CO2 exchange of the endolithic lichen Verrucaria baldensis from karst habitats in northern Italy

CO₂ exchange of the endolithic lichen Verrucaria baldensis was measured in the laboratory under different conditions of water content, temperature, light, and CO₂ concentration. The species had low CO₂ exchange rates (maximum net photosynthesis: c. 0.45 μmol CO₂ m⁻² s⁻¹; maximum dark respiration: c. 0.3 μmol CO₂ m⁻² s⁻¹) and a very low light compensation point (7 μmol photons m⁻² s⁻¹ at 8°C). The net photosynthesis/respiration quotient reached a maximum at 9–15°C. Photosynthetic activity was affected only after very severe desiccation, when high resaturation respiratory rates were measured. Microclimatic data were recorded under different weather conditions in an abyss of the Trieste Karst (northeast Italy), where the species was particularly abundant. Low photosynthetically active radiation (normally below 40 μmol photons m⁻² s⁻¹), very high humidities (over 80%), and low, constant temperatures were measured. Thallus water contents sufficient for CO₂ assimilation were often measured in the absence of condensation phenomena. Received: 22 September 1996 / Accepted: 26 April 1997     

Biological Control of Kudzu ( Pueraria lobata ) with an Isolate of Myrothecium verrucaria

An isolate of the fungus Myrothecium verrucaria ( MV ) was evaluated for biocontrol potential against kudzu ( Pueraria lobata ). In greenhouse tests, MV was highly virulent against kudzu in the absence of dew when conidia were formulated in 0.2% Silwet L-77 surfactant (SW). Inoculum concentrations ≥2 ×10 7 conidia ml -1 were required to satisfactorily control plants in the third leaf stage and larger. In controlled environment experiments, kudzu mortality was greater at higher temperatures (25-40°C) than at lower temperatures (10-20°C), although pathogenesis and mortality occurred at all temperatures tested. In field tests, transplanted kudzu seedlings in the 2-3 leaf growth stage treated with MV at 2 ×10 7 conidia ml -1 in 0.2% SW, exhibited leaf and stem necrosis within 24 h following inoculation, with mortality occurring within 96 h. After 7 days, 100% of inoculated kudzu plants were killed in plots treated with the fungus/surfactant mixtures. Similar results were observed in a naturally occurring kudzu population, where 100% control occurred within 14 days after inoculation with 2 ×10 7 conidia ml -1 in 0.2% SW. In summary, MV effectively controlled kudzu in the absence of dew over a wide range of physical and environmental conditions and under field conditions. These results indicate that, when properly formulated, MV has potential as a valuable bioherbicide for controlling kudzu.