Key message Restricted access of light for stems reduced carbon acquisition there and limited the biomass growth of the roots. Abstract Light access can affect the microatmosphere within stems, creating favourable conditions for photosynthesis. We tested the hypothesis that stem photosynthesis modifies carbon allocation within plants and also can affect root growth. To verify this hypothesis, parts of Clusia minor L. stems were covered with dark material for 8 months to block light access to stems, and then, we compared morphological traits, biomass increment, photosynthetic activity and carbon isotopic signature (δ13C) in plants with dark- and light-exposed stems. Clusia minor stems were characterized by chlorophyll presence from pith to cortex, active photosystem II and 79% re-assimilation of respired CO2. We also revealed 24-h changes in the δ13C of carbohydrates exported from leaves. Keeping stems in darkness led to a significant lowering in root biomass and shoot-to-root weight index (Iw). Moreover, reductions in stem CO2 efflux and the δ13C in the roots and stems were also observed. Our results indicate that the lack of stem photosynthesis affects photosynthate flux to heterotrophic organs, such as roots, stems and probably expanding leaves.

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Innovative low-temperature disintegration (process temperature 55 °C and oxygen concentration 0.2 mg/dm3) can be an economically rational technology to intensifying energy production from renewable sources. The proposed process can achieve a degree of disintegration—under optimal conditions—of about 50%, which is excellent when compared with other methods of feed pre-treatment. The low-temperature disintegration of distillation residue and waste-activated sludge before the co-fermentation process increased biogas production by 30% and methane production by 65% (over a 26 d duration). The obtained results confirm that the low-temperature disintegration method can be effectively used to pre-prepare this type of feed. At the same time, it was discovered that the Gompertz model can be used to mathematically describe the biogas accumulation curves in the methane co-fermentation processes of the tested feeds (the correlation coefficients were higher than 0.98).

Sulphur isotolJe fractionation (345/328) factors were determined for SO2(~as) -SO2(methanol) system. The influence of the temperature on the investigated sulphur isotopes separation between phases was studied as well.