UV-B增加对玉米光合作用日变化的影响

为了探讨地表紫外辐射增强对干旱、半干旱地区农作物生理及生态系统的影响,在宁夏永宁县进行了UV-B增加对玉米光合作用影响的试验研究.试验设置了自然光照组(CK)、R1组(增加0.5W/m 2强度的UV-B)和R2组(增加1.0W/m 2强度的UV-B)3种UV-B照射强度,从玉米三叶期开始每天9:00-17:00照射8h;于2004年5月19日7:00-20:00时,用便携式光合作用测定系统测定玉米叶片净光合速率、蒸腾速率、气孔导度、光合有效辐射、细胞间隙和环境CO2浓度等若干植物生理因子的日变化,并计算了玉米的水分利用效率.结果表明:R1组处理的玉米净光合速率、蒸腾速率、气孔导度和水分利用效率比对照分别下降了57.1%、15.6%、11.0%和49.3%;R2组处理下降了67.5%、18.8%、24.8%和60.6%;地表紫外辐射的增强,对干旱、半干旱地区玉米叶片的净光合速率、蒸腾速率、水分利用效率均随着UV-B的增强而下降,紫外辐射的增强将使该地区玉米产量降低,水资源需求加大.     

镧对汞胁迫下豌豆(Pisum sativum L)幼苗生长及汞积累的影响

以培养 5d的豌豆 (PisumsativumL)幼苗为实验材料 ,研究了 10和 5 0mg·L- 1 的Hg胁迫下不同浓度La对豌豆幼苗生长的生理效应 ,测定并分析了La对Hg胁迫下豌豆幼苗根和叶细胞中Hg吸收及积累的影响。结果表明 ,合适浓度 (≤ 0 .0 10mg·L- 1 La)的La能在一定程度上缓解Hg胁迫所导致的叶绿体叶绿素和可溶性蛋白含量、光合速率和叶绿体Mg2 ATPase、光合膜电子传递链活性及PSII活性的降低 ,减轻Hg胁迫对光合膜室温下吸收光谱和荧光光谱的影响 ;能有效增强或保护Hg胁迫下叶片细胞总抗氧化能力 ,降低细胞内Hg胁迫诱导超氧阴离子(·O2 - )产生的速率和膜脂过氧化产物 (MDA)的积累 ,延缓膜透性的增加。La对 10mg·L- 1 Hg胁迫的缓解能力较强 ,而对 5 0mg·L- 1 Hg的缓解效果较弱。最佳作用浓度为 0 .0 10mg·L- 1 。该浓度的La能有效的减少细胞对Hg的吸收和积累 ,特别是增加根细胞壁对Hg的束缚效应。超过一定浓度范围的La(≥ 0 .0 3 0mg·L- 1 )则加剧Hg的毒害作用。     

Enhanced Solar‐to‐Hydrogen Generation with Broadband Epsilon‐Near‐Zero Nanostructured Photocatalysts

The direct conversion of solar energy into fuels or feedstock is an attractive approach to address increasing demand of renewable energy sources. Photocatalytic systems relying on the direct photoexcitation of metals have been explored to this end, a strategy that exploits the decay of plasmonic resonances into hot carriers. An efficient hot carrier generation and collection requires, ideally, their generation to be enclosed within few tens of nanometers at the metal interface, but it is challenging to achieve this across the broadband solar spectrum. Here the authors demonstrate a new photocatalyst for hydrogen evolution based on metal epsilon‐near‐zero metamaterials. The authors have designed these to achieve broadband strong light confinement at the metal interface across the entire solar spectrum. Using electron energy loss spectroscopy, the authors prove that hot carriers are generated in a broadband fashion within 10 nm in this system. The resulting photocatalyst achieves a hydrogen production rate of 9.5 µmol h^?1 cm^?2 that exceeds, by a factor of 3.2, that of the best previously reported plasmonic‐based photocatalysts for the dissociation of H₂ with 50 h stable operation.     

草甘膦对大豆超微结构及光合指标影响的研究

利用透射电镜和扫描电镜,研究转基因抗草甘膦大豆和非抗草甘膦大豆东农42喷施草甘膦后大豆光合器官叶片的超微结构变化,并结合叶绿素含量、光合速率的测定,对比分析了抗草甘膦大豆和东农42在结构及生理功能上对草甘膦的表现及结构与功能变化的关系.研究结果表明抗草甘膦大豆对草甘膦的胁迫可以看作是一种适应.它首先经过一个损伤期,然后进入修复期,最终到基本恢复,表现出对草甘膦的抗性.而东农42的光合系统及光合功能则被草甘膦所彻底破坏.本文对其原因进行探究,以期为转基因作物育种尤其是超微结构方面的研究及草甘膦作用机理的研究有一定帮助.     

营养液低氧胁迫对网纹甜瓜幼苗生长和生理代谢影响

在水培条件下,研究了营养液低氧胁迫对网纹甜瓜幼苗生长指标、光合作用和生理代谢物质含量的影响。结果表明,低氧处理显著抑制了幼苗的生长,鲜重、干重等生长指标和叶绿素含量、净光合速率等光合指标均显著降低;低氧胁迫诱导幼苗不定根和根系活力显著增加;低氧胁迫下幼苗MDA、H2O2含量显著增加,但是幼苗体内可溶性糖、氨基酸、游离态多胺和热稳定蛋白含量也显著提高。与西域一号相比,星光生长较快,较高的光合速率、根系活力和生理代谢物质含量,缓解了低氧胁迫对幼苗的伤害。     

利用叶绿素荧光参数筛选抗盐菊芋品种的初步研究

对砂培菊芋幼苗试验材料("大丰"品种(耐盐性较强)和"无锡"品种(耐盐性较弱))分别进行了不同 NaCl 浓度(0、50、100、150mmol/L)的胁迫处理,利用叶绿素荧光测定技术,对"大丰"和"无锡"的生物量、叶绿素含量、叶绿素荧光参数和净光合速率(Pn)的变化进行了研究.结果表明,NaCl 胁迫显著影响植株生物量、叶片叶绿素含量、叶绿素荧光参数和Pn,但"大丰"幼苗生长受盐胁迫的影响小于"无锡",其光合机构受盐胁迫的伤害程度小于"无锡";叶片叶绿素含量的下降与荧光参数和Pn的变化呈极显著相关关系,叶片的叶绿素荧光参数和Pn的显著变化同步于叶绿素含量的下降.因此,叶绿素荧光参数可作为菊芋抗盐品种筛选的诊断指标之一.     

Antenna Protein Clustering In Vitro Unveiled by Fluorescence Correlation Spectroscopy

Antenna protein aggregation is one of the principal mechanisms considered effective in protecting phototrophs against high light damage. Commonly, it is induced, in vitro, by decreasing detergent concentration and pH of a solution of purified antennas; the resulting reduction in fluorescence emission is considered to be representative of non-photochemical quenching in vivo. However, little is known about the actual size and organization of antenna particles formed by this means, and hence the physiological relevance of this experimental approach is questionable. Here, a quasi-single molecule method, fluorescence correlation spectroscopy (FCS), was applied during in vitro quenching of LHCII trimers from higher plants for a parallel estimation of particle size, fluorescence, and antenna cluster homogeneity in a single measurement. FCS revealed that, below detergent critical micelle concentration, low pH promoted the formation of large protein oligomers of sizes up to micrometers, and therefore is apparently incompatible with thylakoid membranes. In contrast, LHCII clusters formed at high pH were smaller and homogenous, and yet still capable of efficient quenching. The results altogether set the physiological validity limits of in vitro quenching experiments. Our data also support the idea that the small, moderately quenching LHCII oligomers found at high pH could be relevant with respect to non-photochemical quenching in vivo.     

Enhancing Biosynthesis and Manipulating Flux in Whole Cells with Abiotic Catalysis

Metabolic engineering uses genetic strategies to drive flux through desired pathways. Recent work with electrochemical, photochemical, and chemocatalytic setups has revealed that these systems can also expand metabolic pathways and manipulate flux in whole cells. Electrochemical systems add or remove electrons from metabolic pathways to direct flux to more- or less-reduced products. Photochemical systems act as synthetic light-harvesting complexes and yield artificial photosynthetic organisms. Biocompatible chemocatalysis increases product scope, streamlines syntheses, and yields single-flask processes to deliver products that would be challenging to synthesize through biosynthetic means alone. Here, we exclusively highlight systems that combine abiotic systems with living whole cells, taking particular note of strategies that enable the merger of these typically disparate systems.     

Macrokinetics and mathematical modelling of quinone reduction by cyanobacteria

The kinetics of the reduction of externally added 2-hydroxy-1,4-naphthoquinone by blue-green algae of the strains Anabaena PCC 7120 and Anacystis nidulans PCC 6301 were studied in aqueous cell suspensions by electrochemical monitoring of the concentration of the formed hydroquinone. This reaction is of potential interest for bioelectrochemical fuel cells. The experimental curves obtained could be interpreted by a model that takes into account that both substrate and product have to be transported through the microbial cell walls and that the conversion reaction takes place with firstorder kinetics within the microbial cells. No clear evidence was found for the involvement of photosynthesis. It is suggested that the reduction of the quinone probably occurs via the enzyme-catalyzed oxidation of endogenous storage product(s), presumably glycogen.