Effect of chromium on photosystem 2 in the unicellular green alga, <Emphasis Type="Italic">Chlorella pyrenoidosa</Emphasis>

We investigated the effect of chromium (20–40 g m⁻³, 8–72 h) on the photosystem 2 (PS2) activities of Chlorella pyrenoidosa cells. By using chlorophyll fluorescence transients, thermoluminescence, oxygen polarography, and Western blot analysis for D1 protein we found that inhibition of PS2 can be accounted for by the enhanced photodestruction of the reaction centres in the cells cultivated in the presence of Cr(VI) at 25 °C in “white light” (18 W m⁻²). Hence photodestruction of D1 is caused by an enhanced oxidative stress and lipid peroxidation, as indicated by the appearance of a high-temperature thermoluminescence band.     

Promotion and inhibition by ethylene of chlorophyll degradation in orange fruits

The effect of ethylene concentration on chlorophyll destruction in orange (Citrus sinensis cV. Washington Navel) fruits was examined at 15 °C and 25 °C. The reflectance of the fruits at 680 nm was measured, and the results converted to chlorophyll concentrations through an empirically derived formula based on the Kubelka-Munk equation. In all ethylene treatments chlorophyll destruction was faster at 25 °C than at 15 °C and all ethylene concentrations tested increased the rate of loss at 25 °C. At 15 °C the highest rate of chlorophyll destruction was observed at 1 μl litre^-1 ethylene, while chlorophyll loss at 1250 μl litre^-1 was slower than in untreated fruits.     

Effects of Light on Chlorophyll Formation in Cultured Tobacco Cells I. Chlorophyll Accumulation and Phototransformation of Protochlorophyll(ide) in Callus Cells under Blue and Red light

A marked accumulation of chlorophyll was observed in calluscells of Nicotiana glutinosa when they were grown under bluelight, while under strong red light no chlorophyll accumulated.This blue light effect saturated at an intensity of about 500mW.m^–2. The effects of white, blue and red light on the transformationof protochlorophyll (ide) (Pchl) accumulated in dark-grown calluscells were studied by following the changes in the intensityof fluorescence emitted by Pchl and different forms of chlorophyll(ide) (Chi). Pchl with a fluorescence maximum at 633 nm (absorptionmaximum: 630 nm) decreased slowly, concomitant with an increasein Chl having a fluorescence maximum at 677 nm (absorption maximum:675 nm), which was subsequently transformed, independently oflight, to Chi with a fluorescence maximum at 683 nm (absorptionmaximum: 680 nm). Both blue and red light of low intensitieswere effective for the phototransformation, while red light,but not blue light, of high intensities caused significant destructionof Pchl. An action spectrum for this photodestruction showedthat the maximum destruction took place at 630 nm. White lightof high intensities was effective for the photoreduction withonly slight destruction of Pchl, suggesting that blue lightcounteracts the destructive effect of red light. At low temperatures,however, blue light as well as red light of low intensitiescaused photodestruction of Pchl. It was inferred that blue lightenhances a certain step or steps involved in the productionof a reductant required for the photoreduction of Pchl to Chl. (Received July 3, 1981; Accepted November 11, 1981)     

Temperature and plant adaptation. I. Interaction of temperature and light in the synthesis of chlorophyll in corn

The effect of temperature and light intensity have been studied in relation to the greening of etiolated corn (Zea mays cv. Pioneer 309-B) seedlings. Chlorophyll accumulation is rapid at high temperature (28°) under all conditions of light intensity. At low temperature (16°), and particularly in combination with high light intensity (3000-4500 ft-c), the accumulation of both chlorophyll and carotene is inhibited.

Low pigment content at 16° is not directly due to a block in the pigment synthesizing mechanism, but rather to the photodestruction of chlorophyll prior to its stabilization in the membrane structure of the chloroplast lamellae. The parallel reduction in carotene content at high light intensity is probably a contributing factor, because of its role in protecting chlorophyll from photodestruction. The greater severity of photo-oxidation of chlorophyll at low temperature in corn when compared with wheat, appears to be due to a slower rate of protochlorophyllide synthesis and subsequent esterification. Thus in corn at 16° there is a prolongation of the photosensitive stage during chlorophyll synthesis. Photo-oxidation at 16° has also been shown to be a function of the incident light energy, with the photosynthetic pigments acting as receptors for their own destruction.

In comparison with the behavior of corn, wheat seedlings green rapidly at high light intensity at both 16° and 28°. This contrasting temperature response with respect to chlorophyll synthesis may underlie a fundamental difference in adaptation of these 2 species to growth in the temperate zones of the world.

     

Some Effects of Light on Excised Wheat Roots with Special Reference to Peroxide Metabolism

When excised wheat roots are exposed to blue light, catalase activity changes in a way to he expected as a result of photodestruction with first order kinetics. Wheat root catalase in vivo is less light sensitive than animal catalase in vitro, possibly due to internal screening. Illumination of the roots with red light causes some increase in catalasc activity. Peroxidase activity is much less affected by light. No relation has been found between catalase destruction and chlorophyll formation. The ability of roots to oxidize pyrogallol to purpurogallin (by other workers interpreted as peroxide production) is decreased by light, especially blue light. On the contrary, one peroxide producing enzyme, glycolic acid oxidase, was detected only in roots grown in blue light. The total flavin content, or the fraction present as FAD, is not affected by light. The ascorbic acid content is low, but slightly increased by blue light.     

Interaction of chloroplasts with inhibitors: induction of chlorosis by diuron during prolonged illumination in vitro

A primary symptom of diuron (DCMU) phytotoxicity in plants is the destruction of chlorophyll. To study this process in vitro, chloroplasts from pea leaves (Pisum sativum L.) have been incubated in the light with DCMU for periods of up to 34 hours. The sequence of photodestruction of chlorophylls and carotenoids has been followed to try and establish the nature of the chloroplast protection mechanisms that are destroyed by DCMU. β-Carotene decays most rapidly, followed by chlorophyll a and xanthophylls which are destroyed in a constant ratio, followed finally by chlorophyll b. Bypassing the DCMU block in the electron transport system with an artificial electron donor provides complete protection against chlorophyll and carotenoid photodestruction. The same protection by this electron donor system is afforded to stroma-free lamellae from which soluble reductants have been removed so that NADPH formation, which has been proposed as an essential part of a protective xanthophyll cycle, is not possible. Both this and the simultaneous loss of chlorophyll a and xanthophylls tend to preclude the breakdown of a xanthophyll cycle from the possible protective mechanisms inhibited or destroyed by DCMU.     

Effect of Zinc Nutrition on Photosynthesis and Carbonic Anhydrase Activity in Cotton

Photosynthesis, respiration, carbonic anhydrase activity and chlorophyll concentrations were correlated with zinc nutrition in cotton (Gossypium hirsutum L.). The critical zinc level during early plant growth was 13 μg/g dry weight in recently matured leaves (blade three). Photosynthesis and chlorophyll concentration required a minimum Zn of 13 and 14 μg/g dry weight, respectively, in blade three for maximum activity and synthesis. Respiration was not influenced by zinc status. Carbonic anhydrase activity increased curvilinearly as zinc status improved from deficiency to adequacy.     

Photoautotrophic Growth and Photosynthesis in Cell Suspension Cultures of Chenopodium rubrum

A method is described for growing cell suspension cultures of Chenopodium rubrum photoautotrophically for prolonged periods of time. By using a two-tier culture vessel the growth medium with the cells was separated from the CO₂ reservoir. Definite CO₂ concentrations were established by a K₂CO₃/KHCO₃ buffer. Photoautotrophic growth in C. rubrum cell suspension cultures was correlated with the CO₂ level. At 0.5% CO₂ the cell cultures contained 68 μg chlorophyll/g fresh weight and showed an increase in fresh weight of about 80% in 18 days. At 1% CO₂ an increase in fresh weight of 165% in 18 days was observed. The chlorophyll content rose up to 84 μg/g fresh weight. The photoautotrophic growth was also greatly influenced by the 2,4-D content of the medium. Cell growth was enhanced by lowering the auxin concentration. Best growth was attained (210% increase in fresh weight) at 10^?8M 2,4-D. The photosynthetic activity of the cells was measured by the light dependent ¹⁴CO₂ incorporation. At 0.5% CO₂ the cell suspensions assimilated about 100 μmol CO₂/mg chlorophyll × h. In the presence of 1% CO₂ the light driven assimilation was raised up to 185 μmol CO₂/mg chlorophyll × h. In both cases, the dark incorporation of CO₂ was merely 1.8% of the values obtained in light.     

Remote-sensing of benthic chlorophyll: should ground-truth data be expressed in units of area or mass?

During low tide, field spectrometric data (350-1050 nm) were acquired from intertidal mudflats in the upper reaches of Sydney Harbour, after which samples of sediment were taken using a small contact core. A total of 103 spectra/sediment pairs of samples were acquired. In the laboratory, amounts of chlorophyll in the contact cores were determined spectrophotometrically. The proportion of fine sediment (<63 μm), a major factor influencing bulk-density of sediment, was measured.The relationship between the remotely sensed observations and the amounts of chlorophyll was investigated by comparing chlorophyll expressed as a mass per unit area (area-normalised values) and as a mass per unit mass (content or weight-normalised values) with: (i) reflectance between 350 and 1050 nm and (ii) a ratio of reflectance at 562 and 647 nm (R562/R647). The reflectance at wavelengths >400 nm were found to be more tightly correlated with area-normalised chlorophyll (maximal correlation=−0.51 at 666 nm) than with weight-normalised chlorophyll (maximal correlation=−0.41 at 664 nm). The relationship between R562/R647 and area-normalised chlorophyll was stronger (R²=0.66) than for weight-normalised chlorophyll (R²=0.47). The residuals from the regression of weight-normalised chlorophyll on R562/R647 were strongly correlated with the mass per unit mass of sediment that was <63 μm. There was no such relationship for residuals from the regression of area-normalised chlorophyll on R562/R647. The results demonstrate conclusively that chlorophyll measured as mass per unit mass of sediment, is inappropriate for ground-truthing remotely sensed observations of chlorophyll in intertidal benthic sediments.     

Size-fractionated chlorophyll a and primary productivity in the Chukchi Sea and its northern Chukchi Plateau

Investigations on chlorophyll a and primary productivity were carried out in the Chukchi Sea and its northern Chukchi Plateau during the 2^nd Chinese National Arctic Research Expedition in the summer of 2003. The results showed that chlorophyll a concentrations were 0.009–30.390 μg/dm³ at the surveyed waters; the surface chlorophyll a concentrations were 0.050–4.644 μg/dm³ and the average value was (0.875±0.981) μg/dm³ in the surveyed area. In the Chukchi Sea Shelf, chlorophyll a concentrations at the depth from 10 m to bottom were higher than that in the surface water, and the concentrations were lower at the depth below 75 m in the Chukchi Plateau. Chlorophyll a concentrations descended in 3 sequential samplings on Transect R, with average values of (2.564±1.496) μg/dm³, (1.329±0.882) μg/dm³ and (0.965±0.623) μg/dm³, respectively. The potential primary productivity ((2.305± 1.493) mgC/(m³·h)) in the Chukchi Sea was higher than that ((0.527±0.374) mgC/(m³·h)) in the Chukchi Plateau. The results of the size-fractionated chlorophyll a and primary productivity showed that microplankton accounted for the majority of the total chlorophyll a (63.13%) and primary productivity (65.16%) at the survey stations. The contributions of the nanoplankton and picoplankton to the total chlorophyll a and primary productivity were roughly the same.     

喜钙和嫌钙植物对外源Ca2+的生长生理响应

以喜钙植物伞花木和嫌钙植物大白杜鹃为实验材料,以Hoagland营养液并设置其Ca2+浓度分别为0、5、10、25、50mmol/L培养试验,比较不同浓度外源Ca2+对其生长、叶绿素含量、渗透调节和矿质元素积累的影响,探索喜钙植物生长的适应特征,为喀斯特地区喜钙植物嗜钙机制研究提供基础资料。结果显示:(1)随着外源Ca2+浓度的增加,伞花木植株高度、茎粗以及叶干重、叶长、叶宽和叶形指数均得到不同程度提高,叶绿素和可溶性蛋白质含量增加,脯氨酸和可溶性糖含量无显著变化;而嫌钙植物大白杜鹃的生长却受到抑制,叶绿素和蛋白质含量降低,脯氨酸和可溶性糖含量增加;当Ca2+浓度为50mmol/L时,伞花木叶绿素和蛋白质含量分别为2.99mg/g和17.10mg/g,大白杜鹃叶绿素和蛋白质含量分别为1.39mg/g和14.30mg/g。(2)在实验设置的钙范围内,Ca2+可促进伞花木对P、N吸收并稳定体内Ca、K动态;而低浓度的Ca2+(<10mmol/L)促进大白杜鹃对Ca累积,抑制N、P吸收。     

MOLYBDENUM DEPENDENCE,NITRATE UPTAKE AND PHOTOSYNTHESIS OF FRESHWATER PLANKTON ALGAE1,2

The effects of molybdenum on photosynthesis and nitrate uptake by two species of freshwater algae, Navicula pelliculosa (Bréd.) Hilse and Chlamydomonas reinhardtii Dang. Were examined. Photosynthetic rates in cells of N. Pelliculosa deprived of Mo for 48 h were significantly lower than in nondeprived cells; the rates were 2.6 and 4.5 μg C/10⁶ cells/h, respectively. There was no significant reduction in photosynthetic rates of C. reinhardtii under the 2 treatments, the rates were both ca. 6.0 μg C/10⁶ cells/h. These observed rates in the 2 species were not altered by added Mo concentrations as high as 1.0 ppm. The chlorophyll a values in 48 h Mo-deprived cells were 1.15 μg/10⁶ cells compared to 1.57 μg/10⁶ cells provided with this metal. Molybdenum deficiency did not affect the chlorophyll a concentration in Chlamydomonas; the chlorophyll levels were 2.44μg/10⁶ cells. Nitrate uptake by Mo-deprived cells of N. Pelliculosa was significantly lower than in cells cultured in Mo; the rates were 0.087 and 0.238 μM NO_a⁻/10⁶ cells/h, respectively. Uptake rates by C. reinhardtii were similar with or deprived of Mo. The K_m values for No₃⁻ uptake were 14.9 and 148.0 μM for N. Pelliculosa and C. reinhardtii, respectively.     

Studies on phytoplankton pigments in porto novo waters (India). II. Backwater

The annual variations of phytoplankton pigments were studied from January to December, 1971 at four stations in the backwater area (Porto Novo, India). At these stations, chlorophyll a varied from 2.91–65.56 μg/1; chlorophyll b from 0–1.90 μg/l; chlorophyll c from 0–38.60 μg/1; plant carotenoids from 0.30–22.34 MSPU/m³ and phaeopigments from 0–31.51 μg/l. The main (or primary) maximum of chlorophyll a appeared during June at Stations 3–5 and at Station 6, it was during May. Stations 3 and 4 had secondary chlorphyll a maxima during September and at Stations 5 and 6 during August. In general, all the stations showed an increasing trend of chlorphyll a values before the main peak. The chlorophyll a maximum was mainly due to the presence of phytoplankton species belonging to the genera such as Noctiluca, Coscinodiscus, Thalassiothrix, Biddulphia, Hemidiscus, Melosira and Rhizosolenia. Amongst all the backwater stations, Station 5 had the highest chlorophyll a (65.56 μg/1) and the lowest chlorophyll a was recorded at Station 3. Chlorophyll a concentration was normally affected by rainfall.     

Covariance Analysis of Chlorophyll Distribution in the Sundays River Estuary,Eastern Cape

Summary

An analysis of covariance performed on chlorophyll a distribution data from the Sundays River estuary identified five persistent water masses with significantly different chlorophyll a contents. These corresponded to different hydrodynamic regions within the estuary. The relationship between salinity and chlorophyll a was used to identify a transition zone between the low-salinity upper estuary and the brackish riverine inflow. Chlorophyll a concentrations ranged from <6 μg 1^?1 near the mouth to >100 μg 1^?1 in the middle and upper reaches. High variance of chlorophyll a data in this region was the result of temporal chlorophyll a fluctuations in two time scales. The first related to the daily ebb/tide and the second to the lunar spring/neap tidal cycle. Unlike its importance in larger and deeper estuaries, light played only a minor role in the horizontal distribution of chlorophyll a. The presence of a chlorophyll a maximum in the turbid low salinity region is explained in terms of the relatively constant photic depth/mixed depth ratio along the estuary and the high residence time of water in this region.     

Ultrastructure of the plastids of 3 types of Chlamydomonas reinhardi mutants phenotypically yellow in the light or in darkness]

A study was made of the ultrastructure of plastids of three mutant types of Chlamydomonas reinhardi which are phenotypically revealed either in the light or in the darkness as yellow mutants. Characteristics of pigments for each mutant have been given. Mutant Y-4 unable to synthesize chlorophyll either in the light or in the darkness shows a complete reduction of photosynthesizing membranes. Mutant Y-1 capable of synthesizing chlorophyll develops a normal system of photosynthesizing membranes. The dark synthesis of chlorophyll in this mutant is broken, the mutant accumulates only carotenoids, the membrane system of its plastid being reduced. On the contrary, mutant Y-3 has in the darkness a complete set of pigments and a well developed membrane system. In the light this mutant yellows due to chlorophyll photodestruction that is followed by destruction of the membrane system of chloroplasts.     

Use of natural polymers as immobilizing agents and effects on the growth of Dunaliella salina and its glycerol production

Agar-agar, agarose, carrageenan and calcium alginate were used for the immobilization of Dunaliella salina cells. Out of the four, agar-agar was found to be the most effective and therefore the study was carried out on it using different pH values ranging from 6 to 10 and cell densities from 0.1 to 0.8 μg chlorophyll (chl, a) per bead to find which are is best suited for glycerol production. The maximum glycerol production of 9.2 μM/mg chl a was recorded in agar-agar immobilized algae and this was followed by 8.4 μM/mg chl a in calcium alginate. The maximum cell number 6.2 × 10⁹/ml and the specific growth rate (μ) of 0.80 l/day were reached at pH 8 in agar-agar immobilized algae. It was shown that the maximum amount of glycerol was produced when the cell density was 0.8 μg chl a/ block. Changing the medium after 24 hours affected the rate of glycerol production at different pH values. Using a cell density of 0.8 μg chl a/block at 16 W/m² light intensity increased the glycerol production in comparison with the use of free living cells.     

Light‐induced pigment degradation in leaves and ripening fruits studied in situ with reflectance spectroscopy

Pigment breakdown mediated by activated oxygen species is a consequence and a general symptom of oxidative stress and injury to plants. We have attempted to estimate the patterns of pigment bleaching and follow pigment susceptibility to irradiation as related to the process of senescence/ripening. Light‐induced pigment breakdown was studied in situ in the leaves of a shade‐requiring plant, wax flower ( Hoya carnosa R. Br.), as well as in apple ( Malus domestica Borlh. cv. Zhigulevskoe) and lemon ( Citrus limon Burm. cv. Pavlovsky) fruits, using reflectance spectroscopy. It was found that the sensitivity of plant pigments to photobleaching increases as ripening progresses in lemon fruit. Kinetic analysis showed that in all systems a rapid breakdown of the pigment occurs after a lag‐phase. The signature analysis revealed a common pattern of chlorophyll and carotenoid changes, but degradation of the individual pigments was found to be inhomogeneous. Both in lemon and apple fruits a decrease in reflectance in the band of carotenoid absorption preceded pigment photodestruction. In the fruits, the bulk of chlorophyll b and the long‐wavelength chlorophyll a forms were degraded at early stages of the process whereas the breakdown of both chlorophylls in H. carnosa leaves was more synchronous. Prolonged irradiation induced bleaching of the main chlorophyll a band with maximum at 678 nm in the difference spectra, as well as carotenoids. Some features of reflectance spectra in the bands of chlorophyll and carotenoid absorption were found to be suitable for the differentiation of photo‐induced pigment breakdown from the transformation of the pigments taking place during senescence.     

Effect of Continous Light on CO2 Fixation and Chloroplast Structure of the Mosses Pleurozium schreberi and Ceratodon purpureus

When the mosses Pleurozium schreberi (Brid.) Mitt, and Ceratodon purpureus (Hedw) Brid. were exposed for 4 week to either continuous or rhythmie light of 75 or 150 μE m^?2 s^?1, the photosynthetic rate, calculated on the basis of chlorophyll and of dry weight, was lower in the moss plants exposed to continuous light. RUBP-carboxylase activity was lower in these plants, too. On the other hand more starch was accumulated in the chloroplasts in continuous than in rhythmic light. Neither moss species showed any differences in the dark respiration rates. The chlorophyll content was lower in continuous light, especially at the higher intensity; but Chi a/Chl b ratio showed little change compared with that in rhythmic light. The reduction of chlorophyll did not affect the two chlorophyll protein complexes equally; the percentage of chlorophyll associated with CP I decreased, while that associated with CP II showed liltle change. The decrease in CP I chlorophyll appeared to be due to the partial destruction of stroma thylakoids: the size or the grana increased in continuous light. Many of the effects of continuous light in these mosses resembled those observed in higher plants in the early phases of senescence.     

Hyaluronidase activity of macaque sperm assessed by an in vitro cumulus penetration assay

A model system consisting of cynomolgus macaque sperm and ovulated hamster ova-cumulus complexes (OCCs) was utilized to study the role of the sperm protein PH-20 in cumulus penetration. The hyaluronidase activity of solubilized macaque sperm PH-20 was evaluated using an ELISA-like microplate assay prior to and following the addition of the hyaluronidase inhibitors heparin (0–100 μg/ml) and apigenin (250 μM), as well as the Ig fraction of a polyclonal antibody raised against purified recombinant macaque PH-20 (R10; 10–400 μg/ml). Sperm motility following exposure to enzyme inhibitors was evaluated using computer-aided sperm motility analysis. Macaque sperm were labeled with the permeant fluorescent nuclear dye, Hoechst 33342, and were coincubated with ovulated hamster OCCs for 30 min at 37°C. The addition of heparin, apigenin, or R10 antibody to solubilized sperm extracts resulted in a linear dose-dependent decrease in hyaluronidase activity (P < .01). In the heterologous cumulus penetration assay, fluorescently labeled macaque sperm that were pretreated with heparin (1–100 μg/ml), apigenin (250 μM), or R10 antibody (Ig fraction, 10–400 μg/ml) demonstrated a dose-dependent decrease in the ability to penetrate hamster OCCs (P < 0.01), in the absence of effects on sperm motility. In the homologous assay, experiments using macaque OCCs and fluorescently labeled macaque sperm confirmed that the same concentrations of heparin and R10 antibody similarly suppressed spermatozoal cumulus penetration (P < .01). These results suggest that macaque sperm PH-20-derived hyaluronidase participates in cumulus penetration in this species, and that this model system is useful for further studies into primate gamete interaction. Mol. Reprod. Dev. 46:392–400, 1997. © 1997 Wiley-Liss, Inc.     

Dichlorophenyl dimethylurea (DCMU) induced increase in chlorophyll a fluorescence intensity – An index of photosynthetic oxygen evolution in leaves, chloroplasts and algae

Dichlorophenyl dimethylurea (DCMU) treatment in photosynthetic samples resulted in an increase in the level of steady state chlorophyll a fluorescence at room temperature which was directly proportional to the photosynthetic efficiency. The applicability of this method for the rapid determination of the efficiency of oxygen evolution in leaves, algae, mesophyll cells and chloroplasts has been investigated. Especially reliable values with less than 5% error were obtained if the fluorescence measurements were made under low excitation intensities with a sample chlorophyll concentration below 1.0 μg/ml.