温州蜜柑叶片光合作用的光抑制

中午或模拟中午强光处理后,温州蜜柑叶片表观量子效率（ＡＱＹ）、最大荧光（Ｆｍ）、初始荧光（Ｆｏ）、可变荧光（Ｆｖ）、光化学效率（Ｆｖ／Ｆｍ）、光化学猝灭系数（ｑｐ）和电子传递速率（ＥＴＲ）下降。经强光处理后,虽然叶片的净光合速率（Ｐｎ）和光呼吸（Ｐｒ）均下降,但由于Ｐｒ降低幅度小于Ｐｎ,使Ｐｒ／Ｐｎ比值升高。     

用种、施氮水平对黔糖4号生育和经济性状的影响

为达到节本增效目的,探讨了黔糖4号合理用种量和施氮水平。2007-2009年在坡地针对该品种用种量和尿素施用各设置5个处理:分别为6.0×104芽/hm2、7.5×104芽/hm2、9.0×104芽/hm2、1.05×105芽/hm2和1.2×105芽/hm2(CK);0 kg/hm2、150 kg/hm2、300 kg/hm2、450 kg/hm2、600 kg/hm2(CK)。结果表明:各用种间植株生育、糖分和产量相似,用种7.5×104芽/hm2比CK增产5.7%,增收852元/hm2;产量随尿素用量增大而增加,与对照相比,0 kg/hm2和150 kg/hm2处理减产35.2%和20.0%,其他处理产量表现相似,450 kg/hm2处理比CK减少尿素用量150.0 kg/hm2,降低氮肥成本25.0%,增收节支263元/hm2。该结果对黔糖4号生产上合理用种和尿素施用,降低生产成本,提高种植效益具有指导作用。     

Exogenous ascorbic acid scarcely ameliorates inhibition of photosynthesis in rice leaves by O3

The role of ascorbic acid on acute O₃-induced inhibition of photosynthesis in solution-cultured paddy rice was evaluated. As pre-treatment, ascorbic acid (0, 5, and 10 mM) was added to the culture solution for 5 d before 5 h of O₃ exposure (0, .1, and .3 cm³ m^?3 O₃) during daytime. O₃ decreased photosynthesis-related parameters, total ascorbic acid content, and the redox state (RDS) of ascorbic acid. Ascorbic acid treatment enhanced the total ascorbic acid contents and its RDS level of rice leaves, but scarcely ameliorated O₃-induced inhibition of photosynthesis-related parameters. Inhibition of net photosynthetic rate (P_N) by O₃ was slightly ameliorated by exogenous ascorbic acid only at 1 d after O₃ exposure. These results indicate that ascorbic acid is a component of protection from O₃ injury but has a marginal role in the acute inhibition of P_N by O₃ in rice leaves.     

Stereochemistry of Complex Marine Natural Products by Quantum Mechanical Calculations of NMR Chemical Shifts: Solvent and Conformational Effects on Okadaic Acid

Marine organisms are an increasingly important source of novel metabolites, some of which have already inspired or become new drugs. In addition, many of these molecules show a high degree of novelty from a structural and/or pharmacological point of view. Structure determination is generally achieved by the use of a variety of spectroscopic methods, among which NMR (nuclear magnetic resonance) plays a major role and determination of the stereochemical relationships within every new molecule is generally the most challenging part in structural determination. In this communication, we have chosen okadaic acid as a model compound to perform a computational chemistry study to predict ¹H and ¹³C NMR chemical shifts. The effect of two different solvents and conformation on the ability of DFT (density functional theory) calculations to predict the correct stereoisomer has been studied.     

Jasmonic Acid Differentially Affects Growth, Ion Uptake and Abscisic Acid Concentration in Salt-tolerant and Salt-sensitive Rice Cultivars

Phytohormones play critical roles in regulating plant responses to stress. Here, we investigated the effects of salt stress and stress recovery by applying jasmonate to the two different rice (Oryza sativa L.) cultivars Dongjinchalbyeo (DJC, salt-tolerant) and Dongjinbyeo (DJ, salt-sensitive). Salt stress remarkably decreased the root length of plants even at low NaCl concentration (20 mm ). Salt stress led to a sharp increase in the concentrations of abscisic acid (ABA) in 20 and 40 mm NaCl, when compared with the control values. The concentrations of ABA in the salt-tolerant cultivar DJC plants progressively increased with increasing NaCl levels, whereas in the salt-sensitive cultivar DJ, they sharply decreased in all three parts of rice plants at 80 mm NaCl treatment. The decrease of jasmonic acid (JA) concentrations in salt-tolerant cultivar DJC was lesser than in the salt-sensitive cultivar DJ plants in the shoot. Post-application in the stressed plants with 30 μm JA at 24 and 48 h after NaCl treatment, recovered salt inhibition on dry mass production more effectively than application of JA at 48 and 24 h before salt stress, and during salt stress simultaneously. The uptake of Na decreased especially in the salt-sensitive cultivar DJ plants, whereas there was an increase in Ca and Mg levels and slight increase of K by JA application. Leaf water potential, leaf photosynthetic rate, and maximum quantum yield of photosystem II (PSII) also remarkably recovered when 30 μm JA was applied 24 h after the salt stress compared with the 40 mm NaCl-treated plants. These results clearly indicate that post-application with exogenous JA can ameliorate salt-stressed rice seedlings, especially the salt-sensitive cultivar rather than the salt-tolerant cultivar. This may change the balance of other endogenous plant hormones.     

半导体物理学的发展及启示

半导体物理学是凝聚态物理学的一个重要分支,也是现代微电子器件工艺学的理论核心。研究和探讨半导体物理学的发展规律,对于掌握半导体科学技术今后的发展趋势具有重要意义。文章着重回顾与评述了晶体管的发明过程、半导体超晶格物理的发展以及半导体纳米量子器件的研究进展,展望了新型半导体纳米材料的发展前景,并以半导体物理学的发展历程为依据剖析了其发展规律和特点     

Photosynthetic and antioxidant responses of Mexican lime (Citrus aurantifolia) plants to Citrus tristeza virus infection

The effect of Citrus tristeza virus (CTV) infection on photosynthetic activity and antioxidant metabolism was analysed in plants of the highly susceptible citrus genotype Mexican lime (Citrus aurantifolia). Two virus isolates differing in their virulence (the severe T318 and the mild T385) were used in the experiments. CTV infection caused a reduction in photosynthetic capacity in infected plants. This limitation was mainly due to a reduction in the carboxylative efficiency whereas the limitation of CO₂ diffusion through the stoma had lower impact. The virus did not damage the antennae and did not reduce the efficiency of light harvesting complexes. Oxidative damage occurred in infected plants, as evidenced by the increase in malondialdehyde levels. Indeed, CTV infection caused an increase in ascorbate peroxidase activity in new shoots developed in infected plants during the 2 years of the experiment. Data suggest that the H₂O₂ removal machinery was not damaged as a result of stress but the defence mechanism was overwhelmed with time due to the continuing pressure of biotic stress.     

柱形量子点的能级与电子结构

在EMA(Effective Mass Approximation)的理论框架下,研究了柱形量子点的能级和电子结构.计算了柱形量子点的激发态(m=1)基态(m=0)能量,并作出柱形量子点能量图;还计算了柱形量子点的电子概率密度,并作出电子概率分布图.     

自由落体的双波函数研究

本文完整地给出了自由落体的双波函数量子论，讨论了刚性边界对落体的非局域性影响，研究了非厄密算符（－ｉｈｄ／ｄｘ）＾３｛ｘ∈［０，∞］｝的意义，本文的结果不仅再一次说明了双波函数量子论的优美之处，即经典力学结果是双波函数理论的经典极限，通常的量子力学结果是统计系统中的统计结果，还表明了双波函数量子论对算符厄密性的要求比通常量子力学对它的要求要低。     

应变层超晶格（ZnSe）n／（ZnS）m的激子结合能

在双量子阱近似下,用变分法计算了（ＺｎＳｅ）ｎ／（ＺｎＳ）ｍ应变层超晶格的激子结合能,为光致发光谱和光致发光振荡谱的分析提供了依据和参考数据。