Plant Structure

  1. Plants are different from animals:
    • they are sessile
    • they have indeterminate growth
    • their support system uses organic, inert molecules
    • they store different types of energy
  2. Root function:
    • anchorage
    • storage
    • absorption
  3. taproot
    • single main root with lateral roots growing off of it
    • typical of eudicot
    • adapted for deep soils
  4. fibrous roots
    • adapted for shallow anchorage
    • isodiametric
    • may be adventitious - radical dies, roots emerge from stem itself
    • typical of monocots
  5. modified root types:
    • prop - comes out of root from stem (adventitious)
    • storage
    • strangling "aerial"
    • buttress - supporting
    • pneumatophores - in swampy areas, surface to "breathe" air
  6. stems/shoots are divided into...
    • nodes - where leaves emerge, &
    • internodes - stem between nodes
  7. 2 types of buds:
    • terminal bud - at top of stem, main bud
    • axillary buds - above nodes, on the axis; termination of teminal bud will stimulate lateral growth
  8. modified stem types:
    • stolon - grows horizonally and asexually; above ground
    • bulbs - short, undergound; fleshy leaves surround it (ex: radish)
    • tubers - grow at end of rhizomes (ex: potato)
    • rhizomes - underground, horizontal; stem structures grow from it
  9. leaves on eudicots:
    blades are connected to stem by a petiole
  10. leaves on monocots:
    leaves emerge from stem base, forming a sheath
  11. modified leaf types:
    • tendrils - demonstrate response to touch; may coil
    • spines - nonphotosynthetic; defensive purposes (ex: cactus)
    • storage - for water, nutrients (ex: jade, aloe)
    • bracts - associated with flowers, colorful, main photosynthetic organ (ex: poinsetta)
    • reproductive - serrated edges that grow additional leaves and roots; allots asexual reproduction
  12. parenchyma cells
    • thin primary wall, not lignified
    • useful for storage
    • no chloroplasts, not much inside except for huge vacuoles
    • isodiametric
    • live at maturity
  13. chlorenchyma cells
    • modified type of parenchyma cell with chloroplasts
    • usually found in middle of leaves
  14. collenchyma cells
    • unevenly thickened primary cell walls
    • elongated cells
    • provide support for actively growing cells
    • living at maturity
  15. sclerenchyma cells
    • tough, fibrous
    • lignified secondary cell wall to help maintain shape (fibrous, barrel, star)
    • dead at maturity; achieves correct shape/size then undergoes apoptosis
  16. general secondary cell wall characteristics:
    • not very porous
    • structure eliminates hyrdolic and turgor pressure
    • interior to primary cell wall
    • strengthened with lignin/cellulose
    • thickness depends on what it differentiates into
  17. dermal tissues
    • outer covering of leaves, stems, roots
    • on leaves, may secrete cutin
  18. vascular tissues
    • consist of xylem and phloem
    • transportation tissues
  19. ground tissue
    • neither dermal nor vascular
    • provides bulk and support
    • made of all cell types
    • cortex - found exterior to vascular tissue
    • pith - interior to vascular tissue
  20. meristematic tissue
    • cells that undergo constant mitotic division
    • consist of differentiating cells
    • phloem points outside, xylem points inside
    • apical meristems and lateral meristems
  21. xylem
    • move water and dissolved inorganic nutrients
    • modified sclerenchyma
    • conducting elements are vessels and tracheids
    • vessels: common in angios; wider, more efficient; have end plates - water can move easier from one element to another
    • tracheids: in both angios and gymnos; narrow, spindle-shaped; assist in going through secondary cell walls
  22. phloem
    • transport of photosynthate (dissolved sucrose)
    • not necessarily a one-way flow
    • modified parenchyma
    • conducting elements are sieve cells (gymnos) and sieve-tube members (angios)
    • sieve cells: living, but not a full compartment of organelles; albunious cells are helper cells
    • sieve-tube members: missing many vital organs, but living; barrel-shaped for good efficiency; companion cells assist with organelle functions
    • sieve plates - perforated plates; sap flows through these to adjacent cells
  23. apical meristems
    • on root and shoot tips
    • primary growth for herbaceous plants
  24. lateral meristems
    • secondary growth in woody plants
    • increase in girth, width
    • meristems are the vascular and cork cambiums
  25. In roots, growth occurs in three overlapping zones of cells:
    • zone of cell division - includes the root apical meristem and its derivatives; new cells are produced
    • zone of maturation - most of the growth in roots; cells elongate and push root down further into soil; cell differentiation begins to become noticable
    • zone of differentiation - cells become distinct cell types (at topmost part)
  26. vascular tissue organization in roots:
    • monocots: parenchyma (pith) in center; core is surrounded by ring of xylem (inside) and ring of phloem (outside)
    • eudicots: xylem (inside) and phloem (outside) in center core; stele is the vasculer cylinder appearing as a lobed core
  27. Monocot root tissue organization (outside to inside):
    epidermis --> cortex --> endodermis --> pericycle --> vascular cylinder (phloem, xylem)
  28. Eudicot root tissue organization (outside to inside):
    epidermis --> cortex --> endodermis --> pericycle --> phloem --> xylem --> pith(core of parenchyma cells)
  29. endodermis
    • special layer of cells with super thick walls that are water proof and lignified
    • selective barrier for stele
    • modified parenchyma
    • innermost layer of cortex
  30. primary growth of shoots:
    • leaves develop from leaf primordials - projections along the side of the apical meristem
    • shoot elongation is due to lengthening of internode cells just below the shoot tip
    • branching arises from activation of axillary buds
    • intercalary meristems allow damaged leaves to rapidly regrow
  31. Monocot stem tissue organization (outside to inside):
    epidermis --> [maybe] collenchyma cells --> cortex --> vascular bundle (sclerenchyma --> phloem --> xylem) --> pith
  32. Eudicot stem tissue organization (outside to inside):
    epidermis --> collenchyma cells --> scattered vascular bundles within mass of ground tissue
  33. Leaf tissue organization (top to bottom):
    upper epidermis (cuticle --> layer of dermal tissue interrupted by stomata and guard cells) --> palisade mesophyll (elongated chlorenchyma cells) --> vascular tissue (surrounded by bundle-sheath cells) --> spongy mesophyll (contains air spaces) --> lower epidermis
  34. secondary growth
    • aid from lateral meristems (cambiums)
    • only in woody plants
    • builds on primary growth plan
    • typical in eudicots and gymnos
  35. cork cambium
    • provides protective layer for stem
    • cork on the exteriror
    • corticle cells on the interior
    • entire complex called bark (which also includes secondary phloem)
    • develops within cortex
    • replaces epidermis
    • periderm (cork cambium) secretes suberin into cell walls that makes the bark water proof
  36. vascular cambium
    • produces secondary phloem to exterior and secondary xylem to interior
    • youngest tissue closer to vascular cambium, older tissue towards center of trunk
    • phloem layers are much narrower
  37. bark
    everything outside of vascular cambium : periderm (cork cambium and cork) and secondary phloem
  38. lenticels
    loosely arranged cork cells that oxygen can diffuse through
  39. girdling a tree
    taking an entire ring of bark off of the tree can kill it because of secondary phloem removal
Card Set
Plant Structure
Ch 35