        Guard Cells - Control water loss
        
        Root Hairs - water and mineral ion uptake
      - Woody Plants
        
        Periderm - several tissues**
        
        Reinforced cell walls - lignin and Suberin
        
        Complex Polyphenoids
- - - - Plants are primary producers in many food chains - produce essential sugars, proteins, fatty acids and lipids. Certain bacterial and viral species enter and then try to hijack plant regulatory, biochemical and signalling processes to their advantage.
      - Diseases caused by bacteria
        
        Bacterial Speck: Agrobacterium Type IV secretion system secretes Ti plasmid that implants tDNA into plant chromosome
        
        Crown Gall: Erwinia Type II secretion system secretes cell wall degrading enzymes. Damages plant cells
        
        Blackleg: Pseudomonas Type III secretion system - Type III effector proteins in plant cell
        
        Bacterial Wilt: blocks xylem, plant cannot get water and minerals, wilts.