Evaluating the relationship between leaf chlorophyll concentration and SPAD-502 chlorophyll meter readings

Relationships between chlorophyll concentration ([chl]) and SPAD values were determined for birch, wheat, and potato. For all three species, the relationships were non-linear with an increasing slope with increasing SPAD. The relationships for birch and wheat were strong (r ² ∼ 0.9), while the potato relationship was comparatively weak (r ² ∼ 0.5). Birch and wheat had very similar relationships when the chlorophyll concentration was expressed per unit leaf area, but diverged when it was expressed per unit fresh weight. Furthermore, wheat showed similar SPAD–[chl] relationships for two different cultivars and during two different growing seasons. The curvilinear shape of the SPAD–[chl] relationships agreed well with the simulated effects of non-uniform chlorophyll distribution across the leaf surface and multiple scattering, causing deviations from linearity in the high and low SPAD range, respectively. The effect of non-uniformly distributed chlorophyll is likely to be more important in explaining the non-linearity in the empirical relationships, since the effect of scattering was predicted to be comparatively weak. The simulations were based on the algorithm for the calculation of SPAD-502 output values. We suggest that SPAD calibration curves should generally be parameterised as non-linear equations, and we hope that the relationships between [chl] and SPAD and the simulations of the present study can facilitate the interpretation of chlorophyll meter calibrations in relation to optical properties of leaves in future studies.     

Photoconversion of protochlorophyll to chlorophyll a in a mutant of Chlorella regularis

Dark-grown cells of a mutant strain of Chlorella regularis containedchlorophyll a and protochlorophyll, phytyl ester of protochlorophyllide.Under illumination, protochlorophyll was quantitatively anddirectly converted into chlorophyll a. The photoconversion wasdependent on light intensity and temperature and proceeded ina cell-free preparation. The pathway of chlorophyll formation found in the mutant cellsis entirely different from that from protochlorophyllide byway of chlorophyllide a, which is generally observed in greenplants. ¹Present address: Division of Biology, Medical College of Miyazaki,Miyazaki 889-16, Japan. ²Present address: Division of Environmental Biology, The NationalInstitute for Environmental Studies, Ibaragi 300-21, Japan. (Received October 24, 1975; )     

Biosynthesis of chlorophyll from protochlorophyll(ide) in green plant leaves

Using spectral methods, the biosynthesis of protochlorophyll(ide) and chlorophyll(ide) in green plant leaves was studied. The main chlorophyll precursors in the green leaves (as in etiolated leaves) were photoactive photocholorophyll(ide) forms Pchl(ide)655/650(448) and Pchl(ide)653/648(440). The contributions into Chl biosynthesis of the shorter-wavelength precursor forms ,which were accumulated in darkened green leaves as well, were completely absent (of Pchl(ide) 633/628(440)) or insignificant (of Pchl(ide)642/635(444)).     

Accumulation of protochlorophyll and chlorophyll a as controlled by photomorphogenically effective light

Summary Data are presented which indicate that the rate of synthesis and the pool size of photoconvertible protochlorophyll(ide) in the cotyledons of the mustard seedling are controlled by the active form of phytochrome (P_fr). Inductionreversion experiments show that formation of chlorophyll a through photoconversion of the protochlorophyll(ide) by repeated red pulses (5 min each) has no effect on synthesis of carotenoids and galactolipids. Since the protochlorophyll(ide)-converting activity of the standard far-red light used in this laboratory is very low, chlorophyll-a accumulation is very slow under continuous standard far-red light. It is concluded that photosynthesis (or photosynthetic phosphorylation) does not participate in the high irradiance reaction of photomorphogenesis.     

A mathematical analysis of the relation between (bacterio) chlorophyll fluorescence yield and the concentration of reaction centre traps in photosynthesis

A random walk approach is used to discuss the relation between fluorescence yield and the concentration of reaction centre traps. For the matrix model as used for bacteria, non-negligible deviations are found from the Vredenberg-Duysens relation. An approximately linear re;ationship between the reciprocal of the fluorescence yield and the trap concentration remains. For the unit model as used for system 2, the deviation from Joliot's relation is small. The assumptions of the unit model are debatable. An alternative matrix model is presented.     

Photoconversion and regeneration of active protochlorophyll(ide) in mutants defective in the regulation of chlorophyll synthesis

Seedlings carrying mutations in regulatory genes for protochlorophyll(ide) synthesis accumulate protochlorophyll(ide) in darkness in amounts exceeding the wildtype level. Thus, +/tig-d¹² and $\text{tig-b}{}^{24}\text{tig-b}{}^{24}$accumulate 2-fold, $\text{tig-o}{}^{34}\text{tig-o}{}^{34}$ 5- to 6-fold, and $\text{tig-d}{}^{12}\text{tig-d}{}^{12}$ 15-fold more protochlorophyll(ide) than the wild type.The amount of photoconvertible protochlorophyll(ide) accumulated in darkness is the same in all genotypes, despite the large differences in total protochlorophyll(ide) content, indicating a constant number of photoconversion sites.When briefly illuminated leaves are returned to darkness, regeneration of active protochlorophyll(ide) from the pool of inactive protochlorophyll(ide) takes place in wild-type and mutant leaves. Compared to the wild type, the rate of protochlorophyll(ide) activation during 4- and 10-min dark periods is higher in +/tig-d¹², $\text{tig-b}{}^{24}\text{tig-b}{}^{24}$, and $\text{tig-o}{}^{34}\text{tig-o}{}^{34}$, but lower in $\text{tig-d}{}^{12}\text{tig-d}{}^{12}$.There was no indication that the accumulation of protochlorophyll(ide) influences the conversion sites of the protochlorophyll(ide) holochrome, as the kinetics of photoconversion of initially active protochlorophyll(ide) in leaves with the genotypes +/+, +/tig-o³⁴, and $\text{tig-o}{}^{34}\text{tig-o}{}^{34}$ are similar or identical.     

Migration of electron excitation energy in mixed associates of chlorophyll and its derivatives]

The intracomplex migration is investigated of electron excitation energy between molecules which are a part of a mixed associate. Weakly fluorescent and nonfluorescent associates of chlorophyll and its analogues as well as of bacteriochlorophyll and neoxanthine have been used as donors and acceptors. The migration of excitation energy with variation of quantum yield of donor emission from 5-10(-3) to less than or equal to 10(-4) and also with very weak overlapping of luminescence and absorption spectra for the pair D leads to A is experimentally discovered by luminescence excitation spectra of mixed pigment aggregates. A specific disturbing action of Pd and Cu ions on chlorophyll a luminescence with formation of mixed complexes of chlorophyll with Pd-pheophytin a and Cu-pheophytin b is observed. The presence of Pd and Cu ions in the structure of the mixed complexes gives rise to a considerable reduction of chlorophyll apparently due to increasing intersystem crossing probability in the chlorophyll molecule. The probability of intracomplex energy migration in systems under investigation amounts to approximately 10(12) sec-1 according to the obtained estimations. The probable mechanism of energy migration in mixed associates is discussed. The obtained results may be used for elucidation of a possible role of the mixed aggregates and effective intracomplex migration of excitation energy in photosynthetic apparatus of green plants.     

Correlation between 5-aminolaevulinate accumulation and protochlorophyll photoconversion

A 1-min light pulse delivered to mustard seedlings (Sinapis alba L.) 60 h after sowing initiates the release of cotyledonary 5-aminolaevulinate (ALA) accumulation which continues for at least 2 h in the dark. Phytochrome (P _fr) increases the rate of ALA accumulation after a 24-h red light pretreatment but is not the trigger for this release. It is shown that the rate of ALA accumulation varies with the wave-length and fluence rate of the 1-min light pulse and can be predicted from the degree of protochlorophyll-(ide) photoconversion. There is a linear correlation between the rate of ALA accumulation and the degree of protochlorophyll(ide) (PChl)chlorophyll(ide) a (Chl a) photoconversion in etiolated seedlings. In seedlings pretreated with red light this correlation is non-linear and the rate increases more rapidly with increasing degrees of PChlChl a photoconversion. It is suggested that there may exist an interaction between P _fr and PChlChl a photoconversion in controlling ALA accumulation.Abbreviations ALA 5-aminolaevulinate - Chl chlorophyll(ide) - PChl protochlorophyll(ide) - cp cotyledon pair - LA laevulinate     

Occurrence of protochlorophyll and its phototransformation to chlorophyll in mutant C-2A' of Scenedesmus obliquus

The pigment mutant C-2A' of the unicellular green alga Scenedesmus obliquus accumulates protochlorophyllide and small amounts of protochlorophyll in darkness. Protochlororphyll was isolated and characterized by thin layer chromatography and absorption and fluorescence spectroscopy. The protochlorophyll was photoreduced by light to chlorophyll both in vitro and in vivo.     

Phosphorescence of protochlorophyll(ide) and chlorophyll(ide) in etiolated and greening bean leaves

The assignment is presented for the principal phosphorescence bands of protochlorophyll(ide), chlorophyllide and chlorophyll in etiolated and greening bean leaves measured at -196°C using a mechanical phosphoroscope. Protochlorophyll(ide) phosophorescence spectra in etiolated leaves consist of three bands with maxima at 870, 920 and 970 nm. Excitation spectra show that the 870 nm band belongs to the short wavelength protochlorophyll(ide), P627. The latter two bands correspond to the protochlorophyll(ide) forms, P637 and P650. The overall quantum yield for P650 phosphorescence in etiolated leaves is near to that in solutions of monomeric protochlorophyll, indicating a rather high efficiency of the protochlorophyll(ide) triplet state formation in frozen plant material. Short-term (2–20 min) illumination of etiolated leaves at the temperature range from -30 to 20°C leads to the appearance of new phosphorescence bands at about 990–1000 and 940 nm. Judging from excitation and emission spectra, the former band belongs to aggregated chlorophyllide, the latter one, to monomeric chlorophyll or chlorophyllide. This indicates that both monomeric and aggregated pigments are formed at this stage of leaf greening. After preillumination for 1 h at room temperature, chlorophyll phosphorescence predominates. The spectral maximum of this phosphorescence is at 955–960 nm, the lifetime is about 2 ms, and the maximum of the excitation spectrum lies at 668 nm. Further greening leads to a sharp drop of the chlorophyll phosphorescence intensity and to a shift of the phosphorescence maximum to 980 nm, while the phosphorescence lifetime and a maximum of the phosphorescence excitation spectrum remains unaltered. The data suggest that chlorophyll phosphorescence belongs to the short wavelength, newly synthesized chlorophyll, not bound to chloroplast carotenoids. Thus, the phosphorescence measurement can be efficiently used to study newly formed chlorophyll and its precursors in etiolated and greening leaves and to address various problems arising in the analysis of chlorophyll biosynthesis.Abbreviations Pchl protochlorophyll and protochlorophyllide - Chld chlorophyllide - Chl chlorophyll     

Relationship between energy metabolism and growth

Summary A biphasic dependence of the exponential growth rate on the glucose concentration of the medium was observed in batch culture experiments for a strain of S. cerevisiae and one of its petit mutants. The data can be fitted to an equation of the Michaelis-Menten type with two sets of values of the growth parameters; the switch-over occurs at a glucose concentration of 4 mM. Another petit mutant did not show the biphasic character.Regulation of the energy metabolism in relation to the cell cycle is discussed. It is suggested that the observed shift in the growth parameters may be due to a change in the control point of glycolysis from phosphofructokinase to pyruvate kinase at higher glucose concentrations. This could reduce the duration of the G₁ phase by permitting a faster synthesis of reserve carbohydrates required as intracellular energy reservoirs for DNA synthesis.Nonstandard Abbreviations Used F6P fructose-6-phosphate - FDP fructose-1,6-diphosphate - G1P glucose-6-phosphate - PEP Phosphoenolpyruvate - PYR pyruvate Enzymes PFK phosphofructokinase (EC 2.7.1.11) - PK phosphoenolpyruvate kinase (EC 2.7.1.40)     

Excitation energy transfer in the light-harvesting chlorophyll

The “light-harvesting chlorophyll a/b · protein” described by Thornber has been prepared electrophoretically from spinach chloroplasts. The optical properties relevant to energy transfer have been measured in the red region (i.e. 600–700 nm). Measurements of the absorption spectrum, fluorescence excitation spectrum and excitation dependence of the fluorescence emission spectrum of this protein confirm that energy transfer from chlorophyll b to chlorophyll a is highly efficient, as is the case in concentrated chlorophyll solutions and in vivo. The excitation dependence of the fluorescence polarization shows a minimum polarization of 1.9 % at 650 nm which is the absorption maximum of chlorophyll b in the protein and rises steadily to a maximum value of 13.8 % at 695 nm, the red edge of the chlorophyll a absorption band. Analysis of these measurements shows that at least two unresolved components must be responsible for the chlorophyll a absorption maximum. Comparison of polarization measurements with those observed in vivo shows that most of the depolarization observed in vivo can take place within a single protein. Circular dichroism measurements show a doublet structure in the chlorophyll b absorption band which suggests an exciton splitting not resolved in absorption. Analysis of these data yields information about the relative orientation of the S₀→S₁ transition moments of the chlorophyll molecules within the protein.     

Metabolism of chlorophyll in higher plants IV. Relationship between fatty acid oxidation and chlorophyll bleaching in plant extracts

Tissue extracts of various plants actively bleached chlorophyllin the presence of linoleic or linolenic acid. The activityof lipoxidase (linoleate : oxygen oxidoreductase, E.C. 1.13.1.13 [EC] )was necessary for this process, but our experiements providedno evidence for the participation of hydroperoxide isomerase,as has been suggested by other authors. (Received August 3, 1973; )     

Atmospheric forcing on chlorophyll concentration in the Mediterranean

Recent research suggests the coupling of climatic fluctuations and changes in biological indices that describe species richness, abundance and spatiotemporal distribution. In this study, large-scale modes of atmospheric variability over the northern hemisphere are associated with chlorophyll-a concentration in the Mediterranean. Sea level atmospheric pressure, air temperature, wind speed and precipitation are used to account for climatic and local weather effects, whereas sea surface temperature, sea surface height and salinity are employed to describe oceanic variation. Canonical Correlation Analysis was applied to relate chlorophyll concentration to the above-mentioned environmental variables, while correlation maps were also built to distinguish between localized and distant effects. Spectral analysis was used to identify common temporal cycles between chlorophyll concentration and each environmental variable. These cycles could be interpreted as mechanistic links between chlorophyll and large-scale atmospheric variability. Known teleconnection patterns such as the East Atlantic/Western Russian pattern, the North Atlantic Oscillation, the Polar/Eurasian pattern, the East Pacific/North Pacific, the East Atlantic jet and the Mediterranean Oscillation are found to be the most important modes of atmospheric variability related to chlorophyll-a concentration and distribution. The areas that are mostly affected are near the coasts and areas of upwelling and gyre formation. The results also suggest that this influence may arise either through local effects of teleconnection patterns on oceanic features or large-scale changes superimposed onto the general circulation in the Mediterranean. Guest editor: V. D. Valavanis Essential Fish Habitat Mapping in the Mediterranean     

Specific aspects of energy migration between chlorophyll molecules in the membranes of photosynthetic organisms

Several specific characteristics of energy migration in chlorophyll-protein complexes in vivo justify a suggestion of P.C. Knox to change two main equations of the theory on inductive resonance: to substitute a real lifetime of electronic excitations in donor molecules by the radiative lifetime. Critical distances for excitation migration of the main photosynthetic pigments become more stable constants; this results in appearance of more suitable formula for an average value of the mean time of intermolecular jumps of electronic excitations. In this context, the critical distances of homogenous energy migration within spectral fractions of purple bacterium, B800 and B850, were determined. The question on the possible application of Ferster’s theory to closely positioned molecules of chlorophyll and bacteriochlorophyll in vivo is also critically analyzed.     

Relationship between leptin concentration and insulin resistance.

Available evidences suggest that leptin has inhibitory role on insulin secretion. The aim of the work was to examine the association between plasma leptin concentrations and insulin resistance in patients with gestational diabetes mellitus. As a cross-sectional study we recruited 741 pregnant women. The universal screening was performed with an oral glucose challenge test-50 g. The recruits with plasma glucose levels of > or = 7.2 mmol/l were diagnosed as having gestational diabetes mellitus if they had an impaired oral glucose tolerance test-100 g based on Carpenter and Coustan criteria. In all pregnancies plasma insulin and leptin concentrations were measured. Gestational diabetes mellitus developed in 7% (52) of pregnancies. Elevated leptin concentrations were positively associated with insulin levels, BMI, and HOMA index while it was negatively associated with Quicky index. After adjusting for age and BMI before pregnancy, gestational diabetes mellitus had independent direct correlation with leptin concentration. Indeed, leptin level equal to or more than 20 ng/ml could help to predict the developing gestational diabetes mellitus. Measurement of leptin together with the assessment of other risk factors could help identifying women at risk of developing GDM.