NPC SYSTEM

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                                               NPC SYSTEM (MALE GAMETOPHYTE)

  • NPC refers to number(N), Position(P), character(C) of apertures.
  • Under this system the usage of the term ‘treme’ has been recommended in the place of ‘aperture’ for the purpose of preparing key for the classification of pollen grains.
  • Pollen grains with out aperture are called atreme, also represented as N0.
  • Depending upon the number of apertures the pollen are monotreme(N1), ditreme(N2), tritreme(N3),tetratreme(N4), pentatreme(N5), hexatreme(N6).polllen grains with more than 6 apertures, irrespective of their number, are irregular or irregularly spaced, the pollen grains are described as anomotreme(N8).
  • with regard to the position (P) of apertures, there are seven (P0-P6) groups.
  • The pollen are designated as catatreme (P1) when the apertures is on the proximal face, and anatreme if it is on the distal face(P3) when the centres of apertures are located on the equator, the pollen grains are referred to as zonotreme(P4).
  • The condition is said to be pantotreme when the apertures are more or less uniformly distributed all over the pollen surface(P6).
  • The character-groups, like the position-groups, are also seven (C0-C6).
  • pollen are designated C0(0 stands for a query) when the character of the aperture is not known. C1 pollen have an aperture-like thin area, or leptoma.
  • Pollen with one leptoma are called monolept.
  • They may be catalept (leptoma on proximal face), or analept (leptoma on distal face).
  • The grains with a 3-slit colpus belong to C2 category, and are called trichotomocopate.
  • The remaining characters viz., C3, C4, C5 and C6 comprise colpate, porate, colporate,and pororate pollen grains, respectively.

REFERENCE :

THE EMBROLOGY OF ANGISPERMS 6th EDITION Author; SS BHOJWANI, SP BHATNAGAR ,PK DANTU.      

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