To fully understand the sensitivity of photosystem II (PSII) activity of immature and mature leaves in desert plants to light stress, we explored the chlorophyll a fluorescence kinetics in Alhagi sparsifolia Shap. Plants. Results show that the chlorophyll fluorescence transient intensity of both immature and mature leaves was significantly higher under shaded conditions (about 50 % of natural light intensity) than that under ambient light conditions (100 % of natural light intensity). The energy fluxes per reaction center and cross section of immature and mature leaves were higher under shaded conditions than of those under ambient conditions. By contrast, the quantum yields and efficiencies and performance indices under shaded conditions were lower than of those under ambient conditions. However, the chlorophyll fluorescence transient intensity and parameters of both immature and mature leaves significantly changed under natural light exposure. These results suggest that the PSII activity of immature and mature leaves under shaded irradiance was enhanced, but the PSI acceptor side was affected as compared with that under ambient conditions. Activity of the donor side of PSII of immature leaves was higher than that of mature leaves in both shaded and ambient light conditions, and the electron transport activity at the acceptor side of PSII of both immature and mature leaves was inhibited by high irradiance after being kept in the shade. Furthermore, immature leaves suffered from severe inhibition than did mature leaves after exposure to ambient conditions. This study showed that immature leaves were more sensitive than mature leaves were to light stress.
Comparison of the staminate flower and pollen of Betula platyphylla between autotetraploid and diploid individuals may reveal the reason for cross sterility when an autotetraploid male parent is crossed with a diploid female parent. Staminate flowers and pollen from seven autotetraploid individual trees were examined. The morphologies of the staminate flower and pollen and pollen germination of these autotetraploid individuals were compared with diploid trees. The structure of the staminate flower did not differ between autotetraploids and diploids, whereas the size of the staminate flower was larger in the autotetraploids compared with the diploids. The mean diameter and pore depth of the pollen were significantly larger in autotetraploid individuals compared with diploids, and several abnormalities in pollen morphology were found commonly amongst pollen from the autotetraploid trees. The germination rate of pollen from autotetraploids was significantly inferior to that of diploids and there was a significant negative correlation between germination rate and the percentage of abnormal pollen. These results demonstrate that the autotetraploid should not be chosen as the male parent to obtain hybrid triploid progenies because the pollen is abnormal and results in low fertility despite its large size. The results provide important information for selecting and distributing parent strains with the aim of building seed orchards of triploid birch trees.
Leaves and assimilative branches are crucial to the life cycle of Alhagi sparsifolia Shap. that is one of the main shrubs in the southern fringe of the Taklamakan desert. They reduce photosynthesis at midday during summer and exhibit different degrees of adaptability to severe environments. We investigated the changes in the PSII activity of leaves and assimilative branches of under elevated temperature and whether they have the same response and level of tolerance to different temperatures, thus to understand the roles of leaves and assimilative branches of A. sparsifolia in global warming. In this study, the kinetics of induced chlorophyll a fluorescence under heat-stress-induced inhibition of photosystem II in leaves and assimilative branches of A. sparsifolia after 15 min of treatment was investigated. The results show that both the activity and density of reaction centers of leaves are higher than assimilative branch at 35–48°C, and both in the leaves and assimilative branches were decreased above 45°C, the assimilative branches adapted better to the severe environment in terms of light energy transfer, light usage efficiency, and electron transport at 52°C. Assimilative branches had better adaptability to elevated temperature than leaves of A. sparsifolia suggesting that assimilative branches might be more adaptive to severe environment.
Plant breeders have focused much attention on polyploid trees because of their resistance for forestry. To evaluate the impact of intraspecies genome duplication on NaHCO3 stress, a series of Betula platyphylla autotetraploids and diploids were generated from the same family. The growth, proline content and proline-associated gene expression of these autotetraploid individuals were compared with those diploid trees. Autotetraploids were superior in injury index and relative growth of height and base diameter compared to diploids. The proline content was higher in autotetraploid individuals compared to diploids. Gene expression data revealed autotetraploids were generally higher expression in BpP5CS1, BpP5CS2, Bp- P5CR1, BpP5CR2, BpP5CR3 and BpOAT and were lower expression in BpProDH and BpP5CDH compared to diploid trees. These results shed light on resistance variation in birch autotetraploidization and polyploidy breeding as a new approach for genetic improvement of birch trees.
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Elephants were confined to Mengyang Protected Area in China and their distribution range had reduced greatly compared to past records. A preliminary study of habitat selection by Asian elephantsElephas maximus Linnaeus, 1758 and their distribution was conducted in Mengyang Protected Area and its surrounds using site visits and transect surveys from July 2003 to December 2006. Although no variable significantly influenced their habitat selection, elephants still showed preference for altitudes between 900 and 1200 m, gradients <30°, and orientations to the south-east, south and south-west. Human activities, including habitat transformation and degradation, disturbance by large infrastructure and poaching were considered to be the main factors inducing elephant distribution changes.
This paper studies the association between concentration of ambient air pollutants and daily mortality number in an urban area of Beijing. Different age and gender groups were taken into consideration. The results showed that, for all the groups, the average daily mortality number showed an increasing trend from June to January of next year, and a decreasing trend from February to June. When the concentration of air pollutants increased, the health risk also increased. In multi-pollutants models, the pollutants had a decreasing order NO2, PM10, SO2 for the different gender groups when the concentration of pollutants increased, and had a decreasing order NO2, PM10, SO2 for different age groups when the levels of pollutants increased. Lag effects of air pollutants and seasonal differences also were found. The results of our study could serve to strengthen the local evidence base for air pollution-related health effects that is imminently needed for better air quality management, and also adds valuable information from Beijing.
In order to demonstrate that silicate (SiO3-Si) can be used as an indicator to study upwelling in the northern South China Sea, hierarchical cluster analysis (CA) and principle component analysis (PCA) were applied to analyse the metrics of the data consisting of 14 physical-chemical-biological parameters at 32 stations. CA categorized the 32 stations into two groups (low and high nutrient groups). PCA was applied to identify five Principal Components (PCs) explaining 78.65% of the total variance of the original data. PCA found important factors that can describe nutrient sources in estuarine, upwelling, and non-upwelling areas. PC4, representing the upwelling source, is strongly correlated to SiO3-Si. The spatial distribution of silicate from the surface to 200 m depth clearly showed the upwelling regions, which is also supported by satellite observations of sea surface temperature.
Degradation of shrub meadows and reclamation of alpine meadows may heavily affect the soil sink for atmospheric methane (CH₄), but this is poorly understood. Therefore, in situ measurements of atmospheric CH₄ consumption were conducted in four landuse types: natural alpine meadow (NM), Elymus nutans pasture (EP), herbaceous meadow in shrub (HS), and a P. fruticosa shrub meadow (PS) within two years. CH₄ fluxes were measured using static chambers and gas chromatography. All four types of land use showed atmospheric CH₄ sink throughout the two years, with mean soil CH₄ consumption rates at 24.6±10.9, 33.8±15.0, 39.8±10.3, and 28.1±12.1 µg CH₄·m⁻²·hr⁻¹ for NM, EP, PS, and HS, respectively. Soil CH₄ consumption increased by 40% by reclamation from NM to EP, while it decreased by 30% by degradation from PS to HS. Soil CH₄ consumption in four types of land use was significantly correlated with temperature at 5 cm depth (P<0.01) and the soil water-filled pore space (WFPS) (P<0.05). Temperature showed stronger effects on soil CH₄ consumption than WFPS, except in NM. UV radiation was positively correlated with soil CH₄ consumption with increasing temperature and decreasing soil moisture. These findings indicate that a decrease in the grazing pressure in shrub meadows and increase in the area of artificial pasture reclaimed from alpine meadows would enhance the CH₄ sink in alpine meadows on the Tibetan Plateau.
In the present study we show FISH localization of 4 porcine BAC clones harbouring potential candidate genes for fatness traits: DGAT1 (SSC4p15), PPARA (SSC5pl5), ADIPOR1 (SSC10p13) and CREB (SSC15q24). Until now the CREB and ADIPOR1 genes are considered to be monomorphic, DGAT1 is highly polymorphic, while for the PPARA gene only 1 SNP was identified. Assignment of the studied genes in relation to QTL chromosome regions for meat quality in pig chromosomes SSC4, SSC5, SSC10 and SSC15 is discussed.
This study was aimed at qualifying the methane emission ability of different communities in alpine meadow, and monitoring if the dominant species from these communities could emit methane in a sand culture experiment. Using the static chamber technique and gas chromatography method, two experiments were conducted in the field and in laboratory. First, the methane flux rate was measured in plant communities: natural alpine meadows (NM), Elymus nutans pasture (EP), herbaceous community in shrub (HS), and a Poa fruticosa meadow (PS). A 3-month sand culture experiment was conducted to show the non-microbial methane emission from living plants. Average methane emission rates were estimated to be 16.83 µg m⁻² h⁻¹(range -49.3–107.8), 28.49 µg m⁻² h⁻¹ (range -55.0–96.2) and 20.91 µg m⁻² h⁻¹ (range -31.9– 145.8) for NM, EP, and PS, respectively. Methane emission rate from EP was significantly higher than from NM during the growing season. The reclaim of grassland would enhance the methane emission in this aera through this one year's measurement, but whether this conclusion suit to the whole Tibet Plateau, it remains further longer time and larger spatial scale experiments to verify it. The result of the sand culture experiment showed that some plant species emitted methane in an aerobic, nonmicrobial environment, most of herbaceous species showed a methane emission characteristic, the methane emission from plant may have a species dependent characteristic.
Anatase TiO₂ nanoparticles (NPs) are widely used in food products, capsules, toothpaste, and so on, so the kinds of NPs directly get in touch with human bodies. The potential effect of this kind of material on reproduction must be considered with the increase in infertility. Sixty ICR male mice were intragastrically treated with dosages of 0, 10, 50, and 100 mg kg⁻¹ body weight (BW) anatase TiO₂ NPs to investigate the male reproductive toxicity of the NPs. Sperm quality, morphological changes in mice testes, and oxidative damage indexes were investigated in this study. Results showed that anatase TiO₂ NPs could lead to sperm malformation and increased rate of sperm cell micronucleus. These NPs also reduced the germ cell number and led to spherospermia, interstitial glands vacuole, malalignment, and vacuolization of spermatogenic cells in mice testes. Testicular cells accumulated reactive oxygen species when the mice were intragastrically administrated with TiO₂ NPs. Superoxide dismutase activity decreased, and the malondialdehyde content increased in the TiO₂ NP-treated groups. Anatase TiO₂ NPs exerted potential toxic effects on male reproduction, so the widespread application of this kind of NP in food products needs to be regulated.