Short-Term Pre-Harvest UV-B Supplement Enhances the Polyphenol Content and Antioxidant Capacity of Ocimum basilicum Leaves during Storage

Ocimum basilicum (basil) leaves are rich in polyphenols, conferring them a high antioxidant activity. The application of UV-B can be used to maintain the post-harvest nutraceutical quality of basil leaves. We aimed to investigate the effects of pre-harvest UV-B application on polyphenolic and pigment contents, antioxidant capacity, and the visual quality of basil stored leaves. We also evaluated the applicability of the non-invasive Dualex® for monitoring the accumulation of leaf epidermal phenolics (Flav Index). After exposing plants to white light (control) and to supplemental UV-B radiation for 4 d, the leaves were harvested and stored for 7d (TS7). The UV-B leaves showed both a higher phenolic content and antioxidant capacity than the controls at TS7. In addition, the correlations between the Flav Index and phenolic content demonstrated that Dualex® can reliably assess the content of epidermal phenolics, thus confirming its promising utilization as a non-destructive method for monitoring the phytochemical quality of O. basilicum leaves. In conclusion, a pre-harvesting UV-B application may be a tool for enhancing the content of polyphenols and the antioxidant potential of basil stored leaves without detrimental effects on their visual quality. These results are important considering the nutraceutical value of this plant and its wide commercial distribution.

Silicon Foliar Application Mitigates Salt Stress in Sweet Pepper Plants by Enhancing Water Status, Photosynthesis, Antioxidant Enzyme Activity and Fruit Yield

Silicon is one of the most significant elements in plants under abiotic stress, so we investigated the role of silicon in alleviation of the detrimental effects of salinity at two concentrations (1500 and 3000 ppm sodium chloride) in sweet pepper plants in two seasons (2018 and 2019). Our results indicated that relative water content, concentrations of chlorophyll a and b, nitrogen, phosphorus and potassium contents, number of fruits plant-1, fruit fresh weight plant-1 (g) and fruit yield (ton hectare-1) significantly decreased in salt-stressed sweet pepper plants as compared to control plants. In addition, electrolyte leakage, proline, lipid peroxidation, superoxide (O2-) and hydrogen peroxide (H2O2) levels, soluble sugars, sucrose, and starch content as well as sodium content significantly increased under salinity conditions. Conversely, foliar application of silicon led to improvements in concentrations of chlorophyll a and b and mineral nutrients, water status, and fruit yield of sweet pepper plants. Furthermore, lipid peroxidation, electrolyte leakage, levels of superoxide, and hydrogen peroxide were decreased with silicon treatments.

Carotenoids and Chlorophylls as Antioxidants

Chlorophylls and carotenoids are natural pigments that are present in our daily diet, especially with the increasing tendency towards more natural and healthy behaviors among consumers. As disturbed antioxidant homeostasis capacities seem to be implicated in the progress of different pathologies, the antioxidant properties of both groups of lipophilic compounds have been studied. The objective of this review was to analyze the state-of-the-art advances in this field. We conducted a systematic bibliographic search (Web of Science™ and Scopus®), followed by a comprehensive and critical description of the results, with special emphasis on highly cited and more recently published research. In addition to an evaluative description of the methodologies, this review discussed different approaches used to obtain a physiological perspective, from in vitro studies to in vivo assays using oxidative biomarkers. From a chemical viewpoint, many studies have demonstrated how a pigment's structure influences its antioxidant response and the underlying mechanisms. The major outcome is that this knowledge is essential for interpreting new data in a metabolic networks context in the search for more direct applications to health. A promising era is coming where the term "antioxidant" is understood in terms of its broadest significance.

Safflower (Carthamus tinctorius) Biochemical Properties, Yield, and Oil Content Affected by 24-Epibrassinosteroid and Genotype under Drought Stress

The steroid hormones, including brassinosteroids, regulate plant growth under stress. It is hypothesized that 24-epibrassinosteroids (24-EBR) can affect safflower (Carthamus tinctorius) biochemical properties, crop yield, and oil content under drought stress. The objective of our study was to determine the response of three safflower genotypes (Goldasht, Faraman, and Sina) to exogenous 24-EBR (0 and 10^-7 M) under drought stress, including 85, 65, and 45% of field capacity in 2015. Stress decreased chlorophyll-a, chlorophyll-b, total chlorophyll, carotenoid, relative water content (RWC), seed yield, and oil percentage. The activities of superoxide dismutase (SOD), catalase (CAT), polyphenol oxidase (PPO), and proline contents increased in response to either drought stress or 24-EBR. Genotypes behaved significantly different under stress. 24-EBR significantly increased plant chlorophyll contents and oil percentage, and it significantly reduced the malondialdehyde (MDA) content via increasing the proline and carotenoid contents under stress. 24-EBR can increase safflower oil and seed yield under drought stress.

Influence of Alkaline Treatment on Structural Modifications of Chlorophyll Pigments in NaOH-Treated Table Olives Preserved without Fermentation

Alkaline treatment is a key stage in the production of green table olives and its main aim is rapid debittering of the fruit. Its action is complex, with structural changes in both the skin and the pulp, and loss of bioactive components in addition to the bitter glycoside oleuropein. One of the components seriously affected are chlorophylls, which are located mainly in the skin of the fresh fruit. Chlorophyll pigments are responsible for the highly-valued green color typical of table olive specialties not preserved by fermentation. Subsequently, the effect on chlorophylls of nine processes, differentiated by NaOH concentration and/or treatment time, after one year of fruit preservation under refrigeration conditions, was investigated. A direct relationship was found between the intensity of the alkali treatment and the degree of chlorophyll degradation, with losses of more than 60% being recorded when NaOH concentration of 4% or greater were used. Oxidation with opening of the isocyclic ring was the main structural change, followed by pheophytinization and degradation to colorless products. To a lesser extent, decarbomethoxylation and dephytylation reactions were detected. An increase in NaOH from 2% to 5% reduced the treatment time from 7 to 4 h, but fostered greater formation of allomerized derivatives, and caused a significant decrease in the chlorophyll content of the olives. However, NaOH concentrations between 6% and 10% did not lead to further time reductions, which remained at 3 h, nor to a significant increase in oxidized compounds, though the proportion of isochlorin e₄-type derivatives was modified. Chlorophyll compounds of series b were more prone to oxidation and degradation reactions to colorless products than those of series a. However, the latter showed a higher degree of pheophytinization, and, exclusively, decarbomethoxylation and dephytylation reactions.

Autofluorescence in Plants

Plants contain abundant autofluorescent molecules that can be used for biochemical, physiological, or imaging studies. The two most studied molecules are chlorophyll (orange/red fluorescence) and lignin (blue/green fluorescence). Chlorophyll fluorescence is used to measure the physiological state of plants using handheld devices that can measure photosynthesis, linear electron flux, and CO2 assimilation by directly scanning leaves, or by using reconnaissance imaging from a drone, an aircraft or a satellite. Lignin fluorescence can be used in imaging studies of wood for phenotyping of genetic variants in order to evaluate reaction wood formation, assess chemical modification of wood, and study fundamental cell wall properties using Förster Resonant Energy Transfer (FRET) and other methods. Many other fluorescent molecules have been characterized both within the protoplast and as components of cell walls. Such molecules have fluorescence emissions across the visible spectrum and can potentially be differentiated by spectral imaging or by evaluating their response to change in pH (ferulates) or chemicals such as Naturstoff reagent (flavonoids). Induced autofluorescence using glutaraldehyde fixation has been used to enable imaging of proteins/organelles in the cell protoplast and to allow fluorescence imaging of fungal mycelium.

Quality of Supplementary Morning Lighting (SML) During Propagation Period Affects Physiology, Stomatal Characteristics, and Growth of Strawberry Plants

Artificial light supplementation is widely used in modern agriculture. Due to their numerous advantages, light emitting diodes (LEDs) are widely used to effectively increase the yield or control the development of crops. In the present study, the effects of supplementary morning lighting (SML) with LEDs on the physiology and stomatal characteristics of strawberry plants were studied, with the aim of awakening the plant guard cells before sunrise and enabling strawberry plants to efficiently photosynthesize immediately after sunrise. Young daughter plants of 'Maehyang' and 'Seolhyang' strawberry cultivars that have just rooted were grown under LEDs with different wavelengths-white (W), red (R), mixed blue and red (BR, 1:1), and blue (B)-to investigate the effects of the SML on the physiology, stomatal characteristics, and growth. The SML was provided for 2 h at an intensity of 100 μmol·m-2·s-1 PPFD before sunrise every morning. A group without supplementary lighting was set as the control. The results showed that the different SML qualities have significantly affected the stomatal characteristics. The B SML promoted the stomatal opening more effectively compared to the other SMLs. The stomatal conductance and quantum yield (Fv/Fm) of leaves treated with the SMLs were higher than those of the control group. The B and BR SMLs most significantly affected the stomatal conductance and quantum yield (Fv/Fm). After 30 days of the SML treatments, it was observed that the B SML effectively improved the plant quality, chlorophyll content, and carbohydrate accumulation in the two strawberry cultivars. In general, a short-term exposure to blue light before sunrise can effectively improve the quality and promote the production of strawberry plants.

Biosynthesis of the modified tetrapyrroles-the pigments of life

Modified tetrapyrroles are large macrocyclic compounds, consisting of diverse conjugation and metal chelation systems and imparting an array of colors to the biological structures that contain them. Tetrapyrroles represent some of the most complex small molecules synthesized by cells and are involved in many essential processes that are fundamental to life on Earth, including photosynthesis, respiration, and catalysis. These molecules are all derived from a common template through a series of enzyme-mediated transformations that alter the oxidation state of the macrocycle and also modify its size, its side-chain composition, and the nature of the centrally chelated metal ion. The different modified tetrapyrroles include chlorophylls, hemes, siroheme, corrins (including vitamin B12), coenzyme F430, heme d1, and bilins. After nearly a century of study, almost all of the more than 90 different enzymes that synthesize this family of compounds are now known, and expression of reconstructed operons in heterologous hosts has confirmed that most pathways are complete. Aside from the highly diverse nature of the chemical reactions catalyzed, an interesting aspect of comparative biochemistry is to see how different enzymes and even entire pathways have evolved to perform alternative chemical reactions to produce the same end products in the presence and absence of oxygen. Although there is still much to learn, our current understanding of tetrapyrrole biogenesis represents a remarkable biochemical milestone that is summarized in this review.

Pheophorbide a: State of the Art

Chlorophyll breakdown products are usually studied for their antioxidant and anti-inflammatory activities. The chlorophyll derivative Pheophorbide a (PPBa) is a photosensitizer that can induce significant anti-proliferative effects in several human cancer cell lines. Cancer is a leading cause of death worldwide, accounting for about 9.6 million deaths, in 2018 alone. Hence, it is crucial to monitor emergent compounds that show significant anticancer activity and advance them into clinical trials. In this review, we analyze the anticancer activity of PPBa with or without photodynamic therapy and also conjugated with or without other chemotherapic drugs, highlighting the capacity of PPBa to overcome multidrug resistance. We also report other activities of PPBa and different pathways that it can activate, showing its possible applications for the treatment of human pathologies.

The Main Structural and Functional Characteristics of Photosystem-II-Enriched Membranes Isolated from Wild Type and cia3 Mutant Chlamydomonas reinhardtii

Photosystem II (PSII)-enriched membranes retain the original PSII architecture in contrast to PSII cores or PSII supercomplexes, which are usually isolated from Chlamydomonas reinhardtii. Here, we present data that fully characterize the structural and functional properties of PSII complexes in isolated PSII-enriched membranes from C. reinhardtii. The preparations were isolated from wild-type (WT) and CAH3-deficient mutant cia3 as the influence of CAH3 on the PSII function was previously proposed. Based on the equal chlorophyll content, the PSII-enriched membranes from WT and cia3 have the same amount of reaction centers (RCs), cytochrome b559, subunits of the water-oxidizing complex, Mn ions, and carotenes. They differ in the ratio of other carotenoids, the parts of low/intermediate redox forms of cytochrome b559, and the composition of outer light-harvesting complexes. The preparations had 40% more chlorophyll molecules per RC compared to higher plants. Functionally, PSII-enriched membranes from WT and cia3 show the same photosynthetic activity at optimal pH 6.5. However, the preparations from cia3 contained more closed RCs even at pH 6.5 and showed more pronounced suppression of PSII photosynthetic activity at shift pH up to 7.0, established in the lumen of dark-adapted cells. Nevertheless, the PSII photosynthetic capacities remained the same.

Prediction of Degreening Velocity of Broccoli Buds Using Hyperspectral Camera Combined with Artificial Neural Networks

Developing a noninvasive technique to estimate the degreening (loss of green color) velocity of harvested broccoli was attempted. Loss of green color on a harvested broccoli head occurs heterogeneously. Therefore, hyperspectral imaging technique that stores spectral reflectance with spatial information was used in the present research. Using artificial neural networks (ANNs), we demonstrated that the reduction velocity of chlorophyll at a site on a broccoli head was related to the second derivative of spectral reflectance data at 15 wavelengths from 405 to 960 nm. The reduction velocity was predicted using the ANNs model with a correlative coefficient of 0.995 and a standard error of prediction of 5.37 × 10^-5 mg·g^-1·d^-1. The estimated reduction velocity was effective for predicting the chlorophyll concentration of broccoli buds until 7 d of storage, which was established as the maximum time for maintaining marketability. This technique may be useful for nondestructive prediction of the shelf life of broccoli heads.

Phytochemical analysis of mite-infested tea leaves of Darjeeling Hills, India

INTRODUCTION

Darjeeling tea of India is one of the most famous beverages globally. However, a large amount of tea crop is damaged every year by the attack of mites.

OBJECTIVES

The study aimed to determine the changes in different pigments and biochemical components of tea leaves due to mite infestation.

MATERIALS AND METHODS

We used UV-visible and Fourier-transform infrared (FTIR) spectroscopy simultaneously to understand the damages in pigment contents of the leaves of tea (Camellia sinensis (L.) Kuntze) due to attack of phytophagus mite, Oligonychus coffeae Nietner. Furthermore, chemical analysis of infested tea leaves was also performed to compare the nutrients of the plants, namely total phenol, protein and soluble sugar.

RESULTS

The UV-visible study reveals severe reduction of the pigments such as chlorophyll (Chl), carotenoids and xanthophylls in the tea leaf due to mite infestation. The findings of the FTIR study, also shows variation in different physiochemical components in the leaf Chl. The sugar and protein content of the infested leaves have been reduced compared to uninfested ones. Results in the case of tea leaves plucked during first (March) and third (November) flushes show similar trends.

CONCLUSION

The increase in phenolic and alcoholic components and decrease in Chl contents may affect the quality of Darjeeling tea. The extent of damages done by the pests measured here could aid the pest management in tea gardens.

Multiyear Links between Water Chemistry, Algal Chlorophyll, Drought-Flood Regime, and Nutrient Enrichment in a Morphologically Complex Reservoir

This investigation targeted the largest morphologically complex reservoir (Soyang) in South Korea during 1992–2013. It is a prominent source of domestic water supply, irrigation, flood control, and hydroelectric power generation. Therefore, this investigation focused on regional- to global-scale applications. We revealed the empirical links between chlorophyll (Chl-a) and total nitrogen (TN) and total phosphorus (TP), the impact of the monsoon regime on nutrients, and flood and drought regime. Further, we investigated the trophic status dynamics, tendencies of water chemistry factors, and valuation of zonal water chemistry by the application of a modified multimetric water pollution index (WPI). The physicochemical indicators illustrated significant disparities among the Lacustrine (Lz), Transition (Tz), and Riverine (Rz) zones. The solid contents (TSS) displayed a significant increase in the lake zones in the order of Lz (4.58 ± 13.7 mg/L), Tz (6.16 ± 16.2 mg/L), and Rz (7.38 ± 18.9 mg/L). However, TP and allied chemical species revealed an inverse relationship with the TN:TP ambient ratios. Nevertheless, Chl-a displayed sharp interzonal fluctuations from the Lz (2.90 ± 3.29 µg/L) to Tz (4.61 ± 4.98 µg/L). The seasonal deviations, however, exposed divergent heterogeneities among the TSS, TN, TP, and Chl-a. The regression plot between the observed and predicted Chl-a in the Soyang reservoir displayed a very strong relationship (R² = 0.997). The seasonal and interannual variations of trophic status displayed a higher impact of precipitation, particularly in the case of TP and Chl-a. The flood years indicated phosphorus limitations, while drought years alluded to the non-algal light limitations (biogenic turbidity). Water temperature (WT), dissolved oxygen (DO), biological oxygen demand (BOD), TSS, TP, and Chl-a displayed decreasing trends in the ambient water. In contrast, pH, chemical oxygen demand (COD), electrical conductivity (EC), and TN displayed increasing tendencies by the application Mann–Kendall trend analysis. The WPI outcomes designated Lz with excellent water quality while Tz an Rz indicated good water quality. It also indicated impending sedimentation tendencies in the Rz. In conclusion, our findings indicated fluctuating rainfall patterns (drought and flood conditions) that significantly impacted the Soyang reservoir water quality, flood and drought severity, and trophic status of the reservoir. This study highlights the requirements of further studies to substantiate the drought and flood dynamics and their impacts on nutrients and overall water quality status.

The Water Content Drives the Susceptibility of the Lichen Evernia prunastri and the Moss Brachythecium sp. to High Ozone Concentrations

The aim of this study was to evaluate the tolerance of lichens (Evernia prunastri) and mosses (Brachythecium sp.) to short-term (1 h), acute (1 ppm) O3 fumigation under different hydration states (dry, <10% water content, metabolism almost inactive; wet, >200% water content, metabolism fully active). We hypothesized that stronger damage would occur following exposure under wet conditions. In addition, we checked for the effect of recovery (1 week) after the exposure. Ozone fumigation negatively affected the content of chlorophyll only in wet samples, but in the moss, such a difference was no longer evident after one week of recovery. Photosynthetic efficiency was always impaired by O3 exposure, irrespective of the dry or wet state, and also after one week of recovery, but the effect was much stronger in wet samples. The antioxidant power was increased in wet moss and in dry lichen, while a decrease was found for wet lichens after 1 week. Our results confirm that the tolerance to O3 of lichens and mosses may be determined by their low water content, which is the case during the peaks of O3 occurring during the Mediterranean summer. The role of antioxidant power as a mechanism of resistance to high O3 concentrations needs to be further investigated.

Dark/Light Treatments Followed by γ-Irradiation Increase the Frequency of Leaf-Color Mutants in Cymbidium

Radiation randomly induces chromosomal mutations in plants. However, it was recently found that the frequency of flower-color mutants could be specifically increased by upregulating anthocyanin pathway gene expression before radiation treatments. The mechanisms of chlorophyll biosynthesis and degradation are active areas of plant study because chlorophyll metabolism is closely connected to photosynthesis. In this study, we determined the dark/light treatment conditions that resulted in upregulation of the expression levels of six chlorophyll pathway genes, uroporphyrinogen III synthase (HEMD), uroporphyrinogen III decarboxylase (HEME2), NADPH-protochlorophyllide oxidoreductase (POR) A (PORA), chlorophyll synthase (CHLG), chlorophyllase (CLH2), and red chlorophyll catabolite reductase (RCCR), and measured their effects on the γ-irradiation-induced frequencies of leaf-color mutants in two Cymbidium cultivars. To degrade chlorophyll in rhizomes, 60–75 days of dark treatment were required. To upregulate the expressions of chlorophyll pathway genes, 10 days of light treatment appeared to be optimal. Dark/light treatments followed by γ-irradiation increased chlorophyll-related leaf mutants by 1.4- to 2.0-fold compared with γ-ray treatment alone. Dark/light treatments combined with γ-irradiation increased the frequency of leaf-color mutants in Cymbidium, which supports the wider implementation of a plant breeding methodology that increases the mutation frequency of a target trait by controlling the expression of target trait-related genes.

Yield, Growth, Quality, Biochemical Characteristics and Elemental Composition of Plant Parts of Celery Leafy, Stalk and Root Types Grown in the Northern Hemisphere

Celery is one of the major nutraceutical vegetable species due to the high dietary and medicinal properties of all of its plant parts. Yield, growth and produce quality of six celery genotypes belonging to leafy (Elixir and Samurai), stalk (Atlant and Primus) or root (Egor and Dobrynya) types, as well as the distribution of biomass, sugars, mineral elements and antioxidants among the different plant parts, were assessed. Within the celery root type, cultivar Dobrynya resulted in higher yield than Egor, whereas the genotype did not significantly affect the marketable plant part production of leafy and stalk types. Leaf/petiole ratios relevant to biomass, total dissolved solids, sugars, ascorbic acid, flavonoids, antioxidant activity and ash, K, Zn, Fe, Mn, Cu and Se content were significantly affected by the celery type examined. Ash content was highest in the leaves and lowest in the roots. Celery antioxidant system was characterized by highly significant relationships between ascorbic acid, polyphenols, flavonoids, antioxidant activity and Zn. Among the celery types analyzed, the highest values of chlorophyll, Fe and Mn content as well as antioxidant activity were recorded in leaves from root genotypes, which suggests interesting nutraceutical prospects of the aforementioned plant parts for human utilization.

Selenium and Salt Interactions in Black Gram (Vigna mungo L): Ion Uptake, Antioxidant Defense System, and Photochemistry Efficiency

Salinity is a major abiotic stress which limits crop production, especially under rainfed conditions. Selenium (Se), as an important micronutrient, plays a vital role in mitigating detrimental effects of different abiotic stresses. The objective of this research was to examine the effect of Se fertilization on black gram (Vigna mungo) under salt stress. Our results showed that salt stress (100 mM NaCl) in leaves significantly induced oxidative damage and caused a decline in relative water content, chlorophyll (Chl), stomatal conductance (gs), photochemical efficiency (Fv/Fm), sucrose, and reducing sugars. A low dose of Se (1.5 ppm) significantly reduced hydrogen peroxide content, malondialdehyde formation, cell membrane damage, and also improved antioxidative enzyme activities, including superoxide dismutase, catalase, ascorbate peroxidase, glutathione reductase, and glutathione peroxidase under salt stress. Se-treated plants exhibited higher Chl, gs, Fv/Fm, sucrose, and reducing sugars than untreated plants in response to salt stress. In addition, Se application enhanced Se uptake and reduced Na+ uptake, but Cl- remained unaffected. Our results indicated that a low dose of Se effectively alleviated salt damage via inhibition of Na+ uptake and enhanced antioxidant defense resulting in a significant decrease in oxidative damage, and maintained gaseous exchange and PS II function for sucrose and reducing sugars accumulation in black gram.

Magnesium-Isotope Fractionation in Chlorophyll-a Extracted from Two Plants with Different Pathways of Carbon Fixation (C3, C4)

Relatively few studies have been focused so far on magnesium–isotope fractionation during plant growth, element uptake from soil, root-to-leaves transport and during chlorophylls biosynthesis. In this work, maize and garden cress were hydroponically grown in identical conditions in order to examine if the carbon fixation pathway (C4, C3, respectively) might have impact on Mg-isotope fractionation in chlorophyll-a. The pigment was purified from plants extracts by preparative reversed phase chromatography, and its identity was confirmed by high-resolution mass spectrometry. The green parts of plants and chlorophyll-a fractions were acid-digested and submitted to ion chromatography coupled through desolvation system to multiple collector inductively coupled plasma-mass spectrometry. Clear preference for heavy Mg-isotopes was found in maize green parts (∆²⁶Mg_{plant-nutrient} 0.65, 0.74 for two biological replicates, respectively) and in chlorophyll-a (∆²⁶Mg_{chlorophyll-plant} 1.51, 2.19). In garden cress, heavy isotopes were depleted in green parts (∆²⁶Mg_{plant-nutrient} (−0.87)–(−0.92)) and the preference for heavy isotopes in chlorophyll-a was less marked relative to maize (∆²⁶Mg_{chlorophyll-plant} 0.55–0.52). The observed effect might be ascribed to overall higher production of energy in form of adenosine triphosphate (ATP), required for carbon fixation in C4 compared to C3, which could reduce kinetic barrier and make equilibrium fractionation prevailing during magnesium incorporation to protoporphyrin ring.

[Changes of pigment components in Dendrobium catenatum flower under different storage conditions]

The flower color of Dendrobium catenatum(D. officinale) tends to fade during storage. In order to clarify the influence of storage conditions on the pigment components in flowers, two conditions were applied:temperature and illumination. The contents of pigments in the D. catenatum flower were determined by UV-Vis spectrophotometry and HPLC, and the changes of them during storage were analyzed. The results showed that illumination and temperature had an effect on the pigments of D. catenatum flower during sto-rage. Illumination significantly promoted the degradation of pigments. The contents of total chlorophyll, carotenoids and anthocyanins in the light samples were significantly lower than those in the dark. The total chlorophyll, carotenoids and anthocyanins in the light samples were decreased by 46.5%, 63.4%, and 69.2% respectively. Illumination had a greater effect on fat-soluble pigments than water-soluble pigments. Among the three temperature treatments, the contents of chlorophyll, carotenoid and anthocyanin were as follows:-20 ℃&gt;4 ℃&gt;room temperature, it is indicated that-20 ℃ was the best temperature to maintain the stability of pigment composition. The contents of chlorophyll a, chlorophyll b, β-carotene, lutein and zeaxanthin in the light samples decreased by 34.8%, 69.0%, 72.5%, 61.6%, 36.1%, respectively. After storage for 5 months, the contents of chlorophyll, carotenoid and anthocyanin constituent at-20 ℃ was significantly higher than those at 4 ℃ and room temperature. The results show that light avoiding and low-temperature can effectively slow down the degradation of pigment components. Therefore, it is suggested that D. catenatum flower should be stored in light avoiding and low-temperature conditions in actual production and processing, which can prolong the usable time.

In Vitro Bioaccessibility of Carotenoids and Chlorophylls in a Diverse Collection of Spinach Accessions and Commercial Cultivars

Spinach, a nutrient-dense, green-leafy vegetable, is a rich source of carotenoid and chlorophyll bioactives. While the content of bioactives is known to vary with the genotype, variation in bioaccessibility is unknown. Bioaccessibility was explored in 71 greenhouse-grown spinach genotypes in fall and spring 2018/2019. Spinach was phenotyped for its greenness, leaf texture, leaf shape, and SPAD chlorophyll content. Postharvest, spinach was washed, blanched, and homogenized prior to assessment of bioactive bioaccessibility using a novel high-throughput in vitro digestion model followed by high-performance liquid chromatography with a photodiode array detector analysis. There was a significant variation in the bioaccessible content for all bioactives (p < 0.05), except for chlorophyll b (p = 0.063) in spring-grown spinach. The correlation coefficients of bioaccessible contents between seasons reveal that lutein (r = 0.52) and β-carotene (r = 0.55) were correlated to a greater extent than chlorophyll a (r = 0.38) and chlorophyll b (r = 0.19). The results suggest that carotenoid and chlorophyll bioaccessible contents may vary based on spinach genotypes and may be stable across seasons.

Rethinking phosphorus-chlorophyll relationships in lakes

The empirical relationship between total phosphorus and chlorophyll has guided lake management decisions for decades, but imprecision in this relationship in individual lakes limits the utility of these models. Many environmental factors that potentially affect the total phosphorus-chlorophyll relationship have been studied, but here we hypothesize that imprecision can be reduced by considering differences in the proportions of phosphorus bound to three different "compartments" in the water column: phosphorus bound in phytoplankton, phosphorus bound to suspended sediment that is not associated with phytoplankton, and dissolved phosphorus. We specify a hierarchical Bayesian network model that estimates phosphorus associated with each compartment using field measurements of chlorophyll, total suspended solids, and total phosphorus collected from reservoirs in Missouri, USA. We then demonstrate that accounting for these different compartments yields accurate predictions of total phosphorus in individual lakes. Results from this model also yield insights into the mechanisms by which lake morphometric and watershed characteristics affect observed relationships between total phosphorus and chlorophyll.

[Effects of shading on photosynthetic characteristics and chlorophyll fluorescence parameters of four Corydalis species]

We examined the effects of five shading treatments (0, 20%, 40%, 60% and 80% shading) on chlorophyll content, photosynthetic characteristics, and chlorophyll fluorescence chara-cteristics of four Corydalis species (C. incisa, C. decumbens, C. edulis and C. pallida) in a pot experiment. The results showed that the contents of chlorophyll a, chlorophyll b and chlorophyll (a+b) increased with the increment of shading, with that of C. incisa reaching the maximum under 80% shading treatment and that of C. decumbens, C. edulis and C. pallida reaching a maximum under 60% shading treatment. In contrast, chlorophyll a/b, light saturation point, light compensation point and dark respiration rate decreased with increasing shading. Among the four Corydalis species, C. incisa reached up to the maximum chlorophyll fluorescence parameters under 80% shading treatment, and C. decumbens, C. edulis and C. pallida reached the maximum at 60% shading treatment. The shade tolerance of four species was as follows: C. incisa ＞ C. decumbens ＞ C. edulis ＞ C. pallida. C. incisa under 80% shading treatment and C. decumbens, C. edulis, C. pallida at 60% shading treatment had the highest light energy utilization and photosynthetic capacity, which would facilitate their growth.

Phosphite Application Alleviates Pythophthora infestans by Modulation of Photosynthetic and Physio-Biochemical Metabolites in Potato Leaves

Potato late blight (Phytophtora infestans) is among the most severely damaging diseases of potato (Solanum tuberusom L.) worldwide, causing serious damages in potato leaves and tubers. In the present study, the effects of potassium phosphite (KPhi) applications on photosynthetic parameters, enzymatic and non-enzymatic antioxidant properties, hydrogen peroxide (H₂O₂) and malondialdehyde (MDA), total protein and total carbohydrate of potato leaves challenged with P. infestans pathogen were investigated. Potato leaves were sprayed five times with KPhi (0.5%) during the growing season prior to inoculation with P. infestans. The potato leaves were artificially infected by the LC06-44 pathogen isolate. The leaves were sampled at 0, 24, 48, 72 and 96 h after the infection for evaluations. P. infestans infection reduced chlorophyll (Chl) pigments contents, chlorophyll fluorescence, carotenoid (Car) and anthocyanin contents and increased the accumulation of H₂O₂ and MDA. Meanwhile, our result showed that KPhi treatment alleviated adverse effect of late blight in potato leaves. KPhi application also increased plant tolerance to the pathogen with improved photosynthetic parameters Chl a, b, total Chl, Car, and anthocyanin compare to controls. Moreover, the increased oxidative enzymes activity of superoxide dismutase (SOD), peroxidase (POD), catalase (CAT) and ascorbate peroxidase (APx), and non-enzymatic substances such as phenolics, flavonoids and proline were found in KPhi treated plants, compared to untreated plants after inoculation. In addition, KPhi application followed by P. infestans infection also decreased the content of H₂O₂ and MDA, but increased the total protein and total carbohydrate contents in potato leaves. The consequence of current research indicated that KPhi played a vital role in pathogen tolerance, protecting the functions of photosynthetic apparatus by improved oxidative levels and physio-biochemical compounds in potato leaves.

Diagnosis of Nitrogen Nutrition in Rice Leaves Influenced by Potassium Levels

Evaluation of nitrogen (N) status by leaf color is a kind of classic nutritional diagnostic method. However, the color of leaves is influenced not only by N, but also by other nutrients such as potassium (K). Two-year field trials with a factorial combination of N and K were conducted to investigate the effects of different N and K rates on soil plant analysis development (SPAD) readings and leaf N, K, magnesium (Mg), and chlorophyll concentrations. Visual inspections in leaf greenness revealed darker green leaves with increasing N rates, while paler green leaves with increasing K rates. Data showed that SPAD readings, chlorophyll, N and Mg concentrations, and the chloroplast area increased significantly with raising N rates, while declined sharply with the increase in K rates due to the antagonistic relationships between K⁺ and NH₄ ⁺ as well as Mg²⁺. It was also probable that the increase in K promoted the growth of leaves and diluted their N and Mg concentrations. The paler leaf appearance resulting from the application of K may overestimate the actual demand for N in the diagnosis of rice N status. The strong antagonistic relationships between K⁺, NH₄ ⁺, and Mg²⁺ should be considered in rice production and fertilization.

Structural basis of light-harvesting in the photosystem II core complex

Photosystem II (PSII) is a membrane-spanning, multi-subunit pigment-protein complex responsible for the oxidation of water and the reduction of plastoquinone in oxygenic photosynthesis. In the present review, the recent explosive increase in available structural information about the PSII core complex based on X-ray crystallography and cryo-electron microscopy is described at a level of detail that is suitable for a future structure-based analysis of light-harvesting processes. This description includes a proposal for a consistent numbering scheme of protein-bound pigment cofactors across species. The structural survey is complemented by an overview of the state of affairs in structure-based modeling of excitation energy transfer in the PSII core complex with emphasis on electrostatic computations, optical properties of the reaction center, the assignment of long-wavelength chlorophylls, and energy trapping mechanisms.