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.
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