Ecophysiological factors contributing to the invasion of Panicum maximum into native Miscanthus sinensis grassland in Taiwan

Panicum maximum (guinea grass), a native grass of Africa, has invaded and displaced the native Miscanthus sinensis grassland at Dadu terrace in central Taiwan. The Dadu terrace has distinct wet and dry seasons and is prone to fire during the dry seasons. We compared photosynthesis and growth, as well as the growth response to two water treatments, between P. maximum and M. sinensis plants to understand ecophysiological factors contributing to the successful invasion of the grass. In comparison with M. sinensis, P. maximum had a significantly higher photosynthetic rate, larger specific leaf area and a higher leaf area/total biomass ratio, and thus grew faster and higher, and accumulated more biomass under well‐watered conditions. The growth of P. maximum was more susceptible than M. sinensis to drought stress. Faster growth of seedlings and more biomass accumulation of mature plants would give P. maximum a highly competitive advantage over M. sinensis for resource acquisition in the Dadu terrace during the wet season, which might contribute to the successful invasion of P. maximum into the grassland of M. sinensis.     

Effect of Preserving Condition of Porcine Ovaries on the Development of In Vitro Matured Oocytes

The effect of preservation condition of ovaries on the in vitro maturation of the porcine oocytes was studied. Cumulus‐oocyte complexes (COCs) were obtained from the ovaries preserved in Dulbecco’s phosphate buffered saline (PBS) solution at various temperatures for different time intervals, and cultured in M199 maturation medium. Matured oocytes were obtained from the ovaries preserved in PBS for 8 h and electrically activated. The activated oocytes were then cultured in NCSU23 embryo culture medium for 16 h to observe activation or 144 h to observe embryo development. It was found that the preservation temperature affected the maturation of porcine oocytes greatly. The effect was described as a compromise of the suppressions of autolysis at physiological temperature and frostbite because of low temperature. A preservation temperature of approximately 25°C showed the maximum maturation rate for a preservation time of 8 h. Preservation temperature also affected the activation and embryo development of porcine oocytes greatly, following a trend similar to the effect of preservation temperature on the maturation. Based on maturation rate, activation rate and cleavage rate, a preservation temperature of approximately 25°C would be optimum for a preservation time of 8 h.