Depletion of non-structural carbohydrate reserves in temperate tree seedlings under stress

Background/Question/Methods

Plant species that store larger amounts of non-structural carbohydrates (NSC) could use carbon reserves to sustain respiration during periods of negative carbon balance. This assumes that reserves can be remobilized and that the amount stored is related to performance. We aimed to establish whether resource-stressed seedlings deplete their carbon reserves over time and if differences in allocation of NSC to storage are related to species-level differences in stress tolerance. We tested the effects of stress on NSC reserves in seedlings of five temperate tree species (Acer rubrum, Betula papyrifera, Fraxinus americana, Quercus rubra, and Quercus velutina) in a greenhouse experiment. Seedlings were subjected to combinations of three stress types (shade, drought and defoliation) for a total of eight treatment combinations. We harvested seedlings over a period of 32 to 97 days and measured biomass and NSC concentrations to estimate depletion rates.

Results/Conclusions

Seedling growth ceased for all species under all stress treatments except for defoliation, and in some cases biomass decreased. Across species and all treatments except defoliation alone, NSC accumulation ceased, and in many cases concentrations decreased. Results indicate that NSC can be mobilized in response to stress, but the response depends on the species and type of stress. Thus, NSC depletion could depend on a species-specific ability to mobilize NSC under a given stressor. These results support that NSC depletion plays a role in seedling responses to common stressors, and that species differences in NSC storage are important for understanding carbon starvation as a buffer against stress.