Spores are reproductive haploid structures that is adapted
for dispersal and surviving for extended periods of time in
Spores form part of the life cycles of many plants, algae,
fungi and some protozoans.
A chief difference between spores and seeds as dispersal
units is that spores have very little stored food resources
compared with seeds.
Spores are usually haploid and unicellular and are
produced by meiosis in the sporophyte.
Once conditions are favorable, the spore can develop
into a new organism using mitotic division, producing
a multicellular gametophyte, which eventually goes on
to produce gametes.
Pollens are produced from the microspore mother
cells, but female spores are produced by the
megaspore mother cells
Pollen grains have two outer coats extine and intine
and female spores do not have the extine or intine.
Pollens are dispersed by various mechanisms, but
female spores are retained within the ovary.
Pollens are found inside the pollen sac, and female
spores are found inside the ovule.
In other words, all pollens are spores, but not all
spores are pollens.
NPC is an artificial system of classification of pollen
and spore based on the three features of aperture only,
i.e. number, position and character.
Erdtman and Straka (1961) proposed NPC
classification and palynologists all over the world
According to NPC system each pollen grain has an
arithmetic cardinal number consisting of three digits
The first digit reveals the absence or presence of
aperture, and when present it mentions the total
number of aperture(s) present in a pollen grain
The second digit illustrates the position of aperture(s),
i.e. distal, proximal, and latitudinal, meridonial,
The microspores reveal the position of aperture(s)
with full clarity when they are in tetrad.
The third digit explains the character of an aperture,
i.e. circular/oval or elongated, simple or compound
etc. ‘N’ from number, ‘P’ form position and ‘C’ from
character of aperture compose the NPC-classification.
Classification of Aperture Based
In NPC system ‘N’ denotes the number of aperture(s)
present in a pollen grain.
Aperturate pollen, i.e. pollen having apertures are divided
into seven groups.
The groups are mentioned as N1 to N7.
Each group has characteristic number of aperture, i.e. N1 has
one aperture and N2 has two apertures and so on. The
N7 group has seven or more apertures
N1 to N7 groups are also referred to respectively as
monotreme, ditreme, tritreme, tetratreme,
pentatreme, hexatreme, and polytreme (Greek trema
means hole, opening, aperture; pl. tremata).
There are pollen grains where apertures are absent.
Such pollen grains are termed as inaperturate or
atreme and they are placed in N0group.
Another special group N8—termed anomotreme is
created where the pollen grains and spores have one or
several irregular or irregularly spaced apertures
Classification of Aperture Based
In NPC system ‘P’ denotes the position of aperture in a
pollen grain and spore.
The position may be proximal, distal and equatorial.
There are seven groups of aperture based on position
namely –P0 to P6. Pollen grains having P0 group have
uncertain or unknown position of aperture).
. P1 groups of pollen and spores are catatreme
Catatreme pollen grains have one aperture that occurs
on the proximal part of a grain.
The proximal part is the face of a pollen grain or spore
that faces inward/nearest or toward the centre of
P2 groups of pollen and spores are anacatatreme
Anacatatreme pollen and spores have two apertures.
One aperture with its centre occurs at the proximal pole.
The other aperture with its centre occurs on the distal pole
The distal part is the face of a pollen grain and spore that
faces outward, i.e. away from the centre of tetrad and
opposite the proximal part
P3 groups of pollen and spores are anatreme, i.e. the
aperture is distal in position.
P4 groups of pollen and spore are zonotreme.
A zonotreme pollen grain is characterized in having
apertures on equator or sub-equator
The equator is the part of a pollen grain or spore that runs
midway between the proximal and distal poles and
perpendicular to polar axis.
P5 groups of pollen and spore are dizonotreme
Dizonotreme pollen grains have apertures arranged in two
or more zones.
The apertures occur parallel to equator. P6 groups of pollen
and spore are pantotreme
Pantotreme pollen grains have apertures scattered over
the whole surface uniformly. As a rule, pantotreme
pollen grains are spheroidal.
Classification of Apertures Based
In NPC-system ‘C’ denotes the character of an aperture
in a pollen grain and spore.
The character groups of pollen and spore are seven and
they are mentioned as C0 toC6. C0 groups have
apertures whose character cannot be established with
C1 groups of pollen and spore have leptoma (Greek
leptoma means thin place).
Leptoma is a thin area, aperture like and functions like
Pollen grains having one leptoma are termed as
The leptoma may occur on either proximal-or distal
face of a pollen grain and spore and accordingly
termed as catalept and analept
. C2 groups are trichotomocolpate (Gr. Tricha, in three
parts; tome, cut; kolpos, depression, furrow).
Trichotomocolpate is a three- branched aperture, the
branches of which are more than two times longer
Trichotomocolpate pollen and spores having aperture
on porximal face are termed as trilete
The group C3 has colpate grains.
The group C4 comprises porate pollen grains.
The group C5 comprises colporate pollen.
The group C6comprises pororate pollen. C3, C4, C5 and
C6 groups of aperture are previously discussed under
Merits of NPC classification:
It is a simple system of classification and illustrates the
apertures of a pollen grain and spore.
With the aid of NPC pollen grains and spores of
pteridophyta, monocotyledon and dicotyledon, to
some extent, can be differentiated.
Most of the spores of pteridophyta are monolete or
Monocots are characterized by inaperturate, monosulcate
and monoporate pollen grains.
Dicots, with a few exceptions, have pollen grains that are
mostly with three meridonial furrows and polyaperturate.
Thus NPC narrows the search list of identification of
NPC makes the description of apertures precise.
NPC is supposed to be of primary classificatory
character because apertures are most conservative.
It is supplemented by surface ornamentation, size and
shape etc. of a pollen grain.
Sometimes it becomes possible to identify the family
or genus or even species of a pollen grain with the aid
of NPC in combination with other morphological
Palynologists all over the world accepted NPC-
classification as it is basically simple and consistent
where pollen grains and spores could be arranged
This helps to identify unknown sporomorphs
NPC, sporoderm stratifications, exine patterns, size
and shape etc. of a pollen grain are genetically stable.
This property is utilized for various purposes and the
followings are a few illustrations.
With the aid of NPC and other characters a key can be
formulated that helps to identify unknown pollen and
NPC and the various types of exine patterns and
ornamentation provide characters of taxonomic
significance and thus become one of the sources of
Demerits of NPC classification:
It is an artificial system of classification.
Syncolpate and parasyncolpate pollen grains do not fit
neatly in NPC system
Pollen grains that are characteristically present as
aggregates in tetrads, e.g. Ericaceae, Typhaceae and
polyads, e.g. Orchidaceae, Mimosa etc. are not
grouped in NPC system
NPC-system of classification is always compared with
Linnaeus’s system of classification, because the latter
is also an artificial system of classification.
The characters of stamen were the basis of
‘Linnaeus accepted the weakness of his classification
but claimed that it was propounded mainly as an aid to
This is also applicable to Professor Erdtman.
Palynologists from every discipline of palynology
utilize Erdtman’s NPC classification
Other characters related to pollen morphology as an
aid to the identification of unknown sporomorphs.