Decrease In Chlorophyll Fluorescence Research Articles

The Impact of Different Water Regime on Chlorophyll Fluorescence of Pyrus pyraster L. and Sorbus domestica L.

The water deficit is considered to be significant cause of photosynthesis defects. Measuring of chlorophyll fluorescence is one of the methods revealing defects in the photosynthetic apparatus. The experiment was established with two woody plant (Pyrus pyraster L. and Sorbus domestica L.) cultivated in two different regimes of the substrate saturation. The measurement of the modulated fluorescence of chlorophyll a was done by FMS1 fluorometer during three-week period between June and September (2012 and 2013). There were analysed selected parameters of chlorophyll fluorescence: Fv/Fm – maximum quantum efficiency of PSII, ΦPSII – effective quantum yield of PSII and RFD – chlorophyll fluorescence decrease ratio. According to the obtained results, Pyrus pyraster has probably higher potential for adaptation to water deficiency. There were recorded the significant decreases mainly in the values of parameter RFD and ΦPSII for Sorbus domestica within duration of experiment with different water regime in both growing seasons 2012 and 2013. The results document a weak sensitivity of the parameter Fv/Fm on changes in the amount of available water in the substrate in both taxa.

Enhanced chilling tolerance of banana fruit treated with malic acid prior to low-temperature storage

The effects of postharvest malic acid (MA) treatment on alleviating the occurrence of chilling injury (CI) symptoms in banana (Musa spp., AAA group, cv. Brazil) fruit under 6°C were evaluated. Application of 80mM MA alleviated CI symptoms (surface browning), delayed the decrease in chlorophyll fluorescence (Fv/Fm) and chlorophyll content. The activities of peroxidase (POD) and polyphenol oxidase (PPO) were also suppressed by MA. Furthermore, compared with the control group, fruit that were treated with MA showed lower levels of reactive oxygen species, but higher antioxidant activities. The results suggest that the application of MA, as an organic acid, exhibited the potential for alleviating chilling injury symptoms of banana fruit by reducing skin browning and inducing antioxidant activities under low temperature.

Response of two barley cultivars to increasing concentrations of cadmium or chromium in soil during the growing period.

The heavy metal contamination of soils is a serious environmental issue because excessive metal concentrations pose risks to the health of humans, animals, and plants. For this reason, the interest in understanding the toxic effects of metals on crop growth and physiology has increased in the last decades. A pot trial was performed in a greenhouse to evaluate the effects of contaminated soil with different concentrations of cadmium (Cd) or chromium (Cr) on barley growth and development. Two cultivars of barley were studied, Pedrezuela and CB502. Growth, chlorophyll content, chlorophyll fluorescence, and relative water content (RWC) were analyzed during the plant-growing period. After harvesting, the Cd and Cr contents in plant were analyzed. No significant differences were observed for chlorophyll content and chlorophyll fluorescence between control plants and those treated with Cd. In the case of Cr, a significant decrease of plant growth, chlorophyll content, chlorophyll fluorescence, and RWC was detected with respect to the control. The tolerance index (TI) and translocation factor (TF) were calculated. Data indicated that both varieties are tolerant to these metals; CB502 showed higher tolerance to Cr and Pedrezuela to Cd. The effect of Cd or Cr addition on nutrient concentrations in plants varied among elements and organs of the plant analyzed. The correlations between the physiological and agronomic studied traits were significant (p < 0.01, p < 0.001), so the stress induced by these metals affected the physiology and water relations of the plant, which provoked a decrease of plant biomass, especially in the plants treated with Cr.

Study the effect of insecticide dimethoate on photosynthetic pigments and photosynthetic activity of pigeon pea: Laser-induced chlorophyll fluorescence spectroscopy

Pigeon pea is one of the most important legume crops in India and dimethoate is a widely used insecticide in various crop plants. We studied the effect of dimethoate on growth and photosynthetic activity of pigeon pea plants over a short and long term exposure. Plant growth parameters, photosynthetic pigment content and chlorophyll fluorescence response of pigeon pea (Cajanus cajan L.) plants treated with various concentrations of the insecticide dimethoate (10, 20, 40 and 80ppm) have been compared for 30days at regular intervals of 10days each. Laser induced chlorophyll fluorescence spectra and fluorescence-induction kinetics (FIK) curve of dimethoate treated pigeon pea plants were recorded after 10, 20 and 30days of treatment. Fluorescence intensity ratio at the two fluorescence maxima (F685/F730) was calculated by evaluating curve-fitted parameters. The variable chlorophyll fluorescence decrease ratio (Rfd) was determined from the FIK curves. Our study revealed that after 10days of treatment, 10ppm of dimethoate showed stimulatory response whereas 20, 40 and 80ppm of dimethoate showed inhibitory response for growth and photosynthetic activity of pigeon pea plants, but after 20 and 30days of treatment all the tested concentrations of dimethoate became inhibitory. This study clearly shows that dimethoate is highly toxic to the pigeon pea plant, even at very low concentration (10ppm), if used for a prolonged duration. Our study may thus be helpful in determining the optimal dose of dimethoate in agricultural practices.

Antagonistic and synergistic effects of light irradiation on the effects of copper on Chlamydomonas reinhardtii

The present study showed the important role of light intensity and spectral composition on Cu uptake and effects on green alga Chlamydomonas reinhardtii. High-intenisty light (HL) increased cellular Cu concentrations, but mitigated the Cu-induced decrease in chlorophyll fluorescence, oxidative stress and lipid peroxidation at high Cu concentrations, indicating that Cu and HL interact in an antagonistic manner. HL up-regulated the transcription of genes involved in the antioxidant response in C. reinhardtii and thus reduced the oxidative stress upon exposure to Cu and HL. Combined exposure to Cu and UVBR resulted in an increase of cellular Cu contents and caused severe oxidative damage to the cells. The observed effects were higher than the sum of the effects corresponding to exposure to UVBR or Cu alone suggesting a synergistic interaction.

Impacts of altered precipitation, nitrogen deposition and plant competition on a Mediterranean seed bank

AbstractQuestionsDo increased nitrogen (N) fertilization, altered water supply and increased competition by a nitrophilous plant species alter the establishment of the plant community developed from the soil seed bank present in a semi‐arid Mediterranean ecosystem under greenhouse conditions? Does the nitrophilous plant respond in the same way to N addition under field conditions?LocationThe kermes oak/rosemary shrubland in the Nature Reserve El Regajal‐Mar de Ontígola, central Spain.MethodsIn September 2008, native soil seed bank was collected in open areas dominated by rosemary shrubs. Seeds of the nitrophilous Diplotaxis siifolia were collected in early summer 2008. Pots with aliquots of soil were distributed among eight treatments, which resulted from combinations of two levels of N fertilization, water supply and density of D. siifolia in the seed bank. The plant community was left to grow for 3 mo, when chlorophyll fluorescence measurements and harvests were made. In summer 2008, the soil seed bank density of 0 and 50 kg N·ha−1·yr−1 plots was also manipulated in the field by broadcasting seeds to a density of 8000 D. siifolia seeds·m−2.ResultsIncreased N and competition tended to reduce soil water content in ‘high water’ pots. High water and N fertilization increased total above‐ and below‐ground plant biomass production. Nitrogen fertilization reduced plant root:shoot ratio, had a negative effect on plant richness and, coupled with ‘high competition’ and ‘high water’, reduced forb biomass productivity. The competition treatment decreased chlorophyll fluorescence in grasses. Under field conditions, N fertilization increased D. siifolia density and this effect was dependent on soil phosphorus availability.ConclusionsOur results show that nitrophilous plant species such as D. siifolia can be a threat to local plant communities in the context of increased N deposition and altered precipitation events. In particular, local plant communities from semi‐arid Mediterranean climates, and especially the forb element, may suffer more from competition in highly polluted and invaded sites during unusually wet years. Finally, we predict a future increase in the relative dominance of these species in semi‐arid Mediterranean environments where forb species typically adapted to low‐nutrient environments will fail to successfully compete with weeds.

The Adaptive Ability of Cornus Stolonifera Michx. ´Kelseyi´ in Changing Environment

Abstract Water represents one of the limiting environmental factors having impact on all the processes in plants. Water stress is considered as the most significant cause of photosynthesis defects. Measuring fluorescence of chlorophyll a is one of the methods revealing defects in the photosynthetic aparatus. The examination has been carried out on the plants Cornus stolonifera Michx. ´KELSEYI´ cultivated in two different irrigation regimes (a regime with 40% substrate saturation and a controlling regime with 60% substrate saturation). We have used a fluorometer HANSATECH FMS 1 to measure modulated fluorescence of chlorophyll a. A three-week period of measurement was set between June and August during two years of experiments (2011 and 2012). The selected chlorophyll fluorescence parameters Fv /Fm - maximum quantum efficiency of PSII; ΦPSII - effective quantum yield of PSII; Rfd - chlorophyll fluorescence decrease ratio and NPQ - non-photochemical chlorophyll fluorescence quenching, proved to be insensitive to given water deficit. Cornus stolonifera Michx. ´KELSEY´ appears to be a woody plant capable of water efficiency.

High-resolution airborne hyperspectral and thermal imagery for early detection of Verticillium wilt of olive using fluorescence, temperature and narrow-band spectral indices

Verticillium wilt (VW) caused by the soil-borne fungus Verticillium dahliae Kleb, is the most limiting disease in all traditional olive-growing regions worldwide. This pathogen colonizes the vascular system of plants, blocking water flow and eventually inducing water stress. The present study explored the use of high-resolution thermal imagery, chlorophyll fluorescence, structural and physiological indices (xanthophyll, chlorophyll a+b, carotenoids and blue/green/red B/G/R indices) calculated from multispectral and hyperspectral imagery as early indicators of water stress caused by VW infection and severity. The study was conducted in two olive orchards naturally infected with V. dahliae. Time series of airborne thermal, multispectral and hyperspectral imagery was acquired in three consecutive years and related to VW severity at the time of the flights. Concurrently to the airborne campaigns, field measurements conducted at leaf and tree-crown levels showed a significant increase in crown temperature (Tc) minus air temperature (Ta) and a decrease in leaf stomatal conductance (G) across VW severity levels, identifying VW-infected trees at early stages of the disease. Higher Tc−Ta and G values measured in the field were associated with higher VW severity levels. At leaf level, the reduction in G caused by VW infection was associated with a significant increase in the Photochemical Reflectance Index (PRI570) and a decrease in chlorophyll fluorescence (F). The airborne flights enabled the early detection of VW by using canopy-level image-derived airborne Tc−Ta, Crop Water Stress Index (CWSI) calculated from the thermal imagery, blue/blue–green/blue–red ratios (B/BG/BR indices) and chlorophyll fluorescence, confirming the results obtained in the field. Airborne Tc−Ta showed rising values with a significant increase of ~2K at low VW severity levels, and was significantly correlated with G (R2=0.76, P=0.002) and PRI570 (R2=0.51, P=0.032). Early stages of disease development could be differentiated based on a CWSI increase as VW developed, obtaining a strong correlation with G (R2=0.83, P<0.001). Likewise, the canopy-level chlorophyll fluorescence dropped at high VW severity levels, showing a significant increase as disease progressed. These results indicate the potentials of an early detection of V. dahliae infection and discrimination of VW severity levels using remote sensing. Indicators based on crown temperature such as CWSI, and visible ratios B/BG/BR as well as fluorescence were effective in detecting VW at early stages of disease development. In affected trees, the structural indices PRI, chlorophyll and carotenoid indices, and the R/G ratio were good indicators to assess the damage caused by the disease.

Chlorophyll fluorescence imaging of photosynthetic activity and pigment contents of the resurrection plants Ramonda serbica and Ramonda nathaliae during dehydration and rehydration

The desiccation-tolerant plants of the R. serbica and R. nathaliae are resurrection plants which are able to fully recover their physiological function after anabiosis. A comparison of chlorophyll fluorescence imaging and photosynthetic pigment contents responses of R. serbica and, for the first time, R. nathaliae to dehydration and rehydration were investigated. For this purpose, plants after collection from their natural habitats were kept fully watered for 14days at natural condition. The experiment was conducted with mature leaves of both species. R. serbica and R. nathaliae plants were dehydrated to 5.88% and 7.87% relative water content (RWC) by withholding water for 15days, afterwards the plants were rehydrated for 72hours to 94.67% and 97.02% RWC. During desiccation, R. serbica plants preserved the chlorophyll content about 84%, while R. nathaliae about 90%. During dehydration when RWC were more than 40%, photochemical efficiency of PSII for photochemistry, the Fv/Fm ratio, decreased about 40% in R. nathaliae plants, but a strong reduction with 60% was recorded for R. serbica. Following rehydration, the Fv/Fm ratio recovered more rapidly in R. nathaliae. The higher photosynthetic rates could also be detected via imaging the chlorophyll fluorescence decrease ratio Rfd, which possessed higher values after rehydration leaves of R. nathaliae as compared to R. serbica. The results showed that the photosynthetic activity and chlorophyll contents after rehydration are recovered more rapidly in R. nathaliae in comparison to R. serbica.

알라닌 아미노기전이효소가 상실된 벼(Oryza sativa L.) 돌연변이체의 고염 스트레스에 대한 반응

An AlaAT knock-out mutant (alaat) of rice (Oryza sativa L.) was isolated from T-DNA tagging lines and the genotypes of its progeny were determined with AlaAT1-specific primers. The alaat phenotypes showed decreased growth and grain yield when compared with control plants. The activity of AlaAT1 in the mutant plants was practically undetectable. The responses of alaat plants to growth under salt stress were compared with those of control plants by measuring chlorophyll fluorescence and the activities and mRNA expression of antioxidant enzymes. All abiotic stresses tested (salt, drought, and chilling) caused a similar decrease in chlorophyll fluorescence in both alaat and wild type plants. The activity of peroxidase (POX), an antioxidant enzyme, decreased following salt treatment of alaat plants, while control plant showed an increased activity. The mRNA levels for cAPX (cytosolic ascorbate peroxidase), POX2, and AlaAT were determined by RT-PCR following salt stress. No AlaAT1 mRNA was detected in alaat plants. The POX2 mRNA showed a slightly increased level in the wild type but was not detected in alaat plants, in agreement with the activity assays. The levels of cAPX mRNA were greatly increased in both the wild type and alaat plants. The salt stress effects on rice plant growth are therefore proposed to reflect a loss of function of AlaAT, which alters the activity and synthesis of antioxidant enzymes (especially peroxidases), rather than a direct effect on photosynthesis.

Physiological and biochemical responses of the marine dinoflagellate Prorocentrum minimum exposed to the oxidizing biocide chlorine

Toxic effects of the commonly used biocide chlorine (Cl2) on the marine dinoflagellate Prorocentrum minimum were assessed using growth-, pigment- and enzyme activity-based endpoints. Cell count, chlorophyll a levels, carotenoids, and chlorophyll autofluorescence were monitored up to 72h after exposure to Cl2, and these parameters showed a dose- and time-dependent decrease. The 72-h median effective concentration (EC50) based on growth rate was 1.177mgL−1. Cl2 dose above 0.5mgL−1 were toxic to P. minimum after 6-h exposure to Cl2; the effect increased with increase in exposure time as revealed by a significant reduction in growth rate and decreased chlorophyll fluorescence. Moreover, the activities of antioxidant enzymes, including superoxide dismutase and catalase, were altered proportionally with increasing Cl2 dose. The results of this study show that Cl2 concentrations as observed in power-plant discharges and in drinking-water systems cause physiological and biochemical damage to the microalgae.

On the analysis of non-photochemical chlorophyll fluorescence quenching curves: I. Theoretical considerations

Non-photochemical quenching (NPQ) protects photosynthetic organisms against photodamage by high light. One of the key measuring parameters for characterizing NPQ is the high-light induced decrease in chlorophyll fluorescence. The originally measured data are maximal fluorescence (Fm′) signals as a function of actinic illumination time (Fm′(t)). Usually these original data are converted into the so-called Stern–Volmer quenching function, NPQSV(t), which is then analyzed and interpreted in terms of various NPQ mechanisms and kinetics. However, the interpretation of this analysis essentially depends on the assumption that NPQ follows indeed a Stern–Volmer relationship. Here, we question this commonly assumed relationship, which surprisingly has never been proven. We demonstrate by simulation of quenching data that particularly the conversion of time-dependent quenching curves like Fm′(t) into NPQSV(t) is (mathematically) not “innocent” in terms of its effects. It distorts the kinetic quenching information contained in the originally measured function Fm′(t), leading to a severe (often sigmoidal) distortion of the time-dependence of quenching and has negative impact on the ability to uncover the underlying quenching mechanisms and their contribution to the quenching kinetics. We conclude that the commonly applied analysis of time-dependent NPQ in NPQSV(t) space should be reconsidered. First, there exists no sound theoretical basis for this common practice. Second, there occurs no loss of information whatsoever when analyzing and interpreting the originally measured Fm′(t) data directly. Consequently, the analysis of Fm′(t) data has a much higher potential to provide correct mechanistic answers when trying to correlate quenching data with other biochemical information related to quenching.

고추의 엽록소 형광 이미지 분석법에 의한 한발스트레스 지표화 가능성

The objectives of this study focused on measuring chlorophyll fluorescence related to drought stress comparing some parameters. Almost parameters were declined although they were not significant on the basis of mean values of fluorescence of total leaf area. While the ratio of fluorescence intensity variable chlorophyll () to fluorescence intensity maximal chlorophyll () was not changed, the effective quantum yield of photochemical energy conversion in photosystemII () and chlorophyll fluorescence decrease ratio () were slightly reduced, indicating inhibition of the electron transport from quinone bind protein A () to quinone bind protein B (). Some parameters such as non-photochemical quenching rate () and coefficients of non-photochemical quenching of variable fluorescence (qN) in mid-zone of leaf and near petiole zone leaf were significantly enhanced within 4 days after drought stress, which can be used as physiological stress parameters. Decrease in could was significantly measured in all leaf zones. In conclusion, three parametric evidences for chlorophyll fluorescence responses such as , NPQ, and qN insinuated the possibility of photophysiological indices under drought stress.

Chilling-stress responses by rice seedlings grown with different ammonium concentrations and its relationship to leaf spermidine content

We previously determined that, under salt stress, a growth medium containing a high level of ammonium enhances oxidative damage in rice (Oryza sativa L.) seedlings. This suggested that, to be salt-tolerant, plants must assimilate excess nitrogen efficiently. Here, we investigated the effect of different ammonium concentrations on the chilling-stress sensitivity of rice seedlings. We also examined the relationship between leaf polyamine contents and stress tolerance under low temperatures (13/8°C day/night). Chilling treatment resulted in a striking decrease in chlorophyll fluorescence (ΦII) in the leaf blades. This was especially true for seedlings grown in a high-ammonium medium. Thus, the chilling-stress sensitivity of rice was heightened under excess N, similar to that noted in our earlier salt-stress experiments. Exposure to low temperature caused contents of putrescine and spermidine to increase in leaf blades under all ammonium concentrations, whereas the level of spermine declined under such treatment. The rate of increase in putrescine and spermidine contents was slower when the medium contained a high amount of ammonium, and a positive correlation was observed between leaf ΦII values and leaf spermidine contents. These results imply that an adaptive mechanism operates in rice seedlings and that spermidine is of physiological importance in conveying chilling-stress tolerance.

Spectroscopic studies of photosynthetic responses of tomato plants to the interaction of zinc and cadmium toxicity

The in vivo chlorophyll (Chl) fluorescence spectra of Solanum lycopersicum leaves were recorded in the spectral region 650–800nm using a spectroscopic method based on ultraviolet light emitting diode induced fluorescence spectroscopy (UV-LED IFS). These spectra have been used to analyze the interactive functions of cadmium (Cd2+) and zinc (Zn2+) on photosynthetic activities of S. lycopersicum plants. The fluorescence intensity ratios (F690/F735) of the chlorophyll bands at 685 and 730nm were calculated by evaluating curve fitted parameters using a Gaussian spectral function, for control as well as treated plants. The fluorescence induction kinetics (Kautsky effect) was also measured on dark adapted intact plant leaves at the chlorophyll bands for determining the variable chlorophyll fluorescence decrease ratio (RFd values) and the stress adaptation index (Ap). In addition, metal accumulation in plants, plant growth and photosynthetic pigments content were estimated. It was found that the RFd(690), RFd(730) and Ap values decreased whereas the F690/F735 ratio increased in the case of 10μM Cd2+ treated plants, indicating an impairment of the photosynthetic efficiency. Zn2+ supplementation, at low concentration (10 and 50μM), in combination with Cd2+ protect the photochemical functions. However, the high Zn2+ concentration exacerbated the negative effects of Cd2+ and showed a severe decrease of RFd(690), RFd(730) and Ap values compared to Cd2+ alone. It is seen that F690/F735 ratios are strongly correlated with chlorophyll contents. The results demonstrate the usefulness of F690/F735, Ap and RFd values in determining the potential photosynthetic activity of an intact attached leaf in a non-destructive way.

Photoinhibition of photosynthesis in Antarctic lichen Usnea antarctica. I. Light intensity- and light duration-dependent changes in functioning of photosystem II

The paper deals with the differences in sensitivity of Antarctic lichen to photoinhibition. Thalli of Usnea antarctica were collected at the James Ross Island, Antarctica (57°52´57´´W, 63°48´02´´S) and transferred in dry state to the Czech Republic. After rewetting in a laboratory, they were exposed to 2 high light treatments: short-term (30 min), and long-term (6 h). In short-term treatment, the sample were exposed to 1000 and 2000 µmol m-2 s-1 of photosynthetically active radiation (PAR). In long-term experiment, PAR of 300, 600, and 1000 µmol m-2 s-1 were used. Photosynthetic efficiency of U. antarctica thalli was monitored by chlorophyll fluorescence parameters, potential (FV/FM) and actual (FPSII) quantum yield of photochemical processes in photosystem II in particular. In short-term treatments, the F0, FV and FM signals, as well as the values of FV/FM, and FPSII showed light-induced decrease, however substantial recovery after consequent 30 min. in dark. Longer exposition (60 min) to high light led to more pronounced decrease in chlorophyll fluorescence than after 30 min treatment, however dark recovery was faster in the thalli treated before for longer time (60 min). Long-term treatment by high light caused gradual decrease in FV/FM and FPSII with the time of exposition. The extent of the decrease was found light dose-dependent. The time course was biphasic for FV/FM but not for FPSII. The study showed that wet thalli of Usnea antarctica had high capacity of photoprotective mechanisms to cope well either with short- or long-term high light stress. This might be of particular importance in the field at the James Ross Island, particularly at the begining of growing season when melting water is available and, simultaneously, high light stress may happen on fully sunny days.

Detection of photosynthetic activity under cadmium stress by measurement of the red and far-red chlorophyll fluorescence

In this work it is shown that, with a new spectroscopic method based on ultraviolet light emitting diode-induced fluorescence spectroscopy (UV-LED IFS), the photosynthetic activity of an intact attached leaf can be measured in a non-destructive way within a few seconds. The effects of cadmium (Cd) toxicity on the photosynthetic activity of tomato plants (Solanum lycopersicum) were studied using various CdCl2 (cadmium chloride) concentrations. The Cd treatment decreases the photosynthetic activity, measured via a decline of the variable chlorophyll (chl) fluorescence decrease ratio (R Fd) values, calculated at 690 and 730 nm. The chl fluorescence ratios of intensity (FIR) and band area were also calculated. It was found that the R Fd(690) and R Fd(730) values decreased whereas the FIR increased from 1 μM Cd treatment and this behaviour is enhanced with the increasing of Cd concentrations. At 10 and 25 μM Cd, the decrease in R Fd values was associated with a strong decline in the chlorophyll-a + chlorophyll-b (chl-a + b). The chl-a + b decline could also be followed via an increase of the chl fluorescence ratio F 690/F 730. Our study demonstrates that the UV-LED IFS is a promising technique for early detection of Cd stress (from 1 μM) in tomato plants, before visual symptoms appear.

Effect of high temperature on color, chlorophyll fluorescence and volatile biosynthesis in green-ripe banana fruit

Banana (Musa AAA group) is one of the most consumed fruits in the world. It has been reported that chlorophyll breakdown and color formation in banana is inhibited by ripening temperatures above 24 °C. At this temperature thylakoid membranes are retained resulting in reduced chlorophyll degradation. In this study, green mature, untreated banana fruit were obtained from a local wholesale market and half of the fruit were subjected to ethylene treatment at 10 μL L −1 for 24 d. After ethylene treatment, both treated and untreated fruit were stored at 20 °C or 30 °C for 7 d. Fruit were sampled after 0, 1, 4 and 7 d of storage and evaluated for color, chlorophyll fluorescence, volatile production and expression of genes related to volatile biosynthesis. Storage at 30 °C reduced yellow color development in the peel, decreased chlorophyll fluorescence (Fv/Fm), but increased Fo, indicating possible heat stress of the fruit. A total of 19 volatile compounds were identified using SPME/GC/MS. Both ethylene treatment and high temperature enhanced volatile production. The increase of Fo and hexanoate and acetate esters are coincided with the stress of high temperature. Using real time PCR (qPCR), expression of genes related to volatile biosynthesis including branched-chain amino acid transaminase ( BCAT), lipoxygenase (LOX), hydroperoxide lyase ( HPL), pyruvate decarbolxylase ( PDC), alcohol dehydrogenases ( ADH, short and medium chains), and alcohol acetyl transferase ( AAT) were investigated in both peel and pulp tissues. Among the tested genes, BCAT, HPL, ADH and AAT in peel and pulp tissues increased significantly in response to ethylene and storage at 30 °C. PDC, ADH and BCAT (in pulp tissue) were induced by storage at 30 °C in ethylene-treated fruit. LOX decreased during ripening and storage at 30 °C in the peel, but increased in the pulp tissue of ethylene-treated fruit. This study demonstrates that both ethylene and high temperature influence volatile biosynthesis in banana fruit at the transcriptional level and confirms findings that high temperature causes stress in banana fruit during ripening.

Calcium invigorates the cadmium-stressed Brassica napus L. plants by strengthening their photosynthetic system

Cadmium (Cd) in plants interrupts numerous metabolic processes and reduces the water and nutrient uptake that cause chlorosis, growth retardation, and ultimately plant death. Response of Brassica napus L. to calcium (Ca) enrichment in growth medium for reducing Cd toxicity stress by strengthening the photosynthesis organelles and their functionality was explored in this study. B. napus seedlings of two cultivars (ZS 758 and ZS 72) were exposed to Cd toxicity at 500 μM in hydroponics, and it was ameliorated with Ca at 2.0 mM. The study included determinations and evaluations pertaining to physiological attributes of plant growth, chlorophyll, and photosynthesis. Cadmium stress significantly depressed the seedling growth and reduced photosynthetic rate (Pn), stomatal conductivity (Gs), and transpiration rate (Tr). Further, Cd toxicity markedly decreased the electron transport rate of PSII, effective quantum yield of photochemical energy conversion in PSII [Y(II)], photosynthetic active radiation, coefficient of photochemical quenching (qP), and chlorophyll fluorescence decrease ratio (R(Fd)). Addition of Ca in Cd-stressed plants antagonized the toxicity effects on all the above-mentioned attributes. Calcium amendment also reversed the Cd stress-induced increase in intercellular CO(2) concentration (Ci) and non-photochemical quenching, and countered the Cd accumulation in seedlings. This study suggests that Ca(2+) in the proximity of plasma membrane is proficient in alleviating Cd toxicity by reducing the cell-surface negativity and competing for Cd(2+) ion influx. Consequently, both the plant growth and activity of diurnal photosynthetic system remain the least altered under Cd-provoked toxicity stress.

Leaf stripe form of esca induces alteration of photosynthesis and defence reactions in presymptomatic leaves.

Esca is a destructive disease in grapevines (Vitis vinifera L.) caused by at least three fungi and characterised by two different external symptoms, the apoplectic and leaf stripe form. This latter form can be discerned as soon as symptoms become visible, but the preceding discrete signs during incubation are poorly or not understood. To further understand the development of the leaf stripe form, the period preceding and following the appearance of symptoms was investigated by studying physiological and molecular markers associated with photosynthetic mechanisms and stress response. No perturbation of any targeted metabolism was observed in asymptomatic leaves of asymptomatic canes from vines showing the leaf stripe form of esca. Conversely, drastic alterations of photosynthesis functions were registered in presymptomatic leaves, as revealed by the decrease of gas exchange and chlorophyll fluorescence, and the repression of photosynthesis-related genes. These alterations were amplified during symptom development. Expression of defence-related genes was affected and detected early in presymptomatic leaves and amplified during symptom expression. Our results suggest that grapevines may react precociously by reducing photosynthesis and triggering defence mechanisms in response to the leaf stripe form of esca.