Rhodiola sachalinensis growing in the different habitats, such as Xiaotianchi plot (altitude 1800 m), Tree line plot (altitude 2000 m) and Tianwenfeng plot (altitude 2325 m) of Changbai Mountain (northern slop) were t...Rhodiola sachalinensis growing in the different habitats, such as Xiaotianchi plot (altitude 1800 m), Tree line plot (altitude 2000 m) and Tianwenfeng plot (altitude 2325 m) of Changbai Mountain (northern slop) were transplanted to Harbin Experimental Farm for determining its gas exchange. The study results indicated that the diurnal changes of gas exchange ofRh. sachalinensis transplanted from different habitats were still different though the morphological appearance of the newly sprouted above-ground part had become more similar. For net photosynthesis rate (Pn), stomatal conductance (Gs) and apparent quantum yield (AQY), the diumal change curves ofRh. sachalinensis transplanted from the three plots were similar, but the data value were different. For the dark respiration rate (Rd), transpiration rate (Tr) and water use efficiency (WUE), diurnal change curves of the three plots were obviously different.展开更多
In order to identify the relationship between diurnal changes in the net photosynthetic rate（Pn） of Pueraria lobata and environmental factors,diurnal changes in the Pn of leaves of two P.lobata cultivars were measur...In order to identify the relationship between diurnal changes in the net photosynthetic rate（Pn） of Pueraria lobata and environmental factors,diurnal changes in the Pn of leaves of two P.lobata cultivars were measured using a CIRAS-1 portable photosynthesis measurement system（PP-Systems,UK）.The results show that diurnal changes in Pn of both cultivars could be interpreted as double-peak curves,indicating the occurrence of an obvious midday depression.Further analyses indicate that the correlation between Pn and stomatal conductance was positive and extremely significant（p 〈 0.01）.The correlations of Pn with intercellular CO2 concentration and transpiration rate were positive and significant（p 〈 0.05）,while the correlations of Pn with air and leaf temperatures were negative and significant（p 〈 0.05）.The results indicate that among the factors affecting photosynthetic properties,some can be grouped as stomatal limitations while others are non-stomatal limitations.展开更多
Recent studies by the Hong Kong Observatory show that the urban centre of Hong Kong has considerable Urban Heat Island （UHI） effect that arises from the different thermal properties between urban and the surrounding...Recent studies by the Hong Kong Observatory show that the urban centre of Hong Kong has considerable Urban Heat Island （UHI） effect that arises from the different thermal properties between urban and the surrounding rural areas. The studies have also shown that the urban-rural temperature difference or UHI intensity in the urban centre of Hong Kong can be greater than 10℃. However, the characteristics of UHI in Hong Kong would not be unique were it not for its complex topography and the significant spatial variation in the degree of urbanization within the territory. Making use of the extensive spatial coverage of the automatic weather stations operated by the Observatory, this study attempts to document the spatial variation of the characteristics of UHI effect in Hong Kong in summer and winter through cases studies. Cases in summer and winter with meteorological conditions typical for high UHI effect （that is, clear sky, light wind and stable atmospheric condition） are selected for the study. The characteristics of UHI effect in terms of the daytime warming rates, nocturnal cooling rates and diurnal temperature ranges at the selected automatic weather stations are analysed. The territory of Hong Kong is then classified into different categories according to the identified characteristics with a view to portraying the spatial morphology of UHI effect in Hong Kong.展开更多
文摘Rhodiola sachalinensis growing in the different habitats, such as Xiaotianchi plot (altitude 1800 m), Tree line plot (altitude 2000 m) and Tianwenfeng plot (altitude 2325 m) of Changbai Mountain (northern slop) were transplanted to Harbin Experimental Farm for determining its gas exchange. The study results indicated that the diurnal changes of gas exchange ofRh. sachalinensis transplanted from different habitats were still different though the morphological appearance of the newly sprouted above-ground part had become more similar. For net photosynthesis rate (Pn), stomatal conductance (Gs) and apparent quantum yield (AQY), the diumal change curves ofRh. sachalinensis transplanted from the three plots were similar, but the data value were different. For the dark respiration rate (Rd), transpiration rate (Tr) and water use efficiency (WUE), diurnal change curves of the three plots were obviously different.
基金supported by the "Eleventh Five-year" National Science and Technology Support Program of China (Grant No. 2009BADA7B04 Grant No. 2008BAD95B03the National Science and Technology Major Project of China (Grant No. 2009ZX09308-002)
文摘In order to identify the relationship between diurnal changes in the net photosynthetic rate（Pn） of Pueraria lobata and environmental factors,diurnal changes in the Pn of leaves of two P.lobata cultivars were measured using a CIRAS-1 portable photosynthesis measurement system（PP-Systems,UK）.The results show that diurnal changes in Pn of both cultivars could be interpreted as double-peak curves,indicating the occurrence of an obvious midday depression.Further analyses indicate that the correlation between Pn and stomatal conductance was positive and extremely significant（p 〈 0.01）.The correlations of Pn with intercellular CO2 concentration and transpiration rate were positive and significant（p 〈 0.05）,while the correlations of Pn with air and leaf temperatures were negative and significant（p 〈 0.05）.The results indicate that among the factors affecting photosynthetic properties,some can be grouped as stomatal limitations while others are non-stomatal limitations.
文摘Recent studies by the Hong Kong Observatory show that the urban centre of Hong Kong has considerable Urban Heat Island （UHI） effect that arises from the different thermal properties between urban and the surrounding rural areas. The studies have also shown that the urban-rural temperature difference or UHI intensity in the urban centre of Hong Kong can be greater than 10℃. However, the characteristics of UHI in Hong Kong would not be unique were it not for its complex topography and the significant spatial variation in the degree of urbanization within the territory. Making use of the extensive spatial coverage of the automatic weather stations operated by the Observatory, this study attempts to document the spatial variation of the characteristics of UHI effect in Hong Kong in summer and winter through cases studies. Cases in summer and winter with meteorological conditions typical for high UHI effect （that is, clear sky, light wind and stable atmospheric condition） are selected for the study. The characteristics of UHI effect in terms of the daytime warming rates, nocturnal cooling rates and diurnal temperature ranges at the selected automatic weather stations are analysed. The territory of Hong Kong is then classified into different categories according to the identified characteristics with a view to portraying the spatial morphology of UHI effect in Hong Kong.
