Chlorophyll a fluorescence of flag leaves in a super-high-yielding hybrid rice (Oryza sativa L.) LYPJ, and a traditional hybrid rice SY63 cultivar with lower grain yield, which were grown in the field, were investigated from emergence through senescence of flag leaves. As the flag leaf matured, there was an increasing trend in photosynthetic parameters such as quantum efficiency of primary photochemistry ([Formula: see text] Po) and efficiency of electron transport from PS II to PS I (Ψ Eo). The overall photosynthetic performance index (PIABS) was significantly higher in the high-yielding LYPJ compared to SY63 during the entire reproductive stage of the plant, the same to MDA content. However, [Formula: see text] Po(=F V/F M), an indicator of the primary photochemistry of the flag leaf, did not display significant changes with leaf age and was not significantly different between the two cultivars, suggesting that PIABS is a more sensitive parameter than [Formula: see text] Po (=F V/F M) during leaf age for distinguishing between cultivars differing in yield.
In order to study effects of enhanced Ultraviolet-B ( 280nm-320nm) radiation on the cell mitosis, mature embryos of wheat as explant were cultured in the Murashige and Skoog (MS) medium with different concentration of 2,4-D and 6-BA . The results indicated the inducing rate of the mature embryos from wheat on the MS with 2, 4-D 1.0 mg/L was higher and the callus was better than on the other Culture medium. The chromosomal mutation and mitosis of the callus in wheat were studied under the condition of the enhanced UV-B radiation. The results showed that enhanced UV-B radiation inhibited the cell division of callus in wheat, several types of chromosomal aberration such as micronucleus, multi-nucleus, nuclear aberration occurred during the interphase, which may be the results of UV-B inhabiting the DNA replication of the cell to lead to the cell DNA mutation and form the pyrimidine dimer.
The green development of coastal urban agglomerations, which are strategic core areas of national economic growth in China, has become a major focus of both academics and government agencies. In this paper, China's coastal urban agglomeration is taken as the research area, aiming at the serious air pollution problem of coastal urban agglomeration, geographic information system (ArcGIS10.2) spatial analysis and the spatial Dubin model were applied to National Aeronautics and Space Administration atmospheric remote sensing image inversion fine particulate matter (PM 2.5) data from 2010-2016 to reveal the temporal and spatial evolution characteristics and Influence mechanism of PM 2.5 in China's coastal urban agglomerations, with a view to providing a reference value for coordinating air pollution in the coastal cities of the world. From 2010-2016, the PM 2.5 concentration in China's coastal urban agglomerations decreased as a whole, and large spatial differences in PM 2.5 concentration were observed in China's coastal urban agglomerations; the core highpollution areas were the Beijing-Tianjin-Hebei, Shandong Peninsula, and Yangtze River Delta urban agglomerations. Large spatial differences in PM 2.5 concentration were also observed within individual urban agglomerations, with higher PM 2.5 concentrations found in the northern parts of the urban agglomerations. Significant spatial autocorrelation and spatial heterogeneity were observed among PM 2.5-polluted cities in China's coastal urban agglomerations. The northern coastal urban agglomerations formed a relatively stable and continuous high-pollution zone. The spatial Dubin model was used to analyze the driving factors of PM 2.5 pollution in coastal urban agglomerations. Together, meteorological, socioeconomic, pollution source, and ecological factors affected the spatial characteristics of PM 2.5 pollution during the study period, and the overall effect was a mixed effect with significant spatial variation. Among them, meteorological factors were the greatest driver of PM 2.5 pollution. In the short term, the rapid increase in population density, industrial emissions, industrial energy consumption, and total traffic emissions were the important driving factors of PM 2.5 pollution in the coastal urban agglomerations of China.
Land ecological security is the core of regional coordinated economic development and land ecological security planning. In this paper, with Shenzhen as the research area, 28 evaluation indicators were selected from 5 dimensions based on the DPSIR model to construct an indicator system for land ecological security evaluation, so as to evaluate the land ecological security status in the research area from 2009 to 2019. Based on the TOPSIS evaluation model, regional levels were determined, and finally the GM (1,1) model was adopted to scientifically predict the land ecological security system of Shenzhen from 2020 to 2025. The results showed that: (1) from the perspective of the main influencing factors, the weight of 16 indicators of Shenzhen’s land ecological security exceeds 0.03, including the total output value of agriculture, forestry, animal husbandry and fishery (D5) and Engel coefficient (I4). These factors are the main factors that have led to the deterioration of land ecological security in Shenzhen in the past decade; (2) comprehensive situation analysis revealed that from 2009 to 2019, the level of land ecological security in Shenzhen exhibited an increasing trend overall, but the land ecological security in Shenzhen still needs to be greatly improved; (3) regarding various subsystems, from 2009 to 2019, except the pressure subsystem which was in a downward trend, other subsystems showed a fluctuating and upward trend; (4) after modeling and calculation using the GM (1,1) model, it was concluded that most of the indicator factors are in a slow growing trend with the social and economic development of Shenzhen, but severe land ecological problem still exists. The research result is expected to provide a reference for the stable and sustainable development of society and economy and regional land ecosystem protection.
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