Assembly and composition of the chlorophyll a-b light-harvesting complex of barley (Hordeum vulgare L.): Immunochemical analysis of chlorophyll b-less and chlorophyll b-deficient mutants

The chlorina-f2 mutant of barley (Hordeum vulgare L.) contains no chlorophyll b in its light-harvesting antenna, whereas the chlorina-103 mutant contains approximately 10% of the chlorophyll b found in wild-type. The absolute chlorophyll antenna size for Photosystem-II in wild-type, chlorina-103 and chlorina-f2 mutant was 250, 58 and 50 chlorophyll molecules, respectively. The absolute chlorophyll antenna size for Photosystem-I in wild-type, chlorina-103 and chlorina-f2 mutant was 210, 137 and 150 chlorophyll molecules, respoectively. In spite of the smaller PS I antenna size in the chlorina mutants, immunochemical analysis showed the presence of polypeptide components of the LHC-I auxiliary antenna with molecular masses of 25, 19.5 and 19 kDa. The chlorophyll a-b-binding LHC-II auxiliary antenna of PS II contained five polypeptide subunits in wild-type barley, termed a, b, c, d and e, with molecular masses of 30, 28, 27, 24 and 21 kDa, respectively. The polypeptide composition of the LHC-II auxiliary antenna of PS II was found to be identical in the two mutants, with only the 24 kDa subunit d present at an equal copy number per PS II in each of the mutants and in the wild-type barley. This d subunit assembles stably in the thylakoid membrane even in the absence of chlorophyll b and exhibits flexibility in its complement of bound chlorophylls. We suggest that polypeptide subunit d binds most of the chlorophyll associated with the residual PS II antenna in the chlorina mutants and that is proximal to the PS II-core complex.Abbreviations CP chlorophyll-protein - LHC the chlorophyll a-b binding light-harvesting complex - LHC-II subunit a the Lhcb4/5 gene product - subunit b the Lhcb1 gene product - subunit c Lhcb2 the gene product - subunit d the Lhcb3 gene product - subunit e the Lhcb6 gene product - PMSF phenylmethane sulphonyl fluoride - RC reaction center - Q_A the primary quinone electron acceptor of Photosystem-II - P700 the reaction center of PS I     

Ricerche Comparate Sulla Morfologia e Sulla Fisiologia di Larix e di Picea

Abstract

Comparative researches on morphology and physiology of PICEA and LARIX. The chlorophyll content of seeds and seedlings during germinations in darkness. — Very different are the chlorophyll contents of the seeds and the seedlings of Picea excelsa and Larix decidua grown in darkness.

In Picea chlorophyll is abundantly synthetized in cotyledons in the passage from seed to seedling stages. In Larix however this synthesis is very poor. These differences are more evident after the outgrowth of cotyledons from the primary endosperm and its exhaustion.

If seedlings of both species are exposed to 3.000 lux of light intensity for 24 hours, after development in darkness, one can observe much stronger chlorophyll synthesis in Larix cotyledons than icea.

These figures quanti atively express the different light-dipendence of chlorophyll synthesis in these two plants and offer a more adherent interpretation of the different ecological behaviours that are caracteristic of these two plants.     

Azione della Cinetina sulla Degradazione della Clorofilla in Foglie di Orzo Irradiate

Abstract

The effects of kinetin on chlorophyll breakdown in irradiated barley leaves. — Kinetin is shown to inhibit the breakdown of chlorophyll in isolated barley leaves. Moreover the kinetin is shown to inhibit, even if with lower effect, the chlorophyll breakdown in irradiated barley leaves. This possible correlation of these observations, with kinetin promoted protein synthesis is suggested.     

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.     

Theories on adaptations to high light intensity in the aquatic moss Fontinalis

Abstract

Fontinalis antipyretica, collected from a cold stream in bright sunlight, served as a model for adaptations of Fontinalis to sun and shade. Sun leaves produced red pigments and had less chlorophyll, greater specific leaf weight, and less specific leaf area than shade leaves. The chlorophyll a/b ratio was not significantly different under high and low light conditions. Except for the relatively constant a/b ratio, Fontinalis behaved like higher plants in its sun/shade differences.     

Grimmia homodictyon Dixon

Abstract

We examined photosynthetic responses of two dominant pleurocarpous mosses, Actinothuidium hookeri (Mitt.) Broth. and Hylocomium splendens (Hedw.) Schimp. to low-level nitrogen (N) addition. The study was conducted in an old-growth fir forest on the eastern Tibetan Plateau. The added N, 1 g N/m², was mainly absorbed by the new-growth. The concentrations of chlorophyll a and b both increased 8 days after N addition. The quantum yield of Photosystem II (Φ_PSII) also increased. However, no significant changes were found in terms of gas exchange parameters. The mass-based CO₂ assimilation rate, chlorophyll a content, and chlorophyll a/b ratio (which is related to antenna size of the photosystem), of H. splendens were all higher than those of A. hookeri. Shoot mass per area (SMA) of H. splendens was lower than that of A. hookeri. We conclude that the photosynthetic rate was less sensitive to low-level N addition than chlorophyll contents and chlorophyll fluorescence parameters, suggesting other limiting factors in the photosynthetic process. Additionally, the faster growing H. splendens has a higher photosynthetic capacity than A. hookeri, allocating fewer resources to structural tissue.     

Effects of sodium dodecyl sulphate on the aquatic macrophytes Azolla and Lemna

Abstract

In this work, we determined the tolerance to sodium dodecyl sulphate (SDS) of Azolla filiculoides and of Lemna minor. The presence of the detergent in the media affected growth more than the chlorophyll content. On the basis of the effect indices, Lemna is more tolerant to SDS than Azolla. The fern had a better capacity, compared with duckweed, to remove and accumulate the pollutant.     

Effect of methyl jasmonate (MeJA) on biochemical responses of wheat seedlings infected by Fusarium culmorum

Fusarium culmorum is a ubiquitous soil-borne fungus which is able to cause foot and root rot on different small-grain cereals, in particular wheat and barley. Wheat (Triticum aestivum L.) is among the oldest and most extensively grown of all crops. Systemic acquired resistance (SAR) is a pathogen-induced disease resistance response in plants that is characterized by broad spectrum disease control. SAR is an important component of the disease resistance repertoire of plants. The effect of the resistance inducer, methyl jasmonate (MeJA), was tested by seed-soaking to determine whether this resistance inducer controlled root rot of wheat caused by F. culmorum. MeJA is an inducing disease resistance in a number of dicotyledonous and monocotyledonous plant species. This research has been conducted to determine the effect of MeJA seed treatment on chlorophyll a, chlorophyll b, total protein, peroxidase (POD) enzyme, phenolic compounds and phenylalanine ammonia lyase (PAL) factors. MeJA, which is an important chemical inducer of SAR, can activate resistance to pathogen infection in commercial crops. Seeds treated with MeJA showed an elevation in the total chlorophyll, carotenoid and activity of defence-related enzymes, POD and PAL.     

Influence of nutrient addition on growth and accumulation of cadmium and copper in Lemna gibba

Abstract

Aquatic plants have been identified as potentially useful for accumulating and bioconcentrating heavy metals. This study was developed to test the hypothesis that nutrient enrichment enhances the metal tolerance of floating macrophytes. Relative growth rates (RGR), photosynthetic pigments (chlorophyll a, b and carotenoid), malondialdehyde (MDA) content, and electrical conductivity (EC) were measured in Lemna gibba exposed to different cadmium and copper concentrations in laboratory conditions. Relative growth rates were negatively correlated with metal exposure, but nutrient addition suppressed this effect. Photosynthetic pigment levels were negatively correlated with metal exposures, and nutrient addition attenuated chlorophyll decrease in response to metal exposures. MDA content and EC also showed sharp increases at higher concentrations, indicating oxidative stress. This study indicates that nutrient enrichment increases the tolerance of Lemna gibba to metals, and that Lemna gibba is a suitable candidate for the phytoremediation of low-level copper and cadmium pollution.     

The effect of mercury on the physiology of Rhytidiadelphus squarrosus (Hedw.) Warnst.

Abstract

Laboratory experiments have shown that low concentrations of mercury severely inhibit photosynthesis, temporarily increase respiration, reduce chlorophyll a and b concentrations and cause substantial loss of intracellular potassium from Rhytidiadelphus squarrosus. These changes have been interpreted as being due to mercury causing damage to the membrane systems of the cell.     

台风利奇马对城市淡水系统中微生物群落和抗生素耐药性基因的影响

【背景】极端天气事件(如台风)带来的强风和降水,会给水生生态系统造成短暂和持久的影响。然而,很少有研究关注台风对水生微生物群落和抗生素耐药性基因(antibiotic resistance genes,ARGs)的影响。【目的】对台风前后城市淡水水域的微生物群落和抗性基因组成进行研究分析,更好地认识极端天气对淡水生态系统的干扰。【方法】在台风前后从4个地点采集了水样,通过宏基因组分析,检测了台风利奇马对温州休闲水域微生物群落和抗性基因的影响。除水生微生物群落和抗性基因外,还分析了每个采样点的物理、化学参数,包括温度、pH、溶解氧、叶绿素a、可溶性活性磷、硝酸盐、亚硝酸盐和铵。【结果】台风登陆后,大多数地点的pH、溶解氧和叶绿素a都有所增加。然而,台风对九山湖的影响要弱于对三垟湿地的影响。台风登陆后,变形菌门、蓝菌门和拟杆菌门的相对丰度增加,而放线菌门的相对丰度下降。在属水平上,栖湖菌的微生物多样性和相对丰度显著增加。在所有的环境因子中,铵是影响微生物群落结构的最重要的环境因子。另外,在所有样本中均检测到35个机会性致病菌类群。台风后,铜绿假单胞菌的相对丰度增加。ARGs显示了空间(采样点间)和时间(台风前后)的变化。冗余分析表明,水总无机氮是影响抗性基因分布的主要环境因子。【结论】这些发现为极端天气(如台风)如何影响淡水系统中的微生物群落和抗性基因提供了新的见解。台风登陆增加了城市淡水系统的公共安全风险,因此,检验检疫方法和手段应该前移,加强对环境健康安全的评价和分析,这将有助于减轻抗生素耐药性和致病菌扩散的风险。     

内生真菌KLBMP0506对拟南芥的促生作用

【目的】研究植物内生菌Wickerhamomyces sp.KLBMP0506对拟南芥（Arabidopsis thaliana）的促生作用及潜在的促生机制。【方法】本研究以野生型拟南芥为试验材料,将其与菌株KLBMP0506进行平板共培养及盆栽接种试验,并测定拟南芥鲜重、干重、主根长、侧根数、叶绿素含量和可溶性糖含量等生长、生理指标,同时对筛选的与拟南芥侧根、主根形成及生长素合成和运输相关的11个基因进行实时荧光定量聚合酶链式反应（quantitative real-time polymerase chain reaction,qRT-PCR）分析。【结果】接种目的菌株KLBMP0506后,平板试验的拟南芥鲜重及侧根、盆栽试验的拟南芥鲜重、干重、茎长、叶绿素含量和可溶性糖含量均有一定程度的增加;分隔平板试验及菌株KLBMP0506发酵液中促生活性物质分析显示,该菌株产生的挥发性有机物质及其发酵液中的正丁醇和乙酸乙酯提取物均对拟南芥有明显的促生作用;此外,qRT-PCR分析显示KLBMP0506处理后,拟南芥中与侧根形成相关基因ABI4、FLA1的表达出现不同程度的下调,与生长素合成、运输相关基因AUX1、EIR1、YUC4的表达整体呈上调趋势,表明菌株KLBMP0506可能通过调控拟南芥中与侧根形成以及与生长素合成和运输相关基因的表达,而实现对拟南芥的促生作用。【结论】本研究明确了菌株KLBMP0506对模式植物拟南芥的促生作用,为其开发成为微生物菌肥提供理论依据。     

Seasonal changes in the chlorophyll content and quantum efficiency of the moss Brachythecium rutabulum

Abstract

The concentration of chlorophyll a, b, and total chlorophyll have been monitored on a seasonal basis in Brachythecium rutabulum. Total chlorophyll increases during summer full canopy conditions from 1.70 mg chl g^?1 on 8 May to 11.1 mg chl g^?1 on 11 October. Photosynthetic-illumination curves show that during this period light saturation declines from 200 μmol m^?2s^?1 to 30 μmol m^?2s^?1 by 6 July, and light compensation falls dramatically from 65 μmol m^?2s^?1 to 4 μmol m^?2s^?1. The data also appear to support the conclusion that there is concurrently an increase in the density of photosynthetic units by the end of September.     

L'Azione dell'Ossigeno Liquido Sulla Germinabilità dei Semi Duri di Ginestrino (Lotus Corniculatus L.) e di Ladino (Trifolium Repens L.)

Abstract

Comparative researches on morphology and physiology of PICEA and LARIX. Fresh weight and chlorophyll content in seedlings kept at various light intensities. — The fresh weight and the chlorophyll content of lots of seedlings from Larix decidua and Picea excelsa grown on sand for 12 days in climatic cell at 25 [ddot]C with 86% relative humidity and a light intensity of 90, 250, 500, 1.000, 2.000 and 4.000 lux were determined.

The fresh weight of Picea seedlings is not significantly affected by all light intensities except for 4.000 lux, where it is 20% higher. Even in dim light (90 lux) the fresh weight of Picea seedlings is only 7% inferior to that of the lot kept at 2.000 lux.

The results obtained in Larix are remarkably different; its fresh weight is more influenced by the light intensity: at 4.000 lux, e. g., the fresh weight is considerably higher (more than 20%) than the arithmetical mean of all the lots, while at 90 lux it appears greatly inferior (30%) to the lot kept at 2.000 lux.

No correlation exhists between fresh weight and chlorophyll content variations.

In Larix only the difference between seedlings kept at 250 lux and 90 lux is very strong. In the latter the chlorophyll content for g. f. w. is 40% inferior to the average of all the lots. At the maxime intensities the chlorophyll content of Larix seedlings appears to be particularly increased, while that of Picea seedlings is slightly inferior to that observed at 2.000 lux.

These figures are in agreement with the special ecology of the two plants and particularly with the light need of Larix, as it is clearly demonstrated by the fresh weight and chlorophyll content per g. f. w. and by the different ratio in chlorophyll contents of the lots of seedlings kept at 2.000 and 4.000 lux.     

Rates of photosynthesis of two lichens and of their isolated algal components

Abstract

The rate of photosynthesis of two lichen species (Peltigera leucophlebia and Ramalina farinacea) was found to be 30 to 40% that of spinach leaf dises and 20% that of the free-living alga Chlorella when the results were expressed on a per mg chlorophyll basis. When the algae were isolated from the thalli, the rate of photosynthesis per mg chlorophyll increased for Ramalina farinacea and decreased for Peltigera leucophlebia. Product analysis indicated that the products of photosynthesis depended on the association of the alga with the fungus: algae isolated from the thalli showed a «shift» in products from sugars and sugar alcohols. to compounds such as organic acids. The results suggest that a symbiotic relationship with a fungus alters both the rate and products of algal photosynthesis.     

Chlorophyll fluorometry as a method of determining the effectiveness of a biological control agent in post-release evaluations

ABSTRACT

The impact of the planthopper Megamelus scutellaris, a biocontrol agent of water hyacinth in South Africa, was assessed using chlorophyll fluorometry in a greenhouse study under two different eutrophic nutrient treatments and agent densities (high and low). The results indicated that plants grown in low nutrients with high densities of M. scutellaris showed the greatest reduction in the fluorescence parameters Fv/Fm and PI_abs. The successful use of chlorophyll fluorometry for the detection of subtle insect damage to water hyacinth leaves could have future application in post-release studies to measure the impact of M. scutellaris in the field.     

一株耐盐甲基杆菌Methylobacterium sp.W-1的分离及促生潜能研究

[背景] 多种甲基杆菌属细菌对寄主植物有促生作用,其分布区域较广。筛选具有耐盐与促生特性的甲基杆菌属菌株可为微生物菌肥的开发提供依据。[目的] 从新疆乌尔禾地区盐渍土壤中筛选耐盐促生菌,对其培养基成分进行优化及促生能力进行研究,为微生物菌肥的开发提供依据。[方法] 采用阿须贝无氮培养基筛选耐盐菌株,对菌株进行基因序列分析及生理生化测定,采用平板试验法初步研究该菌对拟南芥的生长影响。[结果] 筛选出中度耐盐菌株W-1,经鉴定为甲基杆菌属（Methylobacteriumsp.）。菌株生长最佳无机盐为NaCl,最适浓度为1%–3%,最高耐受浓度达7%。最佳氮源为酸水解酪蛋白,产生长素最高达33.53 mg/L。溶磷能力达28.71 mg/L。菌株W-1接种拟南芥幼苗后叶绿素a和叶绿素b含量均高于对照组,同时对其根系发育有显著的促进作用。[结论] 菌株W-1促生性能显著,可为生物肥料制备提供菌种资源。     

Effect of Intermittent and Continuous Light on Chlorophyll Formation in Etiolated Plants

Short impulses of white light induce continuous synthesis of chlorophyll a and b in etiolated barley leaves. No lag phase is observed, and the rate of chlorophyll a accumulation is much higher than that of chlorophyll b, so that the a/b ratio is very high (12 to 20). The chlorophyll accumulation reaches a plateau at about 70 flashes after which the rate of their formation decreases appreciably. When the etiolated plants, after exposure to about 80 to 100 flashes, are transferred to continuous light, one can observe that the rate of formation of chlorophyll a and b increases during the first hour, and after that becomes still more rapid. At the same time the a/b ratio falls and it reaches a value of about 3 normally found in green leaves.     

一株可增强莱茵衣藻耐盐能力细菌MEZX29的分离与鉴定

【背景】水体中的藻类、细菌及这些微生物之间的相互作用对水体生态系统的功能有着重要作用。近年来,一些河流、湖泊等淡水资源的盐渍化不断加重,对水体生态系统造成严重影响。然而,高盐胁迫条件如何影响藻类与其他细菌的相互作用,以及是否存在能够促进藻类耐盐能力的有益细菌等问题尚未得到深入研究。【目的】分离和鉴定可以促进淡水藻类莱茵衣藻抗盐能力的细菌,并开展相关机制分析。【方法】通过富集培养、筛选和共接种实验,获得可以促进衣藻耐盐的细菌;基于活细胞浓度、叶绿素含量等参数评价衣藻在不同条件下的生长能力;对菌株进行16S rRNA基因序列分析和基因组分析,预测其可能的菌藻相互作用机制。【结果】获得一株在250-290 mmol/L NaCl条件下可以显著增强衣藻耐盐能力的菌株MEZX29,16S rRNA基因序列分析表明,该菌可能属于Rhodococcus qingshengii;基因组分析结果表明,该细菌含有参与糖代谢、乙烯合成、生物膜形成等途径的基因,这些基因可能在促进衣藻抗盐过程中起到重要作用。【结论】Rhodococcus qingshengiiMEZX29可以增强莱茵衣藻21gr抵抗高盐胁迫的能力,为研究藻类与其他微生物之间的有益相互作用提供了新的材料。     

A PHYTOL-SUBSTITUTED CHLOROPHYLL C FROM EMILIANIA HUXLEYI (PRYMNESIOPHYCEAE)1

A nonpolar chlorophyll c-like pigment was isolated by semi-preparative high performance liquid chromatography from the coccolithophorid Emiliania huxleyi (Lohm.) Hay and Mohler. The visible absorption spectrum of this pigment was similar to that of chlorophyll c₂. However, its nonpolar chromatographic properties were quite different from those of the relatively polar chlorophylls c₂ and c₃ in E. huxleyi and similar to those of chlorophyll a. Analyses by gas chromatography and gas chromatography-mass spectrometry showed that the nonpolar character of this new chlorophyll c was due to the presence of phytol, most likely on the acid side chain of the porphyrin macro-cycle. This is the first example of a phytol-substituted chlorophyll c-like pigment.