A palynological Survey of Aquatic Flora of Karachi-Pakistan



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A Palynological Survey of Aquatic Flora of Karachi-Pakistan

Anjum PERVEEN

Department of Botany, University of Karachi, Karachi-75270, PAKISTAN

Received: 18.02.1998

Accepted: 14.05.1999

Tr. J. of Botany

23 (1999) 309-317

© TÜBİTAK

309

Abstract: The pollen morphology of 16 species of aquatic angiosperms, distributed in 14 families from Karachi was examined by

light and scanning microscope. Pollen grains are usually free, rarely united, mostly radially symmetrical, isopolar-apolar, occasional-

ly heteropolar. Simple aperturate (porate or colpate) pollen are more frequently found. Number of apertures varies from 1-3 or

more than 30, rarely compound aperture as in 

Enhydra fluctuans Lour. Tectum of the families also is quite variable, ranging from

reticulate to rugulate, striate, fossulate, echinate or scabrate/areolate. The pollen morphology of the families is significantly useful

for characterizing the species. Apertural types and tectum types are the most significant pollen characters. On the basis of these

characters 4 distinct pollen types are recognized.

Key Words:

Aquatics; Flora Karachi, Pollen morphology.



Karaçi-PAKİSTAN Sucul Florası Üzerine Palinolojik Bir Araştırma

Özet: Karaçi’de bulunan 14 familyaya dahil 16 sucul angiosperm türünün polen morfolojisi ışık ve taramalı elektron mikroskobu ile

incelenmiştir. Polenler genellikle serbest (tek), nadiren birleşiktir, çoğunlukla radyal simetrili, izopolar-apolar, nadiren heteropolardır.

Çoğunlukla basit apertürlü (porat ya da kolpat) polenler bulunmaktadır. Apertür sayısı 1 ile 3 arasındadır ya da 30’dan fazladır,

Enhydra fluctuans Lour.’da olduğu gibi nadiren bileşik apertür bulunmaktadır. Familyaların tektumu da oldukça değişkendir; retikülat,

rugulat, striat, fossulat, ekinat ya da skabrat/areolatdır. Familyaların polen morfolojisi türlerin karakterize edilmesine büyük ölçüde

yardımcı olmaktadır. Apertür ve tektum tipleri en belirgin polen karakterleridir. Bu karakterleri temel alarak 4 polen tipi

tanımlanmıştır.

Anahtar Sözcükler: Sucul bitkiler, Karaçi Florası, polen morfolojisi.



Introduction

Aquatic flowering plants represent a considerable part

of the world’s flora, About 79 families and 380 genera

contain aquatic species (1). Because of their anatomical,

morphological, reproductive and physiological

peculiarities, the aquatic plants attract a speciel interest

from biologists. However, literature dealing with the

pollen morphology of aquatic flowering plants is rather

scarce. Few reports are available on aquatic plants, such

as the families 

Typhaceae (1, 2) and Pontederiaceae (3).

Some species of 

Potamogetonaceae have been

examined by Sorsa (4). Landolt (5) examined the pollen

morphology of 

Lemnaceae. The flora of Karachi is

represented by 413 plant species of which 162 are

monocots and 251 are dicots, distributed in 60 dicot and

15 monocot families (6). Of these about 20 species

belonging to 18 families are aquatic in nature. There are

no previous reports of palynological surveys of aquatic

plants from Karachi. The present report gives an account

of the pollen morphology of 16 species, belonging to 14

genera distributed in 14 families.



Materials and Methods

Pollen samples were obtained from the Karachi

University Herbarium (KUH) or collected from the field.

The list of voucher specimens is deposited in the KUH.

The pollen grains were prepared for light (LM) and

scanning microscopy (SEM) by the standard methods

described by Erdtman (7). For light microscopy, the

pollen grains were mounted in unstained glycerine jelly

and observations were made with a Nikon Type-2

microscope, under E40, 0.65 and oil immersion (E100,

1.25), using a 10x eye piece. For SEM studies, pollen

grains were suspended in a drop of water and directly

transferred with a fine pipette to a metallic stub using

double-sided adhesive tape and coated with gold in a



Research Article

A Palynological Survey of Aquatic Flora of Karachi-Pakistan

sputtering chamber (Ion-sputter JFC-1100). Coating was

restricted to 150A. The S.E.M examination was carried

out on a Jeol microscope JSM-T200. The measurements

were based on 15-20 readings from each specimen. Polar

area index (P.A.I: Polar area index expressed by the ratio

of the polar area dimension to the largest transverse

dimension of the pollen grains) and cofficent of variation

(coefficient of variation expresses the standard deviation

as a percentage in terms of the arithmetic mean) are also

given. Polar axis (P), equatorial diameter (E), colpi

length, apocolpium, mesocolpium, spine length and exine

thickness were measured.

The terminology used is in accordance with

Wodehouse (8); Erdtman (7); Faegri and Iversen (9);

Kremp (10) and Walker and Doyle (11).



Observations

General pollen characters of Aquatic Families

The pollen grains are mostly apolar or isopolar rarely

heteropolar. The shape is commonly spheroidal or oblate-

spheroidal rarely boat-shaped (

Nymphaea stellate Willd.)

and sub-prolate (

Nelumbo nucifera Gaertn.). However, in

the family 

Juncaceae and in the single species of

Typhaceae (Typha elephantina Roxb.) pollen grains are

united in tetrads. Similarly, exine sculpturing is also

extremely varied, ranging from reticulate to rugulate,

fossulate, foveolate, scabrate, echniate-spinulose or are

olate. Apertures are mostly colpate or porate (number

varies from 1-(3)-40). However, in few taxa non-

aperturate pollen is also found (

Potamogeton L., Juncus

L.) rarely tricolporate as in 

Enhydra fluctuans Lour.

Eichhornia crassipes (Mart.) Sloms (Fig. 1-2).

Pollen grains heteropolar, oblong, size: Length

(37.07)-39.25±0.75 (-42.51) µm, C.V.11, and breadth

(47.50-) 50.98±1.20 (-57.51) µm, C.V.10., mono-

bicolpate, colpi (42.50-) 45.61±1.21 (-50.23) µm long,

C.V.3.01. Exine (0.50-) 2.25±0.21 (-2.52) µm thick,

C.V.4.91, sexine thinner than or as thick as nexine.

Tectum areolate, areolae variable in size.

Enhydra fluctuans Lour. (Figs. 3-4).

Pollen grains radially symmetrical, isolpoar, oblate-

spheroidal, size: polar axis P(13.21-) 19.32±0.40 (-

21.11) µm, C.V. 6.62, and equatorial diameter E(19.61)

21.61±0.70 (-25.21) µm, C.V. 4.41. P/E ratio: 0.89.

Tricolporate, trilobed, fossaperturate, colpi (14.31-)

14.90±0.46 (-15.41) µm long, C.V. 5.36, colpal

membrane sub-psilate. Mesocolpium (15.41-)

16.50±0.34 (-18.21) µm, C.V. 6.65. Apocolpium (2.80)

4.02±0.44 (-7.11) µm, C.V. 21.08. Exine (1.68-)

1.72±0.07 (-2.12) µm thick, C.V. 11.04, sexine thicker

than nexine. Tectum echinate, collumellae branched,

spines pointed, (3.50-) 4.06±0.09 (-4.21) µm, C.V.

7.14.


Ipomoea aquatica Forsk. (Figs. 5-7).

Pollen grains radially symmetrical, apolar, spheroidal,

size: (64.62-) 70.23±2.97 (-82.57) µm in diameter, C.V.

20.30. pantoporate, pores 36-42 or more, ±circular

(3.95-) 5.77±0.30 (-7.18) µm in diameter, C.V.16.6,

pore plate with sparse puncta or granules. Exine (3.59-)

4.71±0.26 (-5.74) µm thick, C.V.18.01, sexine slightly

thinner than nexine. Tectum echinate finely perforated

with granules, spines uniformly distributed, with distinct

perforated base, and blunt apices, (3.59-) 3.74±0.06 (-

3.95) µm long, C.V. 5.04.

Juncus maritimus Lam. (Figs. 8-10).

Pollen grains tetrahedral, tetrads, non a perturate,

size: Length (32.50-) 40.25±2.88 (-42.51) µm, C.V.

20.61, and breadth (37.50-) 40.04±1.29 (-47.91) µm,

C.V. 7.18. Exine (1.25-) 1.35±0.05 (-1.75) µm thick,

C.V. 8.21, sexine thicker than nexine. Tectum lophate-

reticulate, with fine scabrae.

Lemna gibba L. (Fig. 11).

Pollen grains radially symmetrical, apolar, spheroidal,

size: (20-) 21.13±0.37 (-22.51) µm in diameter,

C.V.3.91.monoporate, pore±circular, c.0.5 µm in

diameter. Exine (1.25-) 1.42±0.16 (-1.75) µm thick, C.V.

25.12, sexine thicker than nexine. Tectum spinulose.

Lemna aequinoctialis Welw.

Pollen grains radially symmetrical, apolar, spheroidal,

size: (19.69-) 21.22±0.62 (-23.97) µm in diameter,

C.V.12. monoporate, pore very small. Exine (0.66-)

1.76±0.41 (-3.33) µm thick, C.V. 62.41, sexine as thick

as nexine. Tectum spinulate-punctate.

Myriophyllum verticillatum L. (Figs. 12-14).

Pollen grains radially symmetrical, isopolar, sub-

oblate, size: Polar axis P(18.59-) 19.54±0.16(-20.02)

µm, C.V. 3.27, and equatorial diameter E(21.54-)

23.64±0.23 (-24.31) µm, C.V. 3.84. 4-5 colpate, short

colpi (1.43-) 2.86±0.13 (-3.95) µm long. Exine 1.43 µm

thick, sexine thicker than nexine. Tectum scabrate-

punctate, scabrae fine.

Nelumbo nucifera Gaertn. (Figs.15-18).

Pollen grains radially symmetrical, isopolar, sub-

prolate, size: Polar axis P(68.21-) 78.11±3.20 (-87.90)

µm, C.V.9.11, and equatorial diameter E(55.61-)

310


A. PERVEEN

59.20±1.13 (-61.03) µm, C.V.9.21. P/E ratio: 1.31.

Tricolpate, rounded-trilobed, (50.20-) 66.05±4.61 (-

78.91) µm long, C.V. 15.61, colpal membrane denely

fossulate. Mesocolpium (50.26-) 61.82±2.84 (-71.82)

µm, C.V.11.25. Apocolpium (3.61-) 4.81±1.91 (-7.18)

µm, C.V. 4.33. Exine (3.61-) 3.94±0.06 (-4.31) µm

thick, C.V. 3.94, sexine thicker than nexine. Tectum

rugulate.

P.A.I: 1.04

Nymphaea stellata Willd. (Figs. 19-21).

Pollen grains bilateral, heteropolar, boat-shaped, size:

Length (25.13-) 28.07±0.58 (-32.31) µm, C.V.7.66, and

breadth (32.80-) 37.61±3.71 (-41.04) µm, C.V.6.27.

monosculate, colpi (32.31-) 35.51±0.89 (-39.40) µm

long, C.V.21.92, sexine thinner than nexine. Tectum

rough reticulate.

Nymphoides cristata (Roxb.) O. Ktze. (Figs. 22-23).

Pollen grains heteropolar, oblate, size: Polar axis

P(17.91-) 20.93±0.84 (-25.13) µm, C.V. 9.98, and

equatorial diameter E(25.13-) 31.54±0.65 (-35.91) µm,

C.V. 7.95. A/E ratio: 0.64 Tricolpate, triangular, with

311

Figs.1-2.



Eichhornia crassipes (Mart.) Sloms

Figs.3-4.

Enhydra fluctuans Lour.

Figs.5-7.

Ipomoea aquatica Forsk.

Fig.8.


Juncus maritimus Lam.

1, Pollen grain; 2, Exine pattern; 3,

polar view (LM); 4, Equatorial view

(SEM); 5, pollen grain (LM); 6,

pollen grain (SEM); 7, Exine pattern

(SEM); tetrads (LM).



A Palynological Survey of Aquatic Flora of Karachi-Pakistan

312


Figs.9-10.

Juncus maritimus Lam.

Fig.11.

Lemna gibba L.



Figs.12-14.

Myriophyllum verticillatum L.

Figs.15-16.

Nelumbo nucifera Gaertn.

9, Tetrads (SEM), 10, Exine pattern

(SEM); 11, Exine pattern; 12,

Equatorial view (LM); 13, polar

view (LM); 14, Exine pattern (SEM);

15, polar view (LM); 16, Equatorial

view (LM).

Scale bar= 9, 10, 12 & 13 = 10 =

µm; 15&16=20 µm; 11&14=1 µm.



A. PERVEEN

apertures on the sides of an angular grain in polar view,

colpi (19.74-) 23.03±1.07 (-23.32) µm long, C.V.

11.33. Mesocolpium (21.51-) 24.30±0.56 (-26.72) µm,

C.V. 7.61, para syncolpate (frequently syncolpate) leaving

triangular apocolpium area. Exine (0.35-) 0.79±0.06 (-

0.89) µm thick, C.V. 26.52, sexine thicker than nexine.

Tectum densely spinulose, unequal in size with acute tips.

Persicaria glabra (Willd.) Gomes (Figs. 24-25).

Pollen grains radially symmetrical, apolar, spheroidal,

size: (78-) 50.26±0.77 (-60.26) µm in diameter, C.V.

6.01. polypantoporate, pore±oblong, c. 1.87 µm in

diameter. Exine (5.38-) 6.31±0.21 (-7.18) µm, C.V.

10.76, sexine thicker than or as thick as nexine,

consisting of densely spaced bacula. Tectum very coarsely

reticulate, with regular muri patterns, lumina hexagonal

in shape, provided with intra-luminal bacula which

completely fills the luminal space, lumina shorter towards

the pores, 6.42-7.85 µm in diameter.

313


Figs.17-18.

Nelumbo nucifera Gaernt.

Figs.19-21.

Nymphaea stellata Willd.

Figs.22-23.

Nymphoides cristata (Roxb.) O.

Ktze.

Figs.24.


Persicaria glabra (Willd.) Gomes

17, pollen grain (SEM), 18, Exine

pattern (SEM); 19, pollen grain

(LM); 20, pollen grain (SEM); 21,

Exine pattern (SEM); 22, polar view

(SEM); 23, pollen grain (LM); 24,

pollen grain (SEM).

Scale bar= 17, 20, 22 & 24= 10=

µm; 19 & 23= 20 µm; 18, 21= 1

µm.


A Palynological Survey of Aquatic Flora of Karachi-Pakistan

Potamogeton pectinatus L. (Figs. 26-27).

Pollen grains radially symmetrical, apolar, spheroidal,

size: (32.50-) 35.11±1.87 (-37.51) µm in diameter, C.V.

16.11 nonaperturate. Exine c. 0.12 µm thick, sexine

thicker than or as thick as nexine. Tectum coarsely

reticulate with irregular pattern of muri, lumina variable

in size and shape, 0.22 µm in diameter.

314

Figs. 25.



Persicaria glabra (Willd.) Gomes

Figs. 26-27.

Potamogeton pectinatus L.

Figs. 28-30.

Potamogeton perfoliatus L.

Figrs. 31-32.

Typha angustifolia L.

25, Exine pattern (SEM); 26, pollen

grain (LM); 27, Exine pattern (SEM);

pollen grain (LM); 29, pollen grain

(SEM); 30, Exine pattern (SEM); 31,

monad (SEM); 32, Exine pattern

(SEM).

Scale bar= 25, 26, 28, 29 & 31=



10= µm; 27, 30 & 32= 1 µm.

A. PERVEEN

Potamogeton perfoliatus L. (Figs. 28-30).

Pollen grains radially symmetrical, apolar, spheroidal,

size: (21.25-) 24.28±0.71 (-30.11) µm in diameter, C.V.

8.93. nonaperturate. Exine (0.50-) 0.83±0.22 (-

1.25)µm thick, C.V. 5.01, sexine slightly thicker than

nexine. Tectum coarsely retucilate with irregular pattern

of muri, lumina 0.41-2.11 µm in diameter.

Typha angustifolia L. (Figs. 31-32).

Pollen grains  radially symmetrical, apolar, spheroidal,

size: (22.50-) 23.11±0.38 (-25.11) µm in diameter, C.V.

4.71. monoporate, pore±circular (3.01-) 4.12±0.70 (-

5.11) µm in diameter, C.V. 39, sexine thicker than nexine.

Tectum reticulate-rugulate.

Typha domingensis Pers. (Figs. 33-34).

Pollen grains radially symmetrical, apolar, monads,

spheroidal, size: (20.11-) 22.61±0.43 (-25.11) µm in

diameter, C.V. 5.88, monoporate, pore±circular. (4.75-)

5.32±0.36 (-7.51) µm, diameter, C.V.15. Exine (1.01-)

1.15±0.13 (-1.25) µm thick, C.V. 25, sexine thicker than

nexine. Tectum coarsely reticulate, with±irregular pattern

of muri, lumina 0.2-1 µm in diameter.

Typha elephantina Roxb. (Figs. 35-37).

Pollen grains tetragonal tetrads, size: Length (33.21-

) 35.12±1.19 (-40.11) µm, C.V.10, and breadth (35.21-

315


Figs. 33-34.

Typha domingensis Pres.

Figs.35-37.

Typha elephantina Roxb.

33, monads (SEM); 34, Exine pat-

tern (SEM); 35, Tetrads (SEM); 36,

Exine pattern (SEM); 37, tetrad

(LM).


Scale bar= 33, 34, 35 & 36= 10=

µm; 37= 20 µm.



A Palynological Survey of Aquatic Flora of Karachi-Pakistan

) 38.33±1.15 (-40.12) µm, C.V.11, monoporate, single

grain spheroidal, C.20 µm in diameter, C.V. 24.11 Exine

(2.01-) 2.25±0.14 (-2.61) µm thick, C.V.16, sexine

thicker than nexine. Tectum densely foveolate.

Key to the species and species groups

1.

+ Pollen grains non-aperturate



2

- Pollen grains aperturate

3

2.

+ Pollen grains single



Potamogeton-group

(P. perfoliatus, P. pectinatus)

- Pollen grains tetrads

Juncus maritimus

3.

+ Pollen grains porate



4

- Pollen grains colpate or colporate

7

4.

+ Pollen grains monoporate



5

- Pollen grains pantoporate

6

5.

+ Pollen grains spinulose



Lemna-group

(L. aequinoctiales, L. pectinatus)

- Pollen grains rugulate reticulate 

Typha-group

(T. angustifolia, T. domingensis. T. elephantina)

6.

+ Tectum echinate



Ipomoea aquatica

- Tectum reticulate

Persicaria glabra

7.

+ Polen grains colporate



Enhydra flucatuns

- Pollen grains colpate

8

8.

+ Pollen grains monocolpate



9

- Pollen grains 3-5-colpate

10

9.

+ Tectum areolate



Eichhorina crassipes

- Tectum rough reticulate

Nymphaea stellata

10. + Pollen 4-5 colpate

Myriophyllum verticillatum

- Pollen colpate

11

11. + Pollen grains syncolpate



Nymphoides cristata

- Pollen apocolpate

Nelumbo nucifera

Discussion

Aquatic angiosperms exhibited great diversity in their

pollen characters, such as in shape, size, apertures,

polarity and tectum type. However, the exine pattern and

apertural types are the most significant pollen characters.

On the basis of apertural type 4 distinct pollen types are

recognized.

Pollen type-I is characterized by its non-aperturate

pollen. Two species of 

Potamogeton L., and Juncus

maritimus have non-aperturate pollen. However, in

Potamogeton, monods are found (1, 4, 12), whereas in

Juncus maritimus, tetrahedral tetrads are found.

Pollen type-II is readily delimited by having colpate

pollen the number of colpi varies from mono-

pantocolpate. In the present study aquatic monocots have

mono-bicolpate pollen i.e., 

Eichhornia crassipes (13, 14).

In 2 species of 

Myriophyllum vertcillatum (15-17),

Nelumbo nucifera (18, 19), and Nymphoides cristata, 3-

5-colpate pollen is observed (20).

Pollen type-III is easily recognized by having porate

pollen. Seven species are included in this pollen type.

Monoporate pollen is mostly found in aquatic monocots

as in 


Typha L., and Lemna L. (1, 5), whereas pantoporate

pollen is found in aquatic dicots, such as 

Persicaria glabra

(21, 22) and 

Ipomoea aquatica (23).

Pollen type-IV is characterized by its tricolporate

pollen. Only a single species, Enhydra fluctuans, (24) has

tricolporate pollen.

It is very interesting to note that the most of the

aquatic taxa are wind pollinated. Some aquatic dicots like

Nymphaea stellata (25) Nelumbo nucifera (25), Persicaria

glabra (25) Ipomoea aquatica (25) and Enhydra fluctuans

(25) are pollinated by insects. There is a correlation

between pollen morphology and pollination mechanism.

A definite relationship is exhibited between pollen

characters and pollination types especially in entomophily

and anemophily. Pollen grains of entomophilous taxa are

characterized by compound apertures i.e., 3-colporate,

prolate-spheroidal shape, generally large, thick-waled,

sticky and with reticulate tectum, while pollen grains of

anemophilous taxa are with simple apertures i.e.,

monoporate, spheroidal, small, thin-walled, dry and with

scabrate-areolate tectum (25).

Pollen grains of hydrophilous taxa are spheroidal,

non-aperturate coarsely reticulate tectum with (0.5 µm

thick) thin exine (as in 

Potamogeton). The thin elastic

exine and reduced or omniapertures (non-aperture) are

considered characters of hydrophilous taxa by Punt (26),

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