PLSC Lab two

  1. Morphology
    External structure
  2. Anatomy
    Internal structure
  3. Monocot
    Monocotyledonae, have one seed leaf
  4. Dicot
    Dicotyledonae, have two seed leaves
  5. Nodes
    • Areas along the length of the shoot where leaves or buds (branches) arise
    • Some plants have multiple nodes located along the length of a single large shoot, while other plants may have very short shoots (called crowns) located near the soil surface, with narrow and indistinct nodes and internodes
  6. Internode
    The distance between 2 nodes
  7. Buds
    • where new shoots arise at each node,
    • Contains a shoot apical meristem
    • if a bud occurs at the tip of a shoot, it is called a terminal bud.  Buds arising from nodes below the terminal bud are called axillary buds (occurring about leaf axils)
  8. Basal bud
    Near the soil surface in most grasses.
  9. Culms
    Reproductive shoots, on which leaves seem to be attached at visibly distinct nodes.  The leaves on the culm are formed from the basal bud, but elongation of the stem makes it appear as though the leaves arise from some sort of axillary bud (which is not the case). Nonetheless, distinct nodes and internodes can be identified on grass culms
  10. Tillers
    Are side shoots on grasses (equivalent to branches in dicots)
  11. Opposite branching
    occurs where 2 shoots arise from 2 axillary buds on opposing sides of a single shoot (sometimes called lateral buds)
  12. Decussate
    In opposite branching, when each pair of lateral buds will shift 90o relative to the last pair of buds along the shoot
  13. Alternate branching
    occurs where a single smaller shoot arises from a single axillary bud, and these buds cascade around and along the main stem in a n helical arrangement.
  14. Distichous
    In alternate branching, if the alternations occur at 180o from each other
  15. Whorled branching
    Occurs where 3 or more axillary buds give rise to 3 or more lateral branches at a given node. Most coniferous trees posses a whorled arrangement of branches, as do a few herbaceous plants (horsetails, cleavers, and Joe Pye weed)
  16. Rosette
    Whorled branching that produce a single whorl of leaves near the soil surface. Many herbaceous flowering plants, notably dandelions
  17. Branching Pattern most common amongst the flowering plants (angiosperms)
    Opposite and alternate
  18. Dermal tissue
    The outermost, often a single cell thick and serves to protect the plant body from desiccation and infection, and/or to increase the absorptive surface (usually in roots).  Cells in dermal tissue are mainly parenchyma that specialize as epidermal cells
  19. Stomata
    Dermal tissues above ground and with photosynthesizing organs contain these, that are surrounded by specialized parenchyma cells called guard cells which are capable of opening and closting each stoma
  20. Ground tissue
    Often makes up the bulk of a herbaceous plant, and contains living parenchyma cells that either produce energy (photosynthetic mesophyll) or store moisture and energy (storage parenchyma).  Some ground tissue also function in structural support of the larger plant body, and sclerechyma fibers with thick lignified cells walls, or collenchyma cells with thick cellulose-laden cell walls both serve this purpose
  21. Vascular tissue
    Compromised of specialized water and food conducting cells.  Xylem tissue for water transportation is carried out by vessels, tracheids and parenchyma cells.  Water and nutrients are transported from the soil to actively-growing or metabolizing parts of the plant via these cells. Sclerenchyma fibers are also found in xylem and aid in structural support.  Phloem tissue transports energy-rich sugars from photosynthesizing parts of the plant to all other growth, storage and metabolism centers.  Phloem tissue is made up of several cell cells - sieve tubes, companion cells (angiosperms), albuminous cells (gymnosperms), parenchyma and sclerenchyma
  22. 3 types of tissues
    • Dermal tissue: parenchyma that specialize at epidermal cells
    • Ground tissue: the bulk, made up of living parenchyma cells: photosynthetic mesophyll or storage parenchyma; sclerenchyma fibers with thick lignified cell walls; or collenchyma cells with thick cellulose-laden cell walls for support
    • Vascular tissue: specialized food and water conducting cells. Xylem: vessels, tracheids, parenchyma cells, and sclerenchyma fibers for support. Phloem: sieve tubes, companion cells (angiosperms), albuminous cells (gymnosperms), parenchyma and sclerenchyma
  23. Apical meristem
    Is an area of actively dividing cells in buds that gives rise to all longitudinal growth of the shoot. The initial and outmost dermal tissue is called protoderm, and the initial bundles of vascular tissue are called the procambium
  24. Protoderm
    The initial and outmost dermal tissue in the apical meristem.
  25. Procambium
    The initial bundles of vascular tissue in the apical meristem
  26. Vascular traces
    In early stages of development after cell division, the cells are still actively growing, elongating, and differentiating into their respective cell and tissue types. The vascular tissue is arranged in the stem and leaves as vascular trace.
  27. Ground tissue
    surrounding the vascular tissues and enclosed by the dermal tissues are parenchyma cells collectively called this.
  28. Epidermis
    Monocot shoots are surrounded by an outermost ring of dermal tissue, one layer thick
  29. Leaf primordia
    Surrounds the shoot apical meristem in a longitudinal section
  30. Cuticle
    Waxy substance that thickens the epidermis.  It helps prevent water loss from cells in the shoot to the atmosphere outside.
  31. Phloem tissue in a vascular bundle in the monocot stem
    Clustered toward the outer edge of each bundle, is alive when functional, and composed of sieve tube elements stacked end to end. Companion cells are adjacent to sieve tubes and contain a nucleus that controls the function of the sieve tub.
  32. Dicots stem anatomy
    Unlike monocot, dicot vascular bundles are arranged in a distinct ring, with xylem oriented into the stem and phloem arranged out.  At the innermost pole in the primary xylem, then secondary xylem, then the vascular (fascicular) cambium (which is a lateral meristem). The ground tissue is still dominated by parenchyma cells, but has two types dependant on location in regards to the interfascicular cambium. The innermost is called pith, the outmost is called cortex, which can also have several layers of collenchyma cells for support.
  33. Root morphology, dicots
    Unlike shoots, roots do not have nodes and internodes because they do not posses axillary buds.  Most dicots produce a single, large primary root at an early stage of development, from which many secondary or lateral roots can arise.  Lateral roots arise from the pericycle. The large and primary root is called a tap root, which anchors the plant and stores water and energy.
  34. Root morphology, monocots
    Most monocots lack a thickened primary roots, but have a dense fibrous root system, with many secondary and tertiary roots.  In most monocots the primary root system, which develops from the embryonic root, dies and a secondary or adventitious root system develops from stem tissue. This is an effective root system for rapidly exploiting soil resources, and also functions ecologically to prevent soil erosion
  35. Root apical meristem
    • has many structure and developmental patterns similar to the apical meristem, with the major exception of a root cap.  This mass of dermal tissue helps protect the root apical meristem from damage. Actively growing roots have a mucigel coating on the root cap and dermal tissues to help protect the root.
    • Away from the root cap, you may also see some initial root hair development from the dermal tissue, which helps increase surface area for water and nutrient absorption.
  36. Initial root apical meristem
    gives rise to protoderm, procambium and ground tissue, same as shoot apical meristem, with the important exception of all root vascular tissue arise as a central core called the stele, whereas shoots have multiple vascular bundles.
  37. Root Anatomy (both monocots and dicots)
    • Both monocots and dicots have outermost double cell layer consisting of epidermis (single layer) and exodermis (innermost layer).  There may also be elongated root hairs from the epidermis. Both monocots and dicots have a cortex region, of ground tissue between an outerlayer of exodermis and inner layer of endodermis.  Most parenchyma cells in the cortex serve a storage function and contains grains of starch (complex carbohydrate) that were transported from the photosynthetic portions of the plant above ground.
    • The central core of tissues surrounded by the endodermis is called the stele. The endodermis contained a lignified area called the Casparian strip, that functions to prevent extracellular movement of water and nutrients.  In effect, the casparian strip acts as a filter.  Just inside the endoderm layer is the pericycle, a meristem of sorts, where adventitious root tips are initiated.
  38. Apoplast
    extracellular water movement
  39. Symplast
    intracellular water movement
  40. Differences in root anatomy between monocots and dicots
    • Pericycle is thicker much thicker in the monocots, while in dicots it is only one or two cells thick
    • Dicot roots have an innermost bundle of vascular tissues with a cross or star-like pattern of xylem, and smaller bundles of phloem nestled in the arms of the cross or star.  Monocots have alternating and adjacent bundles of xylem and phloem within a ring surrounding a central core of pith-like parenchyma cells.
  41. Cladophylls
    • are fleshy water-storing stems that you might mistake for a swollen leaf.  Cactus pads are excellent examples of cladophyls, and each individual pad represents an internode. When a cladophyll is young and forming, small soft green leaves will be present. As the cladophyll ages the leaves develop into spines.
    • Modified shoots
  42. Buds (Califlower and broccoli)
    • Modified shoots
    • Another example of fleshy stems, but it is the compact clusters of buds we normally consume
  43. Bulb
    • Modified shoots
    • An enlarged basal bud enclosed in thick, scale-like leaves paced with starch-filled parenchyma (onions and lilies). At the base of a bulb is the basal plate which is composed of stem tissue.  There are 2 types of bulbs - turnicate and imbricate and scaly.  The onion and tulip are examples of a tunicate bulb while the lily is an example of a scaly bulb.
  44. Corms
    similar in appearance to bulbs, but consist of a single fleshy stem with reduced leaves (crocus and gladiolus). Despite being stem modifications, most bulbs and corms grow below ground
  45. Below-ground tubers
    Can either by root or stem modifications.  Tubers have thin epidermal layer covering a mass of carbohydrate-rich parenchyma, and the potato is probably the most familiar example.  The "eyes" on the tubers are nodes with modified buds that give rise to new shoots.  Tuberous fleshy roots from dahlia and peony are root storage organs, not stems.  They do not posses nodes and internodes.
  46. Storage tap roots
    Are true roots, and lack any "eyes". Some fleshy taproots are important food items and agricultural crops (carrots and beets)
  47. Stolons or runners
    are horizontal shoots that grow above the soil surface.  Where a stolon contacts the soil surface, new roots and shoots can form and subsequently become independent from the parent plant (strawberry)
  48. Rhizomes
    are stem modification similar to stolons, but they extend horizontally below the ground much like a root.  Adventious roots commonly sprout all along rhizomes, but new shoots only arise at nodes (iris, may turf and pasture grasses)
  49. Nodules
    On the roots of plants from the Fabaceae family (legumes) as well as other families, superficially resemble tuber.  However, nodules provide a home for nitrogen fixing bacteria and are not storage organs for carbohydrates.  The nitrogen is fixed from the N2 gas in the soil by bacteria and converted into a form suitable for plant uptake from the soil water. Legumes can grow without these nodules, but in nitrogen-poor soil the growth of uninnoculated legumes may be slowed and protein content decreased.  Legumes are often used to help rebuild soil organic matter in mine reclamation, and are among the most important food and forage crops (soy, beans, lentials, pears, alfalfa, and clover)
  50. Adventious roots
    Are roots that arise from a plant part other than the primary root.  They sometimes sprout from shoots to provide additional support to the aboveground portions of a plant.  At an early stage of growth these aerial roots seem a bit out of place, but in humid tropical environments these roots help anchor epipytic plants to the branches of larger plants and absorb water directly from rainfall and water condensation.  Where roots reach the ground these are often called prop roots (corn).  Adventious roots are very important in the propagation of plants in the field of horticulture.  New plants can be started from cutting by placing them in suitable media, and providing good humidity to induce the formation of adventitious roots
Card Set
PLSC Lab two