光照条件对土壤—植物系统氮素状况影响的研究

应用盆栽试验 ,通过调节不同光照强度并控制其它条件相互一致的条件下 ,研究了光照条件对土壤 植物系统N素状况以及作物 (莴笋 )产量的影响 .结果表明 ,光照强度的改变会引起作物生长状况的相应变化 ,同时也导致土壤N素 (NH 4 N、NO-3 N)状况、作物吸收N量以及作物对N素吸收速度等的改变 .在试验所处的光照强度范围内 ,光照较强时 ,则作物吸收N素的速度较快、吸收N量增加 ,且产量高 ,但土壤中相应的N素含量(NH 4 N、NO-3 N)则只能维持在相对较低的水平 ;光照较弱时 ,则出现与此相反的情况 .     

The influence of light and different ATP concentrations on cell aggregation in cyclic AMP sensitive and insensitive species of the cellular slime molds

The influence of light and different concentrations of ATP on cell aggregation in cyclic AMP sensitive (Dictyostelium mucoroides, D. purpureum) and cyclic AMP insensitive species (Polysphondylium violaceum, P. pallidum, D. lacteum) of the cellular slime molds was observed in small and in large amoebal populations.Both light and ATP (optimal concentration:10^-5M) accelerated cell aggregation and increased the number of aggregating centers in large populations. For cyclic AMP sensitive species the effect of ATP in large populations was more pronounced than for the species that do not react to cyclic AMP.A possible explanation for the similar effect of light and ATP has been discussed.     

Light cytokinin interactions in shoot formation in epicotyl cuttings of Troyer citrange cultured in vitro

Ilumination did not affect the pathway of shoot regeneration at the cut edges of epicotyl explants of Troyer citrange (Moreira-Dias et al. 2000, 2001), but signigficantly affected the number of developed shoots and the response to exogenous cytokinins. Shoot regeneration at the apical end occurred through a direct organogenic pathway without callus formation. For explants incubated in the light, this regeneration did not require cytokinin addendum, but the number of shoots formed was significantly increased by benzyl adenine, but not by zeatin or kinetin. Incubation in the dark almost suppressed shoot formation at the apical end. The addition of benzyl adenine or kinetin, but not of zeatin, restored shoot formation in the dark to the value obtained in the light. At the basal end of the explants shoot regeneration occurred through an indirect organogenic pathway after the formation of a primary callus. In explants incubated in the light, callus formation and shoot growth was supported by a low (0.5–1 mg l⁻¹) benzyl adenine concentration and by zeatin. Kinetin did not support callus growth. Shoot formation was higher in the presence of benzyl adenine (0.5–1 mg l⁻¹) than of zeatin, but was inhibited by a high (5 mg l⁻¹) benzyl adenine concentration. Incubation in the dark increased callus growth and shoot formation at the basal cut as compared to explants incubated in the light. The three cytokinins tested supported callus growth and shoot formation in the dark, zeatin being the most effective and kinetin the least. In terms of number of shoots developed, the optimum cytokinin addendum depended on the pathway of organogenesis and the conditions of incubation. The maximum number of shoots developed at the apical end was obtained when the incubation was performed in the light in the presence of benzyl adenine. At the basal end, the optimal conditions were incubation in the dark in the presence of zeatin. It was not always possible to define an optimal cytokinin concentration as the curve concentration/response varied from experiment to experiment, which seemed unrelated to the endogenous cytokinin concentration in the explants.     

Multilayer Mounting for Long-term Light Sheet Microscopy of Zebrafish

Light sheet microscopy is the ideal imaging technique to study zebrafish embryonic development. Due to minimal photo-toxicity and bleaching, it is particularly suited for long-term time-lapse imaging over many hours up to several days. However, an appropriate sample mounting strategy is needed that offers both confinement and normal development of the sample. Multilayer mounting, a new embedding technique using low-concentration agarose in optically clear tubes, now overcomes this limitation and unleashes the full potential of light sheet microscopy for real-time developmental biology.     

槲蕨配子体发育影响因素的初步研究

主要研究了光照、温度、激素和pH值对槲蕨配子体发育的影响。结果表明：光照强度为2500-35001x、温度为25℃以及pH值为7．0～7．5时最适于槲蕨配子体的生长发育;激素6-BA和NAA浓度为0．5～1．0mg／L时有利于槲蕨配子体的增殖和增长。     

光照对光生物反应器中微藻高密度光自养培养的影响

光生物反应器是实现微藻高密度培养的重要装置,其设计的关键技术之一是选择合适的光照方式。根据国内外近十年来的相关研究成果,重点介绍了入射光性质(光源、光强、光质和光暗循环)和光能分布对微藻生长的影响,评述了用于微藻高密度培养的光照技术,展望了进一步的研究方向,为高效光生物反应器的设计和优化提供参考。     

Variations in chloroplast nucleoid number during the cell cycle in the algaScenedesmus quadricauda grown under different light conditions

Summary Synchronous cultures of the green algaScenedesmus quadricauda were grown at different mean irradiances (ranging from 15 Wm^–2 to 130Wm^–2). At each irradiance, the algae were exposed to illumination regimes which differed in light duration and dark intervals (222 to 240 hours). The cells from these cultures were sampled during their cycles, stained with DAPI and the number of nuclei and chloroplast nucleoids estimated.The nucleoids divided semisynchronously in steps which represented doublings in their number. For each doubling a constant amount of light energy (defined as the product of irradiance and light duration) had to be converted by the cells to become committed to this division. The times to the start of the nucleoid divisions were therefore inversely proportional to the irradiances applied and the final number of nucleoids was proportional to the light duration.Temporal relationships between nuclear and nucleoid divisions were also light dependent. Shortage of light energy caused delay in nucleoid division. The cell division rate was higher than the rate of nucleoid division and consequently, the cells tended to decrease their nucleoid number with decreasing irradiance. With increasing irradiance the start of nucleoid division was gradually shifted toward the beginning of the cell cycle. The rate of nucleoid division exceeded the rate of nuclear and cellular division, thus with increasing irradiance cells with increasing numbers of nucleoids were formed.Abbreviations DAPI 46-diamidino-2-phenylindole - pt-DNA chloroplast DNA     

光照条件对土壤-植物系统氮素状况影响的研究

应用盆栽试验,通过调节不同光照强度并控制其它条件相互一致的条件下,研究了光照条件对土壤植物系统N素状况以及作物(莴笋)产量的影响.结果表明,光照强度的改变会引起作物生长状况的相应变化,同时也导致土壤N素(NH₄⁺-N、NO₃^--N)状况、作物吸收N量以及作物对N素吸收速度等的改变.在试验所处的光照强度范围内,光照较强时,则作物吸收N素的速度较快、吸收N量增加,且产量高,但土壤中相应的N素含量(NH₄⁺-N、NO₃^--N)则只能维持在相对较低的水平;光照较弱时,则出现与此相反的情况.     

丁草胺在不同类型水中的光化学降解

研究了除草剂丁草胺在氙灯、高压汞灯光照下的光解动态。结果表明,丁草胺在氙灯光照作用下,其光解速率为纯水>河水>塘水>稻田水;丁草胺在氙灯光源下的光解速度比高压汞灯下低;其光解率与浓度(剂量)呈反相关;充N₂脱O₂使丁草胺的光解速度减缓。