Photosynthesis Performance Index Research Articles

Sugarcane bagasse acts as a metal absorber in the rhizosphere in mitigating arsenic toxicity in wheat

Arsenic (As) is a hazardous element causing environmental pollution and yield loss in wheat. Sugarcane bagasse (SCB) is known to have metal detoxification efficiency in wastewater. However, the role of SCB in As elimination in plants was never investigated. This work examines the role, if any, of sugarcane bagasse (SCB) to alleviate As toxicity in wheat. The addition of SCB under As (V) stress showed significant improvement in shoot biomass, chlorophyll synthesis, membrane stability, total protein, and sugar concentration judged against As-stressed plants, suggesting that SCB is effective in As detoxification. Interestingly, the As-induced damage in the quantum efficiency of PSII (Fv/Fm) and photosynthesis performance index (Pi_ABS) significantly improved due to SCB treatment on As-stressed wheat. This further suggests that the antagonism of essential elements with As might be linked to the nutrient balance responsible for morpho-physiological improvement. Analysis of As in plant tissues and nutrient medium reveals that the adsorption efficiency of SCB is inversely proportioned to As translocation rate resulting in a significant decline of As in roots and shoot. It supports the physiological findings and suggests that the adsorption capacity of SCB leads to less available As in the nutrient medium for the wheat plants under As supplementation. Alongside this, H2O2 and lipid peroxidation significantly decreased subjected to SCB treatment under As. It is correlated with the increased antioxidant (CAT and SOD) activities of SCB in response to As toxicity. This study explores the novel and eco-friendly strategy through the potential application of SCB for the detoxification of crops and soil.

Growth and physiological impairments in Fe-starved alfalfa are associated with the downregulation of Fe and S transporters along with redox imbalance

BackgroundIron (Fe) is an essential plant nutrient. Its deficiency is a major constraint in crop production systems, affecting crop yield and quality. It is therefore important to elucidate the responses and adaptive mechanisms underlying Fe-deficiency symptoms in alfalfa.Materials and methodsThe experiment was carried out on 12-day-old alfalfa plants grown in hydroponics under Fe-sufficient and Fe-deficient conditions.ResultsThe Fe-starved alfalfa showed decreased plant biomass, chlorophyll score, PSII efficiency, and photosynthesis performance index in young leaves under low Fe. Further, Fe shortage reduced the Fe, Zn, S and Ca concentration in root and shoot of alfalfa accompanied by the marked decrease of MsIRT1, MsZIP, MsSULTR1;1, MsSULTR1;2 and MsSULTR1;3 transcripts in root and shoot. It indicates that retardation caused by Fe-deficiency was also associated with the status of other elements, especially the reduced Fe and S may be coordinately attributed to the photosynthetic damages in Fe-deficient alfalfa. The ferric chelate reductase activity accompanied by the expression of MsFRO1 in roots showed no substantial changes, indicating the possible involvement of this Strategy I response in Fe-deficient alfalfa. However, the proton extrusion and expression of MsHAI1 were significantly induced following Fe-deficiency. In silico analysis further suggested their subcellular localization in the plasma membrane. Also, the interactome map suggested the partnership of MsFRO1 with plasma membrane H+-ATPase, transcription factor bHLH47, and nitrate reductase genes, while MsHAI1 partners include ferric reductase-like transmembrane component, plasma membrane ATPase, vacuolar-type H-pyrophosphatase, and general regulatory factor 2. In this study, SOD and APX enzymes showed a substantial increase in roots but unable to restore the oxidative damages in Fe-starved alfalfa.ConclusionThese findings promote further studies for the improvement of Fe-starved alfalfa or legumes through breeding or transgenic approaches.Graphic

Early-stage iron deficiency alters physiological processes and iron transporter expression, along with photosynthetic and oxidative damage to sorghum.

Iron (Fe) starvation in Strategy II plants is a major nutritional problem causing severe visual symptoms and yield reductions. This prompted us to investigate the physiological and molecular consequences of Fe deficiency responses at an early stage in sorghum plants. The Fe-starved sorghum did not show shoot biomass reduction, but the root length, biomass, and chlorophyll synthesis were severely affected. The chlorophyll a fluorescence analysis showed that the quantum yield efficiency of PSII (Fv/Fm) and photosynthesis performance index (Pi_ABS) in young leaves significantly reduced in response to low Fe. Besides, Fe concentration in root and shoot significantly declined in Fe-starved plants relative to Fe-sufficient plants. Accordingly, this Fe reduction in tissues was accompanied by a marked decrease in PS-release in roots. The qPCR experiment showed the downregulation of SbDMAS2 (deoxymugineic acid synthase 2), SbNAS3 (nicotianamine synthase 3), and SbYSL1 (Fe-phytosiderophore transporter yellow stripe 1) in Fe-deprived roots, suggesting that decreased rhizosphere mobilization of Fe(III)-PS contributes to reduced uptake and long-distance transport of Fe. The cis-acting elements of these gene promoters are commonly responsive to abscisic acid and methyl jasmonate, while SbYSL1 additionally responsive to salicylic acid. Further, antioxidant defense either through metabolites or antioxidant enzymes is not efficient in counteracting oxidative damage in Fe-deprived sorghum. These findings may be beneficial for the improvement of sorghum genotypes sensitive to Fe-deficiency through breeding or transgenic approaches.

Downregulation of Zn-transporters along with Fe and redox imbalance causes growth and photosynthetic disturbance in Zn-deficient tomato

Zinc (Zn) deficiency hinders growth and development in tomato. This study unveils the responses of how Zn starvation affects physiological and molecular processes in tomato. Zn deficiency negatively affected the biomass, cellular integrity, and chlorophyll synthesis in tomato. Also, Zn deficiency decreased the maximum yield of PSII, photosynthesis performance index and dissipation energy per active reaction center, although the antenna size, trapping energy efficiency and electron transport flux were stable in Zn-starved leaves. Further, Zn shortage caused a substantial reduction in Zn and Fe concentrations in both roots and shoots along with decreased root Fe-reductase activity accompanied by the downregulation of Fe-regulated transporter 1, Zn transporter-like (LOC100037509), and Zn transporter (LOC101255999) genes predicted to be localized in the root plasma membrane. The interactome partners of these Zn transporters are predominantly associated with root-specific metal transporter, ferric-chelate reductase, BHLH transcriptional regulator, and Zn metal ion transporters, suggesting that Zn homeostasis may be tightly linked to the Fe status along with BHLH transcription factor in Zn-deficient tomato. We also noticed elevated O2.− and H2O2 due to Zn deficiency which was consistent with the inefficient antioxidant properties. These findings will be useful in the downstream approach to improve vegetable crops sensitive to Zn-deficiency.

Photoprotective compounds as early markers to predict holm oak crown defoliation in declining Mediterranean savannahs.

Dehesas, human-shaped savannah-like ecosystems, where the overstorey is mainly dominated by the evergreen holm oak (Quercus ilex L. subsp. ballota (Desf.) Samp.), are classified as a global conservation priority. Despite being Q. ilex a species adapted to the harsh Mediterranean environmental conditions, recent decades have witnessed worrisome trends of climate-change-induced holm oak mortality. Holm oak decline is evidenced by tree vigour loss, gradual defoliation and ultimately, death. However, before losing leaves, trees undergo leaf-level physiological adjustments in response to stress that may represent a promising field to develop biochemical early markers of holm oak decline. This study explored holm oak photoprotective responses (pigments, tocopherols and photosynthetic performance) in 144 mature holm oak trees with different health statuses (i.e., crown defoliation percentages) from healthy to first-stage declining individuals. Our results indicate differential photochemical performance and photoprotective compounds concentration depending on the trees' health status. Declining trees showed higher energy dissipation yield, lower photochemical efficiency and enhanced photoprotective compounds. In the case of total violaxanthin cycle pigments (VAZ) and tocopherols, shifts in leaf contents were significant at very early stages of crown defoliation, even before visual symptoms of decline were evident, supporting the value of these biochemical compounds as early stress markers. Linear mixed-effects models results showed an acute response, both in the photosynthesis performance index and in the concentration of foliar tocopherols, during the onset of tree decline, whereas VAZ showed a more gradual response along the defoliation gradient of the crown. These results collectively demonstrate that once a certain threshold of leaf physiological damage is surpassed, that leaf cannot counteract oxidative stress and progressive loss of leaves occurs. Therefore, the use of both photosynthesis performance indexes and the leaf tocopherols concentration as early diagnostic tools might predict declining trends, facilitating the implementation of preventive measures to counteract crown defoliation.

Morpho-physiological retardations due to iron toxicity involve redox imbalance rather than photosynthetic damages in tomato

Iron (Fe) toxicity is a major nutritional disorder that affects growth and yield in plants. Understanding the responses or damages due to Fe-toxicity may provide useful knowledge to improve tomato varieties. This study investigates the physiological and molecular responses in Fe-toxic tomato plants. The tomato plants were grown in separate hydroponic containers with two concentrations of Fe-EDTA (25 μM and 5 mM) in addition to the other nutrient elements. Fe-toxicity showed a severe reduction in growth parameters, which was accompanied by the increased electrolyte leakage and cell death in tomato. However, the SPAD score, quantum efficiency of PSII, and photosynthesis performance index did not show any changes in leaves, suggesting that damages due to Fe-toxicity are not related to the photosynthetic disturbance in tomato. The FCR (ferric chelate reductase) activity in root along with the Fe concentration in root and shoot significantly increased, being consistent with the upregulation of Fe-related genes (SlNramp1 and SlFRO1) in roots. It suggests that inefficiency to cope with elevated Fe is closely linked to Fe mobilization and uptake in roots of tomato. Consequently, this sensitive genotype was more prone to oxidative damages because of the inefficient antioxidant defense linked to antioxidant enzymes and metabolites. In conclusion, the growth retardation in Fe-toxic tomato is not related to photosynthetic inefficiency but highly associated with oxidative injuries in cells. These findings could be targeted in breeding or transgenic program to improve tomato plants sensitive to Fe toxicity.

Regulation of Zn uptake and redox status confers Zn deficiency tolerance in tomato

Zinc (Zn) is a well-known nutritional problem affecting plant growth and development. Due to Zn deficiency in the soil, tomato plants exhibit yield loss. This study was conducted on two contrasting tomato genotypes (Marglobe and Ratan) subjected to Zn deficiency to unveil the mechanistic foundation of Zn-deficiency tolerance in this vegetable. We found that Zn deficiency adversely affected plant biomass and photosynthesis parameters (chlorophyll score, quantum efficiency of photosystem, photosynthesis performance index) in Zn-deficiency sensitive Ratan. Furthermore, Zn-shortage showed increased electrolyte leakage, cell death %, and hydrogen peroxide concentration in Ratan (Zn-deficiency sensitive), which was not evident in Marglobe (Zn-deficiency tolerant). The metal analysis showed no significant decrease of Zn and Fe in Marglobe; however, Ratan exhibited a significant decline in Zn and Fe in both root and shoot subjected to Zn shortage. It suggests that maintaining Zn status is one of the adaptive mechanisms that Marglobe exhibits subjected to Zn shortage. This was further supported by the constitutive expression of SlIRT1 (Fe-regulated transporter) along with increased ferric reductase activity in addition to the upregulation of ZIP (Irt-like proteins) transporters (SlZIPL and SlZIP2) in roots of Marglobe. It also implies that Zn acquisition was tightly regulated and may also be dependent on Fe homeostasis in Marglobe. Together with Zn status, the elevated CAT (catalase) and SOD (superoxide dismutase) activities were actively associated with Zn-deficiency induced ROS (reactive oxygen species) regulation in Marglobe. Finally, auxin inhibitor resulted in a marked interruption in photosynthesis, growth, and ROS scavenging, indicating its crucial involvement in the adaptive mechanisms that Marglobe showed under Zn deficiency. This study uncovers the mechanistic strategies that confer tolerance to Zn shortage in tomato plants.

Arbuscular mycorrhizal fungi mitigate Fe deficiency symptoms in sorghum through phytosiderophore-mediated Fe mobilization and restoration of redox status.

Sustainable management of iron (Fe) deficiency through the microbial association is highly desirable to ensure crop yield. This study elucidates whether and how arbuscular mycorrhizal fungi (AMF) ameliorate Fe deficiency symptoms in sorghum. AMF inoculation showed a significant improvement in plant biomass, chlorophyll score, Fv/Fm (quantum efficiency of photosystem II), and Pi_ABS (photosynthesis performance index), suggesting its potentiality to diminish Fe deficiency symptoms in sorghum. This AMF-driven prevention of Fe deficiency was further supported by the improvement of biochemical stress indicators, such as cell death, electrolyte leakage, hydrogen peroxide, and superoxide anion. In this study, AMF showed a significant increase in phytosiderophore (PS) release as well as Fe and S concentrations in sorghum under Fe deficiency. Quantitative real-time PCR analysis demonstrated the consistent upregulation of SbDMAS2 (deoxymugineic acid synthase 2), SbNAS2 (nicotianamine synthase 2), and SbYS1 (Fe-phytosiderophore transporter yellow stripe) in roots due to AMF with Fe deficiency. It suggests that the enhancement of Fe due to AMF is related to the mobilization of Fe(III)-PS in the rhizosphere supported by the long-distance transport of Fe by SbYS1 transporter in sorghum. Our study further showed that the elevation of S mainly in the presence of AMF possibly enhances theS-containing antioxidant metabolites (Met, Cys, and GSH) as well as enzymes (CAT, SOD, and GR) to counteract H2O2 and O2- forthe restoration of redox status in Fe-deprived sorghum. Moreover, S possibly participates in Strategy II responses revealing its crucial role as a signaling molecule for Fe homeostasis in sorghum.

Arbuscular Mycorrhizal Symbiosis Mitigates Iron (Fe)-Deficiency Retardation in Alfalfa (Medicago sativa L.) Through the Enhancement of Fe Accumulation and Sulfur-Assisted Antioxidant Defense.

Iron (Fe)-deficiency is one of the major constraints affecting growth, yield and nutritional quality in plants. This study was performed to elucidate how arbuscular mycorrhizal fungi (AMF) alleviate Fe-deficiency retardation in alfalfa (Medicago sativa L.). AMF supplementation improved plant biomass, chlorophyll score, Fv/Fm (quantum efficiency of photosystem II), and Pi_ABS (photosynthesis performance index), and reduced cell death, electrolyte leakage, and hydrogen peroxide accumulation in alfalfa. Moreover, AMF enhanced ferric chelate reductase activity as well as Fe, Zn, S and P in alfalfa under Fe-deficiency. Although Fe-transporters (MsIRT1 and MsNramp1) did not induce in root but MsFRO1 significantly induced by AMF under Fe deficiency in roots, suggesting that AMF-mediated Fe enhancement is related to the bioavailability of Fe at rhizosphere/root apoplast rather than the upregulation of Fe transporters under Fe deficiency in alfalfa. Several S-transporters (MsSULTR1;1, MsSULTR1;2, MsSULTR1;3, and MsSULTR3;1) markedly increased following AMF supplementation with or without Fe-deficiency alfalfa. Our study further suggests that Fe uptake system is independently influenced by AMF regardless of the S status in alfalfa. However, the increase of S in alfalfa is correlated with the elevation of GR and S-metabolites (glutathione and cysteine) associated with antioxidant defense under Fe deficiency.

Arbuscular mycorrhizal fungi alleviate Fe-deficiency symptoms in sunflower by increasing iron uptake and its availability along with antioxidant defense

Iron (Fe)-deficiency causes chlorosis and growth inhibition in sunflower, an important commercial crop. This study examines whether and how arbuscular mycorrhizal fungi (AMF) ameliorate Fe-deficiency symptoms in Fe-deficiency sensitive sunflower plants. AMF supplementation showed a significant improvement in plant biomass, chlorophyll score, Fv/Fm (quantum efficiency of photosystem II), and Pi_ABS (photosynthesis performance index), suggesting its beneficial effect under Fe deficiency. This AM-driven amelioration of Fe deficiency was further supported by the improvement of biochemical stress indicators, such as cell death, electrolyte leakage, superoxide anion, and hydrogen peroxide. In this study, the AMF supplementations resulted in significant improvement in Fe as well as Zn concentrations in root and shoot of sunflower under Fe deficiency. One of the primary Strategy-I responses, ferric reductase activity along with the expression of its respective gene (HaFRO1), significantly increased in roots due to AMF ensuring Fe availability in the rhizosphere under Fe deficiency. Our qPCR analysis also showed a significant upregulation of HaIRT1, HaNramp1, and HaZIP1 in roots of sunflower in the presence of AMF, suggesting that Fe and Zn transporters are concurrently involved with AMF-mediated alleviation of Fe deficiency. Further, AMF accelerates the activities of CAT and SOD, predominantly in roots to protect sunflower plants from Fe-deficiency reactive oxygen species (ROS). This study unveils the mechanistic basis of AMF to limit Fe deficiency retardation in sunflower.

Adaptation of photosynthesis to water deficit in the reproductive phaseof a maize (Zea mays L.) inbred line

Photosynthesis is sensitive to water deficit (WD) stress. Maize (Zea mays L.) yield is vulnerable to water stress, especially if it occurs during the reproductive stage. In this study, the expression patterns of photosynthesis-related genes, together with photosynthetic gas-exchange and fluorescence parameters were investigated in a maize inbred line exposed to 50% of field water capacity (moderate WD) for 15 d after tassel emergence. The results demonstrated that WD down-regulated expression of psbA, psbB, psbC, psbP, psaA, psaB, and cab, especially at later periods of WD stress. Besides, with the increased WD stress, the steady decline in the value of photosynthesis performance index, maximum quantum yield of primary photochemistry, quantum yield for electron transport, quantum yield for the reduction of end acceptors of PSI per photon absorbed, and the efficiency of an electron beyond QA- that reduced PSI acceptors, and a clear increase in the J-step and I-step, K-band as well as L-band were observed. The results suggested that WD might restrict light-harvesting and electron transport. Interestingly, leaf transcript levels of rbcL and rbcS were up-regulated at the later stage of water stress in maize inbred line, which helped repair injury to PSII centers and maintain PSII activity (increased quantum yield of dissipation and effective antenna size of an active reaction center) under 15-d lasting WD.

Green spathe of peace lily (Spathiphyllum wallisii): An assimilate source for developing fruit

Peace lily (Spathiphyllum wallisii Regel) is a herbaceous, commercially important ornamental plant characterized by greening of its originally white spathe during a post-anthesis period and fruit development. It is a useful model plant for gaining insight into source–sink relationship. To clarify what is the triggering signal for spathe greening and its potential physiological role, the greening process has been examined in fertilized vs unfertilized and decapitated (with spadix removed) plants. Results showed that spathe of fertilized plants is viable for a longer period of time and greening process is more intensive in comparison with decapitated or unfertilized plants. Greening process comprised chloroplast differentiation as well as chlorophyll accumulation, and resulted in the photosynthetically active organs. Photosynthesis performance index (PIABS) of spathe in fertilized flowers was significantly higher than that in unfertilized and decapitated plants, indicating its better overall photosynthetic performance. Spathe removal during fruit development revealed approximately 30% smaller fruits in comparison with intact ones, implicating that green spathe contribute significantly as assimilate source for developing fruits. Cytokinin analysis showed that t-Z-type cytokinins were the most abundant in the spadix (t-Z and t-ZR) and the greening spathe (t-ZR), while overall cytokinin pool was significantly lower in the spathe of the decapitated plants. Exogenous treatment of spathe in decapitated plants with t-Z enhanced the intensity of greening. We may conclude that spathe greening in peace lily is genetically programmed process that may be mediated by fructification and, in part, by cytokinins originated in the developing fruit which was confirmed herein for the first time.

Response of adult sour cherry trees to woodchip mulch and drip irrigation

The aim of this study was to evaluate the growth, productivity, and tree condition of sour cherries, depending on the cultivar and soil-moisture treatment. The research was carried out at the Institute of Horticulture, Latvia University of Agriculture. Five sour cherry cultivars were investigated using drip irrigation and woodchip mulch. The following data were collected and processed: trunk cross-section area (TCSA), trunk growth intensity (TGI), fruit set, yield tree(-1) and yield efficiency as a ratio of TCSA, photosynthesis performance index, and the level of defoliation caused by cherry leaf spot after natural infection in the field. Woodchip mulch preserved soil moisture at optimal levels or higher during most vegetation seasons. Sour cherry cultivars differed significantly in terms of growth, productivity, and tree condition, and in the response to soil-moisture treatment. Most of the sour cherry cultivars responded to drip irrigation and woodchip mulch by increasing the growth and productivity of trees; however, a negative (in 'Orlica') or minimal (in 'Bulatnikovskaya') effect of mulch was observed in a few cultivars. Our study highlights the variability of sour cherry cultivars and the necessity of further research before recommendations can be made to growers.

The response of photosynthetic parameters of Triticum aestivum L. and Pisum sativum L. to different levels of salinity stress at different climate conditions

The aim of this work was to investigate the response of physiological parameters of winter wheat (Triticum aestivum L. cv. ʾAdaʾ) and pea (Pisum sativum L. cv. ’Early onward’) to different levels of salinity stress under changing climate conditions. Experimental plants were grown in growth chambers under the conditions of current climate (400 µmol mol-1 CO2 and day/night temperatures of 21/14 °C) and warmed climate (800 µmol mol-1 CO2 and day/night temperatures of 25/18 °C). Under both climate conditions plants were exposed to 100 mM and 200 mM concentrations of sodium chloride. Exposure to salinity stress was initiated when plants developed the second true leaf or their pair. After salinity treatments, which lasted 2 weeks, the response of photosynthetic and transpiration rate, stomatal conductivity, intracellular content of CO2, water use efficiency, II photosystem quantum efficiency rate and photosynthesis performance index were measured. Physiological parameters of pea plants were mostly affected at current climate conditions. The biggest reductions were found in photosynthetic and transpiration rate, which decreased by 57.0 %, and 71.5 %, under 200mM effect respectively. Assessment of intensity of fluctuation of wheat and pea physiological parameters at current climate has shown that changes were bigger in pea plants (51.3 %), in comparison with wheat (29.3 %). While at warmed climate conditions, the changes in physiological parameters of pea and wheat were the opposite: for wheat they have increased and became 52.6 %, and for pea they have decreased till 41.1 %, in comparison with the control plants (p <0.05).DOI: http://dx.doi.org/10.5755/j01.erem.73.4.19444

The effect of various sapropel concentrations on content and fluorescence of photosynthetic pigments of bean

Tarosiskio lake sapropel impact on beans (Vicia faba L.) photosynthesis parameters (content of chlorophylls and chlorophyll a fluorescence) was investigated in this study. Plants were sown in 1 L volume pots by 5 seeds with light loamy soil and grown in growth chambers. Considering sapropel composition, 2.2; 3.1 and 4 t/ha dry sapropel concentrations were chosen for investigation. Sapropel affected plants were compared with plants grown in unfertilised and with synthetic fertiliser fertilised soils. On 14th day of experiment, when the plants reached two leaves growths stage (BBCH 12), chlorophyll a fluorescence parameters of investigated plants were measured. Then plants were grown for 4 weeks more and at stem elongation stage (BBCH 31) chlorophyll a fluorescence parameters were measured repeatedly and also the content of chlorophylls and carotenoids were investigated. The efficiency II photosystem of bean increased by increasing sapropel concentration in soil, but insignificantly (p>0.05). Photosynthesis performance index was increasing (r=0.91; p 0.05). At BBCH 12 stage the highest non photochemical quenching (NPQ) value was measured in control beans, while at BBCH 31 stage, opposite trend was noticed (r=0.86; p 0.05), and the changes in carotenoid contents were similar to chlorophyll a+b.DOI: http://dx.doi.org/10.5755/j01.erem.72.4.16585

Effects of foliar application of nano-fertile fertilizer containing humic acid on growth, yield and nutrient concentration of mint (Mentha sativa) in aquaponic system

Due to recent droughts in Iran and other parts of the world and consequently limited water resources, tending to aquaponic system, in which fish and plants grow together, is a logical and practical method. For this reason, in the current experiment, possibility of mint planting in aquaponic system and the effects of applying nano-fertile fertilizer containing 60% humic acid on its growth was investigated. Mint rhizomes were planted in pure-perlite-contained pots and after reaching trnsferable stage, the plants were transferred to course-sand medium of aquaponic system. Nanofertile fertilizer concentrations for foliar spray were 0 (control), 500, 1000 and 1500 mg/L, with 100 mL for each treatment. Foliar application was continued every week, for 6 weeks, and the plants were harvested after 60 days. Results showed that all concentrations of foliar spray of mint plants with nano-fertile fertilizer increased fresh and dry weight of shoot and root as compared to control. Nano-fertile fertilizer increased chlorophyll content, soluble sugars, Fv/Fm, and PI as compared to control plants. Plant growth enhancement and better physiological conditions of nanofertile sprayed plants were correlated with higher potassium, phosphorus, calcium, iron, manganese and copper content in shoots of the treated plants. Therefore, considering higher concentration of some nutrients and chlorophyll content in the leaves of plants treated with nano-fertile fertilizer and consequently higher photochemical quantum yield (Fv/Fm) and photosynthesis performance index (PI), it is concluded that nano-fertile-treated plants had a better photosynthesis condition and thus carbon fixation was carried out well, dry matter was increased and plant growth was improved.

Effects of Sb(V) on Growth and Chlorophyll Fluorescence of Microcystis aeruginosa (FACHB-905)

In this study, effects of antimony Sb(V) on growth, pigments content, oxygen evolution, and photosystem II (PSII) activity of Microcystis aeruginosa were investigated. JIP-test, Q(A)(-) reoxidation kinetic test and S-state test were used in this study to study the energy distribution and electron transport in PSII. Treatment with Sb(V) at various concentrations ranging from 5 to 100 mg/l had long-term effects on growth, pigments content, and oxygen evolution of M. aeruginosa. Low concentration of Sb(V) had no significant inhibition of the biomass production and PSII activity but inhibited the pigment synthesis. Growth, pigments content, oxygen evolution, and PSII activity were seriously inhibited when treated by high concentration of Sb(V) (100 mg/l). The target sites of Sb(V) toxic effect on the PSII of M. aeruginosa were mainly on the donor side and the apparatus in the light-dependent reaction. The quantum yield for photochemistry, density of reaction centers and photosynthesis performance index decreased, whereas the dissipated energy increased. PSII activity of M. aeruginosa was promoted when exposure to 50 mg/l Sb(V) by increasing the density of active reaction centers and electron transport after Q(A)(-).

Effects of arsenic on growth and photosystem II (PSII) activity of Microcystis aeruginosa

Effects of arsenic on growth, pigments content, oxygen evolution and photosystem II (PSII) activity of Microcystis aeruginosa were investigated in the present study. Various concentrations of As(III) did not show significant effects on growth and total carotenoids content within 24h of treatment. After 48h of treatment, 10mgL−1 As(III) significantly inhibited the growth and synthesis of carotenoids of M. aeruginosa, while As(III) at concentrations ranging from 0 to 1mgL−1 showed no significant inhibition. Chlorophyll a synthesis, oxygen evolution and chlorophyll fluorescence were more sensitive to As(III) exposure than carotenoid synthesis and growth. Chlorophyll a content, fast fluorescence rise transients and fluorescence decay kinetics appeared to be affected after the cells were exposed to 1 and 10mgL−1 As(III) for more than 24h. Treatment with 10mgL−1 As(III) for 24h or longer led to flattening of the fluorescence transient and drastic decrease of amplitude of fast phase of QA− reoxidation kinetics. Exposure to As(III) mainly inhibited the quantum yield for primary photochemistry, density of reaction centers and photosynthesis performance index, and increased the dissipated energy. The decrease in amplitude of the fast and middle phases further revealed that once electron transfer from QA− to QB was inhibited by As(III), more QA− was reoxidized via S2(QAQB)− charge recombination. As(III) stress may result in an increased stability of the S2QB− and S2QA− recombination.

莫莫格湿地芦苇对水盐变化的生理生态响应

Understanding the eco-physiological response characteristics of Phragmites australis to water-salt condition is the key of determining the threshold of wetland ecological water requirement,in order to supply a feasible method for calculating the wetland ecological water requirement and scientific base for wetland restoration.By field investigation of Phragmites australis in Momoge wetland,we analyzed the relationship between eco-physiological characteristics of Phragmites australis and water-salt gradient with method of redundancy analysis(RDA) by using CANOCO software in Version 4.5.The results showed that the combination of three environmental factors including water depth,Na+ and HCO-3,explained 54.7% of the variation of eco-physiological responses of Phragmites australis,suggesting that the three environmental factors led to great changes in eco-physiological responses of Phragmites australis.Water depth was the key environmental factor influencing the growth of Phragmites australis.There was a significant positive correlationship between water depth and the eco-physiological characteristics including plant height,biomass,chlorophyll content,maximum photosynthesis efficient(FV/FM) and maximum photosynthesis performance index(PIABS).There was no significant correlationship between Na+/HCO-3 and the characteristics of Phragmites australis.The results suggested that it is the key point in the process of wetland restoration in mild or moderate saline-alkaline wetland to consider the influence of water depth on the growth of Phragmites australis,and secondly consider the effect of Na+/HCO-3,and determining the ecological water depth and fulfilling the ecological water requirement.

A Significant Loss in Photosynthetic Activity Associated with the Yellow Vine Syndrome of Cranberry

Numerous observations of yellow vine syndrome of cranberry have been reported from commercial cranberry growers. The molecular mechanism resulting in yellow vine syndrome is unknown. We have previously reported on the shading effect as an approach to explore the mechanisms of yellow vine formation and proposed photoinhibition as a possible cause. To compare the photosynthetic performance of yellow vine-affected and normal cranberry leaves, we conducted chlorophyll fluorescence analyses over 1 period of 1 day and 3 weeks, respectively. Both experimental data sets indicated that the maximum quantum efficiency of photosystem II, the size of the quinone pool, the numbers of reaction centers (RCs) per chlorophyll absorption, and the photosynthesis performance index of the yellow vine samples are substantially lower than those of normal cranberry leaves. These results are in line with the data of yellow vine leaves, having 26% to 28% less in chlorophyll than the normal leaves as measured by spectrometric and high-performance liquid chromatography analysis. We concluded that yellow vine syndrome is associated with poor photosynthetic activity and is likely becoming a threat for the long-term growth and crop production of cranberries.