Walls of allergenic pollen: Special reference to the endexine

Figures & data

Figure 1 Pollen grains representing different wall characteristics.A. Salix fragilis. Typical pollen wall organisation with intine, compact endexine and columellate ektexine. U+Pb. B. Corylus avellana. Pollen wall with intine and ektexine. Endexine not detectable, microchannels in ektexine, TCH+Sp (lipid‐test). C. Fraxinus excelsior. Microchannels within the endexine and intine of the apertural region. TCH+Sp (lipid‐test). D. Platanus×hispanica. Endexine laminated/granulose in apertural region. PA+TCH+Sp (short). E. Syringa vulgaris. Ektexine cavities completely sealed by electron‐dense pollenkitt. Endexine compact. PA+TCH+Sp (short). F. Quercus robur. Little electron‐lucent pollenkitt within exine. Endexine compact. TCH+Sp (lipid‐test). A–F. TEM (ekt = ektexine, end = endexine, i = intine, p = pollenkitt).

Figure 2 Pollen walls without compact or detectable endexine.A. Betula sp. Overall view of the birch pollen grain. B. Betula sp. Cross section of pollen grain wall. Microchannels within the ektexine. TCH+Sp (lipid‐test). C. Secale cereale. Overall view of the rye pollen grain. D. Secale cereale. Cross section of pollen grain wall. Microchannels within the ektexine. PA+TCH+Sp (short). E. Phleum pratense. Overall view of the grass pollen grain. F. Phleum pratense. Cross section of pollen grain wall. Microchannels within the ektexine. PA+TCH+Sp (short). A, C & E. SEM. B, D & F. TEM (ekt = ektexine, i = intine).

Figure 3 Pollen walls without compact or detectable endexine(continued). A. Chenopodium album. Overall view of the goosefoot pollen grain. B. Chenopodium album. Cross section of pollen grain wall. Endexine discontinuous. Primexine‐matrix in ektexine cavities (pm). PA+TCH+Sp. C. Brassica napus. Overall view of the rape pollen grain. D. Brassica napus. Cross section of pollen grain wall. Tryphine in ektexine cavities. PA+TCH+Sp (short). A, C. SEM. B, D. TEM (ekt = ektexine, (end) = discontinuous endexine, i = intine, tr = tryphine).

Figure 4 Pollen walls with compact endexine.A. Fraxinus excelsior. Overall view of the ash pollen grain. B. Fraxinus excelsior. Cross section of pollen grain wall. Compact endexine. TEM, PA+TCH+Sp (short). C. Platanus×hispanica. Overall view of the plane pollen grain. D. Platanus×hispanica. Cross section of pollen grain wall. Compact endexine. PA+TCH+Sp (short). E. Ambrosia artemisiifolia. Overall view of the ragweed pollen grain. F. Ambrosia artemisiifolia. Cross section of pollen grain wall. Laminated endexine. KMnO₄. A, C & E. SEM. B, D & F. TEM (ekt = ektexine, end = endexine, i = intine).

Table I. Most important hayfever inducing species, their allergenicity (according to the Austrian Pollen Forecast, http://www.pollenwarndienst.at ), pollen wall characteristics, types of pollen coating and reserve materials, respectively.

Family	Examined species	Allergenicity	Pollen coatings	Pollen wall	Reserve material
Asteraceae	Ambrosia artemisiifolia	very high	none	endexine laminated	none
Betulaceae	Alnus glutinosa	very high	occasionally non‐ electron‐dense pollenkitt	endexine not detectable, microchannels in ektexine	none
	Betula pendula				starch
	Carpinus betulus
	Corylus avellana
Brassicaceae	Brassica napus	moderate	tryphine	endexine absent	lipids
Chenopodiaceae	Atriplex patula	moderate	pollenkitt, primexine‐matrix	endexine discontinuous or not detectable	starch
	Chenopodium album
	Kochia scoparia
Oleaceae	Fraxinus excelsior	high	pollenkitt	endexine compact, microchannels below apertures	starch
	Syringa vulgaris	low
Platanaceae	Platanus×hispanica	high	none	endexine compact, laminated below apertures	lipids
Poaceae	Alopecurus pratensis	very high	occasionally non‐ electron‐dense pollenkitt	endexine not detectable, microchannels in ektexine	starch, polysaccharide‐vesicles
	Apera spica‐venti
	Avena sativa
	Avenula pubescens
	Bromus inermis
	Elymus repens
	Festuca pratensis
	Phleum pratense
	Poa pratensis
	Secale cereale
	Trisetum flavescens
	Triticum aestivum
	Zea mays
Urticaceae	Parietaria officinalis	high	none	endexine thin, hardly detectable	starch
	Urtica dioica	low