CHAPTER 12
PALYNOLOGY
REVIEW QUESTIONS
1. What is the study of spores and pollen called?
Palynology.
2. What are the two types of pollen nuclear number? Of pollen storage product?
a) Binucleate and trinucleate.
b) Starch or oil.
3. What does pollen unit refer to?
Pollen unit refers to the number of pollen grains united together at the time of release.
4. What is the difference between a monad, tetrad, polyad, and pollinium?
Monad-a single unfused pollen grain.
Tetrad-four haploid products of meiosis fusing together.
Polyad-pollen grains united in precise units of more than four, usu. a multiple of eight.
Pollinium-fusion of all pollen grains of an entire theca.
5. What is pollen polarity?
Pollen polarity refers to the position of one or more apertures relative to a spatial reference, the polar axis.
6. What is the difference between an isopolar and heteropolar pollen grain?
Isopolar, one in which the two polar hemispheres are the same but can be distinguished from the equatorial region.
Heteropolar, one in which the two polar hemispheres are different, because of differential displacement of one or
more apertures.
7. What is the definition and function of a pollen aperture?
A pollen aperture is a specially delimited region of the pollen grain wall.
The function of the aperture is primarily to serve as the site of formation of a pollen tube exiting from the pollen grain
body. Apertures may also function to allow volume changes of the pollen grain with changes in water content, e.g.,
humidity, known as harmomegathy.
8. What is the difference between a colpus, porus, sulcus, and ulcerus?
A colpus (plural, colpi) is an elongate aperture with a length/width ratio of greater than 2:1.
A porus (plural, pori) is a circular to slightly elliptic aperture with a length/width ratio of less than 2:1.
A sulcus is an elongate aperture similar in shape to a colpus (length/width ratio >2:1) but either centered at a (usually
distal) pole or, more rarely, parallel to the equator.
An ulcus is a circular to slightly elliptic aperture similar in shape to a porus (length/width ratio <2:1) but occurring at
the (usually distal) pole.
9. What is a tricolporate pollen grain? A pentaporate pollen grain?
Tricolporate-having 3 apertures, shaped like a colpus having a circular region in the center (corresponding to a
different wall architecture).
Pentaporate-having 5 porate apertures.
10. What is the size range of angiospermous pollen grains?
Usually 25–50 μm in diameter, but ranging from < 5 μm to > 200 μm.
11. Name and define six terms that specify pollen sculpturing.
baculate, having rod-shaped elements.
clavate, having club-shaped elements, each element called a clava, plural clavae.
echinate, having spinelike elements > 1 μm long, each element termed an echina, plural echinae.
fossulate, having longitudinal grooves.
foveolate, having a pitted surface caused by pores in the surface.
gemmate, having globose or ellipsoid elements, each element termed a gemma, plural gemmae.
psilate, having a smooth sculpturing.
reticulate, having a netlike sculpturing, each element termed a murus (plural muri) and the space between muri
termed a lumen (plural lumina).
rugulate/rugulose, having irregular to sinuous, tangentially oriented elements, often appearing brainlike.
spinulose (also termed scabrate), having spinelike elements <1 μm long, each element termed a spinule, plural
spinules.
striate, having thin, cylindrical, tangentially oriented elements.
verrucate, having short, wart-like elements, each element termed a verruca, plural verrucae.
12. Name three functions of the pollen grain wall.
a) to provide structural support and protection of the cytoplasm from mechanical damage and dessication.
b) to facilitate pollination, correlated with sculpturing pattern.
c) to store proteins involved in incompatibility reactions.
13. What are the two major layers of a pollen grain wall and how do they differ in chemical composition?
The intine is the innermost layer, which is composed primarily of cellulose and pectins, resembling the primary cell
wall of a typical parenchyma cell.
The exine is the hard, outermost, desiccation-resistant wall layer that provides the major structural support for the
cytoplasm, impregnated with sporopollenin.
14. Name the two layers of exine.
An inner endexine and an outer ektexine.
15. Name and describe the most common type of exine wall structure.
Tectate-columellate-consisting of an inner foot layer, a middle layer of radially elongate columellae, and an outer,
rooflike layer called the tectum.
16. What do nexine and sexine refer to?
Nexine refers to the inner layers, which may include both endexine and the foot-layer of the ektexine.
Sexine refers to the outer, protruding layers, which may include columellae, tectum, and supratectal sculpturing
elements (if present).
17. What is the function of pollenkit or viscin threads?
To stick pollen grains in masses, better effecting transfer of pollen by animal.