光强对砂仁叶片光合作用光抑制及热耗散的影响

通过测定不同光照条件下砂仁 (AmomumvillosumLour.)叶片气体交换和叶绿素荧光参数 ,探讨了光对其光合机构及其光破坏防御的影响。试验期间 ,上午 11:0 0之前有雾 ,光强较弱。上午砂仁阳生叶净光合速率 (Pn)与下午 (6 .5 3μmol·m-2 ·s-1)相似 ,高于阴生叶 (5 .94μmol·m-2 ·s-1) ,下午阴生叶Pn 高于上午 ,与阳生叶相似。下午砂仁叶片表观量子效率低于上午。其初始荧光 (Fo)、最大荧光 (Fm)、光系统Ⅱ (PSⅡ )最大光能转换效率 (Fv/Fm)、Fm/Fo 及PSⅡ的潜在效率 (Fv/Fo)随日光增强而降低 ,15 :0 0降至最低 ,表明光抑制逐渐加剧。之后随光强减弱这些叶绿素荧光参数升高 ,光抑制得到缓解。与此相反 ,非光化学猝灭系数 (qN)随光强的增加而升高 ,并一直维持在较高水平 ,表明依赖叶黄素循环的保护性反应逐渐增强。阳生叶的光抑制比阴生叶强烈 ,当日遮荫处理使光抑制缓解 ,但各处理间qN 差异不大 ,表明热耗散未受显著影响。结论 :弱光下砂仁叶片即发生光抑制 ,在不同光照下其光抑制的普遍发生 ,是依赖叶黄素循环的保护性反应 ,而非光破坏的结果 ;砂仁叶片叶黄素循环的启动不需过剩光能 ,不同光处理对其影响不大 ;砂仁对光的适应能力较强。     

THE DEPENDENCE OF CELL DIVISION IN CHLORELLA ON TEMPERATURE AND LIGHT INTENSITY

The effects of temperature and light on cell division were studied in synchronized suspensions of the high-temperature strain Chlorella 7–11–05. It was found that the time for incipient cell division, the progress in the process after it started, and the number of cells produced are influenced by temperature and light intensity. Within limits, cell division is generally favored by the increase in temperature. The increase in light intensity first favors cell division then, after the optimal light intensity is attained, a further increase in light intensity inhibits cell division. Observations are discussed in connection with the findings of other investigators. The limitations of cell division by temperature and light intensity are considered to be separate from the effects of these factors on growth.     

THE EFFECTS OF LIGHT INTENSITY ON THE ULTRASTRUCTURE OF CHLOROGLOEA FRITSCHII MITRA GROWN AT HIGH TEMPERATURE1,2,3,4

The effects of high and low light intensities on the ultrastructure of the large, single cells (designated as Stage IV cell types in the life cycle) of Chlorogloea fritschii grown at 45 C are described. The most noticeable difference between cells grown at 20–60 ft-c and at 700 ft-c is in the number and arrangement of the photosynthetic lamellae. In the former, the lamellae are in groups of 4–6 units, the component membranes of which are compact and, closely appressed. While the thylakoids are long, continuous, and frequently invaginated into the central cytoplasm to form concentric whorls, there is no evidence of swelling or separation to form vacuole-like structures. In contrast, in cells grown at 700 ft-c, the photosynthetic lamellae are fewer and fragmented, with the segments peripherally arranged dint frequently swollen and vesiculate. There are also differences in the, nature of the sheath, in the amount of cyanophycean starch, and in the cytoplasmic inclusions. At 20–60 ft-c, the sheath, is extensive and. fibrillar; cyanophycean starch is abundant; and cytoplasmic inclusions (e.g., αand β-granules) arc sparse. At 700 ft-c the sheath is less extensive and frequently composed of short segments of fibrils and of particulate material; cyanophycean starch is sparse; and cytoplasmic inclusions are abundant.     

TEMPERATURE AND LIGHT INTENSITY EFFECTS ON GROWTH OF DICTYOSPHAERIUM PULCHELLUM

Growth rate and morphological characteristics of Dictyosphaerium pulchcllum were observed from populations maintained at 20 and 25 C under light intensities varying from 100 to 1200 ft-c. Growth rates, expressed as the number of times the population doubled in chlorophyll content per day, were 0.57 (100 ft-c) and 1.71 (1200 ft-c) at 20 C and 0.80 (100 ft-c) and 2.S7 (1200 ft-c) at 25 C. Cell size varied between 3.0 and 7.0 μ among all treatments at 20 C and mean cell size increased with an increase in light intensity. Agitation of asexually reproducing populations resulted in up to 95% of a population occurring in a unicellular form. The percentage of uni-cells was highest in vigorously agitated test tube cultures.     

光强和温度变化对曲浒苔光合作用的调节机制

实验针对曲浒苔(Ulva flexuosa)光合作用系统对光照与温度变化的响应进行分子水平探究, 从原初反应、电子传递、光合磷酸化到碳的固定等方面对曲浒苔光合作用响应机制进行解析。叶绿素合成基因在高温高光[30℃、400 μmol/(m2·s)]环境下表达下调。类胡萝卜素合成基因在低温高光[4℃、400 μmol/(m2·s)]环境下表达下调。电子传递链、CF₁F₀-ATP合酶等基因对温度和光照变化的适应能力较弱, 各实验组的相关基因表达量均呈现下调趋势。聚光复合体基因表达量上调。各实验组的光系统Ⅱ反应中心基因均下调, 锰稳定蛋白则普遍上调。不同C₄途径关键酶基因在各个环境中的变化趋势不一致。综合实验结果可以发现曲浒苔对于温度和光照变化具有一定的耐受度, 分析得出温度对曲浒苔光合作用基因的影响较大, 而且高温高光对曲浒苔的影响最显著。     

EFFECTS OF SALINITY AND LIGHT INTENSITY ON THE RESUMPTION OF PHOTOSYNTHESIS IN REHYDRATED CYANOBACTERIAL MATS FROM BAJA CALIFORNIA SUR,MEXICO1

Lyngbya mats in the intertidal of the Laguna Ojo de Liebre are metabolically active for only a few days every 2 weeks during spring tides, with environmental conditions varying greatly during these periods of hydration. Pulse amplitude modulated fluorometry (PAM) and oxygen measurements were used to measure photosynthetic activity during the first few hours after rehydration under various light intensities and salinities. Upon rehydration, a transitory maximum in respiratory activity (10–30 min) occurred before the resumption of photosynthesis, which could recover in about 2 h. Salinities outside the mats' natural range (35–50 psu) were detrimental to photosynthetic recovery. Both high (100 psu) and low (0–10 psu) salinities slowed recovery as well as lowered the overall photosynthetic yield. Photosynthesis was initiated earlier and recovered more rapidly with increasing light intensity. In addition, the positive effect of light on rates of recovery was disproportionately greater at lower salinities (10–25 psu) where high light (500 W·m^?2) counteracted the negative effects of low‐salt stress early in recovery. However, higher light intensities became photoinhibitory later in recovery (>2 h). Photosynthesis did not recover uniformly within the mat. Filaments deeper in the mat most likely recovered later than those near the surface due to high light attenuation. The ability of the mats to tolerate desiccation and take advantage of hydration periods even when conditions are suboptimal enables these mats to predominate in the intertidal environment.     

EFFECTS OF ENVIRONMENTAL FACTORS ON PHOTOSYNTHESIS PATTERNS IN PHAEODACTYLUM TRICORNUTUM (BACILLARIOPHYCEAE). I. EFFECT OF NITROGEN DEFICIENCY AND LIGHT INTENSITY1

Cultures of the marine diatom Phaeodactylum tricornutum Bohlin incorporated, a large proportion of the total fixed carbon (50% or more) into amino acids and amides during short periods of photo-assimilation of ¹⁴C-labelled carbon dioxide. Although increasing nitrogen limitation in a nitrate-limited chemostat had little significant effect on the proportion of C incorporated into amino acids and amides combined, it did affect the distribution of radioactivity within individual compounds of this group. In particular, increasing degrees of N deficiency reduced the proportion incorporated into amides to almost undetectable levels, reduced the proportion in alanine and increased the proportion in glutamic acid. Also, increasing N limitation decreased the relative synthesis of sugar phosphates and increased the proportion of C assimilated into intermediates of the tricarboxylic acid cycle. Reduced light intensity did not have any significant effect on the proportion of C incorporated into the total amino acids and amides, but did cause a decrease in the radioactivity     

pH对小球藻Chlorella sp. XQ-200419光合作用、生长和产油的影响

以一种生长快、油脂含量高的小球藻(Chlorella sp. XQ-200419)为实验材料, 利用测定净光合放氧速率的方法研究了pH对其光合作用的影响; 使用改良的BG-11培养基在微藻环形培养池模拟系统中进行分批培养, 培养周期为8d, 培养过程中使用 pH控制仪在线监测藻液的pH, 根据pH变化, 自动接通、关闭CO2通气管道, 将藻液pH分别控制在5.06.0, 7.08.0, 8.09.0, 9.010.0, 10.011.0内, 研究pH对生长速率、生物质面积产率、总脂含量和总脂面积产率的影响。主要结果如下: 藻液pH对小球藻Chlorella sp. XQ-200419光合放氧、生长速率、生物质产率、总脂含量和产率都有显著影响, 适宜的pH范围是7.09.0, 在此范围内, 光合放氧、生长速率、生物质产率、总脂含量和产率均保持较高水平, 且pH的影响不显著; pH低于7.0, 高于9.0, 其光合放氧、生长速率、生物质产率、总脂含量和产率都显著降低。这表明pH对小球藻Chlorella sp. XQ-200419光合作用的影响和对生长、产油的影响是一致的。pH 7.08.0, 小球藻的生物质平均面积产率和总脂平均面积产率都达到最大值, 分别是8.9 g/(m2d)和2269.5 mg/(m2d); 当藻液pH超过10.0, 生物质平均面积产率和总脂平均面积产率分别降低42.1%和60.0%。适合于小球藻生长的pH也有利于其积累油脂, 所以, pH对小球藻产油的影响是一种适宜模式, 而非胁迫模式。规模化培养小球藻Chlorella sp. XQ-200419, 通过补充CO2将藻液pH控制在7.09.0内, 可以获得高生物质产率和总脂产率。研究结果反映出pH对小球藻光合作用、生长和产油影响的规律, 也为规模化培养小球藻生产微藻油脂过程中合理控制藻液pH提供了依据。       

低平均光强下波动光对铜绿微囊藻生长的影响

为了研究波动光对藻类的影响,以典型水华藻种铜绿微囊藻Microcystis aeruginos为研究对象,运用了基于单片机系统的光强控制实验装置,开展了不同光照条件下铜绿微囊藻的生长研究。共设置了四种光照条件,分别为不同周期波动光强FL(Fluctuating Light)组(10min FL、1h FL和6h FL)和平均光强AL(Average Light)组。实验结果表明,在低平均光强下, 6h FL、1h FL和10min FL组铜绿微囊藻藻密度相对于AL组分别增加了28.3%(P<0.05)、18.2%(P<0.05)和7.7(P>0.05)。三组波动光强下铜绿微囊藻的比增长速率、Fv/Fm和r ETR均显著大于平均光强组(P<0.05),且随着波动光周期的增大,各指标也会显著增加(P<0.05),而热耗散NPQ平均值、单个细胞类胡萝卜素含量等指标与上述指标呈相反的规律并且差异显著(P<0.05)。结果也表明在低平均光强下,相比于恒定光照,铜绿微囊藻在波动光下能更好地调节自身光合作用机制去利用光能,且波动周期越大,铜绿微囊藻对光能利用效率越...     

高浓度CO_2对极大螺旋藻生长和光合作用的影响

以极大螺旋藻作为实验材料 ,研究了高CO2 浓度对极大螺旋藻的生长和光合作用效应 ,结果表明在高光强下 (40 0 μmolm- 2 s- 1 ) ,高浓度CO2 对其生长和光合作用有明显的影响 ,高浓度CO2 培养下 ,螺旋藻的比生长速率是低浓度CO2 培养的 1 2倍 ;而在低光强下 ,高浓度CO2 对其生长和光合作用无明显影响。两种不同CO2 浓度和光强下培养的极大螺旋藻 ,在不同的生长时期 ,分别测定其P -I曲线 ,结果表明低光强下培养的极大螺旋藻 ,在 5d、8d、1 1d ,两者的Ik、α值均无显著差异 ,Pmax在第 5d、1 1d差异不显著 ,但在第 8d有显著差异。而在高光强培养条件下 ,第 8、1 1d通高浓度CO2 培养的极大螺旋藻 ,其Pmax、α值明显大于通低浓度CO2 培养的极大螺旋藻 ,但两者在第 5d无明显差异。     

EFFECTS OF LIGHT ON THE DEOXYRIBONUCLEIC ACID FORMATION AND CELLULAR DIVISION IN CHLORELLA PROTOTHECOIDES

1. It has been demonstrated previously that when Chlorella protothecoidesis grown in a medium rich in glucose and poor in nitrogen source(urea), chlorophyll-less cells with markedly degenerated plastids—called "glucose-bleached" cells—are produced eitherin the light or in darkness. When the glucose-bleached cellsare incubated in a medium enriched with the nitrogen sourcebut without added glucose, normal green cells with fully organizedchloroplasts are obtained in the light, and pale green cellswith partially organized chloroplasts in darkness. During theseprocesses of chloroplast development in the glucose-bleachedcells, there occurs, after a certain lag period, an active DNAformation followed by a more or less synchronous cellular division.In the present study the effects of light on the DNA formationand cellular division were investigated in the presence of CMUor under aeration of CO²-free air to exclude the interveninginfluence of photosynthetic process.
2. It was revealed thatlight severely suppresses the DNA formationand cellular divisionof the glucose-bleached cells while enhancingremarkably theirgreening. The suppression was saturated atthe light intensityof about 1,000 lux. Blue light was mosteffective, being followedby green, yellow and red light inthe order of decreasing effectiveness.
3. Further experiments unveiled that light exerts two apparentlyopposing effects on the DNA formation depending upon the timeof application during the incubation of algal cells. When thealgal cells were illuminated only during the lag period beforethe active DNA synthesis, there occurred an enhancement of theDNA synthesis occurring during the subsequent dark incubation.When, on the other hand, the cells were transferred to the lightfrom darkness at or after the start of the DNA synthesis, itcaused an almost complete abolition of the subsequent synthesisof DNA in the algal cells. No such effects of light were observedwith RNA and protein (total)
4. These findings were discussedin relation to the process ofchlorophyll formation occurringconcurrently in the algal cells.

(Received August 10, 1967; )     

THE EFFECT OF ULTRAVIOLET LIGHT ON PHOTOSYNTHESIS

1. An unidentified unit in the mechanism of the photosynthesis of Chlorella pyrenoidosa is rendered inactive by the absorption of one quantum of ultraviolet light (2537 Å wave length). 2. The same irradiation has no effect on the normal respiration of Chlorella pyrenoidosa. Experiments have not yet been made on the respiration inhibitable by HCN. 3. No chemical change was detected in the chlorophyll extracted from irradiated cells.