Contents and isotope carbon compositions (δ13C) of main biochemical fractions in organs at different growth stages in Phyllostachys edulis

Phyllostachys edulis is a spectacularly fast-growing species that completes its height growth within two months after the shoot emerges without producing leaves (fast-growing period, FGP). This phase was considered heterotrophic, the carbon necessary for the growth being transferred from the mature culms via the rhizomes, although previous studies observed key enzymes and anatomical features related to C4-carbon fixation in developing culms. We tested whether C4-photosynthesis or dark-CO2 fixation through anaplerotic reactions significantly contributes to the FGP, resulting in differences in the natural abundance of δ13C in bulk organic matter and organic compounds. Further, pulse-13CO2-labelling was performed on developing culms, either from the surface or from the internal hollow, to ascertain whether significant CO2 fixation occurs in developing culms. δ13C of young shoots and developing culms were higher (-26.3–-26.9‰) compared to all organs of mature bamboos (-28.4–-30.1‰). Develop..., Fraction of carbon compounds in organs
All samples were freeze-dried for at least 72 hours using a vacuum freeze dryer (FDU-1200, EYELA, Tokyo, Japan), and ground to a fine powder in a ball mill (MM-400, Retsch, Düsseldorf, Germany). Weight 50 mg per sample generally (30 mg per sample for bamboo shoots in this study). Soluble and insoluble compounds were separated based on their polar properties in a mixture of methanol–chloroform–water (MCW, 12/5/3, v/v/v). After centrifugation, the supernatant was mixed with 0.5 ml of methanol–chloroform (MC, 1/1, v/v) to separate pigments and lipids in the lower phase from the polar compounds in the upper phase. The pellet was digested with pronase in Tris buffer. Proteins were solubilised while starch remains in the insoluble fraction. The insoluble fraction was washed with ethanol and starch was gelatinised by hydrochloric acid. The starch fraction, recovered in the supernatant after centrifugation, was precipitated with absolute methanol. The str..., Excel is required to open these data files.