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rachis

Line breaks: ra¦chis
Pronunciation: /ˈreɪkɪs
 
/
(also rhachis)

Definition of rachis in English:

noun (plural rachides /-kɪdiːz/)

1 Botany A stem of a plant, especially a grass, bearing flower stalks at short intervals.
Example sentences
  • Inflorescences are the terminal toothbrush type, with five to 70 pairs of flowers on a rachis approx. 35-50 mm long.
  • Hordeum spontaneum and H. vulgare are morphologically similar, with the cultivated form having broader leaves, shorter stem and awns, tough ear rachis, a shorter and thicker spike, and larger grains.
  • This gene did not affect plant height, indicating that the length of rachis and culm are controlled by independent genetic systems.
1.1The midrib of a compound leaf or frond.
Example sentences
  • Because the Sesbania species have pinnately compound leaves, for defoliation the central rachis of the leaf was cut once halfway along its length.
  • Each leaf has a central rachis to which the many small leaflets are attached.
  • The basal leaves can be more than 10 cm long and have three to eleven leaflets along their rachis.
2 Anatomy The vertebral column or the cord from which it develops.
3 Ornithology The shaft of a feather, especially the part bearing the barbs.
Example sentences
  • A contour feather, as a typical feather, has a complex morphology consisting of a central shaft or rachis to which barbs are attached on two margins to form a vane.
  • Beipiaosaurus and Sinomithosaurus bear short fibers similar to those on Sinosauropteryx, but the structures on Caudipteryx and Protarchaeopteryx are unambiguous feathers, with a central rachis and barbs.
  • Feathers, however bizarre or morphologically complex, consist essentially of a rachis, barbs, and barbules.

Origin

late 18th century: modern Latin, from Greek rhakhis 'spine'. The English plural -ides is by false analogy.

Definition of rachis in:

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