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Segment [ Biology  ]

Dictionary of botanic terminology - index of names

Synonym: Article, Joint.
Adjective: Segmented or Segmentary
Adjective (Antonym): Unsegmented
  A segment, in a broad sense, is is a free or almost free part or subdivision of an organ.  
(1) Segment (Cacti & succulents) [ Botany ]
  In cacti, succulents and other plants the segments are distinct, individual parts of stems, like the pads (cladodes) of Platyopuntia, or the "joints" of a phylloclade  

The elongation of segments  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 roots and stems typical of most plant which has not a precisely determined or established limit of growth fixed in advance (indeterminate growth).

Many species of cactus and succulents (For example: Opuntia sp. ) have segmented stems in which terminal joints may be easily separated from the main-stem, these are commonly used for the vegetative propagation. The single joints are allowed to dry for a few days to discourage fungal or bacterial infections. Although this procedure would kill the stems of nearly any other plant, for these cacti it merely allows calluses to form on the cut surfaces. The single joints are then placed vertically in the ground with about one-quarter of their surface area in the soil.

Young stem segments (cladodes) of prickly pear are used as green vegetable throughout Mexico and in the southwestern U.S

(2) Segmented habit  [ Plant Morphology - Botany]
Synonym: Articulated habit

O. compressa Flowers

An segmented  habit is a vegetative features describe a  plant  that grow in distinctly successive articulated segments, which has the stem and branches divided into similar, repeated sections or units joined by narrow connections.

[Compare with: Unsegmented habit]

Left: Segments (cladodes) of Opuntia compressa

(3) Segment of the flower (Perianth segments) [ Botany ]
In flowers a segment is a distinct, individual parts or division of the calyx and corolla (perianth)
Segment of the calyx are called sepals.
Segments of the corolla are called petals
Undifferentiated segments are called tepals.
(4) Segment (Compound leaves) [ Botany]
In compounded leaves a segment is a single leaflet.
(5) Segment (Fruit) [ Botany]
In a fruit a segment is a division or portion. Usually these correspond to the locules.
(6) To segment  [ Transitive. & Intransitive verb ]
(past: Segmented, past participle Segmented, present participle Segmenting, 3rd person present singular Segments)
To divide or become divided into segments.





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