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To examine the effects of decreased CO 2 and O 2 partial pressure on leaf-level photosynthesis in alpine plants at high altitude, we compared the maximal carboxylation efficiency, CE , of Reynoutria japonica Houtt. var. japonica growing in a highland with one growing in a lowland. CE under the native atmospheric conditions (native CE ) of the highland population was significantly lower than that of the lowland one. The O 2 dependency of CE was significantly less in the highland population than in the lowland. Using theoretical analysis, we explained that O 2 dependency of leaf-level photosynthesis became less as internal conductance ( g i ) decreased. We also showed that g i and the content of active Rubisco ( E ) could be estimated from the O 2 dependency of leaf-level photosynthesis. By applying the analysis, a severe limitation of CO 2 diffusion in the leaf was estimated in the highland population, whereas almost the same values of E were estimated in both populations. A reasonable explanation for the difference in the native CE is the smaller O 2 dependency and photosynthetic capacity caused by a smaller g i in the highland population in addition to the differences in the partial pressures of CO 2 and O 2 .

The shoot configuration of each monoclonal patch of phalanx‐forming tallgrass, Miscanthus sinensis, is characterized by the formation of a ‘fairy ring’, which forms as the result of developing vacant inner areas. One large‐sized M. sinensis patch (patch L), observed over a 9‐year survey period, underwent lateral expansion in almost all directions as a result of peripheral shoot births. In the year after the shoots in each part of patch L reached a maximum density (Dmax), the number of shoots decreased by approximately 20% per year. However, the overall number of within‐patch shoots was stable during the survey because the patch area increased at the periphery. Twelve patches (>900 cm2 in area) with orthotropic shoots were selected to observe the distribution pattern of within‐patch shoots, and the patch areas were divided into three parts: the exterior, intermediate and interior areas. In 10 of these 12 patches, shoot densities were lowest in the interior areas and highest in the exterior areas, which led to ring formation. The shoot density of each subarea was inversely related to the age of the subarea. This raises the possibility that in any part of these patches, shoot densities decrease annually from Dmax in a similar way.

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