Changes In Chlorophyll Content Research Articles

Natural variability of surface oceanographic conditions in the offshore Gulf of Mexico

This work characterizes patterns of temporal variability in surface waters of the central Gulf of Mexico. We examine remote-sensing based observations of sea surface temperature (SST), wind speed, sea surface height anomaly (SSHA), chlorophyll-a concentration (Chl-a) and Net Primary Production (NPP), along with model predictions of mixed layer depth (MLD), to determine seasonal changes and long-term trends in the central Gulf of Mexico between the early 1980s and 2012. Specifically, we examine variability in four quadrants of the Gulf of Mexico (water depth >1000m). All variables show strong seasonality. Chl-a and NPP show positive anomalies in response to short-term increases in wind speed and to cold temperature events. The depth of the mixed layer (MLD) directly and significantly affects primary productivity throughout the region. This relationship is sufficiently robust to enable real-time estimates of MLD based on satellite-based estimates of NPP. Over the past 15–20years, SST, wind speed, and SSHA show a statistically significant, gradual increase. However, Chl-a and NPP show no significant trends over this period. There has also been no trend in the MLD in the Gulf of Mexico interior. The positive long-term trend in wind speed and SST anomalies is consistent with the warming phase of the Atlantic Multidecadal Oscillation (AMO) that started in the mid-90s. This also coincides with a negative trend in the El Niño/Southern Oscillation Multivariate ENSO Index (MEI) related to an increase in the frequency of cooler ENSO events since 1999–2000. The results suggest that over decadal scales, increasing temperature, wind speed, and mesoscale ocean activity have offsetting effects on the MLD. The lack of a trend in MLD anomalies over the past 20years explains the lack of long-term changes in chlorophyll concentration and productivity over this period in the Gulf. Understanding the background of seasonal and long-term variability in these ocean characteristics is important to interpret changes in ocean health due to episodic natural and anthropogenic events and long term climate changes or development activities. With this analysis we provide a baseline against which such changes can be measured.

Down-regulation of catalase activity contributes to senescence induction in wheat leaves exposed to shading stress

In shaded wheat (Triticum aestivum L.) leaves, the suppression of blue radiation (BR) triggers senescence. This phenomenon is correlated to an increase in oxidative stress symptoms and a decrease of catalase (CAT) activity, among other traits. Previous data suggest that the radiation signal transduction pathway may involve changes in Ca2+ and H2O2 homeostasis. For better a understanding of the interaction among the spectral composition of radiation, Ca2+ availability, and the antioxidant metabolism in the regulation of shade-induced senescence, detached wheat leaves were placed in a growth chamber and exposed to either blue (B, high BR transmittance) and/or green (G, very low BR transmittance) Lee® filters in the absence or presence of 0.8 mM verapamil (a Ca2+ channels blocker), 4.0 mM EGTA (a Ca2+chelator), or 8.0 mM 3-amino-1,2,4-triazole (a CAT inhibitor). At defined time points, the leaf samples were analyzed for changes in chlorophyll content, specific activities of CAT, ascorbate peroxidase (APX), and guaiacol peroxidase (POX), CAT isozymes, and gene expression of CAT1, CAT2, and two senescence markers (TaSAG1 and TaSAG3). BR transmittance decreased the chlorophyll degradation rate and SAG genes expression either in leaves continuously exposed under the B filter, as well as in leaves previously exposed under the G filter. The effect of BR was associated with the maintenance of a high CAT (but not APX and POX) activity, and it was suppressed either in the presence of 3-AT or when Ca2+ availability was decreased. BR altered the CAT activity both at the transcriptional and at the posttranscriptional level. Nevertheless, different responses of CAT isozymes and CAT genes expression profiles to specific treatment combinations indicate that they differed in their regulatory pathways.

Influence of drought stress on assimilation of carbon, activity of photosynthetic enzymes, heat shock proteins, antioxidants, proline accumulation and protein contents in crop plants

Drought stress is one of the most important abiotic stress factors which are generally accompanied by heat stress in dry season. Drought is perceived as the most significant environmental stress in agriculture worldwide, and improving yield under drought is therefore a major goal of plant breeding. The data on water stress induced regulation of the activity of photosynthetic enzymes other than rubisco are scarce. Recently, most researchers have agreed that the stomatal closure is the main determinant for decreased photosynthesis under mild and moderate stress. Severe drought stress also inhibits the photosynthesis of plants by causing changes in chlorophyll content, by affecting cholorophyll components and by damaging the photosynthetic apparatus. Water availability mostly affects accumulation of some organic compatible solutes such as sugars, betaines and proline which adjusts the intercellular osmotic potential is also early reaction of plants to water stress.

Study on the Effects of Wastewater Duress on Chlorophyll Content of 4 Species Wetland Plants

The research which is the species selection of constructed wetland plants and the resistance of the plants is the key to ecological wastewater treatment technology. This paper studies the change of chlorophyll content in 4 wetland plants (Phragmites communis, Typha orientalis, Arundo donax and Canna generalis) in different wastewater duress time. The results show: chlorophyll contents in Canna generalis and Arundo donax have less change, and their anti-stress capability are stronger.

Influence of pH on the Toxicity of Silver Nanoparticles in the Green Alga Chlamydomonas acidophila

The aim of this study was to investigate the effect of pH 4 and 7 on the cellular toxicity impact of silver nanoparticles (AgNPs) on the green alga Chlamydomonas acidophila. Changes in chlorophyll content, cellular viability, and reactive oxygen species (ROS) formation were determined permitting the characterization of the toxicity of AgNPs. Chemical characterization of AgNPs in suspension showed that nanoparticle size distribution was dependent to the pH of the culture medium, and a higher solubility was observed at pH 4 compared to that at pH 7. After 24 h of exposure, results indicated that the chlorophyll content and cellular viability decreased significantly, while the intracellular ROS production increased significantly, in relation to the increasing concentration of AgNPs (0.1–100 mg/L). Therefore, our results demonstrated that AgNP-induced toxicity was pH dependent as indicated by the cytotoxicity mediated through the induction of oxidative stress. In conclusion, the characterization of the physicochemical properties of AgNPs in aqueous solution having different pH is essential for the understanding of their toxicity impact on algal cells.

Degradation and reorganization of thylakoid protein complexes ofBryum argenteumin response to dehydration and rehydration

We analyzed the desert moss Bryum argenteum Hedw., a dominant moss in biological soil crusts in northwestern China, during dehydration and rehydration. There was almost no change in chlorophyll content between hydrated and almost completely desiccated B. argenteum samples. The amounts of thylakoid protein complexes, including the PSI monomer, PSII supercomplex, the PSII monomer, and LHCII, gradually decreased as the dehydration time of B. argenteum was extended. Analysis by two-dimensional sodium dodecylsulfate-urea- polyacrylamide gel electrophoresis showed that the amount of the PSII core subunits CP47 and CP43 and the PSI core subunits PsaA/B decreased during dehydration. The amount of thylakoid protein complexes increased rapidly during rehydration under light conditions, but increased slowly, and to lower levels, during rehydration in the dark. Rehydration of B. argenteum in chloramphenicol solution under light conditions resulted in a decrease in FV/FM within 10 min. An analysis of chloroplast ultrastructure showed that the number of grana decreased during dehydration. Taken together, our results suggest that the thylakoid protein complexes of B. argenteum degrade during dehydration and then reassemble during rehydration, and that this affects the full recovery of photosynthesis in this species.

Combined effect of ultrasound, mild heat shock and citric acid to retain greenness, nutritional and microbiological quality of minimally processed broccoli (Brassica oleracea L.): An optimization study

Response surface methodology (RSM) and Box–Behnken design were used to study the combined hurdle effect of mild heat time (1–5min) at 50°C, ultrasonic processing time (0–10min) and citric acid concentration (0–2%) on the quality of refrigerated broccoli after 10d of storage at 5°C. Treatment effects were evaluated on weight loss, superficial colour (hue angle (H°) and total colour difference (ΔE)), headspace gas composition (O2 and CO2), overall browning potential, chlorophyll content, ascorbic acid content, mesophilic counts and overall visual quality (OVQ) and optimize the process by means of the desirability function. Predicted models were found to be significant with high regression coefficients (91–97%). High regression coefficients indicated that second-order polynomial models could be used to predict and optimize the quality retention in minimally processed broccoli during storage. The mesophilic counts, ascorbic acid content and the overall visual quality were significantly influenced by the three independent variables either independently or interactively. Both thermal and ultrasonic treatments were found to be critical factors influencing changes in chlorophyll content, O2 concentration inside the package, hue angle and ΔE. On the other hand, thermal treatment and citric acid concentration were found to be significant on overall browning potential. By using the desirability function approach and considering superficial colour parameters, O2 concentration, mesophilic counts, browning potential, ascorbic acid and chlorophyll content, the optimum processing conditions were 7.5min of ultrasonic treatment, 3min of a heat shock treatment and a citric acid concentration of 1.5%. These results were in good agreement with the maximum found from the canonical analysis performed from the response surface when only considering sensorial analysis. Under these optimal processing conditions it is possible to employ citric acid treatment in combination with ultrasonic and thermal treatments as hurdles for retention of green colour, nutritional quality, microbial control and for extending shelf life of refrigerated minimally processed broccoli.

Relationship between fraction of radiation absorbed by photosynthesizing maize and soybean canopies and NDVI from remotely sensed data taken at close range and from MODIS 250 m resolution data

The fraction of incident photosynthetically active radiation absorbed by the photosynthesizing tissue in a canopy (fAPAR) is a key variable in the assessment of vegetation productivity. It also plays tremendous role in accurate retrieval of light use efficiency, which is essential for assessing vegetation health status. The main goal of this work was to study in detail relationships of fAPAR absorbed by photosynthetically active vegetation (fAPARgreen) and Normalized Difference Vegetation Index (NDVI) for two crops with contrasting leaf structures (C3 vs. C4) and canopy architectures, using close range (6m above the canopy) radiometric data and daily MODIS data taken during eight growing seasons over three irrigated and rainfed maize and soybean sites. Our specific goal was to understand differences in fAPARgreen/NDVI relationship when crop canopy was almost vertically homogeneous (with respect to leaf area and leaf chlorophyll content), as in vegetative stage, and vertically heterogeneous as in reproduction stage. Firstly, we established fAPARgreen/NDVI relationships for NDVI, taken at close range, and assessed noise equivalent of fAPARgreen estimation by NDVI, and then we established relationships for NDVI retrieved from daily MODIS 250m data. Daily MODIS data illuminated fine details of this relationship and detected effects of canopy heterogeneity on fAPARgreen/NDVI relationship. In vegetative stage, the fAPAR/NDVI relationships for contrasting in leaf structures and canopy architectures crops were almost linear allowing accurate estimation of fAPARgreen as it is below 0.7. However, very different fAPARgreen/NDVI relationships in reproductive stages for both crops were observed, showing that canopy architecture and leaf structure greatly affect the relationship as leaf chlorophyll content changes and vertical distribution of chlorophyll content and green LAI inside the canopy becomes heterogeneous. We have found fine details of the fAPARgreen/NDVI relationships with two types of hysteresis that prevent the use of a single relationship for fAPARgreen estimation by NDVI over the whole growing season and suggested mechanisms for each type of hysteresis that should be further studied using radiative transfer models.

The rice OsV4 encoding a novel pentatricopeptide repeat protein is required for chloroplast development during the early leaf stage under cold stress

Pentatricopeptide repeat (PPR) proteins, characterized by tandem arrays of a 35 amino acid motif, have been suggested to play central and broad roles in modulating the expression of organelle genes in plants. However, the molecular mechanisms of most rice PPR genes remains unclear. In this paper, we isolated and characterized a temperature-conditional virescent mutant, OsV4, in rice (Oryza sativa cultivar Jiahua1 (WT, japonica rice variety)). The mutant displays albino phenotype and abnormal chloroplasts at the three leaf stage, which gradually turns green after the four leaf stage at a low temperature (20 °C). But the mutant always develops green leaves and well-developed chloroplasts at a high temperature (32 °C). Genetic and molecular analyses uncovered that OsV4 encodes a novel chloroplast-targeted PPR protein including four PPR motifs. Further investigations show that the mutant phenotype is associated with changes in chlorophyll content and chloroplast development. The OsV4 transcripts only accumulate to high levels in young leaves, indicating that its expression is tissue-specific. In addition, transcript levels of some ribosomal components and plastid-encoded polymerase-dependent genes are dramatically reduced in the albino mutants grown at 20 °C. These findings suggest that OsV4 plays an important role during early chloroplast development under cold stress in rice.

Cadmium Removal by Lemna minor and Spirodela polyrhiza

The present study investigates the ability of two genus of duckweed (Lemna minor and Spirodela polyrhiza) to phytoremediate cadmium from aqueous solution. Duckweed was exposed to six different cadmium concentrations, such as, 0.5, 1.0, 1.5, 2.0, 2.5, and 3.0 mg/L and the experiment was continued for 22 days. Water samples were collected periodically for estimation of residual cadmium content in aqueous solution. At the end of treatment period plant samples were collected and accumulated cadmium content was measured. Cadmium toxicity was observed through relative growth factor and changes in chlorophyll content. Experimental results showed that Lemna minor and Spirodela polyrhiza were capable of removing 42–78% and 52–75% cadmium from media depending upon initial cadmium concentrations. Cadmium was removed following pseudo second order kinetic model. Maximum cadmium accumulation in Lemna minor was 4734.56 mg/kg at 2 mg/L initial cadmium concentration and 7711.00 mg/kg in Spirodela polyrhiza at 3 mg/L initial cadmium concentration at the end of treatment period. Conversely in both cases maximum bio-concentration factor obtained at lowest initial cadmium concentrations, i.e., 0.5 mg/L, were 3295.61 and 4752.00 for Lemna minor and Spirodela polyrhiza respectively. The present study revealed that both Lemna minor and Spirodela polyrhiza was potential cadmium accumulator.

Estimating global chlorophyll changes over the past century

Marine phytoplankton account for approximately half of the production of organic matter on earth, support virtually all marine ecosystems, constrain fisheries yields, and influence climate and weather. Despite this importance, long-term trajectories of phytoplankton abundance or biomass are difficult to estimate, and the extent of changes is unresolved. Here, we use a new, publicly-available database of historical shipboard oceanographic measurements to estimate long-term changes in chlorophyll concentration (Chl; a widely used proxy for phytoplankton biomass) from 1890 to 2010. This work builds upon an earlier analysis (Boyce et al., 2010) by taking published criticisms into account, and by using recalibrated data, and novel analysis methods. Rates of long-term chlorophyll change were estimated using generalized additive models within a multi-model inference framework, and post hoc sensitivity analyses were undertaken to test the robustness of results. Our analysis revealed statistically significant Chl declines over 62% of the global ocean surface area where data were present, and in 8 of 11 large ocean regions. While Chl increases have occurred in many locations, weighted syntheses of local- and regional-scale estimates confirmed that average chlorophyll concentrations have declined across the majority of the global ocean area over the past century. Sensitivity analyses indicate that these changes do not arise from any bias between data types, nor do they depend upon the method of spatial or temporal aggregation, nor the use of a particular statistical model. The wider consequences of this long-term decline of marine phytoplankton are presently unresolved, but will need to be considered in future studies of marine ecosystem structure, geochemical cycling, and fishery yields.

The rice OsDG2 encoding a glycine-rich protein is involved in the regulation of chloroplast development during early seedling stage

OsDG2 gene encoded a novel chloroplast-targeted GRP in rice. Disruption of the OsDG2 would lead to delayed greening phenotype and affected expression levels of genes associated with chloroplast development at early leaf stage of rice. Glycine-rich proteins (GRPs) participate in various biological processes in plants. However, the evidence of GRPs involved in chloroplast development in plants is quite limited. In this study, we identified a rice GRP gene mutant named osdg2 (O ryza s ativa d elayed g reening 2), which exhibits delayed greening phenotype characterized as bright yellow leaves before the three-leaf stage and thereafter turns to normal green. Further study showed that the mutant phenotype was consistent with changes in chlorophyll content and chloroplast development. The rice OsDG2 gene, encoding a novel GRP protein, was located on chromosome 2 through map-based cloning method and confirmed by molecular complementation tests. Subcellular localization results showed that OsDG2 was targeted in chloroplasts. In addition, the OsDG2 transcripts were highly expressed in leaves and undetectable in other tissues, showing the tissue-specific expression. In osdg2 mutant, the expression levels of most genes associated with chloroplast development were severely decreased in the 3rd leaves, but almost recovered to wild-type level in the 4th leaves. Our findings indicated that the nuclear-encoded OsDG2 plays important roles in chloroplast development at early leaf stage of rice.

Chlorophyll as an indicator of green tea quality

The objective of this work was to study the changes in chlorophyll contents in green teas stored under different conditions and to suggest the most suitable way and length of green tea storage. A secondary aim was to evaluate the possibility of using the chlorophyll content as an indicator of tea freshness. Samples for analysis were obtained from a range of tea-growing regions. Chlorophyll contents were measured using UV-vis spectrophotometry. Chlorophyll absorbance was measured at 642.5 and 660 nm. Prior to storage, chlorophyll concentration in teas ranged from 1.12 to 1.89 mg per 1 g of tea, which corresponded to data given by other authors. Storage was found to lead to a decline in chlorophyll concentration. From the 6th month of storage onwards, a significant decrease (P < 0.05) was observed in all samples, irrespective of storage conditions. Based on the findings of this study, original and metal packaging can be considered the most chlorophyll-friendly. On the other hand, glass and paper packaging stored in direct daylight were found to have the strongest impact on chlorophyll concentration. Overall, it can be concluded that the storage time can have a strong influence on oolong green tea colour as an important qualitative variable. Thus, the shelf-life of tea should be shorter than the 12 months claimed by most manufacturers. Once the relationship between changes in chlorophyll concentration and length of the storage period had been established, the chlorophyll content was suggested as an indicator of the storage time (freshness) of a tea substance.

Changes in chlorophyll content and fluorescence and fruit yield contributing traits in different genotypes of strawberry (Fragaria x ananassa DUCH.)

Analysis of changes in chlorophyll fluorescence parameters in strawberry leaves was based on a field experiment performed in the years 2009–2010. Ten genotypes including 5 cultivars: ‘Kent’, ‘Teresa’, ‘Senga Sengana’, ‘Chandler’ and the breeding clone 1387 as well as their inbred progeny, were the object of the study. During the experiment the following indicators were evaluated: chlorophyll a and b content in fresh leaf mass as well as fluorescence parameters: minimum (F0) and maximum fluorescence yield (Fm), photochemical efficiency of PS II (Fv/Fm), actual quantum yield of PSII photochemistry (Y), minimum (F0’) and maximum efficiency of fluorescence (Fm’) in the light, coefficient of photochemical (qP) and non-photo- chemical (qN) fluorescence quenching. In this work, we also examined the effect of repeated inbreeding on strawberry fruit yield and yield components. The analysis of changes of these parameters showed that inbreeding caused a reaction in all tested cultivars. In all inbred progeny, chlorophyll a and b content decreased compared to the cultivars. Generally, the photoche- mical efficiency of photosystem II (Fv/Fm) and the parameter ΔF/ Fm’ were not affected by strong inbreeding. In analyzing the values of the coefficients qP and qN, it has been observed that changes in their values depend on the sensitivity of the examined genotypes to self-pollination. The functioning of PS II is the most sensitive indicator of the effect of various factors on plants and is useful, among others, in breeding to select plants with a required genotype. The yield – determining features such as: fruit yield per plant, weight of single fruit, number of fruit per plant and weight of leaves per plant in S3 generation, were lower as compared with parental forms.

Extraction procedures for the study of phytotoxicity and degradation processes of selected triketones in a water ecosystem

Simple and effective extraction methods based on matrix solid-phase dispersion (MSPD), dispersive liquid–liquid microextraction (DLLME), and solid-phase extraction (SPE) coupled with high-performance liquid chromatography with diode array detector (HPLC-DAD) were developed to determine triketone herbicides—sulcotrione (SUL), mesotrione (MES), tembotrione (TEMB), and their degradation products—in plant tissues and water samples. The extraction procedures were employed to enable quantification of the accumulation of selected triketone herbicides and their degradation products in a model aquatic plant, Egeria densa. To obtain comprehensive information about the triketones' influence on an aquatic plant, changes in chlorophyll concentration in plants exposed to these triketones were monitored. The average recovery ranged from 58 to 115 % (coefficients of variation 7–12 %) for plant tissues and from 52 to 96 % (coefficients of variation 8–20 %) for water samples. The limit of detection (LOD) for the MSPD–HPLC-DAD procedure was in the range of 0.06–0.23 μg/g, whereas for DLLME–HPLC-DAD and SPE–HPLC-DAD, LOD was in the range of 0.06–0.26 μg/mL. Symptoms of the phytotoxicity of sulcotrione, mesotrione, tembotrione, and their degradation products (decrease of chlorophyll concentration in plant sprouts) were observed for E. densa cultivated in water with herbicide concentrations of 100 μg/L. Moreover, the tembotrione degradation product exhibited a high level of accumulation and low metabolism in plant tissues in comparison to the other triketones and their degradation products.Electronic supplementary materialThe online version of this article (doi:10.1007/s11356-013-2425-z) contains supplementary material, which is available to authorized users.

Teores de clorofila em cultivares de tomateiro submetidas a aplicações foliares de magnésio

Apesar de a aplicação de nutrientes via foliar ser bem disseminada na horticultura, a tecnologia ainda é controversa, pois a eficiência dos produtos está relacionada às características das formulações, especialmente quanto às fontes de nutrientes utilizadas. Assim, buscou-se, neste trabalho, identificar alterações nos teores de clorofila, utilizando o método colorimétrico e o método indireto por clorofilômetro, bem como alterações no teor de Mg nas folhas de tomateiro, em função de aplicações foliares de soluções contendo Mg(OH)2 ou MgCl2. Foram utilizadas duas cultivares, submetidas a fertirrigações com baixa adição de Mg. Os valores das leituras com clorofilômetro foram corroborados pelo método colorimétrico, indicando que as soluções contendo 1,0 mL L-1 e 2,0 mL L-1 de uma suspensão concentrada (300 g L-1 de Mg, na forma de Mg(OH)2) e a solução contendo 3,75 mL L-1 de MgCl2 foram eficientes em promover aumentos nos teores de clorofila, indicando a absorção e metabolização do Mg. Já a solução contendo 7,5 mL L-1 de MgCl2 causou fitotoxidez, reduzindo os teores de clorofila, mas promovendo maior teor de Mg nas folhas.

Plant biomonitoring: impact of urban environment on seasonal dynamics of storage substances and chlorophylls of Oleander

In the present study seasonal changes of chlorophyll content and storage substances related to the
 metabolic response of the widespread, evergreen plant oleander (Nerium oleander) to air pollution
 were investigated. Mature leaves of oleander shrubs, grown at five sites of differing levels of air
 pollution in the center and the suburbs of the Athens Metropolitan area, were examined during the
 course of a year. Soluble sugars, starch and total lipid content of the leaves showed a peak at the
 end of the cold season, while a decline was detected during the main growth period. Leaf
 chlorophyll content was increased during spring. It seems likely that the level of air pollution in
 Athens did not affect the concentration and the seasonal pattern of storage substances at the leaf
 level. Elevated chlorophyll content was estimated in the polluted with oxides of nitrogen sites. In
 contrast, leaf chlorophyll content declined in sites with ozone pollution.

Kinetics of argy wormwood (Artemisia argyi) leaf peroxidase and chlorophyll content changes due to thermal and thermosonication treatment

The effects of different thermal and thermosonication blanching treatments on the inactivation of peroxidase (POD) and the retention of total chlorophyll in argy wormwood leaves were studied. Inactivation of POD followed a biphasic first-order model under thermal blanching treatments below 90 °C while a first-order model at 90 °C. In contrast, for thermosonication treatments, the inactivation kinetics of POD fit a first-order model well for all the temperatures tested. Thermosonication treatment was found to inactivate POD faster and retain more of the total chlorophyll than thermal blanching treatment. A thermosonication protocol using ultrasonic intensity of 11.94 W/cm2 at 85 °C for 60 s was found to be the most suitable protocol for blanching the argy wormwood leaves. This protocol inactivated 92. 7 % POD while retaining 96.7 % of total chlorophyll.

Biogenesis of photosynthetic apparatus under the inhibition of energy processes in de-etiolated seedlings of barley (Hordeum vulgare L.)

Transformation of protochlorophyllide forms in etiolated barley seedlings and biogenesis of photosynthetic apparatus in greening leaves of 7-day-old etiolated barley seedlings (Hordeum vulgare L.) were studied under the inhibition of energy processes during illumination. Repression of electron transport between photosystem 2 and 1 (PS2 and PS1, respectively) with 3-(3,4-dichlorophenyl)-1,1-dimethylurea (diuron) inhibited the photochemical activity of PS2 but did not affect chlorophyll biosynthesis and ATP content in leaves compared to the control. Inhibition of mitochondrial electron transport with sodium azide increased relative content of nonphotoactive protochlorophyllide in etiolated leaves, decreased the content of ATP, chlorophylls, and carotenoids and completely suppressed the functional activity of PS 2. The inhibitor of glycolysis sodium fluoride affected all the parameters even more strongly. We observed synchronism in the accumulation of chlorophylls and carotenoids during greening for all inhibitor variants other than fluoride (correlation coefficient, r, equal to 0.98, 0.97, 0.97, and 0.47 with the significance level of 0.01; 0.015; 0.015, and 0.27 for control, diuron, azide, and sodium fluoride, respectively). The change in chlorophyll content under the influence of inhibitors positively correlated with the amount of ATP in the leaf tissue (for 24 h greening, r = 0.97 with significance level of 0.015). We suggest that sources of ATP involved in the synthesis of chlorophyll during greening of etiolated barley seedlings are mostly of non-plastid origin.

Spectral reflectance properties of healthy and stressed coniferous trees

This study investigates the properties of hyperspectral reflectance of healthy and stressed coniferous trees. Two coniferous tree species which naturally grow in Lithuania, Scots pine (Pinus sylvestris L.) and Norway spruce (Picea abies (L.) Karst.), as well as an introduced species, Siberian pine (Pinus sibirica Du Tour), were selected for the study. Hyperspectral reflectance data were collected under laboratory conditions by scanning the needles of healthy (no foliar loss) and stressed Norway spruce (foliar loss 66-70%), Scots pine (foliar loss 71-75%) and Siberian pine (foliar loss 86-90%) trees using a Themis Vision Systems VNIR 400H hyperspectral imaging camera. The spectrometer of the camera covers the spectral range of 400-1000 nm with the sampling interval of 0.6 nm. Simultaneously, the chlorophyll a and b content in the needles was determined by spectrophotometrically measuring the needles’ absorbance of ethanol extracts. The statistical analyses included principal component analysis, analysis of variance and partial least squares regression techniques. Relatively large spectral differences between healthy and stressed trees were detected for Norway spruce needles: 884 out of 955 wavebands indicated a statistically different reflectance (p<0.05). The reflectance associated with the stress level was statistically different (p<0.05) in 767 and 698 out of 955 wavebands for Scots pine and Siberian pine, respectively. The most informative wavelengths for spectral separation between the needles taken from healthy and stressed trees were found in the following spectral ranges: 701.0-715.7 nm for Norway spruce, 706.1-718.2 nm for Scots pine, and 862.3-893.1 nm for Siberian pine. The relationship between the spectral reflectance properties of the needles and their chlorophyll content was also determined for each species. Waveband ranges (as well as single bands) most sensitive to changes in chlorophyll content were: 709.9-722.1 nm (715.6 nm) for Norway spruce; 709.3-721.4 nm (715.0 nm) for Scots pine; 710.6-722.7 nm (720.1 nm) for Siberian pine. In general, the study revealed that narrow-band based hyperspectral imaging has the potential for accurately detecting stress in coniferous trees.