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Solar radiation as a factor in the evolution of scleromorphic leaf anatomy in Proteaceae
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Species of the major Southern Hemisphere family, Proteaceae, have many scleromorphic anatomical structures in their leaves. Many of these structures (very thick cuticles and five anatomically distinct structures beneath the epidermis) are associated with the leaf surface exposed to direct light. These structures increase the path through which solar radiation must pass before reaching the mesophyll.
In this study, such structures are proposed to protect the mesophyll from excess solar radiation, including photosynthetically active, ultraviolet, and possibly infrared radiation. Scleromorphic structures of the upper leaf surface and nonscleromorphic photoprotective
structures (dense trichomes and papillae of the upper surface) occur almost exclusively in open vegetation. Open vegetation species of Proteaceae occur in oligotrophic and/or cold and/or dry places, where protection from light in excess of photosynthetic capacity and damage from ultraviolet light should be most important. Data from 123 species and a supertree constructed from available
molecular phylogenies are used to show that the proposed photoprotective structures evolved many times within Proteaceae. In tests of correlated evolution, the proposed photoprotective structures are significantly associated with open vegetation, but not with dry habitats.
|Keywords:||anatomy; cuticle; photoprotection; Proteaceae; scleromorphy; sclerophylly; ultraviolet; xeromorphy|
|Journal or Publication Title:||American Journal of Botany|
|Page Range:||pp. 789-796|
The definitive version is available online at http://www.amjbot.org/cgi/content/abstract/92/5/789
|Date Deposited:||30 Aug 2007|
|Last Modified:||18 Nov 2014 03:21|
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