Journal
NEW PHYTOLOGIST
Volume 222, Issue 1, Pages 144-158Publisher
WILEY
DOI: 10.1111/nph.15522
Keywords
biogenic volatile organic compounds (BVOCs); carbon allocation; carbon limitation; CO2; growth-defense trade-offs; nonstructural carbohydrate (NSC) storage; Norway spruce (Picea abies); secondary metabolites (SM)
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Funding
- Chinese Scholarship Council
- Max Planck Institute for Biogeochemistry
- International Max Planck Research School for Global Biogeochemical Cycles
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Carbon (C) allocation plays a central role in tree responses to environmental changes. Yet, fundamental questions remain about how trees allocate C to different sinks, for example, growth vs storage and defense. In order to elucidate allocation priorities, we manipulated the whole-tree C balance by modifying atmospheric CO2 concentrations [CO2] to create two distinct gradients of declining C availability, and compared how C was allocated among fluxes (respiration and volatile monoterpenes) and biomass C pools (total biomass, nonstructural carbohydrates (NSC) and secondary metabolites (SM)) in well-watered Norway spruce (Picea abies) saplings. Continuous isotope labelling was used to trace the fate of newly-assimilated C. Reducing [CO2] to 120 ppm caused an aboveground C compensation point (i.e. net C balance was zero) and resulted in decreases in growth and respiration. By contrast, soluble sugars and SM remained relatively constant in aboveground young organs and were partially maintained with a constant allocation of newly-assimilated C, even at expense of root death from C exhaustion. We conclude that spruce trees have a conservative allocation strategy under source limitation: growth and respiration can be downregulated to maintain 'operational' concentrations of NSC while investing newly-assimilated C into future survival by producing SM.
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