The mechanism of the low temperature oxidation of gaseous acetaldehyde was investigated in the temperature range of 1 50-400?°C. The minor, intermediate and major products were identified and measured quantitatively by sampling directly into the ionization chamber of an MS10-C2 mass spectrometer from the reactor. The formation of H2O, CO, CO2, HCOOH, H2, HCHO, CH3COOH and CH3OH as the major pro...

open ocean ecosystems. Geochemical approaches indicate that the oceans are net positive autotrophic, but direct observations based on short-term incubation techniques suggest that the ocean is in a state of net heterotrophy. One hypothesis for the apparent discrepancy is that net autotrophic production occurs in aperiodic ‘‘bursts,’’ which are superimposed on a more constant background state of...

Bean plants, trimmed to a simplified "double source, double sink" translocation system (the paired primary leaves serving as the double source and the paired lateral leaflets of the immature first trifoliate leaf as the double sink) were used to study the magnitude and short-term time course of change in the allocation ratio (partition ratio) of assimilates translocated from the labeled primary...

Net photosynthetic carbon uptake of Panamanian lowland tropical forest species is typically optimal at 30-32 °C. The processes responsible for the decrease in photosynthesis at higher temperatures are not fully understood for tropical trees. We determined temperature responses of maximum rates of RuBP-carboxylation (VCMax ) and RuBP-regeneration (JMax ), stomatal conductance (Gs ), and respirat...

Short-term effects of irradiance (0-1560 micromol photons m(-2) s(-1)), temperature (10-25 degrees C), and salinity (40-160) on oxygenic photosynthesis and oxygen consumption in a hypersaline mat (Salin-de-Giraud, France) were investigated with microsensors under controlled laboratory conditions. Dark O(2) consumption rates were mainly regulated by the mass transfer limitations imposed by the d...

In this study, photosynthetic parameters such as the net photosynthesis rate, stomatal conductance, intercellular CO2 concentration, and transpiration rate were examined in selected ginseng varieties and/or lines that are resistant (Yunpoong, HTIR 1, HTIR 2, and HTIR 3) and susceptible (Chunpoong) to high temperature injury (HTI). The net photosynthesis rate increased with the increase in the l...

• Underwater photosynthesis by aquatic plants is often limited by low availability of CO(2), and photorespiration can be high. Some aquatic plants utilize crassulacean acid metabolism (CAM) photosynthesis. The benefits of CAM for increased underwater photosynthesis and suppression of photorespiration were evaluated for Isoetes australis, a submerged plant that inhabits shallow temporary rock po...

Chlorella pyrenoidosa was grown in a continuous-flow chemostat under nitrogen-limited conditions. The population density tended to oscillate very significantly. Net specific growth rate was only approximately a hyperbolic function of nitrate concentration in the chemostat. The best estimate of the half-saturation constant for nitrate is 6 mug of nitrogen per liter and it is unlikely that the va...