Seasonal dynamics of mobile carbon supply in Quercus aquifolioides at the upper elevational limit.

Many studies have tried to explain the physiological mechanisms of the alpine treeline phenomenon, but the debate on the alpine treeline formation remains controversial due to opposite results from different studies. The present study explored the carbon-physiology of an alpine shrub species (Quercus aquifolioides) grown at its upper elevational limit compared to lower elevations, to test whether the elevational limit of alpine shrubs (<3 m in height) are determined by carbon limitation or growth limitation. We studied the seasonal variations in non-structural carbohydrate (NSC) and its pool size in Q. aquifolioides grown at 3000 m, 3500 m, and at its elevational limit of 3950 m above sea level (a.s.l.) on Zheduo Mt., SW China. The tissue NSC concentrations along the elevational gradient varied significantly with season, reflecting the season-dependent carbon balance. The NSC levels in tissues were lowest at the beginning of the growing season, indicating that plants used the winter reserve storage for re-growth in the early spring. During the growing season, plants grown at the elevational limit did not show lower NSC concentrations compared to plants at lower elevations, but during the winter season, storage tissues, especially roots, had significantly lower NSC concentrations in plants at the elevational limit compared to lower elevations. The present results suggest the significance of winter reserve in storage tissues, which may determine the winter survival and early-spring re-growth of Q. aquifolioides shrubs at high elevation, leading to the formation of the uppermost distribution limit. This result is consistent with a recent hypothesis for the alpine treeline formation.

Preparation of inclusion complex of paeonol and beta-cyclodextrin by sealed-control temperature method / 中国中药杂志

<p><b>OBJECTIVE</b>In the present study, using paeonol as model drug, a new sealed-control temperature method of preparing inclusion complex was developed, the effects of heating temperature, heating time, and crystallinity of beta-cyclodextrin (beta-CD) on formation of inclusion complex and release of the drug were investigated.</p><p><b>METHOD</b>A physical mixture of paeonol and beta-CD was sealed in a container, and heated at the desired temperature for the specified time. The inclusion complex of paeonol and beta-CD was confirmed by IR spectrum and powder X-ray diffraction.</p><p><b>RESULT</b>The results indicated that the inclusion complex formation of paeonol beta-CD by sealed-control temperature method was affected by heating temperature, heating time, and crystallinity of beta-CD. The inclusion complex was able to inhibit sublimation of paeonol, and dissolution rate of paeonol was increased when the paeonol was included by beta-CD.</p><p><b>CONCLUSION</b>Preparation of inclusion complex was simple and quick by sealed-control temperature method.</p>