分类： 生物学 >> 植物学 提交时间： 2018-01-22
摘要： Thermal dissipation probes were used to measure xylem sap flux density for a Schima superba plantation growing in the urban area of Guangzhou city, South China. Stand transpiration was calculated by multiplying mean sap flux density by total sapwood area. The peak of sap flux density occurred later in wet season than in dry season. The maximum of daily sap flux density was the highest of 59 g m-2 s-1 in July and August, and the lowest of 28 g m-2 s-1 in December. During November 2007- October 2008 and during November 2008-October 2009, the stand transpiration was 263.2 and 291.6 mm, respectively. In the study periods, stand transpiration in wet season (from April to September) could account for about 58.5% and 53.8% of the annual transpiration, respectively. Heat energy absorbed by tree transpiration averaged 1.4×108 and 1.6×108 kJ per month in the Schima superba plantation with the area of 2885 m2, and temperature could be reduced by 4.3 and 4.7 oC s-1 for 10 m3 air.
分类： 生物学 >> 植物学 提交时间： 2018-01-13
摘要： To assess the water use of a clumped bamboo species, we investigated water use, physiological responses, and structural changes related to culm aging in the clumped bamboo species Bambusa chungii. Anisohydric behavior was characterized by the changed leaf water potential (ΨL), constant stomatal conductance (gs), and the low stomatal sensitivity (–m) in the young (0.52) and mature groups as well as the aged group (0.41). Intercellular CO2 (Ci) was negatively related to gs, especially during the dry season (R2 = 0.62). Hydraulic conductivity (ks) decreased by 57.9% and 58.8% in the mature and aged groups. This was accompanied by a leaf area (AL) that decreased by 55.7% and 63.7% and water transport path (h) that shortened by 8.5% and 23.3% to maintain the hydraulic safety. The photosynthetic rate (An) was similar among the three age groups even during the dry season when water deficits occurred. This might be due to compensation by increased chlorophyll content (5.3% greater for the mature group) and stomata density (7.4% and 8.1% greater for the mature and aged groups). Physiological and structural regulation contributes to reproductive success for B. chungii.
分类： 生物学 >> 植物学 提交时间： 2017-07-12
摘要： Canopy stomatal uptake of NOX (NO, NO2), SO2 and O3 by three mature urban plantations (of Schima superba, Eucalyptus citriodora and Acacia auriculaeformis) were studied using the sap flow-based approach under free atmospheric conditions. The annual mean concentration for NO, NO2, SO2 and O3 were 18.17, 58.05, 12.76 and 42.36 μg•m-3, respectively. The atmospheric concentration exhibited a spring or winter maximum for NO, NO2 and SO2, whereas the concentration maxima for O3 occurred in the autumn. Despite the daytime mean canopy stomatal conductance (GC) being positively related with the photosynthetically active radiation (PAR) and negatively with the vapour pressure deficit (VPD), the maximal daytime mean GC did not appear when the PAR was at its highest level or the VPD was at its lowest level because a positive correlation was noted between the daytime mean PAR and VPD (P<0.001) under field conditions. The GC value was regulated by the cooperation of the PAR and VPD. When analysing the respective effect of the PAR or VPD on GC separately, a positive logarithmical correlation was noted between the daytime mean GC and PAR as the following equation: G_c=a×lnPAR-b (P<0.01), and the daytime mean GC was negatively logarithmically correlated with the VPD: G_c=G_sref-m×lnVPD (P <0.001). The daytime mean GC declined with decreases in the soil water content (SWC) under similar meteorological condition. Differences in the seasonal pattern of the canopy stomatal conductance and atmospheric concentrations led to a differentiated peak flux. The flux for NO, NO2 and SO2 exhibited a spring maximum, whereas the flux maxima for O3 appeared in the autumn or summer. The annual accumulative stomatal flux for NO, NO2, SO2 and O3 was 100.19±3.76, 510.68±24.78, 748.59±52.81 and 151.98±9.33 mg•m-2•a-1, respectively. When we focus on the foliar uptake of trace gases, the effect of these gases on the vegetation in turn should be considered, particularly for regions with serious air pollution problems. These trace gases had not yet reached injury levels, except for NO2. Flux-based measurements were better suited for evaluating the risk of O3 damage to vegetation than the exposure-based method.
分类： 生物学 >> 生物物理学 提交时间： 2016-05-12
Wei, Ming-Yu
Xue, Lu
Tan, Li
Sai, Wen-Bo
Liu, Xiao-Cao
Jiang, Qiu-Ju
Shen, Jinhua
Peng, Yong-Bo
Zhao, Ping
Yu, Meng-Fei
Chen, Weiwei
Ma, Li-Qun
Liu, Qing-Hua
Wei, Ming-Yu
Xue, Lu
Tan, Li
Sai, Wen-Bo
Liu, Xiao-Cao
Jiang, Qiu-Ju
Shen, Jinhua
摘要： The participation of large-conductance Ca2+ activated K+ channels (BKs) in chloroquine (chloro)-induced relaxation of precontracted airway smooth muscle (ASM) is currently undefined. In this study we found that iberiotoxin (IbTx, a selective inhibitor of BKs) and chloro both completely blocked spontaneous transient outward currents (STOCs) in single mouse tracheal smooth muscle cells, which suggests that chloro might block BKs. We further found that chloro inhibited Ca2+ sparks and caffeine-induced global Ca2+ increases. Moreover, chloro can directly block single BK currents completely from the intracellular side and partially from the extracellular side. All these data indicate that the chloro-induced inhibition of STOCs is due to the blockade of chloro on both BKs and ryanodine receptors (RyRs). We also found that low concentrations of chloro resulted in additional contractions in tracheal rings that were precontracted by acetylcholine (ACH). Increases in chloro concentration reversed the contractile actions to relaxations. In the presence of IbTx or paxilline (pax), BK blockers, chloro-induced contractions were inhibited, although the high concentrations of chloro-induced relaxations were not affected. Taken together, our results indicate that chloro blocks BKs and RyRs, resulting in abolishment of STOCs and occurrence of contraction, the latter will counteract the relaxations induced by high concentrations of chloro.
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