Bot lab exercise 3 concepts

• The roots of most plants are found underground
• Plants with roots suspended in the air

  • Xerophytes (e.g. orchids)
• Root system


  The entire mass of roots
• Formation of roots

  1. Radicle becomes the primary root

  2. Branches that develop from the primary roots are called secondary roots

  3. Branches arising from the secondary roots are the tertiary roots, etc.
• Primary function of the root

  Absorption of water and minerals from the soil and anchorage of the plant to the ground
• Roots are often useful in the determination as to whether a plant is annual or perennial
• Roots provide important features for identification and classification especially for grasses and its allies
• Taproot


  Roots that develop from the primary root
• Fibrous roots


  Roots that come out directly from hypocotyl or may branch off from the primary root, usually slender and of about the same diameter and size, with smaller root branches
• Adventitious roots


  Roots that are produced from structures other than the primary root or its branches, could arise from nodes, internodes of stems, or leaves. Foliar roots are roots arising from leaves
• Roots also perform functions than the typical ones and in these cases the shape is greatly modified such that it is difficult to distinguish whether the structure is a root or not
• Fusiform roots


  Roots shaped like a spindle, broad in the middle and tapering on both ends
• Napiform roots


  Roots spherical in shape
• Conical roots


  Roots cone-shaped
• Tuberous roots


  When the taproot becomes thick and fleshy but does not form a definite shape
• Pneumatophores or respiratory roots


  Roots resembling conical spikes, characteristic of mangrove trees, commonly found in marshy and salt lakes
• Nodulose

  When the slender root becomes swollen at the apex
• Moniliform roots


  When the swellings in the root occur at frequent intervals or they assume a bread-like formation
• Annulated roots


  Roots with ring-like swellings, as observed in arrowroot, Maranta arundinacea
• Prop, stilt or brace roots


  Roots produced from the main stem, growing vertically downwards to the ground
• Climbing roots


  Roots that climb and are often attached to a support like a fence, a stake, or to another plant
• Haustoria (-ium) or sucking roots


  Roots of parasitic plants that penetrate the host plant and absorb nutrients from it
• Aerial roots or epiphytic roots


  Roots suspended in the air
• Contractile roots


  Roots that undergo contraction at the uppermost part due to changes in the shape of the cortical cells
• Endodermis


  Single cell layer at the inner edge of the cortex
• Pericycle


  Outermost layer of the vascular cylinder
• Xylem


  Star-shaped group of cells in the center
• Phloem


  Between the "arms" of xylem
• Endodermal cell walls


  • Contain Casparian strips, which are made of suberin and therefore are impermeable to water
• Parts of dicot roots

  • Endodermis
  • Pericycle
  • Xylem
  • Phloem
• Parts of monocot roots

  • Pith tissue
  • Vascular tissue
  • Cortex
• Apical meristem


  Growing tip of the root
• Protoderm


  Develops into the epidermis
• Ground meristem


  Develops into the cortex and endodermis
• Procambium


  Develops into the vascular tissue and pericycle
• Root cap


  Protects the apical meristem
• Casparian strips, which are made of suberin and therefore are impermeable to water.
• The cortex surrounds this ring of vascular tissue.
• In dicot roots, the vascular tissue is typically located in the center of the root and is surrounded by the cortex. In contrast, there is usually pith tissue in the center in monocot roots, with a ring of vascular tissue surrounding the pith.
• apical meristem (growing tip of the root)