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PubMed2004

Comparative effectiveness of cattle manure, poultry manure, phosphocompost and fertilizer-NPK on three cropping systems in vertisols of semi-arid tropics. II. Dry matter yield, nodulation, chlorophyll content and enzyme activity.

A field experiment was conducted on a deep Vertisol of Bhopal, India to compare root and shoot biomass, chlorophyll content, enzyme activity and nodulation in three cropping systems at three combinations of organic manure and inorganic-fertilizer: 75%NPK + 5 t farmyard manure (FYM), 75%NPK + 1.5 t poultry manure (PM), and 75%NPK + 5 t phosphocompost (PC) vis-a-vis 0%, 75% and 100% of fertilizer-NPK. In general, nodule number and its mass were lower in intercrop soybean than sole soybean. Also there was decrease in the nodule number with higher NPK dose. The FYM treated plots recorded 22.0% and 7.6% higher nodule mass than poultry manure and phosphocompost plots, respectively. Also, the total chlorophyll content was higher in organically treated plots than that in 100% NPK particularly at 30 days after sowing (DAS, pre-flowering). In sorghum the peak nitrate reductase (NR) activity was recorded at 60 DAS while in soybean it was at 30 DAS. The NR activity was higher in intercrop sorghum than that in sole sorghum. Maximum NR activity was observed in 100% NPK. Soybean/sorghum intercropping system recorded significantly higher root and shoot biomass than sole soybean and sorghum. The crop growth rates were relatively rapid during 30-60 DAS and followed the order; intercropping > sole sorghum > sole soybean. With the increase in NPK dose from 0% to 100% there was significant improvement in the dry matter (DM) production in sole sorghum and soybean/sorghum intercropping system. Soybean as preceding crop recorded the highest DM, chlorophyll content, NR activity in wheat while these values were the lowest in sorghum-wheat system.

Agriculture↗
PubMed2005

Occurrence of chlorophyll precursors in leaves of cabbage heads--the case of natural etiolation.

In the interior of cabbage (Brassica oleracea) heads (kale, white cabbage, Brussels sprouts), natural leaf etiolation takes place due to a limited light access and chlorophyll biosynthesis is inhibited in a consequence. Instead, apart from carotenoids, whose biosynthesis is not light-dependent, chlorophyll precursors accumulate, mainly protochlorophyllide and to a smaller extent also chlorophyllides a and b. Protochlorophyllide was also detected in green, light-exposed leaves of heads of all the investigated cabbage varieties. Protochlorophyll was not found in the investigated leaves. The analysis of xanthophylls composition showed that the central leaves of kale and white cabbage heads contain relatively high amounts of trans-neoxanthin and lutein epoxide which are found only in trace amounts in green leaves. This is the first systematic study on natural occurrence of chlorophyll biosynthesis precursors in different cabbage varieties.

Brassica↗
PubMed2006

Comparative study of the water oxidizing reactions and the millisecond delayed chlorophyll fluorescence in photosystem II at different pH.

Water splitting activity, the multiline EPR signal associated with S(2)-state of the CaMn(4)-cluster and the fast and slow phases of the induction curve of the millisecond delayed chlorophyll fluorescence from photosystem II (PSII) in the pH range of 4.5-8.5 were studied in the thylakoid membranes and purified PSII particles. It has been found that O(2) evolution and the multiline EPR signal were inhibited at acidic (pK approximately 5.3) and alkaline (pK approximately 8.1) pH values, and were maximal at pH 6.0-7.0. Our results indicate that the loss of O(2) evolution and the S(2)-state multiline EPR signal associated with the decrease of the millisecond delayed chlorophyll fluorescence only in alkaline region (pH 7.0-8.5). Possible correlations of the millisecond delayed chlorophyll fluorescence components with the donor side reactions in PSII are discussed.

Chlorophyll↗
PubMed2004

NTZIP antisense plants show reduced chlorophyll levels.

We have isolated and characterized a new photosynthetic tissue-specific gene NTZIP (Nicotiana tabacum leucine zipper) from tobacco (N. tabacum). Its deduced amino acid sequence has two highly conserved regions, leucine zipper and [EX(n)DEXRH](2) motifs, which are related to the gene's biochemical functions. NTZIP was expressed in leaves and stems, but was not detected in roots or flowers, suggesting that its physiological functions might be associated with photosynthesis. Northern blot analysis showed that NTZIP mRNA accumulation was induced by light signals, increased greatly under low temperatures and was repressed by strong light illumination. Furthermore, a number of homologs of NTZIP were isolated from cucumber (Cucumis sativus), rape (Brassica napus), clover (Trifolium repens), willow (Salix babylonica), rosebush (Rusa dovurica), wheat (Triticum aestivum) and spinach (Spinacia oleracea), proving the ubiquitous existence of the NTZIP-like genes in higher plants. Transgenic tobaccos constitutively expressing antisense RNA to NTZIP displayed chlorosis and a lack of ability to turn green even under normal growth conditions. The chlorophyll deficiency was further confirmed by chlorophyll content determination and gas exchange analysis. Based on these observations, we propose that NTZIP may be involved in chlorophyll biosynthesis, and might define a novel family of evolutionarily conserved proteins with its homologs in other plant species.

Amino Acid Sequence↗
PubMed2002

Resolution of the Photosystem I and Photosystem II contributions to chlorophyll fluorescence of intact leaves at room temperature.

Green leaves illuminated with photosynthetically active light emit red fluorescence, whose time-dependent intensity variations reflect photosynthetic electron transport (the Kautsky effect). Usually, fluorescence variations are discussed by considering only the contribution of PSII-associated chlorophyll a, although it is known that the fluorescence of PSI-associated chlorophyll a also contributes to the total fluorescence [Aust. J. Plant Physiol. 22 (1995) 131]. Because the fluorescence emitted by each photosystem cannot be measured separately by selecting the emission wavelength in in vivo conditions, the contribution of PSI to total fluorescence at room temperature is still in ambiguity. By using a diode array detector, we measured fluorescence emission spectra corresponding to the minimal (F(O)) and maximal (F(M)) fluorescence states. We showed that the different shapes of these spectra were mainly due to a higher contribution of PSI chlorophylls in the F(O) spectrum. By exciting PSI preferentially, we recorded a reference PSI emission spectrum in the near far-red region. From the F(O) and F(M) spectra and from this PSI reference spectrum, we derived specific PSI and PSII emission spectra in both the F(O) and F(M) states. This enables to estimate true value of the relative variable fluorescence of PSII, which was underestimated in previous works. Accurate separation of PSI-PSII fluorescence emission spectra will also enable further investigations of the distribution of excitation energy between PSI and PSII under in vivo conditions.

Chlorophyll↗
PubMed1969

Absorption and fluorescence of chlorophyll a in particle fractions from different plants.

Density-gradient centrifugation of disintegrated cells from a variety of plants gave two kinds of chlorophyll particles from all except the blue-green algae. As in previous procedures using detergents, the lighter Fraction 1 particles usually had greater absorption at longer wavelengths; they always had a lower ratio of short to long wavelength fluorescence at low temperature, and a lower fluorescence yield per chlorophyll than the denser Fraction 2 particles. Although only one kind of particle fraction was found in each blue-green alga, the fine structure of the chlorophyll a absorption band differed significantly among the three species measured.

Chlorophyll↗
PubMed2001

Effects of ozone on chlorophyll and quantum yield of tobacco (Nicotiana tabacum L.) varieties.

Plants of Bel-W3 and of seven commercial tobacco varieties (Nicotiana tabacum L.) were exposed to two relatively low ozone concentrations (90 or 135 ppb) for 20 consecutive days, for 8 h per day. Ozone caused necrotic and chlorotic spots, acceleration of leaf senescence, depression of photosynthetic mechanism, chlorophyll diminution and greater destruction of chl a than of chl b. The higher sensitivity of chl a was also confirmed by exposure of segments of leaves in test tubes to high ozone concentration (>1000 ppb) as well as by bubbling of ozone in extracts of chlorophyll in vitro. The quantum yield (QY) of photosynthesis was positively correlated with the chlorophyll content and negatively correlated with the visible injury and the chl b/a ratio.

Air Pollution↗
PubMed2000

Acute toxicity of excess mercury on the photosynthetic performance of cyanobacterium, S. platensis--assessment by chlorophyll fluorescence analysis.

Measurement of chlorophyll fluorescence has been shown to be a rapid, non-invasive, and reliable method to assess photosynthetic performance in a changing environment. In this study, acute toxicity of excess Hg on the photosynthetic performance of the cyanobacterium S. platensis, was investigated by use of chlorophyll fluorescence analysis after cells were exposed to excess Hg (up to 20 microM) for 2 h. The results determined from the fast fluorescence kinetics showed that Hg induced a significant increase in the proportion of the Q(B)-non-reducing PSII reaction centers. The fluorescence parameters measured under the steady state of photosynthesis demonstrated that the increase of Hg concentration led to a decrease in the maximal efficiency of PSII photochemistry, the efficiency of excitation energy capture by the open PSII reaction centers, and the quantum yield of PSII electron transport. Mercury also resulted in a decrease in the coefficients of photochemical and non-photochemical quenching. Mercury may have an acute toxicity on cyanobacteria by inhibiting the quantum yield of photosynthesis sensitively and rapidly. Such changes occurred before any other visible damages that may be evaluated by other conventional measurements. Our results also demonstrated that chlorophyll fluorescence analysis can be used as a useful physiological tool to assess early stages of change in photosynthetic performance of algae in response to heavy metal pollution.

Biological Assay↗
PubMed2002

Aluminum corrolin, a novel chlorophyll analogue.

A corrole-based chlorophyll analogue has been prepared, based on the notation that the major differences between the prosthetic groups of chlorophylls and hemes are the presence of a non-transition metal (Mg vs. Fe) and one reduced double bond in the porphyrin ligand. As corroles act as tri- rather than dianionic ligands, the analogy requires the insertion of aluminum into the macrocycle and the reduction of one of its double bonds, two reactions that have not been previously reported with any corrole. The aluminum complexes of both the corrole and the corrolin (the dihydrocorrole) display fluorescence quantum yield that are much larger than of chlorophyll and of all other previously reported synthetic analogues. The results suggest that the light metal atom ion is responsible for low intersystem crossing probability to the triplet excited state and the structural rigidity of the hexa-coordinated complexes for reducing the probability of internal conversion.

Aluminum↗
PubMed2003

A new relative referencing method for crop monitoring using chlorophyll fluorescence.

The measurement of plant chlorophyll fluorescence has been used for many years as a method to monitor a plant's health status. These types of methods have been mostly relegated to the laboratory. The newly developed Relative Referencing Method allows for the measurement of chlorophyll fluorescence under artificial lighting conditions. The fluorescence signal can be determined by first taking a reference signal measurement, then a second measurement with an additional fluorescence excitation source. The first signal can then be subtracted from the second and the plant's chlorophyll fluorescence due to the second lighting source can be determined. With this simple approach, a photosynthesizing plant can be monitored to detect signs of water stress. Using this approach experiments on tomato plants have shown that it was possible to detect water stress, while the plants were continuously illuminated by fluorescent lamps. This method is a promising tool for the remote monitoring of crops grown in a CELSS-type application.

Chlorophyll↗
PubMed2000

Relevance of the chlorophyll phytyl chain on lamellar phase formation and organisation.

A series of modified chlorophylls (chlorophyll a, pyrochlorophyll a, Zn-pheophytin a and Zn-pheophorbide a) have been inserted into lamellar phases of sodium bis-(2-ethylhexyl)-sulfosuccinate (AOT). The role played by the different functional groups in affecting the bilayer formation and organisation has been investigated by means of the NMR quadrupolar splitting technique. Evidence is reported for the first time on the capacity of the phytyl chain of the chlorophylls to anchor the tetrapyrroles into the bilayer, favouring at the same time the regular formation of the lamellae.

Chlorophyll↗
PubMed2003

Changes in the energy distribution between chlorophyll-protein complexes of thylakoid membranes from pea mutants with modified pigment content. I. Changes due to the modified pigment content.

The low-temperature (77 K) emission and excitation chlorophyll fluorescence spectra in thylakoid membranes isolated from pea mutants were investigated. The mutants have modified pigment content, structural organization, different surface electric properties and functions [Dobrikova et al., Photosynth. Res. 65 (2000) 165]. The emission spectra of thylakoid membranes were decomposed into bands belonging to the main pigment protein complexes. By an integration of the areas under them, the changes in the energy distribution between the two photosystems as well as within each one of them were estimated. It was shown that the excitation energy flow to the light harvesting, core antenna and RC complexes of photosystem II increases with the total amount of pigments in the mutants, relative to the that to photosystem I complexes. A reduction of the fluorescence ratio between aggregated trimers of LHC II and its trimeric and monomeric forms with the increase of the pigment content (chlorophyll a, chlorophyll b, and lutein) was observed. This implies that the closer packing in the complexes with a higher extent of aggregation regulates the energy distribution to the PS II core antenna and reaction centers complexes. Based on the reduced energy flow to PS II, i.e., the relative increased energy flow to PS I, we hypothesize that aggregation of LHC II switches the energy flow toward LHC I. These results suggest an additive regulatory mechanism, which redistributes the excitation energy between the two photosystems and operates at non-excess light intensities but at reduced pigment content.

Chlorophyll↗
PubMed2001

Modulation of photosystem II chlorophyll fluorescence by electrogenic events generated by photosystem I.

In an attempt to uncover electric field interactions between PS I and PS II during their functioning, fluorescence induction curves were measured on hydroxylamine-treated thylakoids of Chenopodium album under conditions ensuring low and high levels of photogenerated membrane potentials. In parallel experiments with Peperomia metallica chloroplasts, the photocurrents were measured with patch-clamp electrodes and served as indicator of electrogenic activity of thylakoid membranes in continuous light. Inhibition of linear electron flow at PS II donor side by hydroxylamine (0.1 mM) eliminated a slow rise of chlorophyll fluorescence to a peak level and suppressed photoelectrogenesis. Activation of PS I-dependent electron transport using cofactors of either cyclic (phenazine methosulfate) or noncyclic electron transport (reduced TMPD or DCPIP in combination with methyl viologen) restored photoelectrogenesis in hydroxylamine-treated chloroplasts and led to reappearance of slow components in the fluorescence induction curve. Exposure of thylakoids to valinomycin reduced the peak fluorescence in the presence of KCl but not in the absence of KCl. Combined application of valinomycin and nigericin in the presence of KCl exerted stronger suppression of fluorescence than valinomycin alone but was ineffective in the absence of KCl. In samples treated with hydroxylamine and PS I cofactors (DCPIP/ascorbate and methyl viologen), preillumination with a single-turnover flash or a multiturnover pulse shifted the induction curves of both membrane potential and chlorophyll fluorescence to shorter times, which confirms the supposed influence of PS I-generated electrical field on PS II fluorescence. A model is presented that describes modulating effect of the membrane potential on chlorophyll fluorescence and roughly simulates the fluorescence induction curves measured at low and high membrane potentials.

Chenopodium album↗
PubMed2001

Triplet formation on a monomeric chlorophyll in the photosystem II reaction center as studied by time-resolved infrared spectroscopy.

The process of formation of the triplet state of chlorophyll in the photosystem II (PS II) reaction center complex was studied by means of time-resolved infrared (IR) spectroscopy. Using a dispersive-type IR spectrometer with a time resolution of approximately 55 ns, transient spectra in the C=O stretching region (1760--1600 cm(-1)) were measured at 77 K. The data were analyzed by singular-value decomposition and subsequent least-squares fitting. Two distinct spectral components having different kinetic behaviors were resolved. One had spectral features characterized by negative peaks at 1740 and 1680 cm(-1) and an overall positive background and was assigned to the P(680)(+)Phe(-)/P(680)Phe radical pair by static FTIR measurements of the P(680)(+)/P(680) and Phe(-)/Phe differences. The other had prominent negative and positive peaks at 1668 and 1628 cm(-1), respectively, which were previously assigned to the keto C==O change upon triplet formation of the monomeric chlorophyll denoted as Chl(T) [Noguchi, T., Tomo, T., and Inoue, Y. (1998) Biochemistry 37, 13614-13625]. The former component of P(680)(+)Phe(-)/P(680)Phe exhibited a multiphasic decay with time constants of 77 ns (75%), 640 ns (18%), 8.3 micros (4%), and 0.3 ms (3%), while the latter component of (3)Chl(T)/Chl(T) was formed with a single-exponential rise with a time constant of 57 ns and had a lifetime of 1.5 ms. From the observations that only the two spectral components were resolved without any other triplet intermediates and the time constant of (3)Chl(T) formation roughly agreed with or seemed even faster than that of the major phase of the P(680)(+)Phe(-) decay, two alternative mechanisms of triplet formation are proposed. (i) (3)Chl(T) is directly formed from P(680)(+)Phe(-) by charge recombination at Chl(T), and (ii) (3)P(680) is formed, and then the triplet is transferred to Chl(T) with a time constant of much less than 50 ns. The location of Chl(T) in the D1 subunit as the monomer chlorophyll corresponding to the accessory bacteriochlorophyll in the L subunit of purple bacteria is favored to explain the former mechanism as well as the triplet properties reported in the literature. The physiological role of the triplet formation on Chl(T) is also discussed.

Chlorophyll↗
PubMed2002

Identifying the lowest electronic states of the chlorophylls in the CP47 core antenna protein of photosystem II.

CP47 is a pigment-protein complex in the core of photosystem II that tranfers excitation energy to the reaction center. Here we report on a spectroscopic investigation of the isolated CP47 complex. By deconvoluting the 77 K absorption and linear dichroism, red-most states at 683 and 690 nm have been identified with oscillator strengths corresponding to approximately 3 and approximately 1 chlorophyll, respectively. Both states contribute to the 4 K emission, and the Stark spectrum shows that they have a large value for the difference polarizability between their ground and excited states. From site-selective polarized triplet-minus-singlet spectra, an excitonic origin for the 683 nm state was found. The red shift of the 690 nm state is most probably due to strong hydrogen bonding to a protein ligand, as follows from the position of the stretch frequency of the chlorophyll 13(1) keto group (1633 cm(-)(1)) in the fluorescence line narrowing spectrum at 4 K upon red-most excitation. We discuss how the 683 and 690 nm states may be linked to specific chlorophylls in the crystal structure [Zouni, A., Witt, H.-T., Kern, J., Fromme, P., Krauss, N., Saenger, W., and Orth, P. (2001) Nature 409, 739-743].

Chlorophyll↗
PubMed2001

The effect of axial Mg ligation on the geometry and spin density distribution of chlorophyll and bacteriochlorophyll cation free radical models: a density functional study.

Density functional calculations are performed on models of chlorophyll and bacteriochlorophyll to examine the effect of Mg ligation on the geometry and spin density distribution of the cation free radicals formed. It is shown that, whereas the properties of the bacteriochlorophyll model can be explained on the basis of the electron density distribution of the highest occupied molecular orbital (HOMO), for the chlorophyll model the geometry and spin density properties of the ligated species do not follow this trend. For the ligated chlorophyll models it is shown that, due to the closeness in energy of the HOMO and HOMO-1 orbitals, a Jahn-Teller distortion occurs on one-electron oxidation, leading to an admixed hybrid orbital for the cation radical form. Orbital mixing is shown to lead to significant changes in the geometry and spin density distribution of the cation free radical formed. It is also shown that orbital mixing does not lead to an increase in the magnitude of the (14)N hyperfine couplings thereby invalidating reports in the literature which have dismissed mixed orbital states for the primary donor cation radicals of photosynthetic reaction centers based on this criterion.

Bacteriochlorophylls↗
PubMed2002

Relationship between color (instrumental and visual) and chlorophyll contents in soybean seeds during ripening.

The correlation between chlorophyll content and quantitative color parameters was investigated in order to find an indirect method for predicting green pigment in ripening soybean seeds. Five Brazilian soybean varieties harvested at different maturity stages (R(6) to R(8) according to the scale of Fehr & Caviness) and dried under two conditions (in oven at 40 degrees C with circulating air and at ambient temperature around 25 degrees C) were analyzed in two consecutive years. The slow-dried seeds at 25 degrees C lost chlorophyll faster, whereas drying at 40 degrees C did not result in yellowing of seeds. High and significant linear correlations between a value and total chlorophyll were obtained over the whole maturation period and on both conditions of drying. From an industrial point of view it appears that a value, obtained by the CIE-L*a*b* method, seems to be a good tool to be applied for quality control and classifying soybean seeds for different purposes.

Chlorophyll↗
PubMed2006

Noninvasive evaluation of the degree of ripeness in grape berries (vitis vinifera L. Cv. Bacchus and silvaner) by chlorophyll fluorescence.

The use of chlorophyll fluorescence measurements to noninvasively evaluate degrees of ripeness was investigated in berries at various stages of ripening from two white grapevine cultivars (Vitis vinifera L. Cv. Bacchus and Silvaner). Berries were characterized by diameter, weight, and density and by concentrations of fructose, glucose, sucrose, and total sugars, as well as fructose/glucose ratios, and also by chlorophyll fluorescence at F(0) and F(M) levels and the fluorescence ratio F(V)/F(M). Pearson product moment correlation analysis on data from both cultivars revealed clear negative associations between F(0) and concentrations of fructose, glucose, and total sugars, and fructose/glucose ratios (correlation coefficient < -0.89). Curvilinear trend-lines were established for plots of F(0) versus concentrations of fructose, glucose, and total sugars, but a linear relationship between F(0) and fructose/glucose ratios was found: the corresponding coefficients of determination were always >0.82. Therefore, chlorophyll fluorescence measurements are well-suited to determine noninvasively sugar accumulation in grape berries during ripening.

Carbohydrates↗