PLSC 221

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PLSC 221
2013-02-07 14:59:45
Plant Structures

Plant Structures
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  1. Plasmalemma
    • The outer boundary of the protoplasm of a cell; also called plasma membrane or cell membrane
    • Tissues of higher plants are made up eukaryotic cells bunched by rigid cell walls to the exterior of this.
  2. Middle lamella
    • A layer of material, rich in pectin, that cements two adjacent cell walls together.
    • Area between cells, non-living area between adjacent cells and is filled with Ca2+ and Mg2+ pectates (pectin) which cement adjacent cells together.
  3. Plasma membrane (semi permeable)
    • The outer boundary of the protoplasm of a cell: also called cell membrane, particularly in animal cells.
    • Forms a continuum through the plant; selective
  4. Plasmadesmata (pores) (plasmodesma)
    • Minute strands of cytoplasm that extend between adjacent cells through pores in the walls.
    • These occur through the cell wall that allow a continuum of cytoplasm and membrane material from one cell to another.
  5. Symplast
    Continuum of living material, minerals and metabolites can be transported throughout the plant without ever leaving the cytoplasm (living material)
  6. Apoplast
    The non-living portions of plant tissue are called apoplast (for example middle lamella and dead xylem vessels)
  7. Lipids
    • A general term for fats, fatty substances, and oils.
    • Arranged in a bilayer so that the polar portions of the molecules face out and the non-polar parts are in the internal region of the membrane (whole structure called a unit membrane)
  8. Vacuoles
    Principle function
    • Storage: water & various materials (sugar, proteins, organic acids, pigments)
    • Digestion: contain "digestion" enzymes. Can break down and recycle nearly all cellular components
    • pH and ionic homeostasis: Serve as reservoirs of proton and ions such as Ca. (used to control cytosopic pH and enzyme activity
    • Defense against microbial pathogens and herbivores: accumulation of a variety of compounds
    • Sequestration of toxic compounds:
    • Pigmentation: contain anthocyanin pigments are found in many types of plant cells
  9. Plastids, 5 types:
    • Amyloplasts
    • Leucoplast
    • Etioplasts
    • Chloroplasts
    • Chromoplasts
  10. Proplastids
    Are the precursors all other plastids. 
  11. Amyloplasts
    • Unpigmented plastids that contain starch granules
    • Common in storage organs such as potato tubers (used to detect gravity)
  12. Leucoplast
    Colorless plastids involved in the synthesis of monoterpenes (volatile compounds contained in essential oils). Found in secretory gland cells associated with leaf and stem trichomes also found in citrus peel.
  13. Etioplasts
    • Plastids where development from proplastids to chloroplasts has been arrested by absence of light or very low light (not an intermediate stage). Contain no chlorophyll but have colorless chlorophyll precusors (photochlorophyllide)
    • Light triggers development of etioplasts into chloroplasts
  14. Chloroplasts
    • Green photosynthetic plastids responsible for energy capture
    • Bounded by a double membrane (unit membrane)
    • Has an inner membrane system called thylakoids network containing two distinct types of membrane domains: stacked grana thylakoids, unstacked stroma thylakoids
    • Chlorophyll contained in the thylakoid membranes
    • Plants grown in shade generally have more grana and more thylakoids per granum
    • Thylakoid stacking is ubiquitous in green plants and is believed to be involved in regulating te distribution of radiant energy between photosystem I and photosystem II during photosynthesis.
    • Light reactions occur in the thylakoid membrane
    • Dark reaction occur in the stroma
  15. Functions of the light and dark reactions
    • Light rxns = capture of ligt energy and its conversion to chemical bond energy (ATP and NADPH)
    • Dark rxns = enzymatic fixation of CO2 into carbohydrate utilizing the ATP and NADPH from the light rxns
  16. Chromoplasts
    • Synthesize and accumulate carotenoid and xanthophyll pigments making them yellow, orange, or red in color.
    • Find in red tomatoes, carrots, or red peppers