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Roots (Other Types of Roots and Root Modification (storage roots (roots…

- - - - carbs used to produce new shoot in spring
    - - also in a more stable environment
  - - - come in monocots
      - once in contact with soil surface they transport nutrients and H2O back to plant
      - place tension on stem
        
        stabilizers
        
        if undergo secondary growth they can allow branch to grow further
    - - plate like and grow on tropical plants
      - brace against wind
  - - - attached to branches of trees
      - roots spread along surface of bark and roots dangle in air
      - adapted for drought conditions
        
        root epidermis (velamen) composed of several layers of dead white cells
        
        waterproof barrier
  - - - ectomycorrhizal relationship
        
        fungal hyphae invade root cortex but never invade the cells themselves
      - endomycorrhizal association
        
        fungal hyphae invade roots as far as endodermis
        
        can not pass the casparian strip
  - - - develop symbiotic relationship with bacteria
        
        Rhizobium
        
        sit in infection thread
        
        cause formation of root nodule
        
        bacterium released into cell cytoplasm
        
        can now convert N2 into compounds
        
        supply bacteria sugar
  - - - highly modified roots
        
        firmly adhere to a host
        
        secreting sticky adhesive
        
        growing around it
        
        penetrate host
        
        forcing shaft of cells through host's dermal system
        
        expanding haustorium rapidly, cracking host's epidermis
        
        make contact with host's xylem
        
        continuous vessel from host to parasite created
  - - - seeds germinate and grow rapidly around and down the tree
        
        absorbs water that runs down tree
        
        once it reaches soil roots branch
        
        typically results in death of the host
  - - - upper portion contracts slowly
        
        stem pulled down and and kept at soil level
        
        bulbs are buried if any
        
        due to change in shape of cortex cells
- - - - specific structure and growth pattern
      - cells closest to apical meristem are meristematic
        
        files of cells pushed forward
        
        cells on the edge of this group grow towards the sides and proliferate
        
        cells develop dense starch grains and ER displaced to forward end of cell
        
        pushed further towards cap results in changes structure and metabolism
        
        ER less conspicuous
        
        starch digested
        
        dictyosomes secrete mucigel
        
        middle lamella breaks down and releases cells
        
        cells usually crushed
        
        results in cap constantly being regenerated
  - - - root is more orderly
      - cells do not synthesize DNA in the central part
        
        mitotically inactive area is the quiescent center
        
        more resistant harmful agents
        
        reserve of healthy cells
        
        apical damage results in cells becoming active to replace damaged cells
  - - - some meristematic activity, but mostly elongation occurs
        
        cells begin to differentiate in a visible pattern
        
        outer most cells= protoderm that becomes epidermis
        
        center= provascular tissue that becomes primary xylem and phloem
        
        protoxylem and protophloem are closest to stem
        
        ground tissue between protoderm and provascular tissue
        
        uniform parenchyma
        
        tissues are permeable
        
        minerals enter through apoplast by diffusion
  - - - increase in absorption of H2O and minerals
      - have thin cuticle
      - zone of elongation merges with zone of maturation
        
        no distinct boundary between the two
      - cortex cells enlarge
        
        mainly aid in transfer of minerals from epidermis to vascular tissue
        
        diffusion through cell walls intercellular spaces
        
        absorption by cytoplasm
        
        transferred from cell to cell
      - endodermis
        
        innermost cells in cylindrical shape
        
        cells covered in casparian rings
        
        lignin and suberin main componet
        
        control types of minerals that enter xylem
        
        cortex cells do not filter well so the job is put upon rings
        
        cells close together
      - vascular tissues
        
        metaxylem and metaphloem become differentiated and functional
        
        arrangement
        
        xylem is solid mass in the middle surrounded by strands of phloem
        
        no pith
        
        monocots
        
        xylem and phloem distributed through out ground tissue
      - pericycle
        
        between endodermis and vascular tissue
        
        parenchyma cells
        
        initiate lateral root growth
  - - - die and regenerate
    - - casparian strips cover
      - represent passageway for absorption of minerals
    - - watertight sheath
        
        keeps water in older roots
    - - caused by H2O absorption in root hair zone
        
        would cause water to leak out if not for mature endodermal cells
- - - - tap root from embryonic root
        
        radicle
        
        largest root in the system
      - lateral roots can produce more lateral roots
      - may become swollen
      - may go under secondary growth as well
        
        =tree bark or wood
  - - - =fibrous root system
        
        radicle dies after germination
        
        root primordia grout out from radicle base
        
        first stages of fibrous root system
        
        adventitious roots
        
        do not arise from pre-existing roots
        
        are not radicles
        
        increase the absorptive and transport capacities of root system
    - - undergo secondary growth
        
        increased quantity of wood (xylem)
        
        also increases number of leaves, and absorptive roots
    - - do not undergo secondary growth
        
        stem formed
        
        vascular bundles, tracheary elements, and sieve tube is set
        
        conducting capacity can not be increased
        
        however some monocots can produce stolons or rhizomes for increased growth
        
        horizontal shoots branch and form adventitious roots
        
        water supplied directly to new roots
        
        must stay close to the source of water supply though
  - - - no leaf axils or axillary buds
    - - =place where growth in length occurs
      - apical meristem
        
        elongate only at meristematic regions
        
        root embedded in hard matrix
        
        unable for all parts of the root to extend at once
        
        apical growth the tip pushes through soil for growth
        
        protected by thick layer of cells
        
        root cap
        
        constantly worn away by soil
        
        renewed by cell multiplication
        
        dictyosomes secrete mucigel
        
        lubricates root
        
        causes soil to release nutrients
        
        mucigel components foster growth of soil microbes to aid in release of nutrients fro soil
    - - just behind root cap and apical meristem
        
        cells undergo division and expansion
    - - epidermal cells extend out as narrow trichomes
        
        root hairs increase roots surface area
        
        can enter tiny crevices between soil and extract water
        
        give off CO2 by respiration
        
        binds with soil matrix to form carbonic acid
        
        releases nutrients from soil
- - - - crushes endodermis that is torn away
      - pushes outward and destroys cells of cortex and epidermis and breaking into endodermis
        
        once it emerges it has formed a root cap
        
        establishes connection to vascular tissues of parent root