Photosynthese,Transpiration und Spaltöffnungsverhalten verschiedener Holzarten nach Begasung mit SO2

Photosynthesis, transpiration and stomatal response of various species of woody plants exposed to sulfur dioxide. Photosynthesis of Fraxinus excelsior, Piceaabies, Abies alba and Pinus sylvestris declined after 6 and 12 h of fumigation at SO₂ concentrations of 5 and 9mg m^?3. Transpiration also declined, but the maximum depression was only 38%. Stomata began to close after fumigation with ～ 1 mg SO₂m^?3 for 6 h. The diffusion resistance of needles of Pices and Abies increased after fumigation with 9 mg SO₂ for 6h to a peak value of 35–40 scm^?1 and decreased rapidly (Picea) or remained stable (Abies) during the following 30h.     

Ancient biomolecules from deep ice cores reveal a forested southern Greenland

It is difficult to obtain fossil data from the 10% of Earth's terrestrial surface that is covered by thick glaciers and ice sheets, and hence, knowledge of the paleoenvironments of these regions has remained limited. We show that DNA and amino acids from buried organisms can be recovered from the basal sections of deep ice cores, enabling reconstructions of past flora and fauna. We show that high-altitude southern Greenland, currently lying below more than 2 kilometers of ice, was inhabited by a diverse array of conifer trees and insects within the past million years. The results provide direct evidence in support of a forested southern Greenland and suggest that many deep ice cores may contain genetic records of paleoenvironments in their basal sections.     

Transmission dynamics of the etiological agent of SARS in Hong Kong: impact of public health interventions

We present an analysis of the first 10 weeks of the severe acute respiratory syndrome (SARS) epidemic in Hong Kong. The epidemic to date has been characterized by two large clusters-initiated by two separate "super-spread" events (SSEs)-and by ongoing community transmission. By fitting a stochastic model to data on 1512 cases, including these clusters, we show that the etiological agent of SARS is moderately transmissible. Excluding SSEs, we estimate that 2.7 secondary infections were generated per case on average at the start of the epidemic, with a substantial contribution from hospital transmission. Transmission rates fell during the epidemic, primarily as a result of reductions in population contact rates and improved hospital infection control, but also because of more rapid hospital attendance by symptomatic individuals. As a result, the epidemic is now in decline, although continued vigilance is necessary for this to be maintained. Restrictions on longer range population movement are shown to be a potentially useful additional control measure in some contexts. We estimate that most currently infected persons are now hospitalized, which highlights the importance of control of nosocomial transmission.