Production, dispersal, sedimentation and taphonomy of spores/pollen

1. Production, dispersal, sedimentation and taphonomy
of spores/pollen
Birbal Sahni Institute of Palaeosciences, Lucknow
53 University Road, Lucknow-226007, U. P., India
B 3.2: Palynology, Phytoliths and palynofacies analysis

2. .
Stamen
T.S of anther
Pollen development

3. POLLEN
Pollen grain is the first cell of male
gametophyte which is unicellular, haploid
and performs the function of pollination.
Pollen is formed in the anther of
flowers by the reduction division of pollen
mother cell. Initially, they are formed in
tetrad. Most pollen are liberated as a
single grain (monad), but in some families
such as Ericaceae, Orchidiaceae, Typhaceae,
etc. the grains remain united in tetrads.

4. Based on the staining of pollen with fuchsin-B, the exine is divided in two
distinct layers i.e. the outer one ectexine, which takes the dark pink colour and
the inner layer endexine, which takes light pink colour, if not over stained.
Pollen wall
The wall of angiosperm pollen is constituted of three layers:
 Living cell membrane: It is made up of lipo-protein and gets lost after
death.
 The middle wall or intine: This is primarily composed of pecto-cellulose.
It is not usually preserved in the fossilized pollen grains.
 The outer wall or exine: It is made up of sporopollenin (Zetsche, 1932),
which is the most resistant organic compound. Due to presence of this compound,
the pollen remains preserved with all its surface features in the sediments for
longer period of time. Sporopollenin is a complex polymer of carotenoid and
carotenoid esters (Brooks and Shaw, 1968, Brooks, 1971, Shaw, 1971).
Its chemical formula is (C90 H142 O36)n.
Cell membrane
E
X
I
n
e
(Faegri & Iversen, 1975)
(Erdtman, 1952)

6. Based on the gross pollen characters, the angiospermic families
are divided into two major groups as follows:
Eurypalynous: The plant families with taxa exhibiting a great
variation with respect to aperture type and exine pattern. Such
families are Polygonaceae, Rubiaceae, Ranunculaceae,
Papilionaceae, Caryophyllaceae, Sterculiaceae, etc.
Stenopalynous: The plant families with taxa characterised by almost
similar pollen characters with respect to aperture type and exine
pattern. This group includes families such as Chenopodiaceae,
Amaranthaceae, Brassicaceae, Lamiaceae, Poaceae, Cyperaceae,
Euphorbiaceae, etc.

7. Pollen grains are ubiquitous and have prolific
abundance, in general, owing to their small size
(5–200 mm), distinct morphology and resistant
nature.
A major fraction of pollen gets deposited within
a distance of
100m or so immediately after its discharge from
the parent plants as the dense canopied forest
prohibits its easy and longer exit, contrary to
that of the open cultivated area where a distance
of 200m from the source has been observed to
be a normal range for the deposition of bulk
pollen load after dispersal (Luna et al., 2001).

10. Anemophilous species produce enormous
pollen grains and are
over-represented in palynoassemblages. Those
having a zoophilous
mode of pollination produce fewer pollen grains
and are underrepresented (Faegri and Iverson,
1989)
Very little work has been carried out in relation
to pollen production and dispersal in India. Taxa
studied include Holoptelea integrifolia (Nair and
Sharma, 1965; Khandelwal and Vishnu-Mittre,
1973), Mimosa rubicaulis (Saxena and Vishnu-
Mittre, 1977), some anemophilous angiosperms

11. Similar work was carried out on anemophilous
trees (Molina et al., 1996), on the Poaceae family
(Prieto-Baena et al., 2003) and also on selected
species of anemophilous plants (Piotrowska,
2008).
Differences in pollen production, dispersal,
and preservation of taxa are responsible for
the over-representation of some taxa and
under-representation of others in the pollen
samples. The difference in pollen production,
dispersal and surface deposition depends on
plant species and climatic conditions (Hicks,

12. Shorea robusta (Gaertn. f.) produces about
60,000 pollen grains/flower (Atluri et al. 2004).
However, 61,020–94,600 pollen grains
have also been reported per flower (Bera 1990).
Tectona grandis (L. f.) needs special attention
here. In spite of being a high pollen producer
with 7500 average number of absolute
pollen/flower (Bhattacharya et al. 1999).

13. Most species of this family Poaceae are
anemophilous with a few exceptions (some are
cleistogamous and a smaller number of plants are
entomopilous) (Adams et al. 1981).
The species of this family produce large amounts of
pollen grains (Reddy and Reddy 1986; Prieto-
Baena et al. 2003) during a short period ranging
from a few hours to a few days, although some
species develop
new flowers continuously (Lewis et al. 1983; Knox
et al. 1993).
The pollen production per inflorescence of the

14. Poaceae pollen (<60 mm) has also a relatively high fall
speed (0.035–0.018 m/s) (Sugita et al. 1999; Wang et al.
2014).
Furthermore, the dispersion models have shown that
the grass pollen concentration is inversely proportional
to the distance to the source area and the pollen does
usually not disperse more than 1 km from the parental
plants, although special atmospheric conditions may
facilitate long-distance transport (Moseholm et al.
1987).

15. Brostrom et al. (2004) suggested that the
relative poor transportation of Cerealia pollen
could be owing to their large size (>60mm:
Cereal Poaceae) and high fall speed (0.06m/s)
and, therefore, they get deposited near the
parental plants (Bunting et al. 2001).
Brown (1985), Catto (1985) and Fall
(1987) suggested that Poaceae pollen are
deposited under low-energy conditions.
Asteraceae family has different pollen
morphologies (size and ornamentation) and
have entomophilous pollination syndrome as
the main dispersion means, though some

16. Some species of this large family get
deposited by gravity on a local scale because
it generally has a rapid deposition rate (Martin
et al. 2009), consequently the distance from
the parent plants are shorter and would be
available to be transported by surface runoff
to the sites of sample collection.
However, the relatively high fall speed
(0.051m/s) facilitates the uneven distribution
of pollen of Asteraceae family (especially of
Asteroideae and Cichorioideae sub-families)
(Xu et al. 2012).

17. Amaranthaceae family have mainly anemophilous
mode of pollination and, thus, high pollen production
(Perez et al. 2009; Fern andez-Illescas et al. 2010).
The species of the Brassicaceae family have mostly
entomophily
pollination and consequently have a relative lesser
representation in the pollen spectra.
The species of the Cyperaceae family have mostly
anemophily mode of pollen dispersion (Aramayo et
al. 1999), a high pollen production (Jackson, 1994),
and a high fall speed of 0.0291 m/s (Wang et al.
2014). Brown (1985), Catto (1985) and Fall

18. Pinus spp. have high pollen production,
anemophilous mode of pollination, and have air
bladders as well. The sacci increases the buoyancy
of the pollen grains, which favours the transport by
wind,
water (Suc and Drivaliari 1991) and surface runoff
too (Frazer
et al. 2020).
The pollen production per strobilus for Pinus
sylvestris has been estimated to be 158 x 103
(Erdtman, 1943), and 152 x 103 to 162 x 103
(Pohl, 1937); whereas Molina et al. (1996)
suggested that the values of pollen production

19. Khanduri and Sharma (2002a) suggested that
in Pinus roxburghii, the total pollen production
per tree and per hectare varied between
1953.56 to 2727.16 x 109 and 2.91 to 4.26 x 104
at lower altitudes and 1247.5 to 1673.5 x 109
and 2.24 x 1014, and 1599.89 to 2038.96 x 1014 at
higher altitudes.
Khanduri (2019) suggested that the pollen
production in Pinus roxburghii varies between
14.96 x10 ± 2.64 x 10 with a range of variation
in the population to be 12.95 x 10 and 19.09 x
10 pollen grains.

20. The total pollen production of a plant is
influenced by various factors, which vary from
one year to the next (Stanley and Linskens,
1974; Rogers, 1993). It is important to have an
estimate of the total pollen production per plant,
not only from aerobiological and
palaeoecological perspective, but also from
agronomical point of view, as the production of
seeds (edible) often depends on the production
of pollen (Faegri and Iversen, 1989).

21. Flowering periodicity and long-term sampling:
The flowering periodicity varies in many tropical
plants. So, these irregularities of flowering
periodicity act as an impediment in capturing the
full range of inter-annual variations in pollen
production, especially in high-diversity lowland
tropical systems. As a consequence, correlations
between pollen and climate underestimate year-
to-year variability in pollen outputs amongst even
the most commonly sampled plant taxa, and
overemphasize the degree of taxonomic turnover
at a single site (Haselhorst et al. 2013).
Hence, long-term sampling is suggested for
Factors affecting the pollen
production

22. Differences in pollen transport distance: The
pollen transport distance differ amongst the
various concerned forest elements (please read
tropical deciduous forest elements here) owing
to the physical properties of pollen grains
themselves. This difference could be playing a
pivotal role behind the irregularity in the
representation of modern pollen grains,
deposited in the sediments/various natural
pollen trapping media/substrates.

23. Sporopollenin content and pH of the soil: Low
sporopollenin content in the exines of the
pollen grains could be another prominent
factor affecting their preservation in the
sediments (Sangster & Dale 1965, Havinga
1967, 1984). In fact, it becomes easier for
pollen having lower amount of sporopollenin
to be oxidized and more difficult for the pollen
to be preserved in the sediments. The
structure and ornamentation of the external
exine also play crucial role in pollen
preservation.
Pollen grains with psilate exines are

24. Dimbleby (1957, 1961) suggested that the
concentration of pollen taxa decreases with an
increase in pH values. In other words, there
exists an inverse relationship between the pollen
concentration and pH values. When a pH value
was higher than 5.5, it was observed that the
pollen concentrations lowered sharply,
meanwhile, the
upper limit set for the pH value is 7.6 (Dimbleby
1957, 1961, Li et al. 2005). Therefore, high pH
values of the soil, low sporopollenin content in
the exines of the pollen wall structure and
ornamentation of exine, as well as oxidation
coupled with action by fungi (and/or bacteria)

25. Vegetation heterogeneity, inter-specific
variability (of various taxa), climatic factors
(such as temperature, precipitation/rainfall,
relative humidity, air pressure, wind speed and
direction) and Human disturbances (affecting
the original vegetation) could be influencing the
study in various ways (Sugita 2007a, b).
Taxonomic bias, representation bias and
countsize bias could also be affecting the entire
relationship in various ways (Felde et al. 2016,
Birks et al. 2016).

26. Taphonomy is the study of how organic remains
pass from the biosphere to the lithosphere, and this
includes processes affecting remains from the time
of death of an organism (or the discard of shed
parts) through decomposition, burial, and
preservation as mineralized fossils or other stable
biomaterials.
The study of the processes affecting an organism
after death that result in its fossilization.
Taphonomy is the study of the processes of an
organism becoming a fossil.

27. Taphonomy is the study of how organisms decay
and become fossilized or preserved in the
paleontological record.
The
term taphonomy (from Greek táphos, 'burial'
and nomos, 'law') was introduced to palaeontology
in 1940 by Soviet scientist Ivan Efremov to
describe the study of the transition of remains,
parts, or products of organisms from the
biosphere to the lithosphere.

28. Preserved
Deteriorated
Categories of deterioration:
1. Corroded: Where the exine is pitted or etched
(indicates oxidation).
2. Broken: Where the grains are ruptured or split
or pieces have completely broken.
3. Crumpled: Where the grains are folded or
twisted or collapsed.
4. Degraded: Where the structural elements are

30. Bera et al., 2008.
Curr .Sci. 95 (2),
178-180

31. Thank
Further
readings:
Faegri and Iversen, 1964: A text of pollen
analysis
Tweddle and Wdwards, 2010: Rev.
Palaeobot. Palynol.
Tweddle and Bunting, 2010: Rev.
Palaeobot. Palynol.
Quamar and Bera, 2014a: Palynology
Quamar and Bera, 2014b: Quaternary
International