Phylloclade
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Phylloclade
Phylloclades and cladodes are flattened, photosynthetic shoots, which are modified branches. The two terms are used differently or interchangeably by different authors. Phyllocladus, a genus of conifer, is named after these structures. Phylloclades/cladodes have been identified in fossils dating from as early as the Permian.[1]
By one definition, phylloclades are a subset of cladodes, those that greatly resemble or perform the function of leaves,[2] as in Butcher's broom (Ruscus aculeatus) as well as Phyllanthus and some Asparagus species.
By an alternative definition, cladodes are distinguished by their limited growth and that they involve only one or two internodes.[3] By this definition, some of the most leaf-like structures are cladodes, rather than phylloclades. By that definition, Phyllanthus has phylloclades, but Ruscus and Asparagus have cladodes.
Etymology
New Latin phyllocladium; from Greek phyllo, leaf + klados, branch.
Similar structures
- Aristate leaves end in a stiff point that may continue the primary leaf vein; this can resemble the stem end of a phylloclade/cladode.
- Epiphylly: flowers and fruit develop "on a leaf". A stem and a leaf are merged with one another.[4] Examples include Monophyllaea in family Gesneriaceae and Helwingia in Helwingiaceae. Epiphylly also occurs in Bryophytes.
Illustrations
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Botanical illustration of Ruscus aculeatus showing leaf-like phylloclades/cladodes[citation needed]
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Phylloclade/cladode of Ruscus sp. showing the spine formed by the stem axis
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Leaf-like cladodes/phylloclades of Asparagus asparagoides
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Epiphylly in Helwingia japonica for comparison
References
- ^ Karasev, E. V.; Krassilov, V. A.. "Late Permian phylloclades of the new genus Permophyllocladus and problems of the evolutionary morphology of peltasperms". Paleontological Journal 41 (2): 198–206. doi:10.1134/S0031030107020104.
- ^ Goebel, K.E.v. (1905/1969). Organography of plants, especially of the Archegoniatae and Spermaphyta. Part II, Special Organography. New York: Hofner publishing company. pp. 448.
- ^ Bell, A.D. (1997). Plant form: an illustrated guide to flowering plant morphology. Oxford, U.K.: Oxford University Press.
- ^ Dickinson, T.A. (1978). "Epiphylly in angiosperms". The Botanical Review 44 (2): 181–232.
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