In this article we will discuss about the meaning of palynology.
The science concerning the study of pollen and spores is called ‘palynology”, and this term was coined by Hyde and Williams in 1945.
“Pollen grains” or microspores are the male reproductive bodies of the flowering plants, while the term “spore” is very loosely applied to several types of reproductive bodies in algae (e.g. zoospores, exospores, endospores, akinetes, etc.), fungi (e.g. conidiospores, ascospores, uredospores, basidiospores, chlamydospores, etc.) and pteridophytes. Pollen grains develop in the sporogenous tissue of anthers or microsporangia in angiosperms.
According to Zetzsche and Vicuri (1931) the outer walls of pollen and spores are made up of a pectinous substance called “pollenin”. Its chemical formula is C90H129 (OH)5. The protoplasm of pollen grains contains proteins, carbohydrates, lipids, vitamins, hormones and enzymes. It also contains traces of some inorganic substances such as Mg, K, Ca, Cu, Fe, Si, P, S and CI.
Some Common Terms:
1. Proximal Pole:
The end of the pollen grains towards the centre of the tetrad is called proximal pole.
2. Distal Pole:
The end of the pollen grains towards the outside of the tetrad is called distal pole.
3. Polar Axis:
It is a hypothetical line which connects proximal and distal poles.
4. Equatorial Axis:
A hypothetical line perpendicular to the polar axis is called equatorial axis.
5. Colpi and Colpate:
The elongated or furrow-like apertures on the pollen grains are called colpi (sing., colpus) and such grains are called colpate (Fig. 4).
6. Port and Porate:
The circular apertures on the pollen grains are called pori and such grains are called porate (Fig. 5).
In colpi and pori both, the outer face of the aperture is congruent with the inner face.
7. Colporate:
When the outer and inner faces of apertures are incongruent (Fig. 5), the apertures are called colporate.
(In most of the gymnosperms and monocots the apertures are known to be distal while in pteridophytes they are proximal).
8. Zonocolpate and Zonoporate:
When the colpi or pori are zonal in position, they are called zonocolpate or zonoporate, respectively.
9. Pantocolpate and Pantoporate:
When the colpi or pori are uniformly distributed on the exine surface, they are called pantocolpate or pantoporate, respectively.
10. Crassimarginate:
The apertures (colpi or pori) with thickened margins are called crassimarginate.
11. Syncolpate:
When ends of the colpi unite at the poles, die grains are called syncolpate.
12. Intine and Exine:
The protoplasm of the pollen grains is enclosed by a wall made of intine and exine. The intine is a hyaline layer. The exine (Fig. 6) consists of an inner homogeneous layer (called endine or nexine and an outer heterogeneous layer (called ectine or sexine).
13. Columellae and Tegillum:
The radial rods which form the ectine are called colurnellae. The colurnellae are either free at their tips or are fused to form a layer called tegillum.
14. Inaperturate:
A pollen grain without any aperture (Fig. 5).
15. Exine Ornamentation:
Various types of ornamentation patterns are shown by exine surface. As mentioned above, the ectine of exine is composed of radial rods or colurnellae. When the distal surfaces of colurnellae are bright and the intervening regions are dark, the pattern is called pilate (Fig. 6). The colurnellae in most of the grains are fused to form different types of patterns having depressed areas (called lumina) and the intervening areas between lumina (called muri).
When a network is produced by lumina and muri it is called reticulate. In the reticulate pattern, if there is the incomplete fusion of colurnellae, it is called retipilate, if there are circular and closely placed lumina it is called foveolate, if there are circular but distantly placed lumina it is called scrobiculate, if lumina are elongated it is called fossulate, if lumina are parallel it is called striate and; if lumina are anastomosing it is called rugulate.
The exine ornamentation is called areolate when luminoid network surrounds islands of raised areas. If the excrescences (outgrowths) on the exine are in the form of very minute granules the pattern is called granulose, if the excrescences are in the form of spinules with pointed or blunt ends it is called spinulose, if the excrescences are in the form of rounded warts with constricted base it is called gemmate, and if the bases are not constricted it is called verrucate.
When the outgrowths on the exine are in the form of tubercles it is called tuberculate, if these are long with pointed ends the pattern is called spinose, if outgrowths are rod shaped it is called baculate, and when they are club shaped it is called clavate.
16. LO- or OL- Pattern:
In LO or OL pattern ‘L’ (lux) stands for “light” and O (obscuritas) stands for darkness. At different foci, a varying pattern of bright and dark islands is observed. At the uppermost focus, the depressed ends on the surface of pollen grains appear dark, and this darkness changes into brightness when focused down.
17. OLO- Pattern:
A succession of three patterns, i.e., dark (O), bright a) and dark (O) is called OLO-pattern.
18. Ectine and Endine:
Ectine is the outer layer of exine while endine is the inner layer of exine.
19. Ectocolptum and Endocolpium:
The outer and inner faces of a colpus are called ectocolpus and endocolpus, respectively.
20. Tenuimarginate:
The apertures (colpi or pores) with thin margins are called tenuimarginate.