Correlation between the pulse rates of atmospherics and temperature variations of the atmosphere

The pulse rates of atmospherics at 10 and 28 kHz have been compared with the variations of outside air temperature up to a height of 7 km. In the 10 kHz band the pulse rate showed a strong statistically significant correlation with air temperature for all heights up to 7 km, the maximum correlation coefficient beingr=0.78 at a level of significanceP0.001. In the 28 kHz band the correlation is weaker: up to a height of 3 km the correlation coefficient ranges from 0.17 to 0.3 (P 0.001 and 0.02, respectively) and above 3 kmr ranges from 0.15 to 0.17 (P 0.02 and 0.05, respectively).As the outdoor absolute humidity depends mainly on the air temperature, it is now clear why previous investigations showed strong correlations between the difference (S) of the atmospherics pulse rates at 10 and 28 kHz, the absolute humidity (AH) outdoors and the diffusion time (T _D ) of ions in gelatin films, measured in a fully air-conditioned working-room.     

Foam behavior of biological media

Summary The influence of the alcohol concentration on the foaminess, , of-BSA-solutions is considered. This effect is calculated by means of the function (C_BSA . f), where f=1 for pure protein solutions and f>1 for alcohol solutions. f is calculated by f = 2^TT_eff. Here, where T_T is the turbidity temperature change due to solvent structure effects and T_D, the temperature correction due to alcohol-protein interaction. The constants necessary to calculate T_T and T_D are tabulated. The agreement between the calculated and measured foaminess , as a function of the n-propanol concentration is satisfactory and for methanol or ethanol excellent.     

Monitoring the mitochondrial transmembrane potential with the JC-1 fluorochrome in programmed cell death during mesophyll leaf senescence

Summary. Analysis of the mitochondrial transmembrane potential (_m) with the help of the JC-1 fluorochrome (5,5,6,6-tetrachloro-1,1,3,3-tetraethylbenzimidazolcarbocyanine iodide) during mesophyll leaf senescence was performed in order to determine whether a reduction of _m takes place during mesophyll senescence and whether plant mitochondria, like mammalian ones, might be involved in the induction of programmed cell death. Fluorescence analysis of mesophyll protoplasts of Pisum sativum in a confocal microscope, fluorescent spectra analysis and time dependence of fluorescence intensity of monomers and of J-aggregates revealed that JC-1 is incorporated and accumulated specifically in plant mitochondria. Analysis of _m during mesophyll protoplast senescence revealed that two subpopulations of mitochondria which differ in _m exist in all analyzed stages of leaf senescence. The first subpopulation contains mitochondria with red fluorescence of J-aggregates due to an unperturbed high _m. The second subpopulation comprises mitochondria with green fluorescence of monomers due to a low _m, proving total depolarization of mitochondrial membranes. Fluorescence analysis demonstrated that even in the latest analyzed stages of leaf senescence, mitochondria with a high _m still exist. Fluorometric measurements revealed that the fluorescence intensity of J-aggregates decreases with the age of plants, which indicates that a reduction of _m during the mesophyll senescence process takes place; however, it does not take place within the whole population of mitochondria of the same protoplast. The reason of this can be due to a dramatic reorganization of mitochondria in mesophyll cells and the appearance of large mitochondria with local heterogeneity of _m in the oldest analyzed stages. All mitochondria in every stage of senescence maintained their membrane organization even when their size, distribution, and spatial organization in protoplasts changed dramatically. We stated that the reduction of _m does not directly induce programmed cell death in mesophyll cells, as opposed to animal apoptosis.Correspondence and reprints: Department of Plant Anatomy and Cytology, Institute of Experimental Biology of Plants, Warsaw University, Miecznikowa 1, 02-096 Warszawa, Poland.     

Kinetics of Δψ-Dependent Sucrose Transport in Plasma Membrane Vesicles from Higher Plant Cells

The inside-out vesicles of plasma membranes were isolated from pumpkin stem cells, and the kinetics of sucrose efflux induced by the K⁺-diffusion potential (_D) was studied by measuring light transmission. Two phases differing in their rates and duration were identified in _D-dependent changes of light transmission. The increase in _Delevated the rate and magnitude of the fast phase in light transmission changes but did not markedly affect the rate of the slow phase. These two phases also differed in their sensitivity to inhibitors and to changes in sucrose concentration in the external medium. Measurements of _Dduring sucrose transport by means of the fluorescence probe dis-C₃-(5) revealed differences in the magnitude of _Dand its stability in vesicles loaded with sucrose and mannitol, as well as under the action of inhibitors. The two-phase dependence of sucrose efflux from vesicles on the applied diffusion potential is discussed in the context of modern concepts on the functioning of sucrose carriers in the membranes.     

Steady state changes in mitochondrial electrical potential and proton gradient in perfused liver from rats fed a high fat diet

In this work the protonmotive force (p), as well as the subcellular distribution of malate, ATP, and ADP were determined in perfused liver from rats fed a low fat or high fat diet, using density gradient fractionation in non acqueous solvents.Rats fed a high fat diet, despite an enhanced hepatic oxygen consumption, exhibit similar p to that found in rats fed a low fat diet, but when we consider the two components of p, we find a significant decrease in mitochondrial/cytosolic pH difference (pH_m) and a significant increase in mitochondrial membrane potential (_m) in rats fed a high fat diet compared to rats fed a low fat diet, which tend to compensate each other. In rats fed a high fat diet the concentration ratio of malate and ATP/ADP does not reflect the changes in pH_m and _m, which represent the respective driving force for their transport.The findings are in line with an increase in substrate supply to the respiratory chain which is, however, accompanied by a higher energy turnover in livers from HFD rats. By this way the liver could contribute to the lack of weight gain from the high caloric intake in HFD rats.     

Theoretical stability diagram of solvent-containing black lipid films

Recently, we have developed an analytical, semi-microscopic theory for the macroscopic behavior of a solvent-containing black lipid film subjected to an electric cross film voltage, . Here we employ the theoretical expressions derived for the disjoining pressure, _D, the film elasticity, _F, and the film tension, _F, to construct the stability diagram of the film, in the _D-. Depending on its state (_D, ), the film is stable or is prone to squeezing or bending deformations. For a monooleate film we show how the destruction of the plane film due to a periodic thickness fluctuation (squeezing) is facilitated by two mechanisms: i) lowering of _D at fixed ; ii) lowering of at fixed _D, provided that the film is in a stable state characterized by _D<–7.03×10³ dyne/cm² and >0 mV. Bending of a low tension film (single interface tension _s 0.025 dyne/cm¹) can be achieved only for >170 mV and _D > –8.7 × 10⁴ dyne/cm². Finally, we demonstrate the existence of a marginal state ( _D ⁰ , ⁰) where the film is predicted to exhibit strong fluctuations both in the squeezing and in the bending mode.     

DNA/DNA hybridization studies of the carnivorous marsupials. I: The intergeneric relationships of bandicoots (Marsupialia: Perameloidea)

Summary A complete suite of comparisons among six bandicoot species and one outgroup marsupial was generated using the hydroxyapatite chromatography method of DNA/DNA hybridization; heterologous comparisons were also made with three other bandicoot taxa. Matrices of T_m's, modes, and T₅₀Hs were generated and corrected for nonreciprocity, homoplasy, and, in the case of T_m's, normalized percent hybridization; these matrices were analyzed using the FITCH algorithm in Felsenstein's PHYLIP (version 3.1). Uncorrected and nonreciprocity-corrected matrices were also jackknifed and analyzed with FITCH to test for consistency. Finally, sample scores for T_m, mode, and T₅₀H matrices were bootstrapped and then subjected to phylogenetic analysis. These manipulations were carried out, in part, to address criticisms of the statistics used to summarize DNA/DNA hybridization (especially T₅₀H) and the method itself. However, with the exception of an unresolved trichotomy among the twoEchymipera species andPeroryctes longicauda, all trees showed the same branchpoints. Except in the case of the tree generated from reciprocal-corrected T_m data, nodes were stable under jackknifing; and, again excepting the above-mentioned trichotomy, all nodes were supported by 95% or more of the bootstrapped trees. These results suggest that, despite arguments to the contrary, all three summary statistics can be valid for DNA/DNA hybridization data. Of taxonomic interest is the placement ofEchymipera spp. andPeroryctes longicauda together and separate from the more distantPeroryctes raffrayanus; the genusPeroryctes is thus at least paraphyletic. The trees further groupedEchymipera-plus-Peroryctes as the sister group ofIsoodon-plus-Perameles. Limited hybridizations withMacrotis lagotis suggest that its current position as representative of an entirely distinct family of perameloids is correct.This article was presented at the C.S.E.O.L. Conference on DNA-DNA Hybridization and Evolution, Lake Arrowhead, California, May 11–14, 1989     

Effect of L-triiodothyronine on liver microsomal Δ6 and Δ5 desaturase activity of male rats

The effect of different doses of L-triiodothyronine (T₃) on the activity of 6 and 5 desaturases and lipid fatty acid composition was studied in liver microsomes of male rats. The activity of 6 and 5 desaturases was decreased 24 and 28%, respectively, in animals administered a daily intraperitoneal dose of 1000g T₃/100g body wt. for 5 days, whereas with 500g T₃/100g body wt. only 6 desaturase activity was decreased. On the other hand, no enzyme activity changed at a shorter period of hormone treatment. Changes in microsomal fatty acid composition did not seem to be a direct consequence of desaturation activity, since after 1 and 5 days of T₃ treatment, the concentrations of 18:2 (n-6) and 20:3 (n-6) decreased and only after 1 day that of 20:4 (n-6) increased in spite of unchanged or decreased 6 and 5 desaturase activities. Other factors than desaturation activity must be involved in fatty acid composition of thyroid hormonetreated rats, such as diet, membrane lipid synthesis and degradation, fatty acid turn-over and oxidation. (Mol Cell Biochem121: 149–153, 1993)     

Free energy dependence of the direct charge recombination from the primary and secondary quinones in reaction centers from Rhodobacter sphaeroides

The direct charge recombination rates from the primary quinone, k _AD (D⁺Q _A ^– DQ_A) and the secondary quinone, k _BD (D⁺Q _B ^– DQ_B), in reaction centers from Rhodobacter sphaeroides were measured as a function of the free energy differences for the processes, G _AD ⁰ and G _BD ⁰ , respectively. Measurements were performed at 21 °C on a series of mutant reaction centers that have a wide range of dimer midpoint potentials and consequently a large variation in G _AD ⁰ and G _BD ⁰ . As –G _AD ⁰ varied from 0.43 to 0.78 eV, k _AD varied from 4.6 to 28.6 s^–1. The corresponding values for the wild type are 0.52 eV and 8.9 s^–1. Observation of the direct charge recombination rate k _BD was achieved by substitution of the primary quinone with naphthoquinones in samples in which ubiquinone was present at the secondary quinone site, resulting specifically in an increase in the free energy of the D⁺Q _A ^– state relative to the D⁺Q_AQ _B ^– state. As –G _BD ⁰ varied from 0.37 to 0.67 eV, k _BD varied from 0.03 to 1.4 s^–1. The corresponding values for the wild type are 0.46 eV and 0.2 s^–1. A fit of the two sets of data to the Marcus theory for electron transfer yielded significantly different reorganization energies of 0.82 and 1.3 eV for k _AD and k _BD, respectively. In contrast, the fitted values for the coupling matrix element, or equivalently the maximum possible rate, were comparable (25 s^–1) for the two charge recombination processes. These results are in accord with Q_B having more interactions with dipoles, from both the surrounding protein and bound water molecules, than Q_A and with the primary determinant of the maximal rate being the quinone-donor distance.     

Gas exchange and carbon isotope discrimination in lichens: Evidence for interactions between CO2-concentrating mechanisms and diffusion limitation

The characteristics of gas exchange and carbon isotope discrimination were determined for a number of lichen species, representing contrasting associations between fungal (mycobiont) and photosynthetic (photobiont) organism. These parameters were evaluated with regard to the occurrence of any CO₂-concentrating mechanism (CCM) expressed specifically by the green algal (phycobiont) or cyanobacterial (cyanobiont) partner. Carbon isotope discrimination () fell into three categories. The highest , found in lichens comprising a phycobiont plus cyanobacteria limited to pockets in the thallus (known as cephalodia), ranged from 24 to 28, equivalent to a carbon isotope ratio (¹³C) of around -32 to-36 vs. Pee Dee Belemnite (PDB) standard. Further evidence was consistent with CO₂ supply to the carboxylating system entirely mediated by diffusion rather than a CCM, in that thallus CO₂ compensation point and online instantaneous were also high, in the range normally associated with C₃ higher plants. For lichens consisting of phycobiont or cyanobiont alone, organic material formed two distinct ranges around 15 (equivalent to a ¹³C of -23%.). Thallus compensation point and instantaneous were lower in the cyanobiont group, which also showed higher maximum rates of net photosynthesis, whether expressed on the basis of thallus dry weight, chlorophyll content or area. These data provide additional evidence for the activity of a CCM in cyanobiont lichens, which only show photosynthetic activity when reactivated with liquid water. Rates of net CO₂ uptake were lower in both phycobiont associations, but were relatively constant across a wide working range of thallus water contents, usually in parallel with on-line . The phycobiont response was consistent whether photosynthesis had been reactivated with liquid water or water vapour. The effect of diffusion limitation could generally be seen with a 3–4 decrease in instantaneous at the highest water contents. The expression of a CCM in phycobiont algae, although reduced compared with that in cyanobacteria, has already been related to the occurrence of pyrenoids in chloroplasts. In view of the inherent requirement of cyanobacteria for some form of CCM, and the smaller pools of dissolved inorganic carbon (DIC = CO₂ + HCO _inf3 ^su– + CO _inf3 ^su2– ) associated with phycobiont lichens, it appears that characteristics provide a good measure of the magnitude of any CCM, albeit tempered by diffusion limitation at the highest thallus water contents.Abbreviations ANOVA analysis of variance - CCM CO₂-concentrating mechanism - cyanobiont cyanobacterium - DIC CO₂ + HCO _inf3 ^su– + CO _inf3 ^su2– (dissolved inorganic carbon) - photobiont photosynthetic organism present in the association - phycobiont green alga - phycobiont + cephalodia green algae + cyanobacteria in cephalodia - Pmax maximum photosynthetic rate - PPFD photosynthetic photon flux density, 400–700 nm - Rubisco ribulose-1,5-bisphosphate carboxylase/oxygenase - carbon isotope discrimination () - ¹³C carbon isotope ratio () We would like to thank Dr. Enrico Brugnoli (CNR, Porano, Italy) and E.C. Smith (University of Newcastle) for many helpful discussions. Dr. Kristin Palmqvist (Department of Plant Physiology, University of Umeå, Sweden) kindly provided the samples of Peltigera apthosa. In particularly, Cristina Máguas would like to thank to Prof. Fernando Catarino (University of Lisbon) for his support throughout this study. Cristina Máguas has been supported by JNICT-Science Programme studentship (BD/153/90-RN).     

Reaction centers from three herbicide resistant mutants of Rhodobacter sphaeroides 2.4.1: Kinetics of electron transfer reactions

Electron transfer rates were measured in RCs from three herbicide-resistant mutants with known amino acid changes to elucidate the structural requirements for last electron transfer. The three herbicide resistant mutants were IM(L229) (Ile-L229 Met), SP(L223) (Ser-L223 Pro) and YG(L222) (Tyr-L222 Gly). The electron transfer rate D⁺Q_A ^-Q_BD⁺Q_AQ_B (k _AB) is slowed 3 fold in the IM(L229) and YG(L222) RCs (pH 8). The stabilization of D⁺Q_AQ_B ^- with respect to D⁺Q_AQ_B ^- (pH 8) was found to be eliminated in the IM(L229) mutant RCs (G⁰ 0 meV), was partially reduced in the SP(L223) mutant RCs (G⁰=–30 meV), and was unaltered in the YG(L222) mutant RCs (G⁰=–60 meV), compared to that observed in the native RCs (G⁰=–60 meV). The pH dependences of the charge recombination rate D⁺Q_AQ_B ^-DQ_AQ_B (k _BD) and the electron transfer from Q_A ^- (k _QA ^-Q_A) suggest that the mutations do not affect the protonation state of Glu-L212 nor the electrostatic interactions of Q_B and Q_B ^- with Glu-L212. The binding affinities of UQ₁₀ for the Q_B site were found in order of decreasing values to be native IM(L229) > YG(L222) SP(L223). The altered properties of the mutant RCs are used to deduce possible structural changes caused by the mutations and are dicscussed in terms of photosynthetic efficiency of the herbicide resistant strains.Abbreviations Bchl bacteriochlorophyll - Bphe bacteriopheophytin - cholate 3,7,12-trihydroxycholanic acid - D donor (bacteriochlorophyll dimer) - EDTA ethylenediamine tetraacetic acid - Fe²⁺ non-heme iron atom - LDAO lauryl dimethylamine oxide - PS II photosystem II - Q_A and Q_B primary and secondary quinone acceptors - RC bacterial reaction center - Tris tris(hydroxymethyl)aminomethane - UQ₀ 2,3-dimethoxy-5-methyl benzoquinone - UQ₁₀ ubiquinone 50     

Relationships between carbon and hydrogen isotope ratios and nitrogen levels in leaves ofClusia species and two other Clusiaceae genera at various sites and different altitudes in Venezuela

Samples of the Clusiaceae generaClusia, Oedematopus andDystovomita were collected at various sites and different altitudes in northern and south-western Venezuela. Analyses of stable isotopes of carbon and hydrogen and of leaf-nitrogen levels were performed on the dried samples. Correlations among these variables, i.e. carbon isotope discrimination (), hydrogen isotope ratio (D) and N-levels, and with altitude were assessed. In the samples, where values of above 15 indicate predominant performance of C₃ photosynthesis, there were slight tendencies of increasing , D and N-levels with increasing altitude and of increasing with increasing N. Although these correlations taken separately were not statistically significant, they support each other and indicate increasing transpiration and increased leaf-nutrient supply at increasing altitude. Performance of crassulacean acid metabolism (CAM) in species ofClusia appears to be restricted to altitudes below 1500 m a.s.l. There was a significant negative correlation of with altitude in the samples, where values of below 10 indicated predominant performance of CAM. This suggests that phases II and IV of CAM are progressively suppressed towards the upper altitudinal limit of CAM inClusia in northern Venezuela. It is concluded that among the large number of environmental factors and combinations thereof, which determine the expression of CAM inClusia and trigger C₃-CAM transitions in C₃/CAM intermediate species, low availability of water is the most important.     

Tetramethyl Rhodamine Methyl Ester (TMRM) is Suitable for Cytofluorometric Measurements of Mitochondrial Membrane Potential in Cells Treated with Digitonin

A new method for cytofluorometric analysis of mitochondrial membrane potential has been developed by using TMRM as a cationic, mitochondrial selective probe. The method is based on limited treatment of cultured cells with digitonin which permeabilises the plasma membrane and leaves mitochondria intact. The resulting signal of TMRM-stained cells thus represents only the probe accumulated in mitochondria. Fibroblasts and cybrids were used as a model cell systems and optimal conditions for digitonin treatment and staining by TMRM were described. The TMRM signal collapsed by valinomycin, KCN and antimycin A and FCCP titration was used to gradually lower and characterise the stability of . The method is suitable for sensitive measurement of in different types of cultured cells.     

Adenylate regulation of photosynthetic electron transport and the coupling sites of phosphorylation in spinach chloroplasts

The regulation by adenylates of activities of various partial electron transport systems in spinach chloroplasts was studied using systems from H₂O to 2,5-dimethyl-p-benzoquinone, H₂O to 2,6-dichlorophenolindophenol, reduced 2,6-dichlorophenolindophenol to methyl viologen, and H₂O to methyl viologen or ferricyanide. Adenylates regulated all of them. The ratio of the amount of esterified Pi (P) to that of electrons transported (e) in coupling with phosphorylation manifested that there are two phosphorylation sites: one between H₂O and 2,5-dimethyl-p-benzoquinone or 2,6-dichlorophenolindophenol and another between reduced 2,6-dichlorophenolindophenol and methyl viologen, under the proposed stoichiometries,i.e., P/H⁺=0.5 and H⁺/e=1, where H⁺ is the amount of protons pumped by electron transport (= those translocated during phosphorylation), when the basal electron transport (the part not regulated by adenylates) was excluded. The effects of pH, phlorizin, and methylamine on the adenylate regulation of electron transport, and the stimulation profile of electron transport coupled with quasiarsenylation suggested no distinction between the two phosphorylation sites.     

Frequency of the F508 deletion in cystic fibrosis patients from the European part of the USSR

Summary The frequency of the F508 deletion (F508) has been analyzed in 189 cystic fibrosis (CF) patients from the European part of the USSR, viz. 127 nothern Slavonians (Leningrad region), 30 southern Slavonians (the Ukraine), 10 central Slavonians (Moscow region), 14 Moldavians (Kishenev region) and 8 Lithuanians (Vilnius region). The distribution of CF⁺ chromosomes with and without F508 varied significantly in the different ethnic groups studied and correlated with the clinical manifestation of CF. The overall frequency of F508 in Slavonian patients is equal to 62.5%, approximately 90% of them being heterozygous or homozygous for this mutation. The frequency of the deletion among 99 Slavonian patients with severe disease manifestation (pancreatic insufficiency, PI) is equal to 67.5%, only 12 patients having pancreatic sufficiency (PS, 17.5%). The highest value of F508 (77.4%) is registered in PI/CF patients of the southern Slavonian group; it is much less frequent (about 57%) in relevant groups of Slavonians from the northern and central parts of the country. Unusually low frequencies (24% and 26%) of F508 are detected in a few samples of Lithuanian and Moldavian CF patients, respectively. All F508⁺CF-chromosomes of Slavonian origin are associated with haplotypes 2.2.2. defined by the restriction fragment length polymorphism sites KM19/PstI, CS.7/Hin6I and MP6d-9/MspI, although a high proportion (about 25%) of unknown mutations is associated with the same haplotype. Haplotype B (allele 1XV2c/TaqI; allele 2 KM19/PstI) accounts for 91% of F508⁺CF chromosomes. Our data are consistent with the hypothesis of a single origin and subsequent diffusion of this major CF mutation; however, its interpopulational dissemination in Eastern Europe does not follow the suggested south-east to north-west gradient in Western Europe. The significance of these data for prenatal diagnosis and carrier screening of CF mutations is briefly discussed.     

Characterization of a structurally and functionally diverged acyl-acyl carrier protein desaturase from milkweed seed

A cDNA for a structurally variant acyl-acyl carrier protein (ACP) desaturase was isolated from milkweed (Asclepias syriaca) seed, a tissue enriched in palmitoleic (16:1⁹)* and cis-vaccenic (18:1¹¹) acids. Extracts of Escherichia coli that express the milkweed cDNA catalyzed ⁹ desaturation of acyl-ACP substrates, and the recombinant enzyme exhibited seven- to ten-fold greater specificity for palmitoyl (16:0)-ACP and 30-fold greater specificity for myristoyl (14:0)-ACP than did known ⁹-stearoyl (18:0)-ACP desaturases. Like other variant acyl-ACP desaturases reported to date, the milkweed enzyme contains fewer amino acids near its N-terminus compared to previously characterized ⁹-18:0-ACP desaturases. Based on the activity of an N-terminal deletion mutant of a⁹ -18:0-ACP desaturase, this structural feature likely does not account for differences in substrate specificities.     

A hypothesis concerning the absorption of atmospherics in photo gelatin films

Gelatin is a protein, consisting of long polypeptide chains which form left-handed triple helixes. Incident atmospherics impulses can change the bond angles of distinct atoms (the socalled C-atoms) in these structures. This mechanism alters the widths of the pores in gelatin and thus determines the diffusion behavior of ions penetrating that material.     

Basis of the Relationship between Ash Content in the Flag Leaf and Carbon Isotope Discrimination in Kernels of Durum Wheat

The relationship between ash content and carbon isotope discrimination () was studied in durum wheat (Triticum durum Desf.) grown in a Mediterranean region (Northwest Syria) under three different water regimes (hereafter referred to as environments). In two of these environments, 144 genotypes were cultivated under rain-fed conditions. In the third environment, 125 genotypes were cultivated under irrigation. Ash content was measured in the flag leaf about 3 weeks after anthesis, whereas was analysed in mature kernels. Total transpiration of the photosynthetic tissues of the culm contributing, from heading to maturity, to the filling of kernels was also estimated. Leaf ash content, expressed either on dry matter or leaf area basis or as total ash per blade, correlated positively (p< 0.001) with in the three environments. However, this relationship was not the result of a positive correlation across genotypes between and tissue water content. Moreover, only a small part of the variation in across genotypes was explained by concomitant changes in ash content. When all genotypes across the three environments were plotted, and ash content followed a non-linear relationship (r ² = 74), with tending to a plateau as the ash content increased. However, for the set of genotypes and environments combined, total ash content per leaf blade was positively and linearly related (r ² = 0.76) with the accumulated culm transpiration. The non-linear nature of the relationship between ash content and is sustained by the fact that culm transpiration also showed a non-linear relationship with kernel . Therefore, differences in leaf ash content between environments, and to a lesser extent between genotypes, seem to be brought about by variations in accumulated transpiration during grain formation.     

The effects of elevated light on Photosystem II function: A thermoluminescence study

We have used the technique of thermoluminescence (TL) to investigate high-light-induced chlorophyll fluorescence quenching phenomena in barley leaves, and have shown it to be a powerful tool in such investigations. TL measurements were taken from wild-type and chlorina f2 barley leaves which had been dark-adapted or exposed to 20 min illumination of varying irradiance or given varying periods of recovery following strong irradiance. We have found strong evidence that there is a sustained trans-thylakoid pH in leaves following illumination, and that this pH gives rise to quenching of chlorophyll fluorescence which has previously been identified as a slowly-relaxing component of antenna-related protective energy dissipation; we have identified a state of the PS II reaction centre resulting from high light treatments which is apparently able to perform normal charge separation and electron transport but which is non-photochemically quenched, in that the application of a light pulse of high irradiance cannot cause the formation of a high fluorescent state; and we have provided evidence that a transient state of the PS II reaction centre is formed during recovery from such high light treatments, in which electron transport from Q_Ato Q_Bis apparently impaired.