a1_Attention should be paid to ozone (O3) sensitivity of greening plant since ground-level O3 concentrations are increasing especially in urban and suburban area. We studied the ecophysiological responses to elevated O3 of four shrub species [Euonymus bungeanus Maxim. (EB), Photinia × fraseri (PF), Chionanthus retusus Lindl. & Paxt. (CR) and Cornus alba L. (CA)], which are often used for garden greening in China. Saplings of those species were exposed to high O3 concentration (70 nmol mol-1, 7 h d-1 for 65 d) in open-top growth chambers. Responses to O3 were assessed by gas exchanges, chlorophyll (Chl) fluorescence and dry mass. We found that elevated O3 significantly decreased lightsaturated net photosynthetic rate (PNsat), transpiration rate (E) and stomatal conductance (gs). The ratio of intercellular CO2 to ambient CO2 concentration (Ci/Ca) did not reduce under O3 fumigation which suggested that the O3-induced depressions of P Nsat under O3 fumigation were probably due to limitation of mesophyll processes rather than stomatal limitation. High O3 exposure also significantly depressed the maximum efficiency of photosystem II (PSII) photochemistry in the dark-adapted state (Fv/Fm) which meant the O3-induced photoinhibition. Both root dry mass and root/shoot ratios were significantly decreased under ozone fumigation, but the total mass was unchanged. The responses of gas exchange such as PNsat in these four shrubs to O3 exposure were species-specific. Highest loss of PNsat was observed in EB (-49.6%), while the CR had the lowest loss (-36.5%). Moreover, the O3-exposed CR showed similar gs as CF, reflecting that its O3 flux might be unchanged under elevated O3 environment. Ozone drastically decreased actual quantum yield of PSII (ΦPSII) and electron transport rate (ETR) in EB while increased ΦPSII and ETR in CR., a2_Furthermore, the relative losses in P Nsat positively correlated with the relative decreases in ΦPSII and ETR which indicated that the impairment of photosynthesis was probably affected by the light reaction process. The light reaction of EB was impaired most seriously but that of CR was not damaged. All results indicated that EB was probably the most sensitive shrub species to O3 while CR the most tolerant one. Therefore, CR might be an ideal choice for greening in ozone-polluted areas., L. Zhang ... [et al.]., and Obsahuje bibliografii
Intercropping, a traditional and worldwide cropping practice, has been considered as a paradigm of sustainable agriculture based on complementary mechanisms among different crop species. Soybean (Glycine max) is widely relay intercropped about 60 days before maize (Zea mays) harvest in Southwest China. However, shade caused by tall maize plants may be a limiting factor for soybean growth at a seedling stage. In field research, we studied the ecophysiological responses of two widely cultivated soybean varieties [Gongqiudou494-1 (GQD) and Gongxuan 1 (GX)] to maize shading in a relay intercropping system (RI) compared with monocropped soybean plants (M). Our results showed that soybean seedlings intercropped with maize exhibited significantly downregulated net photosynthetic rate (PN) (-38.3%), transpiration rate (-42.7%), and stomatal conductance (-55.4%) due to low available light. The insignificant changes in intercellular CO2 concentration and the maximum efficiency of PSII photochemistry suggested that the maize shading-induced depressions in PN were probably caused by the deficiency of energy for carbon assimilation. The significantly increased total chlorophyll (Chl) content (+27.4%) and Chl b content (+52.2%), with lowered Chl a/b ratios (-20.5%) indicated soybean plants adjusted their light-harvesting efficiency under maize shading condition. Biomass and leaf area index (LAI) of seedlings under RI decreased significantly (-78.7 and -71%, respectively) in comparison with M. Correlation analysis indicated the relative reduction in biomass accumulation was caused by the decline in LAI rather than PN, it affected negatively the final yields of soybean (32.8%). Cultivar-specific responses to maize shading were observed in respects of LAI, biomass, and grain yield. It indicated that GX might be a better cultivar for relay intercropping with maize in Southwest China., B. Y. Su, Y. X. Song, C. Song, L. Cui, T. W. Yong, W. Y. Yang., and Obsahuje bibliografii
A sand-culture experiment was conducted in open-top chambers which were constructed in a greenhouse to investigate the responses of salt-stressed wheat (Triticum aestivum L.) to O3. Plant seeding of JN17 (a popular winter wheat cultivar) was grown in saltless (-S) and saline (+S, 100 mM NaCl) conditions combined with charcoal-filtered air (CF, < 5 ppb O3) and elevated O3 (+O3,
80 ± 5 ppb, 8 h day-1) for 30 d. O3 significantly reduced net photosynthetic rate (PN), stomatal conductance, chlorophyll contents and plant biomass in -S treatment, but no considerable differences were noted in those parameters between +O3+S and CF+S treatments. O3-induced loss in cellular membrane integrity was significant in -S plants, but not in +S plants evidenced by significant elevations being measured in electrolyte leakage (EL) and malondialdehyde (MDA) content in -S plants, but not in +S plants. Both O3 and salinity increased proline content and stimulated antioxidant enzymes activities. Soluble protein increased by salinity but decreased by O3. Abscisic acid (ABA) was significantly elevated by O3 in -S plants but not in +S plants. The results of this study suggested that the specificity of different agricultural environments should be considered in order to develop reliable prediction models on O3 damage to wheat plants. and Y. H. Zheng ... [et al.].