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Variation in carbon availability, defense chemistry and susceptibility to fungal invasion along the stems of mature trees
Author(s) -
Goodsman Devin W.,
Lusebrink Inka,
Landhäusser Simon M.,
Erbilgin Nadir,
Lieffers Victor J.
Publication year - 2013
Publication title -
new phytologist
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.742
H-Index - 244
eISSN - 1469-8137
pISSN - 0028-646X
DOI - 10.1111/nph.12019
Subject(s) - pinus contorta , phloem , monoterpene , carbohydrate , botany , biology , inoculation , fungus , crown (dentistry) , sink (geography) , sugar , carbon sink , woody plant , horticulture , chemistry , ecology , food science , biochemistry , ecosystem , medicine , cartography , dentistry , geography
Summary If carbon ( C ) sinks withdraw carbohydrates as they are transported along tree stems, carbohydrate availability may depend on local sink strength and distance from sources. Defenses, including monoterpenes – a major component of resin – limit the invasibility of pines. Since carbohydrate reserves fund monoterpene synthesis, we hypothesized that monoterpene concentrations in pine stems would decrease from the crown to the lower stem, and susceptibility to fungal infection would increase. Here, we measured carbohydrate and monoterpene concentrations along the stems of lodgepole pine trees ( P inus contorta var. latifolia ) before inoculating with a blue‐stain fungus at different heights. After 6 wk, we assessed tree responses to fungal infection based on lesion length and carbohydrate mobilization. Concentrations of carbohydrates and monoterpenes in the phloem before inoculation decreased with distance from the crown, whereas lesion lengths after inoculation increased. However, trees mobilized sugars in response to fungal infection such that carbohydrate reserves near lesions were similar at all heights. Despite C mobilization, the lower stem was more vulnerable than the upper stem. Consistent with predictions based on sink–source relationships, vulnerability occurred where carbohydrates were less available, and likely resulted from C withdrawal by sinks higher in the supply chain.