EVIDENCES FROM PALYNOLOGY

Palynology has numerous applications:

Geochronology - dating of rocks.

Biostratigraphy - correlation of rock sections.Proper indentification of indicative palynomorphs could lead to the discovery of oil, coal, and gas deposits.

Paleoecology - past environments. Non-geological uses - archeaological palynology, forensic palynology, aeroallergy.

Pollen wall structure

Sporoderm1.Exine (sporopollenin + glycocalyx)

a) sexine- supratactal + tectum + columella

b) nexine- foot layer + endexine

2. Intine (cellulose)

TEM of cross-section of Arabidopsis pollen. P- pollen grain cytoplasm, i- intine, e- bacula of exine, pc- pollen coat.

Function of exine Protects protoplasm from impacts

& abrasion Allows expansion & reduction of

grain size with changing humidity Provides the pollen tube at the

time of fertilization Yields identifying characteristics

Pollen varies in size, exine ornamentation, and number and arrangement of apertures.

Section of pollen wall showing structure and some features

Types of apertures in pollen

Pores- usually isodiametric; can be slightly elongated but have rounded ends.

Colpi (fissures)- elongated, with

pointed ends; more primitive

Monoaperturate- Describing a pollen grain or spore with a single aperture.

Examples: monocolpate , monoporate, monosulcate (Erdtman, 1952).

Tricolpate- Describing pollen grains with three ectocolpi, three compound apertures or three pores.

SULCUS- An elongated latitudinal ectoaperture situated at the distal or

proximal pole of a pollen grain. It has the same shape as a colpus, but

differs in orientation. Sulci are essentially latitudinal apertures whereas colpi are essentially

longitudinal apertures.

Equatorial view, Nasturtum

Polar view, Nasturtum, with 3 colpi equidistantly arranged along the equator (trizonocolpate); triangle in polar view

This image shows the isodiametric apertures, pori

There are 6 pori arranged equidistantly around the axis of the pollen grain and therefore this pollen grain is hexazonoporate.

Schumbergera bridgesii

Camellia japonica, equatorial view; elliptic; granulate

Camellia japonica

Polar view of the pollen grains:  Three of the very long and pointed apertures equidistantly arranged along the equator of the pollen grain.  This type of grain is therefore a trizonocolpate. 

Golden Rod (echinate), Oak pollen(colpi) and Birch pollen (pores). SEM images of pollen.

Porus with clear annulus and operculum (lid), Plantago

SEM image of pollen grains from : sunflower (Helianthus annuus), morning glory (Ipomoea purpurea), prairie hollyhock (Sidalcea malviflora), oriental lily (Lilium auratum), evening primrose (Oenothera fruticosa), and castor bean (Ricinus communis).

IH

O

L

S

R

Helianthus annuus

Ipomoea purpurea

Lilium auratum

Oenothera fruticosa

Scanning electron micrograph of pollen of Meliosma pinnata (Sabiaceae). Polar view showing three colporate apertures. Scale bar = 5µm.

Ricinus communis

POLLEN SHAPES

PROLATE- the polar axis is larger than the equatorial diameter (1.33-2.0)

PROLATE-SPHEROIDAL: the ratio between the polar axis and the equatorial diameter is 1.00-1.14.

OBLATE- the polar axis is shorter than the equatorial diameter.

OBLATE-SPHEROIDAL- the ratio between the polar axis and the equatorial diameter is 0.88-1.00

SUBOBLATE- the ratio between the polar axis and the equatorial diameter is 0.75-0.88

Echinate- pollen and spores with an ornamentation comprising spines longer than 1µm.

Transmission electron micrograph showing the point of contact between a pollen grain (P) and a stigma papillus (S).

Two basic kinds of pollen in angiosperms: monosulcate and tricolpate

MONOSULCATE: boat-shaped, with one long germinal furrow and aperture; characteristic of primitive dicots, most monocots, cycads & pteridosperms

TRICOLPATE: globosesymmetrical, typically have 3 germinal apertures; characteristic of advanced dicots

a) Convallaria (monosulcate); b) and c) Aizoaceae (tricolpate)

EQUATORIAL POLAR VIEW

A typical pollen of Asteraceae with a spiky (echinate) surface; tricolpate (g- polar view; h- equatorial view))