Soil respiration constitutes the second largest flux of carbon (C) between terrestrial ecosystems and the atmosphere. This study provides a synthesis of soil respiration (R s ) in 20 European grasslands across a climatic transect, including ten meadows, eight pastures and two unmanaged grasslands. Maximum rates of R s (R s max ), R s at a reference soil temperature (10°C; R s 10 ) and annual R s (estimated for 13 sites) ranged from 1.9 to 15.9 μmol CO 2 m −2 s −1 , 0.3 to 5.5 μmol CO 2 m −2 s −1 and 58 to 1988 g C m −2 y −1 , respectively. Values obtained for Central European mountain meadows are amongst the highest so far reported for any type of ecosystem. Across all sites R s max was closely related to R s 10 .Assimilate supply affected R s at timescales from daily (but not necessarily diurnal) to annual.Reductions of assimilate supply by removal of aboveground biomass through grazing and cutting resulted in a rapid and a significant decrease of R s . Temperature-independent seasonal fluctuations of R s of an intensively managed pasture were closely related to changes in leaf area index (LAI). Across sites R s 10 increased with mean annual soil temperature (MAT), LAI and gross primary productivity (GPP), indicating that assimilate supply overrides potential acclimation to prevailing temperatures. Also annual R s was closely related to LAI and GPP. Because the latter two parameters were coupled to MAT, temperature was a suitable surrogate for deriving estimates of annual R s across the grasslands studied. These findings contribute to our understanding of regional patterns of soil C fluxes and highlight the importance of assimilate supply for soil CO 2 emissions at various timescales.

Abstract. Herbaceous C3 plants grown in elevated CO2 show increases in carbon assimilation and carbohydrate accumulation (particularly starch) within source leaves. Although changes in the partitioning of biomass between root and shoot occur, the proportion of this extra assimilate made available for sink growth is not known. Root:shoot ratios tend to increase for CO2‐enriched herbaceous plants and decrease for CO2‐enriched trees. Root:shoot ratios for cereals tend to remain constant. In contrast, elevated temperatures decrease carbohydrate accumulation within source and sink regions of a plant and decrease root:shoot ratios. Allometric analysis of at least two species showing changes in root: shoot ratios due to elevated CO2 show no alteration in the whole‐plant partitioning of biomass. Little information is available for interactions between temperature and CO2. Cold‐adapted plants show little response to elevated levels of CO2, with some species showing a decline in biomass accumulation. In general though, increasing temperature will increase sucrose synthesis, transport and utilization for CO2‐enriched plants and decrease carbohydrate accumulation within the leaf. Literature reports are discussed in relation to the hypothesis that sucrose is a major factor in the control of plant carbon partitioning. A model is presented in support.

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The development of engineered skeletal muscle would provide a viable tissue for replacement and repair of muscle damaged by disease or injury. Current tissue engineering methods result in three-dimensional (3-D) muscle constructs that generate tension, but do not advance phenotypically beyond neonatal characteristics (Larkin et al., 2006). To develop to an adult phenotype, innervation and vascularization of the construct must occur. In this study, 3-D muscle constructs were implanted into the hindlimb of a rat along the sciatic nerve with the sural nerve isolated, transected and sutured to the construct to encourage innervation. Aortic ring anchors were sutured to the tendons of the biceps femoris muscle so that the construct would move dynamically with the endogenous muscle. After 1 week in vivo, constructs were explanted, evaluated for force production, and stained for muscle, nerve, and collagen markers. Implanted muscle constructs showed a developing capillary system, an epimysium-like outer layer of connective tissue, and an increase in myofiber content. The beginning of alpha-bungarotoxin clustering suggests that neuromuscular junctions (NMJ) could form on the implanted muscle given more time in vivo. Additionally, the constructs increased maximum isometric force from 192±41μN to 549±103μN (245% increase) compared to in vitro controls that increased from 276±23μN to 329±27μN (25% increase). These findings suggest that engineered muscle tissue survives 1 week implantation and begins to develop the necessary interfaces needed to advance the phenotype toward adult muscle. However, in terms of force production, the muscle constructs need longer implantation times to fully develop an adult phenotype.