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Contribution of the vegetation layers in the nitrous oxide emission from Alpine Kobresia humulis Serg. meadow ecosystem on the Tibetan Plateau

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Du Y. , Cao G. , Deng Y. , Sun G. , Cui X.

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nr 1

EN

Nitrous oxide (N₂O) was one of the major atmospheric greenhouse gases. Its budget was poorly understood in alpine meadow, a dominant vegetation type on the Tibetan Plateau. To characterize a Kobresia humilis meadow on the plateau, N₂O emission rates were monitored from June 2003 to June 2006 in the study area located at 3280 m a.s.l. Nine plots with 1 m × 1 m each were divided into three treatments, i.e. intact herbaceous community (HCK), removal of aboveground plant biomass (CBK), and removal of both above and belowground plant biomass (BSK), to estimate contribution of plants, r hizosphere and bulk soil to the total N₂O emission. N₂O emission from plant aboveground biomass was calculated by flux difference between HCK and CBK, denoted as F (HCK-CBK), from rhizosphere by F (CBK-BSK), and from bulk soil was the flux in BSK treatment. Static chambers (height 50 cm, area 0.5 × 0.5 m²) were used for gas collection. N₂O emission rate was significantly correlated with soil temperature at 5 cm depth in both HCK and BSK (P <0.001). Both treatments demonstrated a seasonal peak rate in growing season and minimum rate in dormancy period. The mean emission rates in the three years were 39.7±2.9 and 30.6±2.5 μg m⁻² h⁻¹ in HCK and BSK, respectively, with the former significantly higher than the latter (P <0.05). In CBK, however, the emission rate did not show consistent correlation with soil temperature, especially in growing season. Its three-year mean emission rate was 36.2±3.3 μg m⁻² h⁻¹. In the K. humilis meadow, bulk soil contributed much more than plants and rhizosphere. The mean emission rate was 3.5±2.9, 5.7±3.8, and 30.6±2.5 μg m⁻² h⁻¹ (P <0.001) from plants, rhizosphere and bulk soil, and these accounted for 9, 14 and 77%, separately. Our results implied that N₂O emission rate decreased little with grazing as indicated by the difference between HCK and CBK in K. humilis meadow (P <0.05). N₂O emission from alpine meadow could not be ignored in addressing regional greenhouse gases budget on the Tibetan Plateau, considering the vast area and much higher radiative forcing of N₂O.

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Morphology of two Eschaneustyla species (Ciliophora, Urostylida), with notes on morphogenesis of Eschaneustyla lugeri

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Deng Y. , Lu X. , Li J. , Ba S. , Paiva T. S.

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tom 57

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nr 2

3

Comparison of jasmine antioxidant system responses to different degrees and durations of shade

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Deng Y. , Jia X. , Sun X. , Liang L. , Su J.

Acta Physiologiae Plantarum

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2018

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tom 40

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nr 02

EN

Jasmine [Jasminum sambac (L.) Aiton] growth and development is affected by long-term shade. To determine the effects of short-term shade on jasmine physiology, the contents of soluble proteins, malondialdehyde (MDA) and antioxidative enzymes were comparatively investigated during 24 h (short-term, ST) and 7 days (medium-term, MT) of varying light regimes. The results showed that the protein content exhibited two peaks under ST treatment, and shade postponed the first peak 2 h later than full light. On the whole, protein synthesis was reduced by ST shade and induced by MT shade, whereas MDA content decreased during all shade treatments. Under ST shade, superoxide dismutase (SOD), peroxidase (POD) and ascorbate peroxidase (APX) activities were enhanced, but catalase (CAT) activity was repressed by limited irradiances. However, the antioxidant enzymes responded differently—SOD activity increased after 2 h of shading and then kept on a high level, whereas POD, APX and CAT activities increased mainly during the first hour and deceased subsequently. Under MT shade, these antioxidative enzymes responded differently to varying light irradiances, too. In general, POD and CAT activities were repressed, SOD activity was induced by weak (50% irradiance) shade and reduced by moderate (20% irradiance) and severe (5% irradiance) shade. APX activity was rather more complicated and irregularly responded to different degrees and durations of shade, meaning it might not be the main enzyme to remove ROS in jasmine plants under shading condition. The increase protein content with prolonged shade represents the sound adaptive ability of jasmine plants to restricted irradiances. At the same time, rapid changes in proteins and antioxidants reflect the efficient metabolic apparatus of the plant in response to shade. Therefore, the jasmine cultivar is shade tolerant. Furthermore, shade could help the plants protect themselves from full light, and some degrees of shade were beneficial to their antioxidant system. However, severe shade (5% of irradiance) is only suggested for a few hours to protect the plants at solar noon. If the plants are continuously shaded for 3–7 days, weak (20%) to moderate (50%) level of irradiance should be applied.

4

Foliar responses of Abie fargesii Franch. To altitude in the Taibai Mts, China

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Xu P. , Zhang X. , Zhao C. , Chen L. , Gao X. , Yao B. , Deng J. , Deng Y.

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2014

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tom Vol. 62, nr 3

479--492

EN

Physiological and ecological adaptations of altitudinal gradients reveal alpine plants’ ecological and evolutionary responses to environmental changes. Here we quantitatively investigated the variation in the foliar physiological and morphological traits of alpine tree species (Abies fargesii) along the altitudinal gradient in the Taibai Mountains, China. We collected the needle samples of Taibai fir (A. fargesii) from seven sites at altitudes of 2550, 2650, 2750, 2850, 2950, 3050 and 3150 m, respectively, and measured the 12 foliar physiological and morphological traits. Each set of needle sample (100 needles) was randomly selected from the upper- third of A. fargesii canopies. The results showed that leaf mass per unit area (LMA), stable carbon isotope composition (δ13C), stomatal rows (SR), leaf carbon concentration per unit area (Carea), leaf nitrogen concentration per unit leaf mass (Nmass) and area (Narea) linearly increase significantly while stomatal density (SD), number of stomata per unit nitrogen concentration (St/N) and per unit leaf mass (St/LM) decrease with the altitudes raise. Moreover, all measured traits presented both strong correlations and significantly linear relationships with the main climate factors such as the mean temperature, rainfall and relative humidity during the growing season as well as the altitudes, except for leaf free water concentration (LWC), leaf carbon concentration per unit leaf mass (Cmass) and C: N ratio. The patterns of foliar traits in response to altitudes imply that the alpine plants need higher cost (e.g. higher nutrient concentration) to adapt to the harsher environments along altitudinal gradient. Moreover, our results show that the variation patterns of the leaf traits for A. fargesii plants should be driven by the interactions of multi-climate factors because the abiotic factors that directly influence the growth of plants covary with the increasing altitudes.

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Ca2plus/Hplus exchange in the plasma membrane of Arabidopsis thaliana leaves

72%

Zhai J. , Xu H. , Cong X. , Deng Y. , Xia Z. , Huang X. , Hao G. , Jiang X.

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nr 01

EN

A large number of plant Ca2+/H+ exchangers have been identified in endomembranes, but far fewer have been studied for Ca2+/H+ exchange in plasma membrane so far. To investigate the Ca2+/H+ exchange in plasma membrane here, inside-out plasma membrane vesicles were isolated from Arabidopsis thaliana leaves using aqueous two-phase partitioning method. Ca2+/H+ exchange in plasma membrane vesicles was measured by Ca2+-dependent dissipation of a pre-established pH gradient. The results showed that transport mediated by the Ca2+/H+ exchange was optimal at pH 7.0, and displayed transport specificity for Ca2+ with saturation kinetics at Km = 47 lM. Sulfate and vanadate inhibited pH gradient across vesicles and decreased the Ca2+-dependent transport of H+ out of vesicles significantly. When the electrical potential across plasma membrane was dissipated with valinomycin and potassium, the rate of Ca2+/H+ exchange increased comparing to control without valinomycin effect, suggesting that the Ca2+/H+ exchange generated a membrane potential (interior negative), i.e. that the stoichiometric ratio for the exchange is greater than 2H+:Ca2+. Eosin Y, a Ca2+-ATPase inhibitor, drastically inhibited Ca2+/H+ exchange in plasma membrane as it does for the purified Ca2+-ATPase in proteoliposomes, indicating that measured Ca2+/H+ exchange activity is mainly due to a plasma membrane Ca2+ pump. These suggest that calcium (Ca2+) is transported out of Arabidopsis cells mainly through a Ca2+-ATPase-mediated Ca2+/H+ exchange system that is driven by the proton-motive force from the plasma membrane H+-ATPase.

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Physiological responses and tolerance of flax (Linum usitatissimum L.) to lead stress

58%

Pan G. , Zhao L. , Li J. , Huang S. , Tang H. , Chang L. , Dai Z. , Chen A. , Li D. , Li Z. , Deng Y.

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tom 42

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nr 07