Plants III: Higher Plant Form and Function

  1. parenchyma cells
    • form much of the ground tissues
    • living when mature
    • variety of functions: metabolism (photosynthesis), storage (in cortex)
    • makes up, for ex: phloem, epidermis, fruit and veggie edibles, sieve-tube members
    • primary cell walls are generally thin and flexible
    • some have chloroplasts, but usually don't
    • divide when needed
    • can elongate
    • lack secondary cell walls
    • some have colorless plastids that store starch
    • mature, unspecialized cells do not generally undergo cell division, but can be induced to differentiation under special conditions, such as repair/replacement of organs after injury
  2. collenchyma cells
    • provide flexible support for parts of still-growing plants, support the vascular tissues
    • primary walls are unevenly thickened
    • grouped into strands/cylinders
    • living when mature
    • do not have chloroplasts
    • can elongate
  3. sclerenchyma cells
    • thick secondary cell walls strengthened by lignin
    • provide support in nongrowing regions
    • cannot elongate
    • dead at functional maturity
    • ex: vessel elements and tracheids in xylem
    • types:
    • *fibers - specialized for support, long, slender, and tapered, usually occur in groups (ex hemp)
    • *sclereids - specialized for support, shorter, irregular in shape, (ex hard shells of nuts and seed coats, gritty texture in pears)
  4. meristematic cells
    • retain the capacity to undergo cell division (mitosis)
    • small, six-sided cells with large nuclei
    • produced cells that eventually become the other cells
    • types include apical meristems, primary meristems, lateral meristems
  5. apical meristems
    • tips of young shoots and roots
    • produce all other cells of the plant, via primary and lateral meristems
  6. primary meristems
    • produced by the apical meristem
    • responsible for the primary growth (increase in length)
    • protoderm - produces the outer epidermis to stems and roots
    • procambium - produces the vascular tissues in stems and roots
    • ground meristem - produces the ground tissues of stems and roots
  7. lateral meristems
    • responsible for secondary growth
    • increase the girth of individual stems and roots
    • encompass vascular cambium and cork cambium
  8. vascular cambium
    • produce secondary xylem and phloem
    • layers of secondary xylem form over time and harden to produce wood
  9. cork cambium
    • produce a thick covering for large stems and roots
    • replace the epidermis
    • made of parenchyma cells in mostly the cortex
    • produces cork cells and secondary cortex cells
    • periderm - the cork and cork cambium
    • bark - periderm + secondary phloem
    • old roots do not absorb water
  10. nonmeristematic tissues include...
    dermal, vascular, ground tissues
  11. dermal tissues
    • consist of the epidermis
    • acts as the outer "skin"
    • produces the waxy substance cutin to form the cuticle, which helps the shoot system to retain water
  12. vascular tissues
    • transport of materials throught the plant
    • consists of xylem and phloem
  13. ground tissues
    • tissues other than the epidermis and vascular tissues
    • parenchyma cells are the dominat cell type
  14. phloem
    • phloem sap moves through tubes formed by chains of cells (sieve-tube members) lined up from end to end, forming sieve tubes
    • sieve plates - porous end walls; allows for unimpeded movement from one cell to the next
    • alive at functional maturity; lack nuclei, ribosomes, distinct vacuoles
    • have companion cells
  15. companion cells
    • nonconducting
    • adjacent to and connected to sieve-tube members
    • retain their nuclei and are living when mature
    • assist sieve-tube members in maintaining cell metabolism and function
  16. phloem sap
    • aqueous solution; carbohydrates, sugar(is the dominant solute); minerals, amino acids, hormones
    • translocation - sugars are moved by active transport into sieve tube members, and water follows by osmosis
    • ATP needed
    • increase in hydrostatic pressure then moves the sugar solution from one cell to the next, going from sources to sinks
  17. xylem
    • conducts water and dissolved minerals upward from roots into the shoots
    • consists of tracheids and vessel elements
    • elongated cells, dead at functional maturity
    • nonconducting sclerenchyma fibers may also be present
    • secondary walls interupted by pits - thinner regions where only primary walls are present
  18. tracheids
    • long, thin cells with tapered ends
    • water/xylem sap moves from cell to cell mainly through pits
    • generally moves upward through transpiration
  19. vessel elements
    • generally wider, shorter, thinner walled, less tapered
    • aligned end to end, forming long pipe-like structures called xylem vessels
    • completed perforated
  20. The flow of water is enhanced by...
    • ... transpiration (provides the pull) and the cohesion of water (to each other) due to hydrogen bonding.
    • no ATP needed
  21. stems
    • main aerial stalk
    • produce buds, flowers, leaves
    • support the leaves and conduct water and inorganic minerals to them
    • transport sugars and other photosynthetic products to the roots
    • may be green (photosynthetic), store water/food (cacti), adaptions to thwart herbivores (spines)
  22. stem features:
    • node, internode
    • lenticels
    • buds
  23. node
    • portion of the stem from which leaves and buds and branches arise
    • contain meristematic tissues
  24. internode
    portion of the stem between 2 nodes
  25. lenticels
    slightly raised circular or elongated slit-like structures on the bark of young woody twigs that function in gas exchange
  26. buds
    • undeveloped shoots in which internodes are present but generally are not elongated
    • may be protected (covered with specialized leaves called bud scales) or naked (lacking bud scales)
    • terminal buds - found at the tips of stems
    • axillary (lateral) buds - found in the axils of the leaves at the nodes
  27. dicot stem organization
    • >epidermis [single layer of parenchyma cells derived from the protoderm; cuticle; guard cells surrounding stomata may be present]
    • >cortex [multi-layered; originates from the ground meristem, consists mainly of collenchyma/parenchyma]
    • >vascular tissue [consists of primary xylem, primary phloem, and vascular cambium; typically form discrete, concentrically arranged in vascular bundles; vascular cambium is found between the xylem and phloem and called fascicular cambium]
    • >pith [center of the stem, composed of parenchyma cells, large]
  28. monocot stem organization
    • origin and development of the primary tissues are all the same as those of dicots
    • >vascular bundles are scattered throughout the ground tissue
    • >cortex and pith are indistinguishable, and all tissue tissue derived from the ground meristem is called ground tissue; vascular bundles are surrounded by a sheath of sclerenchyma
  29. secondary growth of stems
    • a meristem (interfascicular cambium) develops between the vascular bundles from cortical parenchyma cells --> forms a complete ring called the vascular cambium
    • secondary xylem to the inside
    • secondary phloem to the oustide
    • >these will form as complete rings or cylinders of conducting tissue
    • cork cambium (phellogen) forms from parenchyma of the cortex
    • monocots typically do not exhibit secondary growth
  30. woody dicot stems and annual rings
    • wood is made of secondary xylem
    • if there is a yearly cessation of this growth, annual growth rings will be formed (like in temperate regions)
    • yearly addition of phloem is not as conspicuous as that of xylem
    • xylem is composed of spring wood and summer wood
    • cells produced during the wetter parts of the growing season is less dense (larger cells and thinner cell walls; designed for transport)
    • summer wood is composed of smaller cells and thicker walls (designed for support)
  31. As the secondary xylem and phloem become differentiated (during secondary growth) ...
    ... a cork cambium arises in the outer cortex; forms boxy cork cells which become impregnanted with a fatty compound called suberin, which acts as a waterproofing agent. epidermis and outer cortical layers are sloughed off; periderm becomes the outermost tissues.
  32. rays
    • streaks of parenchyma cells
    • radiating outward from the center of the trunk
    • function is the lateral conduction of water and nutrients across the stem
  33. heartwood
    • older annual rings near the center become discolored by the deposition of various organic compounds
    • prevent further conduction of water
    • darkened
    • functions only in mechanical support
  34. sapwood
    • outer, lighter region
    • functions in both support and transport
  35. specialized stems:
    • stolons - below ground, horizontal (runners of strawberry plants)
    • rhizomes - underground horizontal stems (ginger)
    • tubers - modified stems for storing food (white potatoes)
    • bulbs - a shoot made of modified leaves surrounding a short stem (onion)
  36. leaf features:
    • principle organs of photosynthesis
    • no secondary growth
    • come about by primary meristems
    • blade - thin, flattened, photosynthetic part
    • petiole - stem-like stalk of a leaf that attaches the blade to the stem node
  37. leaf venation:
    • netted (reticulate) venation - one of more large veins from which smaller veins diverge; dicots
    • parallel venation - several veins that are more or less of equal size, which run parallel; monocots
  38. internal anatomy of angio leaves:
    • epidermis - single layer of modified parenchyma cells with a waxy cuticle, covering both upper and lower blade surfaces; guard cells, stomata (lower surface on dicots, evenly distributed on monocots)
    • mesophyll - photosynthetic parenchyma between the upper/lower epidermis
    • >differentiated into 2 layers in dicots
    • >palisade mesophyll - layers of elongated cells, adjacent to upper epidermis
    • >spongy mesophyll - loosely organized, adjacent to lower epidermis
    • bundle sheath surrounds the xylem and acts in a fashion that is analogous to the endodermis of the roots; prevents exposure of vascular tissue to the air
  39. abscission zone
    • the process of leaf shedding; preceded by the active resorption of nutrients from the leaves
    • a zone develops at the base of the petiole with the formation of a protective cell layer and an adjacent separation layer of cells
    • leaf scar - protected area on the stem, left after abscission
    • deciduous plants - plants whose leaves drop periodically with the change in seasons
    • evergreen plants - do not periodically drop their leaves
  40. roots
    • anchor the plant in the soil, absorb minerals and water, store food
    • primary root is first organ to emerge from the germinating seed
    • system of roots composed mainly of lateral roots become established
  41. fibrous root system
    • monocots
    • shallow, dense
    • increases the plant's exposure to soil water and minerals
    • high surface area
    • no secondary growth
    • no lateral meristems
  42. taproot system
    • dicots
    • one large vertical root that produces many small lateral roots
  43. Development of a root...
    ... may involve both primary growth and secondary growth (esp dicots).
  44. root cap
    • thimble-like structure composed of rather loosely arranged parenchyma cells that covers the root apex
    • protection of root apical meristem
    • produce a slimy polysaccharide lubricant that facilitates the movement of the root through the soil
    • may perceive gravity
  45. zone of division
    compact tissue immediately behind the root cap composed of small, densely cytoplasmic cells
  46. zone of cell elongation
    • adjacent to the apical meristem
    • consists of cells that are increasing in size longitudinally
    • some differentiation has begun
    • have 3 primary meristems:
    • >protoderm - single layer of cells on the outside that will differentiate into the epidermis
    • >ground meristem - several cell layers thick between protoderm and center (procambium); produces the cortex and the endodermis
    • >procambium - give rise to the tissues of the stele (vascular cylinder)
  47. zone of differentiation
    • aka root hair zone
    • root hairs form and other cells differentiate
    • comprise primary tissues
  48. epidermis (primary tissue in roots)
    • derived from the protoderm
    • consists of a single layer of parenchyma cells
    • normally lack a cuticle
  49. cortex (primary tissue in roots)
    • broad area of parenchyma cells
    • derived from the ground meristem
    • store starches
  50. endodermis (primary tissue in roots)
    • innermost layer of cortex cells
    • characterized by Casparian strip
    • surrounds the stele and regulates which minerals pass from cortex to vascular tissue
  51. casparian strip
    • an area of cell wall that has been secondarily thickened with lignin and waterproofed with suberin
    • ensures that no minerals can reach the vascular tissue of the root without crossing at least one selectively permeable plasma membrane of a living cell
  52. pericycle (primary tissue in roots)
    • outermost layer of the stele
    • unspecialized parenchyma cells that retain a potential to undergo cell division
    • lateral roots are created
  53. primary phloem (primary tissue in roots)
    • derived from the procambium
    • occurs in strands between the radiating arms of the primary xylem
  54. vascular cambium (primary tissue in roots)
    • undifferentiated procambial cells between the primary xylem and primary phloem
    • appear roughly rectangular in cross section
  55. primary xylem (primary tissue in roots)
    • derived form the procambium
    • occupies center of the root
    • 3+ radiating arms
  56. pith (primary tissue in roots)
    • central region
    • parenchyma cells
    • characteristic of monocot roots
  57. stele (primary tissue in roots)
    • central part of the root
    • includes all tissues interior to the cortex (pericycle, vascular tissues)
  58. hypodermis/exodermis (primary tissue in roots)
    • outermost layer of cortex cells, just underneath the epidermis
    • may have Casparian strips and suberin
    • important in preventing absorbed water and nutrients from escaping
Card Set
Plants III: Higher Plant Form and Function
Unit 14