Strobilus
A strobilus (pl.: strobili) is a structure present on many land
Leaves that bear sporangia are called
Lycophytes
Some members of both of the two modern classes of
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Strobili of Diphasiastrum
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Strobili of Lycopodium
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Liquid-preserved strobili of Lycopodium, showing reniform sporangia through translucent sporophylls
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Micrograph of the strobilus of Lycopodium sp., showing spores borne in sporangia
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Strobili of Selaginella
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Liquid-preserved strobili of Selaginella, showing mega- and microsporangia through translucent sporophylls
Sphenophytes
The single extant genus of
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Strobilus of Equisetum
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Strobilus of Equisetum
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Liquid-preserved strobilus of Equisetum, showing sporangiophores
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Cross-section of liquid-preserved strobilus of Equisetum, showing sporangiophores bearing sporangia
Seed plants
With the exception of flowering plants, seed plants produce ovules and pollen in different structures. Strobili bearing microsporangia are called microsporangiate strobili or pollen cones, and those bearing ovules are megasporangiate strobili or seed cones (or ovulate cones).
Cycads
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Dioon edule, seed cone
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Cycas circinalis, pollen cone
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Abaxial surface of Cycas revoluta microsporophyll, showing microsporangia
Ginkgos
The single living member of the
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Pollen cones of Ginkgo
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Pollen cone of Ginkgo, showing microsporophylls each with two microsporangia
Conifers
Pollen strobili of
Gnetophytes
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Seed cones of Welwitschia
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Pollen cones of Welwitschia
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Pollen cones of Ephedra
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Pollen cone of Ephedra showing microsporangia
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Ephedra intermedia seed cone.
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Seed cones of Gnetum
Flowering plants
The
A number of flowering plants have inflorescences that resemble strobili, such as catkins, but are actually more complex in structure than strobili.
Evolution
It is likely that strobili evolved independently in most if not all these groups. This evolutionary convergence is not unusual, since the form of a strobilus is one of the most compact that can be achieved in arranging lateral organs around a cylindric axis, and the consolidation of reproductive parts in a strobilus may optimize spore dispersal and nutrient partitioning.
Etymology
The word strobilus is related to the ancient Greek strobilos = whirlwind. The
According to Liddell & Scott, the Greek: strobilos (στρόβιλος) had many meanings, generally of anything twisted up...hence of the hedgehog,... of an egg-shell,... as a name of various twisted or spinning objects. For example:
1. a kind of seasnail... 2. a top... 3. a whirlpool, a whirlwind which spins upwards... 6. the cone of the fir or pine, fir-apple, pine-cone,… also of the tree itself.[1]
References
- ^ Henry George Liddell, Robert Scott, assisted by Prof. Henry Drisler of Columbia College: Greek-English Lexicon, 8th ed. 1897 p. 1439. Pub:Harper New York 1882.
- Gifford, E. M. & Foster, A. S. (1988). Comparative morphology of vascular plants, 3rd ed. New York: WH Freeman.