The size and the age of the metabolically active carbon in tree roots

Little is known about the sources and age of C respired from tree roots. Previous research in tree stems has identified two functional pools of non-structural carbohydrates (NSC): an ‘active’ pool supplied directly from canopy photo-assimilates that supports metabolism and a ‘stored’ pool used when fresh C supplies are limited. We compared the C isotope composition of water soluble NSC and respired CO for aspen roots (Populus tremula hybrids) that were cut off fresh C supply via stem-girdling and prolonged incubation of excised roots. We used bomb radiocarbon to estimate the time elapsed since C fixation for respired CO, water-soluble C, and structural α-cellulose. While freshly excised roots respired CO with mean age <1 yr, within a week the age increased to 1.6-2.9 yr. Freshly excised roots from trees girdled ~3 months previously had similar respiration rates and NSC stocks as un-girdled trees, but respired older C (~1.2 yr). We estimate the NSC in girdled roots must be replaced 5-7 times by reserves remobilized from root-external sources. Using a mixing model and observed correlations between ΔC of water-soluble C and α-cellulose, we estimate ~30% of C is ‘active’ (~5 mg C g).

β-Cyclodextrin functionalized carbon quantum dots as sensors for determination of water-soluble C60 fullerenes in water

A selective photoluminescence method based on Carbon Quantum Dots (CQDs) functionalized with carboxymethyl-β-cyclodextrin for the direct determination of water-soluble C60 fullerene has been developed.

Studies on the Interaction of Water-Soluble Fullerols with BSA and the Effects of Metallic Ions

ABSTRACTThe interaction of water-soluble C60 derived fullerols with bovine serum albumin (BSA) in physiological environment was studied in detail by the fluorescence method. Experiments showed that the interaction of fullerols with BAS is mainly in the manner of non-covalent hydrogen bond. Based on the measurements of fluorescence intensity, the apparent binding constant K and the binding site number n were obtained with K=4000 and n=1, and the energy transfer efficiency in the reaction is 0.63. Besides, the effects of metallic ions such as Cu2+, Fe3+ and Cr(VI) on the interaction of fullerols with BSA were investigated. It was found that the effects of the metallic ions are quite different from each other. Low concentrations of Cu2+ can promote the interactions between fullerols and BSA, while high concentrations of Fe3+ or Cr(VI) favorite the interactions between fullerols and BSA.