Role of foliar spray of plant growth regulators in improving photosynthetic pigments and metabolites in Plantago ovata (Psyllium) under salt stress–A field appraisal

Salinity is one of the major abiotic factors that limit the growth and productivity of plants.Foliar application of plant growth regulators(PGRs)may help plants ameliorate the negative impacts of salinity.Thus,a field experiment was conducted at the Botanical Garden University of Balochistan,Quetta,to explore the potential role of PGRs,i.e.,moringa leaf extract(MLE;10%),proline(PRO;1μM),salicylic acid(SA;250μM),and thiourea(TU;10 mM)in ameliorating the impacts of salinity(120 mM)on Plantago ovata,an important medicinal plant.Salinity hampered plant photosynthetic pigments and metabolites but elevated oxidative parameters.However,foliar application of PGRs enhanced photosynthetic pigments,including Chl b(21.11%),carotenoids(57.87%)except Chl a,activated the defense mechanisms by restoring and enhancing the metabolites,i.e.,soluble sugars(49.68%),soluble phenolics(33.34%),and proline(31.47%),significantly under salinity stress.Furthermore,foliar supplementation of PGRs under salt stress led to a decrease of about 43.02%and 43.27%in hydrogen peroxide and malondialdehyde content,respectively.Thus,PGRs can be recommended for improved photosynthetic efficiency and metabolite content that can help to get better yield under salt stress,with the best and most effective treatments being those of PRO and MLE to predominately ameliorate the harsh impacts of salinity.

Effect of Enhanced Ultraviolet-B Radiation on Photosynthetic Pigments and Flavonoids in the Leaves of Grapevine

[Objective] The study aimed at investigating the influence of enhanced UV-B radiation on photosynthesis of grapevine.[Method] The seedlings of Cabernet sauvignon were treated with different intensities of UV-B radiation under outdoor conditions,and then the contents of photosynthetic pigments and flavonoids in leaves were determined by measuring the absorbance of leaves extracts at 663,645,470 and 300 nm,respectively.[Result] The content of photosynthetic pigments in the leaves of grapevine obviously increased with time under the treatments of different enhanced UV-B radiation.Compared with the control,the chlorophyll a,chlorophyll b,total chlorophyll and carotenoid were obviously increased by 5%,2%,4% and 3% in the enhanced UV-B radiation treatment of 10.8 μW/cm2（T1）,and in the treatment of 25.6 μW/cm2（T2） the corresponding levels were subsequently increased by 11%,9%,10% and 7% with a significant increase in the content of chlorophyll a.On the other hand,the flavonoids content in the leaves of grapevine were obviously increased by 13%,9% in T1 and T2.[Conclusion] The grapevine has strong adaptability to UV-B radiation,and appropriate enhanced UV-B radiation couldn＇t decrease the photosynthesis of grapevine leaves.

Involvement of anti-oxidative enzymes, photosynthetic pigments and flavonoid metabolism in the adaptation of Reaumuria soongorica to salt stress

Reaumuria soongorica is a short woody shrub widely found in semi-arid areas of China. It can survive severe environ- mental stress including high salinity in its natural habitat. Thus, we investigated the involvement of anti-oxidative enzymes, photosynthetic pigments and flavonoid metabolism in the adaptation of R. soongorica to saline environments. R. soon- gorica was treated with 0, 100, 200 and 400 mM NaC1 solutions for 14 days. Soil salt content increased significantly by watering with high content of NaC1 solution, and no variation between 8 and 14 days during treatment. The levels ofpe- roxidation of lipid membranes （measured by malondialdehyde content） and the activities of three antioxidant enzymes （superoxide dismutase （SOD）, peroxidase （POD） and ascorbate peroxidase （APX）） increased under salt stress. Chlorophyll and carotenoid content decreased with increasing salt content. The ratio of Chl a/Chl b and carotenoid/Chl exhibited sig- nificant increase under 400 mM NaC1. However, total flavonoid and anthocyanin contents and key enzyme activities in the flavonoid pathway including phenylalanine ammonialyase （PAL） and Chalcone isomerase （CHI） decreased under salt stress. These findings possibly suggest that R. soongorica has an adaptation protection mechanism against salt-induced oxidative damage by inducin~ the activity of antioxidant enzymes and maintaining a steady level of carotenoid/Chl.

Photosynthetic Pigments Affected by Fertilizer Source in Four Brassica Vegetables

Effect of fertilizer source （mineral fertilizer or organic manure） on photosynthetic pigments leaves content of four brassica vegetables （Pak choi, Kohlrabi, Cauliflower and Cabbage） was tested. Among treatments, cauliflower fertilized with chicken manure had the highest content of chlorophyll a and b （10.08 and 9.37 μm·g^-1）, while, pak choi had the lowest values （2.00 and 2.44 μm·g^-1） in non-fertilized plants. These differences in chlorophyll a and b content may have a great impact on photosynthetic rate and activity. Total carotenoids and total xanthophylls （lutein, zeaxanthin, antheraxanthin and violaxanthin） were the highest in cauliflower while the lowest was in pakchoi, β-carotene, on the other hand, was the highest percentage of total carotenoids （65.7%） in pak choi while Kohlrabi had the lowest percent （57.4%）. This high percentage offl-carotene of total carotenoids may compensate for lower content of chlorophylls and assist for efficient light harvesting process. Lutein showed to be the major components of xanthophyll pigments brassica vegetables and ranged from 0.462μm·g^-1 in cabbage to 0.626μm·g^-1 in kohlrabi but not differed significantly which may refer to genetically controlled. However, lutein, antheraxanthin and zeaxanthin content were increased significantly by the application of chicken manure regardless ofbrassica vegetable type. Violaxanthin was only detected in pak choi and not affected by fertilizer source. It can be concluding from the increasing contents of total xanthophylls pigments that may increase photosynthetic efficiency through non-photochemical quenching process.

Nitrogen Metabolising Enzymes and Photosynthetic Pigments as Influenced by Nitrogen Application in Oilseed Rape(Brassica napus L.)

Nitrogen(N)assimilation is a wide pathway in plants because of its fundamental importance for growth and development.The transport,assimilation and recycling of nitrogen is a highly complex and regulated process,as it is the mineral nutrient that is required in great abundance by the plants.Basic approach to enhance agriculture sustainability is dependent on exploration of the elite germplasm where new cultivars could perform better even under low N.To test the effect of nitrogen levels at 100 and 125 kg ha-1 on photosynthetic pigments and N assimilation in oilseed rape(B.napus L.)canola variety GSC-7 and hybrid Hyola PAC 401 were selected for comparison with new hybrid PGSH-52 in pipeline.N assimilating enzymes were assayed at vegetative,flowering and siliquing stages of crop growth to visualise the impact of N on the productivity.Nitrogen assimilating enzymes were highest at flowering stage and enhanced with increased N level.Nitrate reductase(NR)activity improved by 11.5%,nitrite reductase(NiR)by 24.2%,glutamine synthetase(GS)by 12.2%and glutamate synthase(GOGAT)by 35.2%over recommended N dose(N100)at flowering stage.Hyola PAC 401 registered maximum enzymatic activities trailed by GSC-7 at all the three stages of crop growth.Differences existed within the genotypes for photosynthetic pigments which varied with N levels.Chlorophyll a,chlorophyll b,total chlorophyll and carotenoids increased with nitrogen at 125 kg N ha^(-1)whereas chlorophyll a/b declined at three stages of crop growth.At flowering total chlorophyll and carotenoids were maximum and enhanced by 12.8%and 5%respectively with higher nitrogen level.

Differences between two wheat genotypes in the development of floret primordia and contents of pigments and hormones

Promoting more floret primordia within a spike to acquire fertile potential during the differentiation and pre-dimorphism phases is critical for increasing the number of fertile florets per spike(NFFs).However,it is yet unknown the physiological mechanism regulating the complex and dynamic process.This study aimed to clarify how intra-spike hormones,pigments,and assimilates coordinate with each other to regulate spike morphology and then floret primordia development.A two-year field experiment was conducted with two winter wheat genotypes:N50(big-spike with greater NFFs)and SM22(mediumspike with fewer NFFs).We monitored high temporal and spatial-resolution changes in the number and morphology of floret primordia within a spike,as well as in intra-spike hormones,pigments,and assimilates.Our results revealed that the big-spike genotype had more NFFs than the medium-spike genotype,not only because they had more spikelets,but also because they had greater NFFs mainly at central spikelets.More floret primordia at central spikelets had sufficient time to develop and acquire fertile potential during the differentiation phase(167-176 d after sowing,DAS)and the pre-dimorphism phase(179 DAS)for the big-spike genotype than the medium-spike genotype.Floret primordia with fertile morphology during the pre-dimorphism phase always developed into fertile florets during the dimorphism phase.Those early-developed floret primordia most proximal and intermediate to the rachis in the big-spike genotype developed faster than the medium-spike genotype.Correspondingly,the spike dry matter and pigments(chlorophyll a,chlorophyll b,carotene,and carotenoids)content during 170-182 DAS,auxin(IAA)and cytokinin(CTK)content on 167 DAS were significantly higher in the big-spike genotype than in the medium-spike genotype,while jasmonic acid(JA)content was significantly lower in the big-spike genotype compared to the medium-spike genotype during 167-182 DAS.Since the significant differences in intra-spike hormone content of the two genotypes appear earlier than those in dry matter and pigments,we propose a possible model that helped the N50 genotype(big-spike)to form more fertile florets,taking the intra-spike hormone content as a signaling molecule induced assimilates and pigments synthesis,which accelerated the development of more floret primordia during the differentiation phase and then acquired fertile potential during the pre-dimorphism phase,finally improved the NFFs.Our high temporal and spatial-resolution analysis provides an accurate time window for precision cultivation and effective physiological breeding to improve the number of fertile florets in wheat.

Effect of cadmium on photosynthetic pigments,lipid peroxidation,antioxidants,and artemisinin in hydroponically grown Artemisia annua

The effects of different cadmium （Cd） concentrations （0, 20, 60, and 100 μmol/L） on hydroponically grown Artemisia annua L. were investigated. Cd treatments applied for 0, 4, 12, 24, 72, 144, 216, and 336 hr were assessed by measuring the changes in photosynthetic pigments, electrolyte leakage, malondialdehyde （MDA） and antioxidants （ascorbic acid and glutathione）, while the artemisinin content was tested after 0, 12, 144, 216, and 336 hr. A significant decrease was observed in photosynthetic pigment levels over time with increasing Cd concentration. Chlorophyll b levels were more affected by Cd than were chlorophyll a or carotenoid levels. The cell membrane was sensitive to Cd stress, as MDA content in all treatment groups showed insignificant differences from the control group, except at 12 hr treatment time. Ascorbic acid （AsA） content changed slightly over time, while glutathione （GSH） content took less time to reach a maximum as Cd concentration increased. Cd was found to promote synthesis and accumulation of artemisinin, especially at concentrations of 20 and 100 ~tmol/L. In conclusion, Cd stress can damage to photosynthetic pigments, and vigorously growing A. annua showed a strong tolerance for Cd stress. Appropriate amounts of added Cd aided synthesis and accumulation of artemisinin.

Selenium-induced Changes in Activities of Antioxidant Enzymes and Content of Photosynthetic Pigments in Spirulina platensis

Spirulina platensis exposed to various selenium （Se） concentrations （0, 10, 20, 40, 80, 150, 175, 200, 250 mg/L） accumulated high amounts of Se in a dose- and time-dependent manner. Under low Se concentrations （〈150 mg/L）, Se induced increases in biomass concentration, content of photosynthetic pigments, and activities of glutathione peroxidase （GPX）, superoxide dismutase （SOD）, catalase （CAT） and Gua-dep peroxidases （POD）, which indicates that antioxidant enzymes play an important role in protecting cells from Se stress. Higher Se concentrations （≥175 mg/L） led to higher Se accumulation and increases in activities of GPX, SOD, CAT and POD, but also induced lipid peroxidation （LPO） coupled with potassium leakage and decreases in biomass concentration and contents of photosynthetic pigment. The results indicate that increases in activities of the antioxidant enzymes were not sufficient to protect cell membranes against Se stress. Time-dependent variations in the activities of antioxidant enzymes, contents of chlorophyll a and carotenoid and the LPO level were also investigated under representative Se concentrations of 40 and 200mg/L. Opposite variation trends between SOD-CAT activities, and GPX-POD-APX activities were observed during the growth cycles. The results showed that the prevention of damage to cell membranes of S. platensis cells could be achieved by cooperative effects of SOD-CAT and GPX-POD-APX enzymes. This study concludes that S. platensis possessed tolerance to Se and could protect itself from phytotoxicity induced by Se by altering various metabolic processes.

Deep chemometrics for nondestructive photosynthetic pigments prediction using leaf reflectance spectra

The need for the rapid assessment of the photosynthetic pigment contents in plants has encouraged the development of studies to produce nondestructive quantification methods.This need is driven by the fact that data on the photosynthetic pigment contents can provide a variety of important information that is related to plant conditions.Using deep chemometrics,we developed a novel one-dimensional convolutional neural network(CNN)model to predict the photosynthetic pigment contents in a nondestructive and real-time manner.Intact leaf reflectance spectra from spectroscopic measurements were used as the inputs.The prediction was simultaneously carried out for three main photosynthetic pigments,i.e.,chlorophyll,carotenoid and anthocyanin.The experimental results show that the prediction accuracy is very satisfying,with a mean absolute error(MAE)=0.0122±0.0004 for training and 0.0321±0.0022 for validation(data range of 0–1).

Comparative Analysis of the Photosynthetic Characteristics and Active Compounds of Semiliquidambar cathayensis Chang Heteromorphic Leaves

In the present study,the variation patterns of leaf shape in different populations of individual Semiliquidambar cathayensis plants were analyzed to investigate the relationship among leaf shape variation,photosynthetic properties,and active compounds to understand the genetic characteristics of S.cathayensis and screen elite germplasms.The leaf shape of 18 offspring from three natural S.cathayensis populations was analyzed to investigate the level of diversity and variation patterns of leaf shape.Furthermore,photosynthetic pigment content,physiological parameters of photosynthesis,and the active compounds in leaves of different shapes were determined.Statistical analysis showed that the leaf shape variation in S.cathayensis indicated a high level of genetic diversity among and within the populations.Cluster analysis showed that the three natural populations formed two clusters,one whose offspring was dominated by entire leaves and another characterized by palmately trifoliate leaves.The differences in photosynthetic characteristics and active compounds of leaves of three different shapes were comprehensively evaluated using principal component analysis.Two principal components with a cumulative contribution rate of 92.768%were extracted,of which the highest comprehensive score was for asymmetrically lobed leaves.The leaf shape in different S.cathayensis germplasms exhibited distinct patterns,and there were some correlations between the photosynthetic properties and active compounds in leaves of different shapes.Thus,the leaf shape can be used to predict active compound content,and in turn,select varieties based on that purpose;it also provides a simple and effective method to classify S.cathayensis germplasms.

Photosynthetic activity and antioxidative response of seagrass Thalassia hemprichii to trace metal stress

This study concerned the accumulation of trace metals in tissues of seagrass ( Thalassia hemprichii) exposed to various concentrations of Zn2+,Cd2+,Pb2+ and Cu2+ for 10 d,and the effect of excessive metals on quantum yield (△F/F′m),photosynthetic pigments and antioxidative enzymes like superoxide dismutase (SOD),guaiacol peroxidase (POD) were also examined.Cadmium was the most highly accumulated metal.Meanwhile,high metals levels led to a remarkable breakdown of photosynthetic parameters.Especially,△F/F′m,chlorophyll and carotenoid were significantly low during prolonged Cu exposure.Besides,△F/F′m was more severely depressed by Cu and Zn than Pb and Cd.However,T.hemprichii had positive response by increasing the activity of SOD and POD.The results indicate that T.hemprichii is the most sensitive to Cu,and the antioxidative protection mechanisms of T.hemprichii are more efficiently activated to avoid damage of Zn,Cd and Pb stress. Finally,due to the high Cd-accumulation and strong Cd-tolerance capacity,T.hemprichii can be used for phytoremediation in Cd-contaminated areas.

Responses of Photosynthetic Functions to Low Temperature in Flag Leaves of Rice Genotypes at the Milky Stage

To examine the chilling resistance of a newly developed super hybrid rice （Oryza sativa） Liangyou 122 at the different temperatures, an experiment was conducted to investigate the photosynthetic pigments contents, changes in fatty acids content of thylakoid membrane and the activities of several anti-oxidative enzymes at milky stage with traditional hybrid rice Shanyou 63 as control, by growing rice under the 25/15℃ and 25/20℃ day/night temperature. The results showed that the malondialdehyde（MDA） content and superoxide anion（O2^-·） were increased remarkably, while the activities of superoxide dismutase（SOD） and catalase（CAT） were obviously decreased with the duration of low temperature treatment. Moreover, the change enhanced with the increased difference between day and night temperatures. Meanwhile, the index of unsaturated fatty acid （IUFA） of both varieties also increased. As a result, the photosynthetic rate and the chlorophyll content were decreased considerably, while at beginning the carotenoids content increased and then decreased. Of all the parameters investigated, the variation range In Llangyou 122 was less than that in Shanyou 63, but the values of the former were more than the latter, which means that Llangyou 122 may be more resistant to chilling temperature at the milky stage.

Photosynthetic Behaviour and Mineral Nutrition of Tamarix gallica Cultivated Under Aluminum and NaCl Combined Stress

The lack of knowledge of plant tolerance and differential response to aluminum(Al)encouraged many researchers,in the last decade,to elucidate Al toxicity and tolerance mechanisms.The current study reported the impact of Al,a toxic element with negative effects on plant growth and development,in halophytic plant Tamarix gallica.Plants were subjected to different Al concentrations(0,200,500 and 800μM)with or without NaCl(200 mM)supplementation.Growth,photosynthesis and mineral content were assessed.Al stress had a significant decrease on shoots’biomass production between 19 to 41%,and a little variation on chlorophyll content and photosynthetic efficiency(Fo,Fm,Fv fluorescence’s and Fv/Fm).Furthermore,the Al-treatments did not affect significantly the content of potassium,calcium,and magnesium in different plant parts,whereas NaCl addition to the medium induced a decrease in these elements’concentrations.Our results have shown that T.gallica is able to accumulate the high levels of Al in shoots and roots,6288μg.g^(-1) DW and 7834μg.g^(-1) DW respectively.It is considered as a hyperaccumulator plant of Al.In addition,Na+contents in shoots and roots exceed 23000μg.g^(-1) DW.Therefore,T.gallica presents a high tolerance at the same time to Al and NaCl phytotoxicity,so it is interesting to use in phytoremediation programs.

Effects of Different Light Qualities on the Growth Characteristics of Populus trinervis

Populus trinervis is native to China and plays an irreplaceable role in maintaining the ecological balance of boreal and temperate forests.P.trinervis mainly grows in high-altitude areas.At present,there are limited studies on the response of P.trinervis to different light qualities,so it is necessary to investigate the photosynthetic physiological changes of P.trinervis in different light environments.In our study,P.trinervis was grown for 8 months under light filtered by three different colored films.The three treatments were blue film,green film,and white plastic film.The effects of blue(B),green(G),and white(W)light on photosynthetic pigment content,absolute growth,photosynthetic parameters,soluble sugar content,and chlorophyll fluorescence parameters were studied,respectively.Compared to the Wtreatment,the chlorophyll a and b,carotenoids,total chlorophyll content(a+b),absolute growth of seedling height,net photosynthetic rate(PN),water use efficiency(WUE),total soluble sugars,sucrose,and nonphotochemical quenching(NPQ)of P.trinervis were significantly increased under B treatment.Meanwhile,chlorophyll a and b,carotenoids,total chlorophyll(a+b),transpiration rate(Tr),intercellular CO_(2) concentration(Ci),stomatal conductance(gs),absolute growth of seedling height and leaf length,reducing sugar,total soluble sugar content,and NPQ were significantly increased under G treatment.The results showed that the absolute growth and chlorophyll content of P.trinervis were increased under B light,while the sugar and photosynthetic parameters were increased under G light.Additional studies may look into how B light impacts absolute growth and promotional mechanisms,as well as how G light affects the accumulation of sugar levels.

Responses of Photosynthetic Pigment, Phenol and Total Saponin Contents of Panax notoginseng to Supplemental UV-B under Field Conditions

[Objective] The aim of this study was to investigate the content changes and their correlations of the photosynthetic pigment,phenols,including total phenols,total flavonoids and anthocyanins,and total saponins of the one-year-old P.notoginseng plants under supplemental UV-B stress in fields.[Method] The one-year-old plants were irradiated by UV-B in field for 1 min per day,and the plants under the UV-B lamp were regarded as a circle center,achieving an annular leaf-sampling.The photosynthetic pigment,phenols and total saponins of the leaves were determined spectrophotometrically.[Result] With the increase of sampling radius,the supplemental UV-B intensity decreased significantly,the contents of chlorophyll （Chl） a,Chl b,Chl （a＋b）,carotenoid （Car） and total photosynthetic pigment （Chl＋Car） of the leaves increased extremely significantly,the Chl a/b and total phenol content （TPC） decreased extremely significantly,but the Chl （a＋b）/Car changes were not significant.The contents of total flavonoids,anthocyanins and saponins all increased due to the increasing of UV-B,displaying dose effects.The UV-B intensity was positively correlated with the Chl a/b,and negatively with the Chl a,Chl b,Chl （a＋ b）,Car and （Chl＋Car） contents; and the two of TPC,total flavonoid content （TFC）,total anthocyanin content （TAC） and total saponin content （TSC） were positively correlated,all reaching extremely significant level.The UV-B intensity was positively and significantly correlated with the total flavonoid content （TFC）,negatively and significantly with the Chl （a＋b）/Car,and positively and insignificantly with the TPC,TAC and TSC.[Conclusion] For one-year-old plants of P.notoginseng,UV-B can decrease the contents of the Chl a,Chl b,Chl （a＋b）,Car and （Chl＋Car） and increase the Chl a/b and TPC,and,furthermore,induce the increases of the TFC,TAC and TSC in a dose-dependent manner.However,UV-B can hardly change the Chl （a＋b）/Car.The supplemental UV-B of well-suited dose might be one of the effective measures to improve the TSC of P.notoginseng.

A study of chlorophyll-like and phycobilin pigments in the C endosymbiont of the apple- snail Pomacea canaliculata

Pigments present in the brown-greenish C morph of an intracellular endosymbiont of Pomacea canaliculata were investigated.Acetone extracts of the endosymbiotic corpuscles showed an absorption spectrum similar to that of chlorophylls.Three fractions obtained from silica gel column chromatography of the acetone extracts(CI,CII and CIII),were studied by positive ion fast atom bombardment-mass spectrometry(FAB–MS)and hydrogen-nuclear magnetic resonance(H-NMR).Results indicated the presence of(1)a sterol in the yellow colored CI fraction;(2)a mixture of pheophorbides a and b in the major green fraction,CII;and(3)a modified pheophorbide a in the smaller green fraction,CIII.Aqueous extracts of the C endosymbiont did not show evidence of the occurrence of C-phycocyanin,allophycocyanin or phycoerithrin(light absorption,fluorescence emission,and electrophoresis of the protein moieties)while cyanobacterial cells(Nostoc sp.)showed evidence of C-phycocyanin and allophycocyanin.The possible phylogenetic and functional significance of the pigments present in the C endosymbiont is discussed.

Effects of silica nanoparticles on growth and photosynthetic pigment contents of Scenedesmus obliquus

To assess the aquatic ecosystem safety for silica （SiO2） nanoparticles （NPs）, the growth inhibition and photosynthetic pigment contents of Scenedesmus obliquus in logarithm growth phase exposed to SiO2 NPs and SiO2 bulk particles （BPs） suspensions were measured. SiO2 NPs with 10-20 nm diameters were found to be toxic. The 20% effective concentration （EC20） values for 72 and 96 hr were 388.1 and 216.5 mg/L, respectively. The contents of chlorophyll decreased significantly under moderate and high concentration （50, 100, and 200 mg/L） of SiO2 NPs after 96-hr exposure, but the carotenoids did not. SiO2 BPs were found to be nontoxic up to 200 mg/L. The toxicity of SiO2 NPs probablely due to their sorption to algal cells surface. The results imply that there is potential harm to aquatic environment by using SiO2 NPs, and it should deserve special concern.

Effects of drought stress on antioxidant enzyme,photosynthetic pigment and flavonoid pathway in two desert shrubs

Antioxidant enzyme activity, photosynthetic pigment content, and free malondialdehyde （MDA）, as well as flavonoid content and the key enzyme activity in the flavonoid pathway were determined in two desert shrubs, Caryopteris mongolica Bunge and Reaumuria soongorica （Pall.） Maxim. under drought stress. The free MDA content was enhanced during the experimental period, which may be an indicator of oxidative stress. Superoxide dismutase （SOD）, peroxidase （POD）, and ascorbate peroxidase （APX） activities in C. mongholica showed a significant increase during the experiment, but catalase （CAT） activity was slightly decreased. On the other hand, POD and APX activities showed a significant increase and SOD and CAT activity data had no significant changes in R. soongorica. APX, SOD, and CAT activities were higher in R. soongorica than in C. mongholica, but MDA content was lower, indicating that the lower values of MDA were attributed to higher activities of antioxidant enzyme in R. soongorica. Chlorophyll content decreased significantly in the two shrubs during the experiment, which indicated that there was a photoprotection mechanism through reducing light absorbance by decreasing pigments content. Caretonoids content increased in C. mongholica and decreased in R. soongorica. The ratio of Chla/Chlb decreased significantly but caretonoids/Chl revealed a significant increase in the two shrubs, which could be explained as no decrease of peripheral light-harvesting complexes and a higher tolerance to drought. Total flavonoid content and the activities of phenylalanine ammonialyase （PAL） and chalcone isomerase （CHI） showed different changes between C. mongholica and R. soongorica after treatment. These values decreased in R. soongorica and increased in C. mongholica except for PAL activity. However, anthocyanin content increased in the two shrubs, indicating that there was a different regulation response in the ftavonoid pathway in the two shrubs under drought stress, and anthocyanin should be an important antioxidant both in the shrubs. Our results demonstrated the different responses of antioxidant defense and drought tolerance ability between the two shrubs.

Changes in the Photosynthetic Pigment Contents and Transcription Levels of Phycoerythrin-Related Genes in Three Gracilariopsis lemaneiformis Strains Under Different Light Intensities

Three Gracilariopsis lemaneiformis strains,including wild type and high-temperature-resistant cultivars 981 and 2007,were studied with the changes in their photosynthetic pigment contents and related gene transcription levels under different light intensities(10,60,100,and 200μmolm^(−2)s^(−1)).The three G.lemaneiformis strains had the following photosynthetic pigments with high-to-low contents:phycoerythrin(PE),phycocyanin(PC),allophycocyanin(APC),and chlorophyll a(Chl a).Among the three strains,cultivar 981 had the highest PE content,followed by cultivar 2007.The PC and APC contents were similar among the three strains,but they were higher in cultivars 981 and 2007 than in the wild type.The Chl a contents in the three G.lemaneiformis strains were equal.A low light intensity(10μmolm^(−2)s^(−1))promoted photosynthetic pigment accumulation in G.lemaneiformis and improved the relative PE gene transcription(peA and peB)in a short period(≤6 d).A high light intensity decreased the PE content.PebA and PebB,which catalyzed phycoerythrobilin synthesis,showed no compensatory upregulation at a low light intensity among the strains except for the wild type.At a high light intensity,transcription levels of pebA and pebB in the three strains were upregulated.This study provided an experimental basis for elucidating the photosynthesis of G.lemaneiformis.As key genes of algal growth,photo-synthesis-related genes served as useful gene markers for screening elite varieties with good traits in breeding.Cultivar 2007 was superior to cultivar 981 in terms of maintaining high pigment levels in a wide range of light intensities,which is the most suitable for aquaculture.

Exploring the nano-fungicidal efficacy of green synthesized magnesium oxide nanoparticles(MgO NPs)on the development,physiology,and infection of carrot(Daucus carota L.)with Alternaria leaf blight(ALB):Molecular docking

In this research,green synthesized magnesium oxide nanoparticles(MgO NPs)from lemon fruit extracts and their fungicidal potential was evaluated against Alternaria dauci infection on carrot(Daucus carota L.)under greenhouse conditions.The scanning and transmission electron microscopy(SEM and TEM)and ultra-violet(UV)visible spectroscopy were used to validate and characterize MgO NPs.The crystalline nature of MgONPs was determined using selected area electron diffraction(SAED).MgO NPs triggered substantial antifungal activity against A.dauci when exposed to 50 and 100 mg L^(–1)concentrations but the higher antifungal potential was noticed in 100 mg L^(–1)under invitro conditions.In fungal inoculated plants,a marked decrease in growth,photosynthetic pigments,and an increase in phenol,proline contents,and defense-related enzymes of carrot were seen over control(distilled water).However,foliar application of MgO NPs at 50 and 100 mg L^(–1)resulted in significant improvement of plant growth,photosynthetic pigments,phenol and proline contents,and defense enzymes activity of carrots with and without A.dauci infection.Spraying of MgO NPs at 100 mg L^(–1)had more plant length(17.11%),shoot dry weight(34.38%),plant fresh weight(20.46%),and root dry weight(49.09%)in carrots when challenged with A.dauci over inoculated control.The leaf blight indices and percent disease severity were also reduced in A.dauci inoculated plants when sprayed with MgO NPs.The non-bonding interactions of Alternaria genus protein with nanoparticles were studied using molecular docking.