Journal Article

Intra-plant variation in cyanogenesis and the continuum of foliar plant defense traits in the rainforest tree <i>Ryparosa kurrangii</i> (Achariaceae)

Bruce L. Webber and Ian E. Woodrow

in Tree Physiology

Volume 28, issue 6, pages 977-984
Published in print June 2008 | ISSN: 0829-318X
Published online June 2008 | e-ISSN: 1758-4469 | DOI: http://dx.doi.org/10.1093/treephys/28.6.977
Intra-plant variation in cyanogenesis and the continuum of foliar plant defense traits in the rainforest tree Ryparosa kurrangii (Achariaceae)

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At the intra-plant level, temporal and spatial variations in plant defense traits can be influenced by resource requirements, defensive priorities and storage opportunities. Across a leaf age gradient, cyanogenic glycoside concentrations in the rainforest understory tree Ryparosa kurrangii B.L. Webber were higher in young expanding leaves than in mature leaves (2.58 and 1.38 mg g−1, respectively). Moreover, cyanogens, as an effective chemical defense against generalist herbivores, contributed to a defense continuum protecting foliar tissue during leaf development. Chemical (cyanogens and phenolic compounds) and phenological (delayed greening) defense traits protected young leaves, whereas mature leaves were largely protected by physical defense mechanisms (lamina toughness; explained primarily by leaf mass per area). Cyanogen concentration was considerably higher in floral tissue than in foliar tissue and decreased in floral tissue during development. Across contrasting tropical seasons, foliar cyanogenic concentration varied significantly, being highest in the late wet season and lowest during the pre-wet season, the latter coinciding with fruiting and leaf flushing. Cyanogens in R. kurrangii appear to be differentially allocated in a way that maximizes plant fitness but may also act as a store of reduced nitrogen that is remobilized during flowering and leaf flushing.

Keywords: chemical defense; chlorophyll; cyanide; delayed greening; floral defense; leaf nitrogen; leaf toughness; phenolic compounds; seasonal variation

Journal Article.  0 words. 

Subjects: Plant Sciences and Forestry

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