Collenchyma

• Collenchyma is a living tissue composed of more or less elongated cells with thickened primary walls
• First part of the word, derived from the Greek colla, “glue”, refers to the thick glistening wall characteristic of collenchyma
• It is a simple tissue, for it consists of a single cell type, the collenchyma cell.
• Collenchyma are Living tissue also capable to resume meristematic activity
• Have unevenly thickened primary cell walls

  • Despite having thick cell walls, the tissues they comprise of are still soft, pliable, compared to the sclerenchyma cells
  • They contain, in addition to cellulose, large amounts of pectins and hemicelluloses and no lignin
• Isodiametric in shape (cross section), elongated (longitudinal section)\
• Found in actively growing parts or regions of the plant body
• Chloroplast is also found in collenchyma cells
• Collenchyma are the first supporting tissues of the primary plant body
• Collenchyma - It has its origin in the ground meristem (close to or against epidermis) or procambium (may be common in vascular tissues)
• Peripheral Collenchyma

  • It may be present immediately beneath the epidermis or it may be separated from the epidermis by one or more layers of parenchyma cells of the cortex
• (Peripheral) Continuous: Form a continuous or single ring of tissues, but may be interrupted by parenchyma
• (Peripheral) Strand: axial strands separated from one another by parenchyma, found as bundles

  
• (Fascicular) Supracribral: bordering the vascular bundle at the phloem pole

  
• Infraxylary: bordering the vascular bundle at the xylem pole

  Circumfascicular: completely surrounding the vascular bundle
• Stem

  • usually in a continuous layer
  • in others, it is in patches or discontinuous
• Roots

  • rarely to be present
• Leaves

  • in petioles it is discontinuous
  • in blades, they are found near major veins
• Collenchyma are common in mature herbaceous organs
• Distribution allows it to perform its function better
• Collenchyma supports the organ, facilitates the organ expansion, and protects the vulnerable tissues (xylem & phloem).
• Lamellar/plate - tangential walls are relatively thicker than radial sides

  
• Angular - thickening is localized in the sides or corners of collenchyma cells

  
• Lacunar - much like angular in pattern of thickening, it only differs in that air spaces are found in the corners

  
• Annular - uniform thickening and usually more or less circular in outline