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Genus: Opuntia     [ Cactaceae ]

Dictionary of Genus names

The genus name "Opuntia" refers to a Greek name used by Pliny for a diverse plant which grew in the region of the town of Opus in Greece (The genus name implies: “plant of the town of Opus”).
 
 


Opuntia aciculata


Opuntia compressa

    Opuntias are distinguished from other cacti by 4 characteristics:
  1. The stems grow in distinctly jointed segments (cladodes). The elongation of joints is permanently terminated at the reach of a certain size or by onset of the dry season (determinate growth); subsequent growth of the plant occurs by the initiation of new joints by branching from the ends of older segments. That is segments are genetically programmed to expand for a limited time, then stop growing. This determinate growth characteristic of segmented plant is in stark contrast to the indeterminate (virtually unlimited) growth of stems typical of other cacti which has not a precisely determined or established limit of growth fixed in advance (indeterminate growth) subsequent growth of the plant occurs by the initiation of new joints by branching from the areoles. (Other cacti, like saguaro have indeterminate growth).
     
  2. Whether the stems have spines or not, Opuntia stems always have glochids in the areoles.
     
  3. Rudimentary and ephemeral leaves are present on new joints.
     
  4. Seeds have a pale hard covering called an aril; most other cacti have black, shiny seeds.

A flower of Opuntia
 
A fruit of Opuntia
   

 

 

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