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(1) Calyptra   [ Botany ]
Synonym:
Calypter
Adjective:  Calyptrate

Dictionary of botanic terminology - index of names

     
  Calyptra, in a broad sense, is any cap-like, hood-like, lid-like, structure covering or partly covering a  body or organ, such as a root cap.  
     
(2) Calyptra (root cap)    [ Botany ]
     
  The calyptra or root cap is a cap-shaped structure at the tip of the roots.  
     

The elongation of the parenchyma cells pushes the root tip into the soil, the calyptra covers and protects the delicate apical meristem from abrasion as it grows through the soil.

The calyptra is formed by several layers of cells that envelop the root tip externally. This covering of cells, of which the outermost ones are dead, envelops and protects the growing tip very much as a thimble protects the finger.  It extends back over the root for a distance usually of about a millimetre.
As the root-cap cells mature, they become parenchyma and are constantly pushed out by the addition of new cells from within. Those on the outside next to the soil are more or less flattened by pressure from within and slough off as they rub against soil particles when the root grows deeper. The root cap produces a slimy layer of mucilage, known as mucigel that lubricate the tip. But throughout the life of the root, even if it penetrates many feet into the soil, the root cap is so constantly renewed by new cells from within that the delicate tip is actually pushed through the soil without, as it were, coming in contact with it. This explains why roots can penetrate even into stiff clay soils without buckling.

     
(3) Calyptra (of flowers)    [ Botany ]
     
  A cap-like covering or lid on a flower bud. The calyptra is formed by fusion or cohesion of the perianth  segments and cover the stamens and carpels as a calyx that comes off like a lid.  
     
(For example The cap on the buds of Eucalypts and on the California poppy)
     
(4) Calyptra (of fruits)     [ Botany ]
     
  A  cap-like structure on a  fruit that becomes detached at maturity by abscission; e.g. the lid of circumsciss capsules.  
     
(5) Calyptra (of mosses)    [ Botany ]
     
  In bryophytes (moss or related plant), the calyptra is a little hood or veil, resembling an extinguisher in form and position,  it  protects each of the small flask-like sporangium capsules and it is composed of gametophyte tissue  from the neck of the archegonium  
     
This cap is lost when the sporangium capsule is mature and ready to release the spores.
     

 


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Holdfast roots  [ Botany  ]

Dictionary of botanic terminology - index of names

 
     
  Some species of climbing plants develop holdfast roots which help to support the vines on trees, walls, and rocks. By forcing their way into minute pores and crevices, they hold the plant firmly in place.  
     
Climbing plants, like the poison ivy (Toxicodendron radicans), Boston ivy (Parthenocissus tricuspidata), and trumpet creeper (Campsis radicans),  develop holdfast roots which help to support the vines on trees, walls, and rocks. By forcing their way into minute pores and crevices, they hold the plant firmly in place. Usually the Holdfast roots die at the end of the first season, but in some species they are perennial. In the tropics some of the large climbing plants have hold-fast roots by which they attach themselves, and long, cord-like roots that extend downward through the air and may lengthen and branch for several years until they strike the soil and become absorbent roots.

Major references and further lectures:
1) E. N. Transeau “General Botany” Discovery Publishing House, 1994
   

 

 

 

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