Decrease In Chlorophyll Content Research Articles

Morphological and biochemical characterization of peel of different coloured mango cultivars

Some morphological and biochemical parameters were studied to characterize only mango fruit peel. Morphological evaluation of ripe fruits using mango descriptors revealed considerable variation amongst mango cultivars. Parameters ‘L’, ‘b’, ‘C’ and ‘h’ showed strong correlation with carotenoids in peel of different coloured cultivars. Also, Biochemical analysis showed a wide variation amongst different coloured mango cultivars with their changing pattern during ripening. The higher content of total chlorophyll, total carotenoids and anthocyanins were noticed in peel of green, yellow and red coloured cultivars respectively. The presence of small quantities of lycopene was also noticed in peel of these cultivars. Mango peel was found to be associated with a decrease in chlorophyll content and increase in the total carotenoids and total anthocyanin contents during ripening of fruit. This study reports some morphological and biochemical parameters of mango peel helpful in breeding (selection of parents) and processing (peel utilization) of fruits.

Effect of exogenous catechin and salicylic acid on rice productivity under ozone stress: the role of chlorophyll contents, lipid peroxidation, and antioxidant enzymes.

Increasing ozone concentration is one of the oxidative stresses that affects rice yield loss in many countries. Catechin and salicylic acid were proposed as tools for alleviating oxidative stress in plants, but their roles in protecting rice productivity under ozone stress still remained unknown. We investigated the mechanism of catechin and salicylic acid on rice under ozone stress at the vegetative stage and at the reproductive stage. Rice was sprayed with catechin and salicylic acid before exposure to ozone in the range of 100-150ppb (8hday-1). Ozone and salicylic acid led to a decrease in chlorophyll contents, magnesium contents, and stomatal conductance. This evidence led to a decrease in rice productivity and quality. In contrast, under rice + catechin, both ambient air and elevated ozone conditions had to higher rice productivity and quality than under rice alone and rice + salicylic acid conditions. Catechin could mitigate ozone stress in rice plants through maintaining chlorophyll contents, magnesium contents, and stomatal conductance. Moreover, catechin could induce an unregulation ofascorbate peroxidase, and catalase genes led to increasing their antioxidant enzyme activity. Increasing of antioxidant enzyme activity under rice + ozone + catechin conditions attributed to lower lipid peroxidation than under rice + ozone especially at vegetative stage. This study confirmed that catechin, which is naturally found in tea leaves, could be used as an ozone protectant. The protective role of catechin on chlorophyll contents and antioxidant systems at the vegetative stage attributed to maintaining rice yield under ozone stress. Graphical abstract.

Leaf structure and chlorophyll content in Torreya grandis 'Merrillii' with Nalepella abiesis infestation

Objective The aim is to provide a theoretical basis for the prevention and control of Nalepella abiesis and to study the damage mechanism and chlorophyll content from N. abiesis on leaves of Torreya grandis 'Merrillii'. Method Dynamic changes in leaf tissue structure, stomatal structure, chloroplast ultrastructure, and chlorophyll content were studied using the fluorescence microscope, transmission electron microscope (TEM), scanning electron microscope (SEM), and spectrophotometer. Result The palisade cells changed in shape and decreased in number for an increase in days after inoculation (DAI) with mites. By the 40th day, thickness of the palisade tissue decreased considerably; spongy cells shrank; spongy tissue became looser; around stomata the cuticular peg was destroyed; guard cells shrank; and stomata shrank revealing obvious injury. Mesophyll cells gradually swelled and became deformed with the gap between cells becoming larger and larger. Also, the number of chloroplasts gradually decreased with the appearance of starch grains. By the 12th day, the number of osmiophilic granules within the chloroplast had increased with grana lamellae becoming more and more irregular in structure, especially on the 25th day, and finally disintegrating and disappearing on the 40th day. There was no significant difference in chlorophyll content between ck and the treatment with mite infection from 0 to 12 d, but a significant difference occurred from 25 to 40 d(P Conclusion N. abiesis infestation could destroy the structure of the mesophyll cells and leaf stomata of T. grandis 'Merrillii' leading to a decreased chlorophyll content that could affect photosynthesis.

Studies on the Impact of Automobile Exhaust Emissions (From Vehicles using Diesel and Petrol) on Chlorophyll Content and Leaf Biomass of Lemon

Air quality is getting poor day by day due to air pollution. Automobile exhaust pipe emission has been a major contributor to the problem of air pollution in the present scenario. This study was aimed for observing the effects of exhaust pipe emissions on chlorophyll, which is the most important plant pigment. Lemon plants were given exposure to exhaust emissions from vehicles using fuel types in open top chambers for the set duration of time. Determination of total chlorophyll, chlorophyll a and chlorophyll b and leaf biomass of all exposed population of lemon was done. Decrease in chlorophyll content was observed in all exposed plants with maximum reduction noticed in those exposed to exhaust from diesel using vehicle. Leaf biomass was also reduced in exposed population. Exposure to harmful exhaust emissions causes changes in normal physiology of plant and alters its responses. Keywords : Air pollution, automobile exhaust, chlorophyll content, lemon Cite this Article S Kaur. Studies on the impact of automobile exhaust emissions (from vehicles using diesel and petrol) on chlorophyll content and leaf biomass of lemon. Research & Reviews: A Journal of Life Sciences . 2020; 10(1): 1–4.

Yield, Essential Oil and Quality Performances of Artemisia dracunculus, Hyssopus officinalis and Lavandula angustifolia as Affected by Arbuscular Mycorrhizal Fungi under Organic Management.

Utilization of arbuscular mycorrhizal fungi (AMF) for enhancing growth and development as well as production of essential oil in aromatic plants has been increasingly drawing research interest. In order to assess the AMF effects on different aromatic species, an open-field experiment was carried out using Artemisia dracunculus (tarragon), Lavandula angustifolia (lavender) and Hyssopus officinalis (hyssop). AMF stimulated the growth of tarragon and lavender plants, whereas hyssop showed a slight developmental slowing; nonetheless, a significant increase in essential oil content in the three species was seen. AMF application increased the biomass of A. dracunculus and H. officinalis by 20–35%. No differences in antioxidant activity and phenolics content were recorded at harvest between the control and AMF-inoculated plants, but the latter showed a significant increase in antioxidant status upon storage at high temperature and humidity compared to the untreated control. The enhancement of abiotic stress resistance during storage in plants inoculated with AMF was the highest in A. dracunculus, and the lowest in H. officinalis, while the untreated control plants showed a significant decrease in phenolics, ascorbic acid and chlorophyll content, as well as antioxidant activity, upon the abiotic stress. AMF inoculation differentially affected the mineral composition, increasing the accumulation of Se, I and Zn in A. dracunculus, and decreasing the levels of heavy metals and Co, Fe, Li, Mn in H. officinalis. Based on the outcome of the present research, AMF inoculation resulted in a significant enhancement of the overall performances of A. dracunculus, L. angustifolia and H. officinalis, and also in the improvement of plant antioxidant status upon storage in stress conditions.

Photosynthetic acclimation of rhododendrons to light intensity in relation to leaf water-related traits

Leaves under high light may suffer from risks caused by excessive light energy and dehydration. However, it remains unclear how leaf water-related traits affect the photosynthetic acclimation of plants to light intensity. We investigated the photosynthesis and leaf water-related traits of two hybrids (Rhododendron ‘XXL’ and ‘Furnivall’s daughter’) and one native species (Rhododendron delavayi) under different growth irradiances to determine the importance of leaf water-related traits on the photosynthetic acclimation of rhododendrons to irradiance. Compared to plants under low light, the values for light saturation point (LSP), stomatal density (SD), leaf dry mass per unit area, and vein density (Dv) in the three rhododendrons were higher under high light, but the values for chlorophyll content and leaf size were lower. There were significant differences in light-saturated photosynthetic rate (Pmax), stomatal conductance (gs), transpiration rate (Tr), and non-photochemical quenching (NPQ) in R. delavayi and Rhododendron ‘XXL’ between plants grown under high and low irradiance levels, but not in ‘Furnivall’s daughter’. The positive correlations of Dv and SD with Pmax, Tr, and LSP indicate that the increase in water transport capacity can improve water supply to meet transpirational demand and regulate photosynthetic performance under high irradiance. Meanwhile, the decrease in chlorophyll content and the increase in NPQ prevent the photodamage of photosystem II by decreasing light absorption and enhancing heat dissipation, respectively, when the plants are exposed to high light. These results suggest that adjusting leaf water-related traits and reducing the damage on photosystem II caused by excess light play important roles in the photosynthetic acclimation of rhododendrons to growth irradiance.

The Role of Gibberellins in Regulation of Nitrogen Uptake and Physiological Traits in Maize Responding to Nitrogen Availability.

Modified gibberellin (GA) signaling leads to semi-dwarfism with low nitrogen (N) use efficiency (NUE) in crops. An understanding of GA-mediated N uptake is essential for the development of crops with improved NUE. The function of GA in modulating N uptake capacity and nitrate (NO3−) transporters (NRTs) was analyzed in the GA synthesis-deficient mutant zmga3ox grown under low (LN) and sufficient (SN) N conditions. LN significantly suppressed the production of GA1, GA3, and GA4, and the zmga3ox plants showed more sensitivity in shoots as well as LN stress. Moreover, the higher anthocyanin accumulation and the decrease of chlorophyll content were also recorded. The net NO3− fluxes and 15N content were decreased in zmga3ox plants under both LN and SN conditions. Exogenous GA3 could restore the NO3− uptake in zmga3ox plants, but uniconazole repressed NO3− uptake. Moreover, the transcript levels of ZmNRT2.1/2.2 were downregulated in zmga3ox plants, while the GA3 application enhanced the expression level. Furthermore, the RNA-seq analyses identified several transcription factors that are involved in the GA-mediated transcriptional operation of NRTs related genes. These findings revealed that GAs influenced N uptake involved in the transcriptional regulation of NRTs and physiological responses in maize responding to nitrogen supply.

Tolerance responses in wheat landrace Bolani are related to enhanced metabolic adjustments under drought stress

Physio-biochemical adaptations of wheat landraces may have great importance in their growth, survival and yield under drought stress. Here, we evaluated the effects of drought stress on some defense systems of wheat cultivar “Sistan” (drought-sensitive) and landrace “Bolani” (drought-tolerant). Under drought stress, Bolani plants showed lower increases in hydrogen peroxide content compared to Sistan ones, which was accompanied with significant decrease in malondialdehyde and electrolyte leakage indices. Increasing the transcript levels and activity of enzymatic and non-enzymatic antioxidants along with phenylpropanoid metabolites improved relative tolerance to drought-induced oxidative stress, particularly in Bolani plants, results which may be confirmed by a significant decrease in the damage indices. In the phenylpropanoid pathway, the biosynthetic pathway of total phenol, flavonoids and anthocyanins was more active than lignin-biosynthetic pathway, which could early respond to drought stress. These results may be confirmed by their negative significant correlations with damage indices as well as a non-significant correlation of lignin with most enzymatic and non-enzymatic antioxidants in plants. Lower decrease of chlorophyll (Chl) and carotenoid contents in Bolani plants compared to Sistan ones indicated the relative stability of photosynthetic pigments under drought stress. Our results suggested that integrating metabolic pathways could coordinately alleviate oxidative stress that can lead to introducing suitable genetic sources for drought tolerance.

Pigment variation and transcriptional response of the pigment synthesis pathway in the S2309 triple-color ornamental kale (Brassica oleracea L. var. acephala) line

Ornamental kale is popular because of its colorful leaves and few studies have investigated the mechanism of color changes. In this study, an ornamental kale line (S2309) with three leaf colors was developed. Analysis of the anthocyanin, chlorophyll, and carotenoid contents and RNA-seq were performed on the three leaf color types. There was less chlorophyll in the white leaves and purple leaves than in the green leaves, and the anthocyanin content was greatest in the purple leaves. All the downregulated DEGs related to chlorophyll metabolism were detected only in the S2309_G vs. S2309_W comparison, which indicated that the decrease in chlorophyll content was caused mainly by the inhibition of chlorophyll biosynthesis during the leaf color change from green to white. Moreover, the expression of 19 DEGs involved in the anthocyanin biosynthesis pathway was upregulated. These results provide new insight into the mechanisms underlying the three-color formation.

Ecological state assessment of recreational areas in Nizhny Novgorod on heavy metal soil pollution and bioindication indicators of <i>Betula pendula</i> Roth leaves

In this paper the ecological state of recreational areas in Nizhny Novgorod was assessed by the level of soil contamination with heavy metals (HM) and the values of bioindication indicators of the birch (Betula pendula Roth). The objects of the study were 4 recreational areas. The forest park Shelokovsky Farm located far from pollution sources was chosen as a control site. The excess of normative indicators (in multiplicities of normative indicators) on gross content of HM was observed in soils only for nickel: in the park Switzerland in 1,3 times, in Raspberry Ridge - in 2,3 times. The soils with the pollution category moderately dangerous were the most polluted by HM according to the total indicator of pollution: in the protected area Crimson Ridge and in the park Oaks. Bioindication indicators of a birch leaf deviated from the conventional norm in a number of studied areas. The quality of the environment, estimated by fluctuating asymmetry of birch leaves in Shelokovsky Farm and the park Oaks, correspond to 2 points (a slight deviation from the norm), in the Park Switzerland - to 3 points (the average deviation from the norm), and in Crimson Ridge - to 4 points (a significant deviation from the norm). In the two most contaminated sites (Oaks and Crimson Ridge), a decrease of chlorophyll content in birch leaves relative to the control (Shelokovsky Farm) was observed.

Effect of Greenhouse CO2 Supplementation on Yield and Mineral Element Concentrations of Leafy Greens Grown Using Nutrient Film Technique

Carbon dioxide (CO2) concentration is reported to be the most important climate variable in greenhouse production with its effect on plant photosynthetic assimilation. A greenhouse study was conducted using a nutrient film technique (NFT) system to quantify the effect of two different levels of CO2 (supplemented at an average of 800 ppm and ambient at ~410 ppm) on growth and nutritional quality of basil (Ocimum basilicum L.) ‘Cardinal’, lettuce (Lactuca sativa L.) ‘Auvona’, and Swiss chard (Beta vulgaris L.) ‘Magenta Sunset’ cultivars. Two identical greenhouses were used: one with CO2 supplementation and the other serving as the control with an ambient CO2 concentration. The results indicate that supplemented CO2 could significantly increase the height and width of hydroponically grown leafy greens. Supplemented CO2 increased the fresh weight of basil ‘Cardinal’, lettuce ‘Auvona’, and Swiss chard ‘Magenta Sunset’ by 29%, 24.7%, and 39.5%, respectively, and dry weight by 34.4%, 21.4%, and 40.1%, respectively. These results correspond to a significant reduction in Soil Plant Analysis Development (SPAD) and atLEAF values, which represent a decrease in leaf chlorophyll content under supplemented CO2 conditions. Chlorophyll, nitrogen (N), phosphorus (P), and magnesium (Mg) concentrations were generally lower in plants grown in supplemented CO2 conditions, but the results were not consistent for each species. Supplemented CO2 reduced tissue N concentration for basil ‘Cardinal’ and lettuce ‘Auvona’ but not Swiss chard, while Mg concentration was reduced in supplemented CO2 for Swiss chard ‘Magenta Sunset’ only. In contrast, Fe concentration was increased under supplemented CO2 for basil ‘Cardinal’ only. These findings suggest CO2 supplementation could increase yield of leafy greens grown with hydroponics and have varying impact on different mineral concentrations among species.

SALICYLIC ACID INDUCES PHYSIOLOGICAL AND BIOCHEMICAL CHANGES IN PEONY UNDER WATERLOGGING STRESS

In this study, the effects of salicylic acid to antioxidative activity and photosynthetic characteristics in waterlogging stress of two peony cultivars (‘Fengdanbai’ and ‘Mingxing’) were investigated. 4-year-old peony grown in different levels of waterlogging stress and then different concentration prepared SA (0.0, 0.1, 0.5 and 1.0 mmol L–1) sprayed on fresh leaves of peony. The antioxidative enzymes activities include superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT), chlorophyll content, relative conductivity and MDA content were measured in leaves about different waterlogging treatment, the photosynthetic characteristics were also measured using photosynthetic measurement system. The results showed that waterlogging stress decreased the chlorophyll content in all peony cultivars leaves, but with SA treatment can inhibit the decrease of chlorophyll content. Relative conductivity increased as the extension of waterlogging time in two cultivars. SA treatment could effectively inhibit the increase of relative conductivity, and 0.5 mmol L–1 of SA was the most suitable concentration. SOD, POD, CAT activity increased first and then decreased in different waterlogging condition, SA significantly increased the activity of various enzymes. MDA content was increase as the expansion of waterlogging time in two cultivars. SA inhibits the increase of MDA content. Of all concentration of SA, 0.5 mmol L–1 was the best concentration to inhibit the waterlogging stress. For the photosynthetic characteristics, the net assimilation rate (Pn), stomatal conductance (Gs), transpiration rate (Tr) and intercellular CO2 (Ci) were decreased under different waterlogging condition. SA treatment can increase Pn, Gs, Tr and Ci of peony.

Assessment of ZnO-NPs toxicity in maize: An integrative microRNAomic approach

Rapid expansion of nanotechnology and indiscriminate discharge of metal oxide nanoparticles (NPs) into the environment pose a serious hazard to the ecological receptors including plants. To better understand the role of miRNAs in ZnO-NPs stress adaptation, two small RNA libraries were prepared from control and ZnO-NPs (800 ppm, <50 nm particle size) stressed maize leaves. Meager performance of ZnO-NPs treated seedlings was associated with elevated tissue zinc accumulation, enhanced ROS generation, loss of root cell viability, increased foliar MDA content, decrease in chlorophyll and carotenoids contents. Deep sequencing identified 3 (2 known and 1 novel) up- and 77 (73 known and 4 novel) down-regulated miRNAs from ZnO-NPs challenged leaves. GO analysis reveals that potential targets of ZnO-NPs responsive miRNAs regulate diverse biological processes viz. plant growth and development (miR159f-3p, zma_18), ROS homeostasis (miR156b, miR166l), heavy metal transport and detoxification (miR444a, miR167c-3p), photosynthesis (miR171b) etc. Up-regulation of SCARECROW 6 in ZnO-NPs treated leaves might be responsible for suppression of chlorophyll biosynthesis leading to yellowing of leaves. miR156b.1 mediated up-regulation of CALLOSE SYNTHASE also does not give much protection against ZnO-NPs treatment. Taken together, the findings shed light on the miRNA-guided stress regulatory networks involved in plant adaptive responses to ZnO-NPs stress.

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.

Role of glutathione reductase and catalase enzyme in antioxidant defense mechanism in controlling fluoride-induced oxidative stress

Antioxidant enzymes play a protective role in plant with oxidative stress. . Fluoride negatively affects plants by increasing the level of ROS species and by negatively regulating the growth of plants. Fluoride stress this is one of the most important abiotic stresses. In this studio; Vigna radiata L was exposed to fluoride stress in a half-diluted Hoagland solution. In this study, a concentration-dependent analysis (0, 2.5 and 5, 7.5, 10, 12.5 and 15 mM NaF) of antioxidant enzyme activity performed against the most significant inhibition of growth levels and content of MDA, the decrease in chlorophyll content, was reported in seedlings treated with NaF compared to controls. Antioxidant expression (CAT, GR) showed the highest activity at 7.5 mM NaF and showed a significant defense against fluoride stress during the harvest. This study would help to understand the role of antioxidants in the survival of plants against fluoride stress

Chlorophyll Content in Two Medicinal Plant Species Following Nano-TiO2 Exposure.

Chlorophyll content in leaves is a convenient indicator of the physiological state of the plant following exposure to a stressor. In the present study, a pot experiment was carried out using two medicinal plant species - peppermint (Mentha X piperita L.) and common sage (Salvia officinalis L.) to determine the link between the chlorophyll content in the plant leaves and the exposure of the plants to nano-TiO2 either through the leaves (in suspension) or through the root system (in soil). Following the exposure, the shoots were analysed for the contents of Ti, Al, Ca, K, Mg, Mn, Na and chlorophyll. Significant decrease in chlorophyll content was observed in all but one of the nano-TiO2 treatments, the differences in the determined element content were mostly species-dependent: Ti exposure was found to be related to the decrease in the chlorophyll and Mn content in both species as well as to the decrease in Mg content in common sage.

Proteasome inhibition rapidly exacerbates photoinhibition and impedes recovery during high light stress in Chlamydomonas reinhardtii

BackgroundProteasomes remove regulatory proteins in eukaryotic cells, and control a variety of plant processes. Proteasomes are localized to the cytosol and nuclear, but their role in plant biology has recently been extended to chloroplasts, where it regulates TOC complex. This is turn controls the import of nuclear-encoded chloroplastic proteins, which remodels the chloroplast proteome and facilitates proper developmental transitions. Proteasomal regulation of the TOC complex also alleviates stressors that generate reactive oxygen species. These recent advances motivated us to determine if proteasome inhibition rapidly alters photosynthetic processes stemming from photoinhibition induced by high light.ResultsThe short-term effects of proteasome inhibition on photosystem II during light stress was measured in Chlamydomonas reinhardtii, which allowed the dual monitoring of both chlorophyll fluorescence and cell viability. After 48 h at low light, proteasome inhibition did not affect viability or photochemistiry, but decreased cell concentration and increased cell volume. Two hours of high light stress impaired the efficiency of photosystem II in proteasome-inhibited cells, as determined by a decrease in Fv/Fm and the electron transport rate. Elevated photoinhibition in proteasome inhibited cells was not caused by a decrease in cell viability or chlorophyll content. Recovery from photoinhibition was attenuated in MG132-treated cells, and suppressed growth of a reestablished culture. Proteasome inhibition decreased de novo protein synthesis, which possibly constrained the ability to remodel the plastid proteome, and thus hampering the ability to adjust to high light stress.ConclusionThe proteasome is implicated in protecting photosystem II from photoinhibition. In addition to high light stress, other stressors- including metals, drought, and salt- are also known to generate reactive oxygen species localized to the chloroplast. Therefore, proteasome maintenance in plants may help protect photosynthesis during abiotic stress, which could increase crop yield during adverse conditions.

Influence of Weeds on Yacon Initial Growth and Development

ABSTRACT: The consumption of yacon has been increasing around the world due to the nutritional and pharmaceutical properties of this plant. The growing commercial interest in yacon (Smallanthus sonchifolius) generates a demand for crop management research studies, including the effect of weed competition on yacon, which was not yet studied. Thus, this study was performed with the objective of evaluating the effects of weed competition on yacon development and growth. The experimental design was completely randomized with four treatments and seven replicates. Treatments were yacon with the interference of four weed species: Cyperus rotundus L. (nutgrass), Commelina benghalensis L. (tropical spiderwort), Amaranthus viridis L. (slender amaranth) and Bidens pilosa L. (hairy beggarticks). The experiment was conducted in a greenhouse, using 10 dm3 pots. Plant height, number of leaves, number of stems, leaf area, fresh and dry mass weight (total and partial), and chlorophyll A, B and total were evaluated. The weed competition resulted in a decrease in the yacon development (height, number of leaves, number of stems, leaf area), photosynthetic rate (decreased chlorophyll content A, B and total) and yield, as also decreased the accumulation of fresh and dry biomass of tuberous roots. C. benghalensis L. and A. viridis L. were the weeds most affecting the development and growth of yacon.

Is leaf age a predictor for cold tolerance in winter oilseed rape plants?

In the present study, low temperature-dependent physiological changes were investigated through photosynthetic activity and some endogenous mechanisms in two winter oilseed rape cultivars (Brassica napus L. ssp. oleifera cvv. Eurol and Hansen) on the basis of leaf age. Chlorophyll fluorescence measurements demonstrated that low temperature caused decreased photosynthetic activity in both cultivars. However, photosynthetic apparatus in the young leaves of Hansen is more tolerant to low temperature as demonstrated by lower F0 (minimum fluorescence yield) and 1-qp (excitation pressure of photosystem II), higher Fm (maximum fluorescence yield), Fv/Fm and non-photochemical quenching (NPQ) compared with Eurol. In addition, young leaves of Hansen represented marked increase in some antioxidant enzyme activities (superoxide dismutase (SOD), ascorbate peroxidase (APX) and glutathione reductase (GR)) during cold exposure. In the young leaves of Eurol, however, APX and GR activity was decreased by low temperature, indicating lower efficiency of ascorbate-glutathione cycle. Lower antioxidant activity in the young leaves of Eurol may be responsible for increased malondialdehyde (MDA), H2O2 and membrane damage and decreased chlorophyll content as a result of oxidative damage during cold exposure. In the cold-stressed mature leaves, both cultivars represented similar antioxidant capacities and photosynthetic efficiency. As a consequence, coordinated increase in SOD, APX and GR activities, increased capacity to keep quinone A (QA) in an oxidised state (as indicated by lower 1-qp) and accumulation of soluble sugar and proline could be mainly attributed to higher level of tolerance of the young leaves of Hansen to low temperature when compared with Eurol.

Directed cultivation of Chlorella sorokiniana for the increase in carotenoids’ synthesis

The metabolism of Chlorella sorokiniana is subjected to changes caused by various cultivation conditions. If dosed ultraviolet radiation is used, there is a possibility of a compensatory increase in the synthesis of carotenoids which prevent oxidative stress. Strain 211-8k was cultured under various lighting conditions: control sample was subjected to fluorescent light; sample 1 was subjected to dosed periodic ultraviolet irradiation for 15 minutes every day and fluorescent lighting; sample 2 was subjected to ultraviolet irradiation for 30 minutes in the stabilization phase. Periodic UV exposure negatively affects the population growth of C. sorokiniana which was possible to detect only on the ninth day and the biomass yield significantly decreased. A single UV exposure for 30 minutes lead to a slight decrease in the yield of air-dry biomass which with a further population growth may be compensated. Periodic exposure to UV radiation stimulates carotenoids synthesis, the yield in terms of dry biomass exceeded the control sample on average by 30%. A single ultraviolet irradiation for 30 minutes in the stabilization phase lead to a decrease in the biomass content of both chlorophyll and carotenoids. Microscopy of microalgae showed that ultraviolet radiation leads to the formation of cells with signs of apoptosis.