Ground tissue system

Ground  or Fundamental tissue System

Consists of the main bulk of plant body and extends from below the epidermis to the center, leaving vascular tissues apart.

Type of cells & tissues of ground systems

1.         Parenchymatous tissue

 Origin:   •       That of ground system develops from ground meristems.

                 •      That of the vascular elements derived from procambium.

Cell wall composition: with primary cell wall of cellulose, hemicellulose and pectic 

                                       compounds.

Functions: •     Play a role in healing of wounds where it can retain the ability to divide.

                   •    Storage.

                   •    Secretion.

Shapes & arrangement of parenchyma:

     •      Polyhedral:- with equal diamerers.            •      Lobed (Plicate) :- with folds.

     •      Armed:- with arms and air spaces.            •      Lacunate:- forming air spaces. 

2.         Chlorenchymatous Tissue

Nature: Parenchyma with chloroplasts.

Location: Characterizes the wings of leaves & herbaceous stems.

Functions:  •    Photosynthesis.

                    •   Storage.

Shapes and types:     •            Palisade & Spongy tissue                     •       Isodiametric.

3.         Collenchymatous Tissues

Origin: Develops from elongated cells rsemble procambium or from isodiametric cells of the ground meristem.

Cell wall composition: with secondary cell wall thickened with Pectin.

Locations:  •    below the epidermis in a cylinder or strips in stems

                     •  on one or both sides of mid-vein or wings in leaves.

Function:    • mechanical support:

Shapes:          1.          Angular                                                        2.            Annular

               Thickening lies on corners.                             Thickening around the cell .

                    3. Lamellar                                                       4.           Lacunar (tubular)

               Thickening in lamellae                                   Thickening in parts facing the

                (on tangential walls).                                                intercellular space.

4. Sclerenchymatous Tissue

Origin: Originate from procambium, cambium, ground meristem or protoderm .

Cell wall composition: With secondary cell wall thickened with lignin.

Functions: Mechanical supporting tissue

Classification of sclerenchyma:

1.         Fibers:- Elongated cells with pointed ends, occur in patches, bands or singly

     a.    Xylary (Wood) fibers: Derived from procmbium,  in between xylem elements.

     b. Extraxylary (Bast) fibers: Occur out side the xylem elements.

    •       Phloem fibers          •    Cortical fibers        •     Pericyclic fibers  •         Bundle sheath fibers

  In secondary phloem. May form cylinder.    Close to phloem.    Around V. bundle

2.         Sclereids:

       Development:  from parenchyma or from  sclereids primordia.

       Locations: Occur in epidermis, ground tissue & vascular tissue.

Shapes: 

1.         Brachysclereids (grit cells, stone cells): Unbranched, with  branched canal pits, in the gritty parts of the  pears.

2.         Macrosclereids (rod cells, palisade–like): Forming the palisade layer of many seeds.

3.         Asterosclereids (stellate cells):

Star shaped, with arms, in some xerophytes.

 4.        Osteosclereids (bone cells):

In hypodermal layers in xerophytic leaves.