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The cytochrome b 6 f (Cyt b 6 f) complex, which functions as a plastoquinol-plastocyanin oxidoreductase and mediates the linear electron flow between photosystem II (PSII) and photosystem I (PSI) and the cyclic electron flow around PSI, was isolated from spinach (Spinacia oleracea L.) chloroplasts using n-octyl-β-D-glucopyranoside (β-OG). The preparation was also able to catalyze the peroxidase-like reaction in the presence of hydrogen peroxide (H2O2) and guaiacol. The optimal conditions for peroxidase activity of the preparation included: pH 3.6, ionic strength 0.1, and temperature 35°C. The apparent Michaelis constant (K m) values for H2O2 and guaiacol were 50 mM and 2 mM, respectively. The bimolecular rate constant (k obs) was about 26 M−1 s−1 and the turnover number (K cat) was about 60 min−1 (20 mM guaiacol, 100 mM sodium phosphate, pH 3.6, 25°C, [H2O2]

Four synthetic manganese complexes in which Mn atoms have different coordination environments and valence states were used to reconstitute water-oxidizing complex (WOC) in Mn-depleted photosystem 2 preparations. Three Mn-complexes restored a significant rate of electron transfer and oxygen evolution except one complex in which Mn atom ligated to the O-atoms within the ligands by covalent linkage. The effect of coordination environment of the Mn-atom within the Mn-complexes on their efficiencies in reconstituting the electron transport and oxygen evolution was analysed.

We investigated the effect of large isoform of ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBPCO) activase (RuBPCO-A) on photosynthesis and constructed two plant expression vectors and introduced them into rice cultivars (Oryza sativa f. japonica cv. Nipponbare) through Agrobacterium tumefaciens-mediated transformation. Plasmid pCBrbcSRca contained the cDNA of RuBPCO-A large isoform (rca) controlled by RuBPCO small subunit gene promoter (rbcS), and plasmid pCBUbi-antirca contained a reversed rca sequence driven by maize ubiquitin promoter. Transformants were screened by polymerase chain reaction (PCR), Southern and Western blot analysis. Compared to the control rice plants, RuBPCO activity was improved in the pCBrbcSRca rice plants, which is opposite to RuBPCO activity in the pCBUbi-antirca rice plants. Net photosynthetic rate, quantum yield of electron transport in photosystem 2, and steady state photochemical fluorescence quenching increased in the pCBrbcSRca plants, but decreased in the pCBUbi-antirca plants as compared to the controls. The pCBrbcSRca plants had heavier grains and accelerated development, while the pCBUbi-antirca plants showed reverse changes. Thus RuBPCO-A large isoform exerts considerable effect on photosynthesis and is a promising target for plant breeding to improve rice crop yield.

Energy transfer of aromatic amino acids in photosystem 2 (PS2) core antenna complexes CP43 and CP47 was studied using absorption spectroscopy, fluorescence spectroscopy, and the 0.35 nm crystal structure of PS2 core complex. The energy of tyrosines (Tyrs) was not effectively transferred to tryptophans (Trps) in CP43 and CP47. The fluorescence emission spectrum of CP43 and CP47 by excitation at 280 nm should be a superposition of the Tyr and Trp fluorescence emission spectra. The aromatic amino acids in CP43 and CP47 could transfer their energy to chlorophyll (Chl) a molecules by the Dexter mechanism and the Foster mechanism, and the energy transfer efficiency in CP47 was much higher than that in CP43. In CP47 the Foster mechanism must be the dominant energy transfer mechanism between aromatic amino acids and Chl a molecules, whereas in CP43 the Dexter mechanism must be the dominant one. Hence solar ultraviolet radiation brings not only damages but also benefits to plants.

The structural characteristics of the extra-membrane domains and guanidine hydrochloride-induced denaturation of photosystem 2 (PS2) core antenna complexes CP43 and CP47 were investigated using fluorescence emission and circular dichroism (CD) spectra. The extra-membrane domains of CP43 and CP47 possessed a certain degree of secondary and tertiary structure and not a complete random coil conformation. The tertiary structure and the chlorophyll (Chl) a microenvironment of CP47 were more sensitive to guanidine hydrochloride (GuHCl) than that of CP43. Changes in energy transfer from β-carotene to Chl a corresponded well to changes in the tertiary structure while their correlation with changes in the secondary structure was rather poor. Unlike most of water-soluble proteins, both CP43 and CP47 are partly resistant to denaturation induced by guanidine hydrochloride (GuHCl); the denaturation of CP43 or CP47 is not a two-state process. Those features most probably reflect their character as intrinsic membrane proteins.

In order to investigate the effect of large isoform of ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBPCO) activase (RuBPCO-A) on photosynthesis, cDNA of the enzyme (rca) was transferred to rice cultivars (Oryza sativa f. japonica cv. Nipponbare) under the control of RuBPCO small subunit gene promoter (rbcS) via Agrobacterium tumefaciens-mediated transformation. Transgenic rice plants were identified by polymerase chain reaction (PCR) and Southern and Western blot analyses. Net photosynthetic rate (P N) values of the T1 transgenic lines 34 (T34) and 40 (T40) were 45.26 and 46.32 % higher than that of the control plants, respectively. At the same time, their carboxylation efficiency and RuBPCO initial activity, quantum yield of electron transport in photosystem 2 (ΦPS2), and steady state photochemical fluorescence quenching (qP) increased. In addition, heading time of the transgenic rice was advanced. Thus increasing the amount of large isoform of RuBPCO-A in the transgenic rice might have a stimulatory effect on both photosynthesis and plant growth.

The distribution of rare earth elements (REEs) in the fern Dicranopteris dichotoma Bernh plants from a light rare earth elements mine (LRM) and a non-mining (NM) area in Longnan county of Jiangxi province, China were investigated by means of inductively coupled plasma-mass spectrometry, transmission electron microscopy, and energy-dispersive X-ray microanalysis. The photosynthetic characteristics of D. dichotoma were studied by chlorophyll (Chl) a fluorescence kinetics. Contents of REEs in the lamina and the root of D. dichotoma were higher than those in soils, and were mainly distributed in lamina. A part of them was found in the chloroplast. By comparing with D. dichotoma from NM area, the efficiency of photosystem 2 photochemistry and electron transport rate were significantly enhanced in lamina of the plant from LRM because most of REEs deposits were distributed along cell wall, in vacuole, and in chloroplast. High contents of REEs in lamina did not decrease the photosynthetic activities in LRM plants of D. dichotoma. Besides, D. dichotoma could change its β-carotene content to avoid the damaging effect of high REEs content.

The protein secondary structure and pigments' microenvironment in photosystem 1 (PS1) complexes were studied in the temperature range of 25–80 °C using Fourier transform infrared (FT-IR) and circular dichroism (CD) spectroscopy, respectively. Quantitative analysis of the component bands of the amide I band (1 700–1 600 cm−1) showed no significant change below 50 °C. However, apparent conformational changes occurred at 60 °C and further continued at 70 and 80 °C accompanied with transitions of secondary structure mainly from α-helix to the β-sheet structures. CD analysis demonstrated that the regular arrangement, viz. protein microenvironment of pigments of PS1 complexes, was destroyed by heat treatment which might come from the changes of protein secondary structure of PS1. The CD signals at 645 nm contributed by chlorophyll (Chl) b of light-harvesting complex 1 (LHC1) were easily destroyed at the beginning of heat treatment (25–60 °C). When temperature reached 70 and 80 °C, the CD signals at 478 nm contributed mainly by Chl b of LHC1 and 498 nm contributed by carotenoids decreased most rapidly, indicating that LHC1 was more sensitive to high temperature than core complexes. In addition, the oxygen uptake rate decreased by 90.81 % at 70 °C and was lost completely at 80 °C showing that heat treatment damaged the regular function of PS1 complexes. This may be attributed to heat-induced changes of pigment microenvironment and protein secondary structure, especially transmembrane α-helix located in PsaA/B of PS1.

Genes differentially expressed under high irradiance (HI) stress in mature flag leaves of super-hybrid rice Liangyoupeijiu (Oryza sativa ssp. indica) were studied by the silver-staining mRNA differential display technique. We obtained 167 differentially displayed bands on silver-stained polyacrylamide gels and searched for their genetic origins. Five cDNA fragments, which were upregulated by HI stress, were cloned and sequenced. The clones of G25×320, A31×380, and G29×280 putatively encode a cytosolic monodehydroascorbate reductase (MDAR), a phosphatidylinositol 4-kinase (PI-4-K), and a DEAH-box RNA helicase, respectively. Most differentially expressed genes in hybrid rice were inherited from parents and many of them were related with both parents, although some were derived from one parent only. The differentially expressed cDNA fragments having no distinct genetic origins indicated the involvement of some unclear mechanisms in the inheritance processes from parents to hybrid.

The effects of glucose, sodium thiosulphate and a combination of these two compounds in culture medium on growth kinetics and fatty acid production of Chlorella sp. were investigated. Two different concentrations (2.5 mmol and 5.0 mmol) of both components in culture medium were used. Results showed that glucose induced an increase in cell concentration and sodium thiosulphate enhanced accumulation of fatty acids in the cells. When cells were grown in a medium containing both glucose and sodium thiosulphate, the production of fatty acids depended on the concentration of these two components. At a given glucose concentration, an increase in fatty acid production was obtained by increasing the sodium thiosulphate concentration. In contrast, an increase in glucose concentration caused a decrease in fatty acid production when the sodium thiosulphate concentration was fixed. These results suggest that an appropriate concentration of glucose in combination with sodium thiosulphate can enhance the accumulation of lipids of Chlorella sp. cells.

Phosphatidylglycerol (PG) is the sole phospholipid in thylakoid membranes. Phosphate deficiency clearly affected the thylakoid membrane lipid composition of cucumber leaves. Phosphate deficiency induced the decrease in PG content and the concomitant increases in the content of digalactosyl diacylglycerol (DGDG) and sulfoquinovosyl diacylglycerol (SQDG) in cucumber leaves. Although phosphate deficiency led to the 44 mol% decrease of thylakoid PG, the chlorophyll fluorescence coefficients and photosystem II (PSII) oxygen-evolving activity under phosphate deficiency showed virtually no difference compared with those under phosphate sufficiency. It was suggested that phosphate deficiency had no clear effect on PSII function. Besides, PG still maintained in a high level in PSII under phosphate-deficient conditions. These results showed that phosphate deficiency could result in PG decrease in some thylakoid membrane domains but had little effect on the content of PG existed in PSII membrane domains of thylakoid. Maybe, there were two types of PG in thylakoid membrane. Some PG molecules only played a role in the structure of thylakoid membrane and other lipid molecules such as SQDG can substitute for them under phosphate deficiency while some PG molecules may play an important role in maintaining the structure and function of PSII and other lipid molecules cannot substitute for them.

The activity of carbonic anhydrase (CA; EC 4.2.1.1.) was examined in leaf and ear parts of wheat plants ( Triticum aestivum L.) using physiological measurement and histochemical staining. CA activity in leaves increased to the maximum at flag-leaf visible stage, and then decreased to a minimum before increasing at dough stage. From milk to dough stage, CA activities tended to decrease in both glumes and paleas, but increased in the lemmas and pericarps. CA activities in the tissues of ear parts at milk stage were higher than that in leaf tissue, and cv. Xiaoyan54 possessed higher activity of CA in flag-leaves, glumes, lemmas and pericarps than cv. Jing411 at dough stage. Histochemical staining indicates that CA was localized mainly in the chloroplasts of mesophyll cells in flag-leaves and glumes, and also in the xylem vessels of vascular bundles and cytosol of mesophyll cells in lemmas and paleas, but little CA activity was found in the bundle sheath cells (BSC) of both flag-leaf and ear parts. The results suggest that the presence of CA in the mesopyll chloroplasts of glumes, as well as in the xylem vessels of vascular bundles and cytosol of mesophyll cells in lemmas and paleas, might play a functional role for C 4 photosynthesis at dough stage of wheat plants, and cv. Xiaoyan54 had a higher rate of CO 2 delivery than cv. Jing411.

Fluorescence spectroscopy at 77 K showed that the application of glucose lead to the depletion of phycobilisomes (PBS) and photosystems (PS) 2 and 1, and that PS2 was more sensitive to glucose than PS1. The application of sodium thiosulfate, an effective scavenger of reactive oxygen intermediates, counteracted the effects of glucose. Sodium thiosulfate effectively protected photosynthetic apparatus, PS2, PS1, and PBS against glucose-induced depletion. Sodium thiosulfate showed strong capability to inhibit the disappearance of chlorophyll induced by glucose. At a relatively low concentration of glucose, the application of sodium thiosulfate can even be helpful for the assembly of photosynthetic apparatus. Hence the reactive oxygen species might be involved in the depletion of the photosynthetic apparatus in the cyanobacterium Synechocystis sp. PCC 6803 cells grown in the presence of glucose.

Three winter wheat (Triticum aestivum L.) cultivars, representatives of those widely cultivated in Beijing over the past six decades, were grown in the same environmental conditions. Net photosynthetic rate (PN) per unit leaf area and instantaneous water use efficiency (WUE) of flag leaves increased with elevated CO2 concentration. With an increase in CO2 concentration from 360 to 720 µmol mol−1, PN and WUE of Jingdong 8 (released in 1990s and having the highest yield) increased by 173 and 81 %, while those of Nongda 139 (released in 1970s) increased by 88 and 66 %, and Yanda 1817 (released in 1945, with lowest yield) by 76 and 65 %. Jingdong 8 had the highest PN and WUE values under high CO2 concentration, but Yanda 1817 showed the lowest PN. Stomatal conductance (gs) of Nongda 139 and Yanda 1817 declined with increasing CO2 concentration, but gs of Jingdong 8 firstly went down and then up as the CO2 concentration further increased. Intercellular CO2 concentration (Ci) of Jingdong 8 and Nongda 139 increased when CO2 concentration elevated, while that of Yanda 139 increased at the first stage and then declined. Jingdong 8 had the lowest Ci of the three wheat cultivars, and Yanda 1817 had the highest Ci value under lower CO2 concentrations. However, Jingdong 8 had the highest PN and lowest Ci at the highest CO2 concentration which indicates that its photosynthetic potential may be high.

The mechanistic basis for protection of exogenous ascorbate against photoinhibition at low temperature was examined in leaves of rice (Oryza sativa L.). Exposure of intact leaves to chilling temperature resulted in a drastic decrease in the speed of development of non-photochemical fluorescence quenching (NPQ). This was related to the low temperature-imposed restriction on the formation of the fast relaxing component of NPQ (qf). Feeding with 20 mM ascorbate markedly increased the rate of qf development at chilling temperature due primarily to the enhanced rate of zeaxanthin (Z) formation. On the other hand, ascorbate feeding had no influence on photosystem 2 (PS2)-driven electron flow. The reduced state of the PS2 primary electron acceptor QA decreased in ascorbate-fed leaves exposed to high irradiance at chilling temperature owing to the increased Z-associated thermal energy dissipation in the light-harvesting antenna system of PS2. Furthermore, ascorbate feeding increased the photosynthetic apparatus of rice leaves to resist photoinhibition at low temperature. The protective effect of exogenous ascorbate was fully accounted for by the enhanced xanthophyll cycle activity.

Variables of gas exchange of flag leaves and grain yield potentials of five representative winter wheat (Triticum aestivum L.) cultivars varied greatly across different development stages under the same management and irrigation. The cultivars with high yield potential had higher net photosynthetic rate (PN), PPFD (photosynthetic photon flux density) saturated photosynthetic rate (Psat), stomatal conductance (gs), and maximum apparent quantum yield of CO2 fixation (Φm,app) than those with low grain yield, but their dark respiration rate (RD) and compensation irradiance (Ic) were remarkably lower. Compared with overall increase of yield potential of 71 % from low yield cultivars to high yield ones, PN, Psat, Φm,app, and gs were 13, 19, 57, and 32 % higher, respectively; but RD and Ic decreased by 19 and 76 %, respectively. Such difference was evidently large during anthesis stage (e.g., PN by 33 %), which indicated that this period could be the best for assisting further selection for better cultivars. However, transpiration rate (E) and water use efficiency (WUE) differed only little. At different development stages, especially at anthesis, PN and Psat were positively correlated with Φm,app, gs, and yield potential, and negatively correlated with RD and Ic. Thus the high-yield-potential winter wheat cultivars possess many better characters in photosynthesis and associated parameters than the low-yield cultivars.

The generation of superoxide anion radical (O2·−) in the cytochrome b6f complex (Cyt b6f) of spinach under high-light illumination was studied using electron paramagnetic resonance spectroscopy. The generation of O2·− was lost in the absence of molecular oxygen. It was also suppressed in the presence of NaN3 and could be scavenged by extraneous antioxidants such as ascorbate, β-carotene, and glutathione. The results also indicate that O2·−, which is produced under high-light illumination of the Cyt b6f from spinach, might be generated from a reaction involing 1O2, and the Rieske Fe-S protein could serve as the electron donor in the O2·− production. The mechanism of photoprotection of the Cyt b6f complex by antioxidants is discussed.

Photosynthetic rates in different development stages were carefully investigated in 18 cultivars of winter wheat released in the period between 1945 and 1995 in the area of Beijing, China. During this period, the recorded grain yield has increased eightfold. However, when those cultivars were planted and managed in the same environment, the difference was reduced to only 36%, indicating that agronomic practices are the most important factors for grain yield. Agronomic features have changed greatly in the past 50 years, through increasing the harvest index (R2 = 0.89, P < 0.05), shortening plant height (R2 = 0.77, P < 0.05) and slightly increasing flag leaf areas (R2 = 0.45, P < 0.05), which is mostly in agreement with many other researchers. In contrast to many reports, however, this study found a genetic increase in the rate of photosynthesis per unit leaf area. From the mid-stem elongation to soft dough stages, the average photosynthetic rates at saturated photosynthetic photon flux density (P(sat)) increased by 44%. In the process, the stomatal conductance (g(s)) also increased by 122%. Grain yield was positively related to the mean values of P(sat) (R2 = 0.61, P < 0.01) and g(s) (R2 = 0.67, P < 0.01) in the six development stages. Our experiment may suggest that increase in grain yield was associated with the elevation of leaf photosynthetic rate and stomatal conductance over the past 50 years.

Differences in fatty acid composition contribute to different membrane fluidity, which is very important for cells to survive unfavorable growth conditions (Nakashima et al., 1999). The demonstration of the roles of lipids is mostly based on differences in the composition of polar head groups. In fact, some fatty acids show characteristic roles in constructing membrane protein complexes. For example, trans-3-palmitoleic acid, is only found in PG of higher plants, and its percentage is related to the level of trimeric LHCII (Siegenthaler and Tremoli res, 1998). So it is very necessary to determine the fatty acid composition for a novel lipid in order to demonstrate its roles. This paper reported the fatty acid composition in a novel glycolipid in Synechocystis sp. PCC 6803 cells grown in BG-11 medium with glucose applied and the polar head group of the glycolipid was also investigated.

The lignification process and lignin heterogeneity of fibre, vessel and parenchyma cell walls for various age classes of bamboo stems of Phyllostachys pubescens Mazel were investigated. It was shown that protoxylem vessels lignified in the early stage of vascular bundle differentiation, metaxylem vessel and fibre walls initiated lignification from the middle lamella and cell corners after the completion of vascular bundle differentiation. Most of the parenchyma cell walls lignified after the stem reached its full height, while a few parenchyma cells remained non-lignified even in the mature culm. The cell walls of fibres and most parenchyma cells thickened further during the stem growth to form polylamellate structure and the lignification process of these cells may last even up to 7 years. The fibre walls were rich in guaiacyl lignin in the early stage of lignification, and lignin rich in syringyl units were deposited in the later stage. Vessel walls mainly contained guaiacyl lignin, while both guaiacyl and syringyl lignin were present in the fibre and parenchyma cell walls.

Studies with positron-emission tomography have indicated that muscarinic acetylcholine receptors may be involved in the mechanism of enhancement of cerebral blood flow (CBF) by neuronal functional activation. We examined the effects of muscarinic receptor blockade by scopolamine on the local CBF responses to vibrissal stimulation in the whisker-to-barrel cortex sensory pathway in unanesthetized rats. Local CBF was measured by the quantitative autoradiographic [(14)C]iodoantipyrine method. Scopolamine (0.4 or 0.8 mg/kg) was injected i.v. 30 min before measurement of local CBF; control rats received equivalent volumes of physiological saline. Vibrissae on the left side of the face were stroked continuously throughout the 1-min period of measurement of CBF. Local CBF was determined bilaterally in four structures of the pathway, i.e., spinal and principal sensory trigeminal nuclei, ventral posteromedial thalamic nucleus, and barrel field of the sensory cortex, as well as in four representative structures unrelated to the pathway. The higher dose of scopolamine raised baseline CBF in the two trigeminal nuclei, but neither dose diminished the percentage of increases in local CBF because of vibrissal stimulation in any of the stations of the pathway. These results do not support involvement of muscarinic receptors in the mechanism of enhancement of local CBF by functional neuronal activation, at least not in the whisker-barrel cortex sensory pathway in the unanesthetized rat.

The hydroxylation of S-mephenytoin exhibits a genetic polymorphism in humans and there are a large interethnic differences in the frequency of the poor metabolizer phenotype. A S-mephenytoin P450-hydroxylase termed P450 UK was purified and identified to be CYP 2C19 by amino-terminal amino acid analyses. The levels of P450 2C19 and the ability of the human liver samples to 4'-hydroxylate S-mephenytoin were found to be strongly correlative. Recent report showed that the principle defect in S-mephenytoin poor metabolizers is a single base pair (G--A) mutation in exon 5 of CYP 2C19 resulting in an aberrantly spliced mRNA and a non-functional P450 2C19 protein in liver of S-mephenytoin PM. Further investigations demonstrate that this major defect is responsible for about 75% of poor metabolizer phenotype in both caucasians and orientals who are homozygous for S-mephenytoin hydroxylation defect. This genetic defect (CYP 2C19) also affects metabolism of several other widely clinical used drugs.

A gas chromatographic method equipped with nitrogen-phosphorus detector was developed for the determination of the S- and R-enantiomers of the anticonvulsant, mephenytoin (MP) in human urine. Dichloromethane (4 ml) was added to 1 ml urine, the mixture was shaken and centrifuged. The organic phase was transferred to another tube and blown to dryness under nitrogen on water bath (37 degrees C). The residue was dissolved in 10 microliters ethylacetate and 1-2 microliters was injected into the GC. Our results showed that direct enantiomeric separation of mephenytoin was obtained by using a chiral capillary column, the retention times for S- and R-mephenytoin were 25.5 and 26.2 min respectively, with a detection limit less than 50 ng/ml of mephenytoin. Similar linear and reproducible standard curves were obtained over the concentration range of 53.2 to 2128.0 ng/ml (for S-MP, r = 0.9914 +/- 0.0070, n = 6; and for R-MP, r = 0.9939 +/- 0.0070, n = 6), and the mean recoveries of S- and R-MP were 95.4% and 95.8% respectively. The within-day relative standard deviations were less than 8.8% for both S- and R-MP, and that of between-days were less than 14.3%. There was a good reproducibility of the urine S/R mephenytoin determined in China and in Sweden by using similar method in 107 Chinese volunteers after a single oral dose of 100 mg racemic mephenytoin (r = 0.9091, P0.001).

The metabolic ratio of debrisoquine hydroxylation (MR) determined as the ratio of debrisoquine over 4-OH-debrisoquine in 8 h urine after a single oral dose of DB (10 mg) in unrelated Chinese Zang and Wei volunteers was studied by using gas chromatography. The MR of 132 healthy Chinese Zang subjects ranged from 0.20 to 34.32, and that of 158 healthy Chinese Wei subjects ranged from 0.13 to 29.73. Two phenotypes were apparent in the frequency distribution histograms with an antimode at log MR = 1.10 (MR = 12.6). Two subjects were therefore identified as poor metabolizers (PMs) of DB in 132 Zang volunteers (the frequency of PMs was found to be 1.52%), and only one in 158 Wei volunteers (0.63%). Neither sex nor smoking habit affected the DB hydroxylation (P greater than 0.2). The recoveries of DB and 4-OH-DB in Zang volunteers were 19.83 +/- 10.99 and 11.57 +/- 7.04%, and in Wei volunteers they were 22.74 +/- 14.41 and 17.77 +/- 10.82%, respectively.

It has been now established that PSI has two kinds of light-harvesting chlorophyll protein complexes (i.e. LHCIa and LHCIb), while PSII contains three, of which CP-47, CP-43 both acting as the internal antennae of PSII and LHCII consist (1–4). It was demonstrated that the phosphorylation of LHCII in vitro resulted in its lateral migration from grana to stroma and in this way promoted the distribution of excitation energy to PSI. On the contrary, the pretreatment of thylakoids with Mg2+ caused the migration of LHCII and LHCI from stroma to grana so as to favourably distribute the excitation energy to PSII(5–7). Our recent experiment comparing the effects of Ca2+ and Mg2+ on the organization and function of chlorophyll-protein complexes on thylakoid membrane have provided new informations in this respect.

It has been recognized since 1969 (1) that chloroplast has a regulatory mechanism which influences the properties of light harvesting pigments. in 1980, Bennet, Steinback and Arntzen proposed a biochemical mechanism to explain how these “State I and State II” changes were regulated (2). A light harvesting chlorophyll-protein associated with PSII is reversibly phosphorylated, thereby controls the extent of excitation energy transfer from PSII to PSI.