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Annulus  [ Botany  ]

Dictionary of botanic terminology - index of names

Synonyms: aaa 
Adjective: aaa 
Adverbbs: aaa 
     
In geometry:
  • An annulus is the portion of a plane bounded by two concentric circles in the plane.
 
In anatomical terminology:
  • An annulus is a tissue structure forming a ring or arranged in a circle.
 
In Asclepiadaceae anathomy:
  • An annolus or corona is the raised inner rim around the centre of a flowers corolla.
 

The annulus is a projecting central circle found in the flowers of some genera of the Asclepiadaceae family (e.g. Orbea, Huernia, Orbeanthus and Duvalia)
The asclepiads flowers has a pedicle ending with five sepals and a five segmented corolla (Usually it is 5-lobed, but sometimes we can find flowers with more or fewer free lobes) this segment are basally fused to form the annulus a raised shiny circular structure around the base of the gynostegium, it might have some prominent hairs.

Left: floral structure of Huernia


 

 


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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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