Ratio Of Carotenoids Research Articles

Uptake and Effects of Cylindrospermopsin: Biochemical, Physiological and Biometric Responses in The Submerged Macrophyte Egeria densa Planch

Cylindrospermopsin (CYN) is being detected in surface waters more commonly and frequently worldwide. This stable, extracellular cyanotoxin causes protein synthesis inhibition, thus posing a risk to aquatic biota, including macrophytes, which serve as primary producers. Nevertheless, data regarding the effects caused by environmental concentrations of CYN is still limited. In the presented study, the uptake of CYN at environmental concentrations by the submerged macrophyte Egeria densa was investigated. Bioaccumulation, changes in the plant biomass, as well as shoot-length were assessed as responses. Variations in the cellular H2O2 levels, antioxidative enzyme activities, as well as concentrations and ratios of the photosynthetic pigments were also measured. E. densa removed 54% of CYN within 24 h and up to 68% after 336 h; however, CYN was not bioaccumulated. The antioxidative enzyme system was activated by CYN exposure. Pigment concentrations decreased with exposure but normalized after 168 h. The chlorophyll a to b ratio increased but normalized quickly thereafter. Carotenoids and the ratio of carotenoids to total chlorophylls increased after 96 h suggesting participation in the antioxidative system. Growth stimulation was observed. The ability to remove CYN and resistance to CYN toxicity within 14 days proved E. densa as suitable for phytoremediation; nonetheless, prolonged exposure (32 days) resulted in adverse effects related to CYN uptake, which needs to be studied further.

Dependence of Pepper Fruit Colour on Basic Pigments Ratio and Expression Pattern of Carotenoid and Anthocyanin Biosynthesis Genes

Fruit biochemical analysis of four pepper (Capsicum annuum L.) cultivars, contrasting in immature and ripe fruit colour, was performed, and chlorophylls, carotenoids and anthocyanins were profiled in the peel and pulp during fruit ripening. It was found that pericarp parts (peel and pulp) differ in pigment composition and accumulation mode. In the same fruit tissues, the expression pattern of structural genes of the carotenoid (PSY1, PSY2, LCYb, and CCS) and anthocyanin (CHS, F3 '5 'H, DFR, ANS, and UFGT) pathways was evaluated. It was shown that carotenoid content positively correlates with the PSY1, LCYb and CCS expression level in the fruit pulp and with CCS expression level in the fruit peel. In pepper cultivars with purple-coloured immature fruits (Sirenevyj cub, Otello), a positive correlation was shown between the CHS, F3 '5 'H, DFR, ANS, and UFGT expression levels and the anthocyanin content in the peel. Thus, it was shown that in the pepper fruit, peel and pulp colours are regulated independently and determined by the main pigment ratio and the activity of carotenoid and anthocyanin biosynthesis genes.

A Special Summer Pruning Method Significantly Increases Fruit Weight, Ascorbic Acid, and Dry Matter of Kiwifruit (‘Jinyan’, Actinidia eriantha × A. chinensis)

Jinyan (Actinidia eriantha × A. chinensis) is one of the gold-fleshed kiwifruit cultivars currently being promoted in south China. However, its fruit dry matter is usually less than 16%, which seriously affects fruit quality including taste and flavor. This causes a financial loss to growers: not only are the prices paid for the fruit low because of their bad reputation for quality, but some orchards have been removed. Improvement of fruit quality is essential. In this study, a method is described for squeezing and twisting flowering shoots before flowering and removing the distal vegetative parts of flowering shoots after fruit set. The effects on fruit quality were determined. The dry matter of fruit was increased by 6.6%. Fruit size also increased as did the chlorophyll a content and the chlorophyll:carotenoid ratio. The significantly increased fruit dry matter, resulting in significant increases in fruit soluble solids concentrations (P < 0.01), thereby possibly improving fruit taste. Fruit weight, fruit length, and carotenoid and ascorbic acid concentrations were significantly enhanced in comparison with controls (P < 0.01), increasing by 20%, 7%, 12%, and 19%, respectively. However, there was no significant difference in soluble sugar concentrations, titratable acid concentrations, and the reduced chlorophyll b concentrations. This research provides a practical method to increase fruit dry matter, and hence a way to allow fruit quality to reach commercial requirements for cultivars such as Jinyan, which under previous management systems had significant shortcomings in fruit flavor and taste.

Photochemical responses to light in sun and shade leaves of Theobroma cacao L. (West African Amelonado)

Theobroma cacao is a tropical understory tree that is traditionally grown in an agroforestry system under a shade canopy; but is increasingly being grown in an orchard system with limited shade or no shade. This study investigated the light response of sun and shade leaves from mature trees of one of the most cultivated cacao accession (West African Amelonado), grown under full sun conditions. Chlorophyll fluorescence was used to measure Fv/Fm, and to generate light response curves for photosynthetic and non-photosynthetic quenching parameters. The light response curves indicated an increased capacity for photosynthesis in the sun leaves however the Fv/Fm and NPQ data showed that the sun leaves were subject to photoinhibition. Biochemical assays were used to compare sun and shade leaves for photosynthetic pigment content and a range of parameters related to reactive oxygen species scavenging and cellular damage. The sun and shade leaves demonstrated typical pigment plasticity however the chlorophyll carotenoid ratio was low for both types of leaves. There was no observed plasticity in superoxide dismutase activity between the sun and shade leaves however the plant was able to respond to the increased photosyntheically active radiation by increasing the activity of ascorbate peroxidase and to a lesser extent catalase. Increased electrolyte leakage in the sun leaves however suggests that the ability to mitigate reactive oxygen species was limited. The results point to limitations in the ability of currently cultivated cacao to acclimate to full sun conditions.

Pigments Content (Chlorophylls, Fucoxanthin and Phycobiliproteins) of Different Commercial Dried Algae

Algae are a complex, polyphyletic group of organisms, affordable and naturally rich in nutrients, but also valuable sources of structurally diverse bioactive substances such as natural pigments. The aim of this work was to evaluate the polar and non-polar pigment contents of different commercial dried algae (brown: Himanthalia elongata, Undaria pinnatifida, Laminaria ochroleuca; red: Porphyra spp.; and a blue-green microalga: Spirulina spp.). The pigment extraction was carried out using different solvents (100% methanol, 100% methanol acid free, 100% ethanol, 90% acetone, N,N-dimethylformamide, dimethyl sulfoxide-water (4:1, v/v) and pH 6.8 phosphate buffer), selected according to their affinity for each class of pigments. Acetone proved to be an efficient solvent to extract chlorophylls from brown and red algae, but not from Spirulina spp. Porphyra spp. presented considerably higher levels of all pigments compared to brown algae, although Spirulina spp. presented significantly higher (p < 0.05) levels of chlorophylls, carotenoids and phycobiliproteins, compared to all macroalgae. The content of fucoxanthin extracted from the three brown algae was highly correlated to the carotenoid content. Within this group, Himanthalia elongata presented the highest fucoxanthin/total carotenoids ratio. Although the yield of extraction depended on the solvent used, the algae studied herein are an interesting source of pigments of great value for a wide range of applications.

Possibility of Using Astaxanthin-Rich Dried Cell Powder from Paracoccus carotinifaciens to Improve Egg Yolk Pigmentation of Laying Hens

The study investigated egg quality aspects such as astaxanthin concentration, E/Z-isomer ratio, and yolk color in laying hens fed with astaxanthin-containing diets. Dried Paracoccus carotinifaciens cell powder (Panaferd-AX) and fine cell powder (Panaferd-P) were used as sources of astaxanthin, with average particle diameters of approximately 100 μm and 10 μm, respectively. Paracoccus carotinifaciens contains valuable rare carotenoids such as adonirubin and adonixanthin, and thus the concentrations of these carotenoids in egg yolk were also evaluated. The E/Z-isomer ratios of the egg yolk carotenoids were determined by normal-phase high-performance liquid chromatography (HPLC) with an improved solvent system. Feeding diets containing P. carotinifaciens resulted in increased concentrations of astaxanthin, adonirubin, and adonixanthin in egg yolk, as well as a marked increase in the yolk color fan score; values associated with the Panaferd-P-containing diet were higher than those associated with the Panaferd-AX-containing diet. For example, the astaxanthin concentration in egg yolks of hens fed with the Panaferd-AX- and Panaferd-P-containing diets for 21 days were 1.21 μg/g and 1.85 μg/g, respectively. This indicates that the pulverization treatment of the P. carotinifaciens powder increased the efficiency of carotenoid accumulation in the egg yolk. Moreover, more than 95% of astaxanthin in P. carotinifaciens was present as the all-E-isomer. However, approximately 25% of astaxanthin in egg yolk was present as the Z-isomers. In recent years, astaxanthin Z-isomers have attracted substantial attention as they exhibit a greater bioavailability and bioactivity than the all-E-isomer. These data are important not only for understanding egg yolk pigmentation but also for improving the nutritional value of hens’ egg yolk through the addition of P. carotinifaciens to their diet.

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.

A combination of morphological and photosynthetic functional traits maintains the vertical distribution of bryophytes in a subtropical cloud forest.

The distribution and performance of bryophyte species vary with vertical gradients, as a result of changes in environmental factors, especially light. However, the morphological and physiological drivers of bryophyte distribution along forest vertical gradients are poorly understood. For 18 species of mosses and liverworts distributed among three vertical microhabitats (ground, tree trunk, and branch, variance in 28 morphological and photosynthetic functional traits was comparatively analyzed among the microhabitats and bryophyte life-forms in a subtropical cloud forest in Ailao Mountain, Yunnan, southwestern China. Principal component analysis (PCA) was used to summarize trait differences among bryophyte species. In contrast to trunk and ground dwellers, branch dwellers tended to reduce light interception (smaller leaf and cell sizes, lower chlorophyll content), protect against damage from intense irradiation (higher ratios of carotenoids to chlorophyll), raise light energy use (higher photosynthetic capacity), and cope with lower environmental moisture (pendant life-forms, thicker cell walls). The PCA showed that ecological strategies of bryophytes in response to levels of irradiation were specialized in branch dwellers, although those of ground and trunk dwellers were less distinct. Environmental filtering shaped the combination of functional traits and the spatial distribution of bryophytes along the vertical gradients. Bryophyte species from the upper canopy of cloud forests show narrow variation in functional traits in high-light intensity, whereas species in the lower vertical strata associated with low-light intensity used contrasting, but more diverse ecological strategies.

Environmental Factors Affecting the Diversity and Photosynthetic Pigments of Trentepohlia Species in Northern Thailand’s Chiang Dao Wildlife Sanctuary

This study addressed the environmental factors that affect <em>Trentepohlia</em> spp. in the Chiang Dao Wildlife Sanctuary at altitudes of 399 to 1,503 meters above sea level (m a.s.l.) during the rainy, winter, and summer seasons. Species were identified using characteristic morphological identification. The influence of environmental factors on the algae was analyzed using a statistical program, and seasonal changes in the quantity of photosynthetic pigments in the dominant species were evaluated. The average relative humidity was 69.34 ± 12.90%, the average temperature was 26.23 ± 3.79 °C, and the average light intensity was 139.78 ± 42.21 µmol photon m<sup data-id="superscript-1">−2</sup> s<sup data-id="superscript-2">−1</sup>. Thirteen species were found: <em>Trentepohlia chapmanii</em>, <em>Trentepohlia</em> sp. 1, <em>Trentepohlia</em> sp. 2, <em>Trentepohlia sundarbanensis</em>, <em>Trentepohlia</em> sp. 3, <em>Trentepohlia rigidula</em>, <em>Trentepohlia</em> sp. 4, <em>Trentepohlia effusa</em>, <em>Trentepohlia monilia</em>, <em>Trentepohlia abietina</em>, <em>Trentepohlia</em> sp. 5, <em>Trentepohlia aurea</em>, and <em>Trentepohlia umbrina</em>. The largest number of species (seven to nine) were found at lower altitudes, from 473 to 517 m a.s.l. Species diversity was greatest in the winter season (13 species). Species found at low attitude were grouped together (Group 1) and had the greatest diversity, and the remaining species were divided into Groups 2, 3, and 4. Environmental factors had both positive and negative influences on the species, especially <em>T. chapmanii</em>, which was found below 1,003 m a.s.l., and <em>T. monilia</em>, which was found in areas with a high relative humidity of 74.50% to 83.93%. The ratio of the total carotenoids to chlorophyll of <em>T. rigidula</em>, the dominant species, was relatively high at 4.96:1, and the β-carotene content (46.89 %w/w) was highest during winter.

Polyploidy induction in Physalis alkekengi

Physalis alkekengi is an ornamental plant that can also be used as a medicinal plant due to its anti-inflammatory, bactericidal, antitumor and fungicidal properties. Polyploidization can be an important tool in the genetic improvement of this species. The objective this work was to obtain tetraploids in vitro and to evaluate the phytotechnical traits of P. alkekengi. For this, nodal segments of P. alkekengi var. Franchettii were inoculated into petri dishes containing 100 ml of MS medium supplemented with colchicine at concentrations 0; 0.04; 0.08; 0.12; and 0.16% and kept in the dark for 24 and 48h. After the respective treatment periods with colchicine the segments were inoculated into test tubes. The tetraploids were identified by flow cytometry and classical cytogenetics. In vitro seedlings were measured: root length, nodal segment length, leaflet number and total leaf area. In the acclimatization phase, the area of ​​the second leaf and total leaf, petiole radius, stem length, fruit weight with calyx, without calyx, fruit diameter, number of seeds and brix of the pulp were evaluated. Chlorophyll a, chlorophyll b, total chlorophyll, total carotenoid, total chlorophyll / total carotenoid ratio and chlorophyll a / b ratio were also estimated. The treatment that most produced tetraploid seedlings was with 0.08% colchicine per 24h. No significant difference was observed in 7 (seven) variables, these being all variables of photopigments, stem diameter (steam) and brix. In general, diploid (2x) plants were better in 9 (nine) while tetraploid seedlings were better in 6 (six) of the phytotechnical variables. It was concluded that the MS medium supplemented with 0.08% colchicine for 24 h allowed P. alkekengi tetraploides to be obtained with better phytotechnical qualities.

Physiological and Root Exudation Response of Maize Seedlings to TiO2 and SiO2 Nanoparticles Exposure

How the NPs effect the growth and physiological response like the release of organic acids along the root exudates is largely unknown yet. In this study, the effects of titanium dioxide (TiO2) and silicon dioxide (SiO2) nanoparticles (NPs) treatments (1000 mg/L) on maize seedlings for 6 days were examined. Plant biomass, pigment, malondialdehyde (MDA), reactive oxygen species (ROS) production, and contents of organic acids in root exudates were analyzed. SiO2 NPs significantly reduced (p 0.05) in chlorophyll a content compared to the CK, while chlorophyll b increased by 28.9% (p < 0.05), and chlorophyll a/b ratio and content of carotenoid decreased by 16.8% and 54.7% (p < 0.05), respectively. MDA content significantly diminished in roots and leaves under SiO2 NPs. However, O2·ˉ production increased in roots by 17.2% and 23.8% (p < 0.05), respectively, under TiO2 and SiO2 NPs treatment. The pH of root exudates was declined by 17.4% and 14.2% (p < 0.05) respectively under both NPs treatment. Organic acid contents under TiO2 NPs significantly heightened (p < 0.05) by 60.7%, 31.2%, and 50.5% for citric, lactic, and fumaric acid, respectively, while formic and oxalic acid decreased by 27.8% and 26.4% respectively compared to the CK. In SiO2 NPs case, oxalic acid increased by 41.1% (p < 0.05), while malic and citric acid decreased by 62.6% and 45.7% respectively compared to the CK. In conclusion, both NPs treatments showed alternative impacts on maize seedlings.

Physiological and Anatomical Differences and Differentially Expressed Genes Reveal Yellow Leaf Coloration in Shumard Oak.

Shumard oak (Quercus shumardii Buckley) is a traditional foliage plant, but little is known about its regulatory mechanism of yellow leaf coloration. Here, the yellow leaf variety of Q. shumardii named ‘Zhongshan Hongjincai’ (identified as ‘ZH’ throughout this work) and a green leaf variety named ‘Shumard oak No. 23’ (identified as ‘SO’ throughout this work) were compared. ‘ZH’ had lower chlorophyll content and higher carotenoid content; photosynthetic characteristics and chlorophyll fluorescence parameters were also lower. Moreover, the mesophyll cells of ‘ZH’ showed reduced number of chloroplasts and some structural damage. In addition, transcriptomic analysis identified 39,962 differentially expressed genes, and their expression levels were randomly verified. Expressions of chlorophyll biosynthesis-related glumly-tRNA reductase gene and Mg-chelatase gene were decreased, while pheophorbide a oxygenase gene associated with chlorophyll degradation was up-regulated in ‘ZH’. Simultaneously, carotenoid isomerase gene, z-carotene desaturase gene, violaxanthin de-epoxidase gene and zeaxanthin epoxidase gene involved in carotenoid biosynthesis were up-regulated in ‘ZH’. These gene expression changes were accompanied by decreased chlorophyll content and enhanced carotenoid accumulation in ‘ZH’. Consequently, changes in the ratio of carotenoids to chlorophyll could be driving the yellow leaf coloration in Q. shumardii.

A Non-Vector Approach to Increase Lipid Levels in the Microalga Planktochlorella nurekis.

Microalgae are freshwater and marine unicellular photosynthetic organisms that utilize sunlight to produce biomass. Due to fast microalgal growth rate and their unique biochemical profiles and potential applications in food and renewable energy industries, the interest in microalgal research is rapidly increasing. Biochemical and genetic engineering have been considered to improve microalgal biomass production but these manipulations also limited microalgal growth. The aim of the study was the biochemical characterization of recently identified microalgal strain Planktochlorella nurekis with elevated cell size and DNA levels compared to wild type strain that was achieved by a safe non-vector approach, namely co-treatment with colchicine and cytochalasin B (CC). A slight increase in growth rate was observed in twelve clones of CC-treated cells. For biochemical profiling, several parameters were considered, namely the content of proteins, amino acids, lipids, fatty acids, β-glucans, chlorophylls, carotenoids, B vitamins and ash. CC-treated cells were characterized by elevated levels of lipids compared to unmodified cells. Moreover, the ratio of carotenoids to chlorophyll a and total antioxidant capacity were slightly increased in CC-treated cells. We suggest that Planktochlorella nurekis with modified DNA levels and improved lipid content can be considered to be used as a dietary supplement and biofuel feedstock.

Sphagnum outcompetes feathermosses in their photosynthetic adaptation to postharvest black spruce forests

Mosses dominate the understory of black spruce forest, and changes in moss community composition and functional traits may influence many important ecosystem processes, particularly paludification due to accumulation of peat (mainly Sphagnum). To understand performance and fitness of ground-cover mosses in early forest succession following clearcutting, we investigated photosynthetic traits in Sphagnum and three feathermoss species (i.e., Hylocomium, Ptilium, and Pleurozium) coexisting in mature stands and decade-old black spruce harvest blocks. The results showed that all of these mosses have a significantly higher light saturation point at the harvested plots than the forested plots. Feathermosses at the harvested plots all underwent a reduction in quantum efficiency, chlorophyll b content, and chlorophylls:carotenoids ratio related to photoinhibition, particularly Pleurozium, which experienced a significant decrease in maximum net photosynthesis. In contrast, Sphagnum showed a significant increase in maximum gross photosynthesis, dark respiration, and the ratio of chlorophyll a:b at the harvested plots compared with the forested plots. The distinctive responses of moss photosynthetic traits indicate the potential proliferation of Sphagnum and decrease of feathermosses, and thus consequent peat accumulation. Our results emphasize the importance of the photosynthetic traits of moss as indicators of postharvest conditions for enhancing understory vegetation management to maintain and improve productivity of black spruce.

Effects of Temperature on Growth and Quality of Dormancy-released Sedum aizoon L.

The effects of recovery growth were compared by measuring the biomass and quality indices when dormancy-released Sedum aizoon L. were treated at 25°C, 20°C and 15°C respectively. The results showed that with the increasing temperature, the plant height and aboveground fresh weight all showed an upward first and then downward trend. The contents of chlorophyll, carotenoids, calcium and zinc all showed an upward trend, while magnesium and iron all showed a downward first and then upward trend in fresh food part. The contents of soluble protein, vitamin C, free amino acid and flavonoid all showed a downward trend, while total soluble sugar, caffeine and oleanolic acid all showed an upward first and then downward trend. The plant height, aboveground fresh weight, the total chlorophyll to carotenoid ratio, the contents of total soluble sugar, caffeine and oleanolic acid were all the highest under 20°. In conclusion, the best recovery growth temperature was 20° for dormancy-released Sedum aizoon L.

Dynamics of β-carotene and fucoxanthin of tropical marine Navicula sp. as a response to light stress conditions

We investigated the dynamics of β-carotene and fucoxanthin produced by the tropical marine Navicula sp. that were cultured indoors and outdoors. To obtain high biomass and carotenoid levels, the growth of Navicula sp. in three different nitrogen media (ammonium, urea, and nitrate medium) was evaluated. Navicula sp. showed the most growth in the nitrate medium with a ratio of total carotenoid to chlorophyll a of 1.94 observed on the 7th d. When Navicula sp. growth reached the stationary phase, the ratio of total carotenoid to chlorophyll a increased due to chlorophyll damage. The biomass productivity of Navicula sp. cultivated indoors and outdoors was 153 ± 3 and 93 ± 3 mg dried cell L−1 culture d−1, respectively. Under light stress conditions, the Navicula sp. cell size was reduced. Among Navicula sp. carotenoids, the amount of β-carotene and fucoxanthin expressed by the cell in response to light stress was very dynamic. The fucoxanthin content of Navicula sp. decreased from 5.40 ± 0.05 (indoor) to 2.61 ± 0.06 (outdoor) mg g−1 dried biomass. However, the β-carotene content of Navicula sp. increased from 19.99 ± 0.16 (indoor) to 24.08 ± 0.16 (outdoor) μg g−1 of dried biomass, which indicates the importance of β-carotene for the photoprotection of cells.

Photoacclimation State of an Arctic Underice Phytoplankton Bloom

AbstractRecent reports on Arctic underice phytoplankton blooms have directed attention to primary production below the sea ice cover. Such underice blooms cannot be detected from space; thus, methods for autonomous underice measurements are critically needed to extend observations beyond ship‐based surveys. One central aspect of the ecology of these blooms is whether they were advected from open‐water areas or were able to develop below the ice cover under typically low light conditions. The photoacclimation state of the bloom can provide clues about the growth conditions and therefore its origin. Here we investigate the photoacclimation state of a Phaeocystis pouchetii‐dominated underice bloom in the Arctic Ocean using ratios of photoprotective carotenoids (PPC) to photosynthetic carotenoids (PSC) and chlorophyll a. The pigment proxies indicate local growth under the ice pack. Furthermore, a method using in situ light absorption measurements to estimate the PPC:PSC ratio was in agreement with the pigment data. The slope of in situ phytoplankton absorption between 488 and 532 nm, affected by both PPC and PSC, had a significant linear relationship to the PPC:PSC ratio, indicating that prediction of photoacclimation state can be obtained from absorption profiles. We also review, with regard to the pigment function, different ways of grouping pigments into PPC or PSC applied in previous studies. Although more validation data sets are needed to assess the impact of pigment packaging on the relationship between PPC:PSC and absorption measurement slopes, our study shows the potential for using in situ absorption measurements to collect information about phytoplankton physiology below sea ice.

Specific Features of the Ultrastructure and Biochemical Composition of Triticum spelta L. Leaf Mesophile Cells in the Initial Period of Stress Temperature Action

Under controlled conditions, the effect of high (40°C, 2 h) and positive low (4°C, 2 h) temperatures on the ultrastructure of mesophyll cells of the leaf and the content of photosynthetic pigments, phenols, and flavonoids in 2-week-old Triticum spelta plants was studied. The ultrastructure of the mesophyll cells of the leaf of the control plants was typical: a developed thylakoid system was clearly seen that was immersed in a fine-grained stroma in the chloroplasts of regular lenticular shape. Short-term hyperthermia caused a partial destruction of thylakoid membranes. Wave-shaped packing of grana thylakoids, significant expansion of lumen intervals, disturbance of the structural bond between the grana thylacoids and stroma thylakoids was noted. With hyperthermia, the mitochondria noticeably “swelled,” while the cristae membranes became less contrasting. The number of lipid droplets increased in the cytoplasm of cells. In the leaves, the content of chlorophylls and carotenoids decreased, however, the number of common phenols and flavonoids increased. Short-term hypothermia caused intense formation of plastoglobules, and an increase in the number and size of starch grains. Destruction of thylakoid membranes was not observed. Some of the mitochondria were rounded (40%), with their size being close to the control values, and some organelles were lenticular, “dumbbell,” and “cup-shaped.” Under hyper- and hypothermia, the T. spelta leaf mesophyll cells showed a tendency to increase the degree of chromatin condensation in the nucleus. Under hypothermia, the content and ratio of chlorophylls and carotenoids in leaves did not differ much from the control plants, and no significant quantitative changes in the total phenols and flavonoids were recorded.

A novel combined spectral index for estimating the ratio of carotenoid to chlorophyll content to monitor crop physiological and phenological status

Accurate estimation of the ratio of carotenoid (Car) to chlorophyll (Chl) content is crucial to provide valuable insight into diagnoses of plant physiological and phenological status in crop fields. Studies for assessing the ratio of Car to Chl content have been extensively conducted with semi-empirical approaches using spectral indices. However, spectral indices established in previous studies generally relied on site- or species-specific measured data and these indices typically lacked sufficient estimation accuracy for the ratio of Car to Chl content to be used across various species and under different physiological conditions. In this study, we propose a novel combined carotenoid/chlorophyll ratio index (CCRI) in the form of the carotenoid index (CARI) divided by the red-edge chlorophyll index (CIred-edge): The value of the index is illustrated using synthetic data simulated from the leaf radiative transfer model PROSPECT-5 and with extensive measured datasets at both the leaf and canopy level from the ANGERS dataset and winter wheat and maize field experiments. Results show that CCRI was the index with the highest correlation with the ratio of Car to Chl content in PROSPECT-5 simulations (R2 = 0.99, RRMSE = 8.65%) compared to other spectral indices. Calibration and validation results using the ANGERS and winter wheat leaf level data showed that CCRI achieved accurate estimation of the ratio of Car to Chl content (R2 = 0.52, RRMSE = 14.10%). CCRI also showed a good performance (R2 = 0.54, RRMSE = 17.08%) for estimation of the ratio of Car to Chl content in both calibration and validation with the winter wheat and maize canopy spectra measured in field experiments. Further investigation of the effect of the correlation between leaf Chl and Car content on the performance of CCRI indicated that variation of the correlation affected the retrieval accuracy of CCRI, and CCRI might not be very sensitive to changes of the ratio of Car to Chl content with low values (<0.10).

Leaf Spectral Reflectance of Maize Seedlings and Its Relationship to Cold Tolerance

Increasing early‐season cold tolerance of maize (Zea mays L.) has the potential to lengthen its growing season, reduce its environmental impact, and enhance its yields. Cold‐ and warm‐grown plants differ for biomass accumulation and spectral reflectance, the latter caused by differences in leaf chlorophyll content, carotenoid content, or other chemical and morphological attributes. Here, we evaluate genetic leaf spectral reflectance diversity across 38 inbred and 14 hybrid maize genotypes grown in cold and control temperatures. Genotypes varied for spectral reflectance indices correlated with chlorophyll content and for an index correlated with the ratio of leaf carotenoids to chlorophylls. Genotypic differences greatly contributed to spectral reflectance variation across all visible wavelengths, with the greatest genetic variation between 500 and 600 nm and around 700 nm. Cold treatment effects were most significant across the same wavelengths. Spectral indices indicated lower chlorophyll and a higher carotenoid/chlorophyll level in cold‐exposed plants relative to control plants. Genotype × temperature interactions were small relative to genotype effects. Cold tolerance, measured as the ratio of dry matter accumulation in cold‐treated plants relative to control plants, varied among hybrids and inbreds. Correlations of cold tolerance with known spectral reflectance indices, reflectance first derivatives, and novel, normalized spectral indices were mostly low and occurred only in certain germplasm. One reflectance parameter, the reflectance curve slope at 828 nm, was consistently related to genotypic cold tolerance, even when measured on plants that had not been exposed to cold.