Film-mulched continuous ridge-furrow planting improves soil temperature,nutrient content and enzymatic activity in a winter oilseed rape field,Northwest China

Film mulching system is a widely employed agricultural practice worldwide. However, the effects of different planting and mulching patterns on soil nutrient content and enzymatic activity have not been well documented. In this study, we examined the impact of four planting and mulching patterns（including control, flat planting without mulching; M1, flat planting with film mulching; M2, ridge-furrow planting with film mulching on both ridges and furrows; and M3, ridge-furrow planting with film mulching on continuous ridges） on the seed yield of winter oilseed rape, soil moisture, soil temperature, soil organic carbon（SOC） content, soil nutrient content, and soil enzymatic activity over three growing seasons from 2012 to 2015 in a winter oilseed rape field in the semi-arid area of Northwest China. Seed yield of winter oilseed rape, soil moisture, soil temperature, enzymatic activities, and contents of nitrate-nitrogen, available phosphorus, and available potassium were all significantly higher in mulching treatments（M1, M2 and M3） than in control treatment over the three growing seasons, whereas SOC content was significantly lower in mulching treatments than in control treatment during 2013–2014 and 2014–2015. Among the three mulching treatments（M1, M2 and M3）, the M3 treatment showed consistently higher seed yield, SOC content, nutrient contents, and enzymatic activities than the other two treatments. Seed yield of winter oilseed rape was 41.1% and 15.0% higher in M3 than in M1 and M2, respectively. SOC content and soil enzymatic activities in the top 0–20 cm soil layers and nitrate-nitrogen content in the top 0–30 cm soil layers were all significantly higher in M3 than in M1 and M2. Therefore, we advise the ridge-furrow planting with film mulching on continuous ridges（i.e., M3） as an efficient planting and mulching pattern for sustainably improving the seed yield of winter oilseed rape and preserving soil fertility in the semi-arid area of Northwest China.

Single Nucleotide Polymorphism of CYP3A4 Intron 2 and Its Influence on CYP3A4 mRNA Expression and Liver Enzymatic Activity in Human Liver

Summary： In adult liver, CYP3A4 plays an important role in the metabolism of a wide range of en- dogenous and exogenous compounds. To investigate whether there is a single nucleotide polymorphism （SNP） of CYP3A4 intron 2 in the liver and its effects on the mRNA expression and enzymatic activity of CYP3A4, genomic DNA was extracted from 96 liver tissue samples obtained from patients who had undergone liver surgery. An SNP of CYP3A4 intron 2 was identified by polymerase chain reaction （PCR）-single-strand confirmation polymorphism and DNA sequencing. The mRNA expression of CYP3A4 was determined by the fluorescence quantitative PCR technique. The enzymatic activity of CYP3A4 was measured using erythromycin and testosterone as probe substrates. Twelve patients were found to have the SNP/T4127G CYP3A4 within intron 2. The mRNA levels of CYP3A4 in wild-type and SNP/T4127G samples were 2.62±1.09 and 2.79±1.63, respectively （P〉0.05）. Erythromycin N-demethylase activity in wild-type and SNP/T4127G samples were 121.2±32.8 and 124.7±61.6 nmol·mg^-1min^-1, respectively （P〉0.05）. The activity of testosterone 613-hydroxylase was significantly different between wild-type （648±173 pmol·mg^-1·min^-1） and SNP/T4127G samples （540-4-196 pmol.mg-l-minl; P〈0.05）. In conclusion, the SNP/T4127G of CYP3A4 intron 2 exists in the liver. This SNP does not affect the mRNA expression of CYP3A4 but significantly decreases the hepatic micro- somal testosterone 613-hydroxylase activity of CYP3A4. Furthermore, this study indicates that the ap- propriate selection of probe substrates is very important in studying the relationship between the geno- type and phenotype of CYP3A4.

Cobra phospholipase A2 protect cerebellar granule neurons from apoptosis with mechanism independent of enzymatic activity

A fraction of cobra （Naja naja atra） venom has been discovered to have protective effect on rat cultural cerebellar granule neurons （CGNs） from apoptosis induced by removing serum and reducing the extracellular potassium concentration from 25 to 5 mM. This component has been purified and identified as secreted phospholipase A2 （cobra sPLA2）. In order to study the relationship between the protection on CGNs and enzymatic activity of phospholipase A2, CGNs stained by Hoechst 33258 were quantified to determine survival rate under the fluorescence microscopy; the protective potencies on apoptosis of cultural CGNs were compared among cobra sPLA2, the cobra sPLA2 modified in carboxylate groups with water soluble carbodiimide and semicarbazide, and the heated cobra sPLA2 at 80℃ for 30 rain. The results showed that the CGN survival rate was unaffected significantly both in modified cobra sPLAz whose enzymatic activity of PLA2 had decreased by 80%, and in cobra sPLA2 adding 7, 7-Dimethyleicosadienoic acid, an inhibitor of sPLA2 at concentration of 10-fold IC50; contrary, the neuronal survival rate fell about 60% in heated cobra sPLA2, although its PLA2 activity only decreased by 10%. The protection on CGNs were also found in some of sPLA2s derived from venoms of bee, Naja naja mossambica, Crotalus atroxalso and Vipera Ammodytes Ammodytes but could not be found in other sPLA2s from bovine pancreas and Streptomyces violaceoruber. Above results suggest that the protection on CGNs of cobra sPLA2 is independent of its enzymatic activity.

Metal natural product complex Ru-procyanidins with quadruple enzymatic activity combat infections from drug-resistant bacteria

Bacterial infection hampers wound repair by impeding the healing process.Concurrently,inflammation at the wound site triggers the production of reactive oxygen species(ROS),causing oxidative stress and damage to proteins and cells.This can lead to chronic wounds,posing severe risks.Therefore,eliminating bacterial infection and reducing ROS levels are crucial for effective wound healing.Nanozymes,possessing enzyme-like catalytic activity,can convert endogenous substances into highly toxic substances,such as ROS,to combat bacteria and biofilms without inducing drug resistance.However,the current nanozyme model with single enzyme activity falls short of meeting the complex requirements of antimicrobial therapy.Thus,developing nanozymes with multiple enzymatic activities is essential.Herein,we engineered a novel metalloenzyme called Ru-procyanidin nanoparticles(Ru-PC NPs)with diverse enzymatic activities to aid wound healing and combat bacterial infections.Under acidic conditions,due to their glutathione(GSH)depletion and peroxidase(POD)-like activity,Ru-PC NPs combined with H2O2 exhibit excellent antibacterial effects.However,in a neutral environment,the Ru-PC NPs,with catalase(CAT)activity,decompose H2O2 to O2,alleviating hypoxia and ensuring a sufficient oxygen supply.Furthermore,Ru-PC NPs possess exceptional antioxidant capacity through their superior superoxide dismutase(SOD)enzyme activity,effectively scavenging excess ROS and reactive nitrogen species(RNS)in a neutral environment.This maintains the balance of the antioxidant system and prevents inflammation.Ru-PC NPs also promote the polarization of macrophages from M1 to M2,facilitating wound healing.More importantly,Ru-PC NPs show good biosafety with negligible toxicity.In vivo wound infection models have confirmed the efficacy of Ru-PC NPs in inhibiting bacterial infection and promoting wound healing.The focus of this work highlights the quadruple enzymatic activity of Ru-PC NPs and its potential to reduce inflammation and promote bacteria-infected wound healing.

Near infrared light-induced dynamic modulation of enzymatic activity through polyphenol-functionalized liquid metal nanodroplets

Dynamic manipulation of enzymatic activity is a challenging task for applications in chemical and pharmaceutical industries due to the difficult modification and variable conformation of various enzymes.Here, we report a new strategy for reversible dynamic modulation of enzymatic activity by near-infrared light-induced photothermal conversion based on polyphenol-functionalized liquid metal nanodroplets(LM). The metal-phenolic nanocoating not only provides colloidal stability of LM nanodroplets but also generates nanointerfaces for the assembly of various enzymes on the LM nanodroplets. Upon near infrared(NIR) irradiation, the localized microenvironmental heating through photothermal effect of the LM nanodroplets allows tailoring the enzymatic activity without affecting the bulk temperature. A library of functional enzymes, including proteinase K, glucoamylase, glucose oxidase, and Bst DNA polymerase, is integrated to perform a reversible control and enhanced activities even after five times of cycles, demonstrating great potential in bacterial fermentation, bacteriostasis, and target gene amplification.

Effect of invasive weed biochar amendment on soil enzymatic activity and respiration of coal mine spoil:a laboratory experiment study

Mining and excavation activities cause massive degradation of land,leading to complete loss of soil resources,vegetation,and biodiversity.Mine spoils support invasive weeds(predominantly Lantana)which can strive in these harsh conditions,causing allelopathy during plantation stage of reclamation.It is hypothesised that biochar produced from invasive weeds will enhance enzymatic activity,CO_(2)flux and overall fertility of coal mine spoil.A 6-month incubation study was conducted on the effect of biochar amendment(2 and 3%,w/w)on mine spoil enzymatic activities(dehydrogenase,invertase,amylase and cellulase),respiration and coal mine spoil fertility.The study showed that biochar significantly improved dehydrogenase(83%)and cellulase activity(78%)at 3%amendment.Geometric mean of enzymatic activities increased from 1.87 in control to 4.51 at 2%and 3.25 at 3%biochar amendment.Mine spoil physio-chemical properties such as soil organic carbon(65%),cation exchange capacity(54%),bulk density(25%)and water holding capacity(19%),were improved significantly com-pared to the unamended mine spoil.Biochar amendment reduced mine spoil CO_(2)flux at 2%(2.85μmol CO_(2)m^(−2)s^(−1))and 3%(2.60μmol CO_(2)m^(−2)s^(−1))compared to control(4.92μmol CO_(2)m^(−2)s^(−1)).The cost of biochar production and application(2%,w/w)in pit plantation during reclamation is estimated to be 844 USD t ha−1(plantation density:1600 trees ha−1).On the basis of present study,biochar preparation from invasive weeds can be used for sustainable reclamation of coal mine spoil.

Studies on gene structure, enzymatic activity and regulatory mechanism of acetohydroxy acid isomeroreductase from G2 pea

The AAIR genomic DNA of G2 pea (Pisum sativum L.) was amplified by PCR method. Sequence analysis showed that it was composed of 8 introns and 9 exons with three of the introns containing specific A/T-rich endogenous promoter regions. Molecular hybridization experiments revealed that the expression of AAIR remained at a high level before and after flowering if grown in short day growth chambers. However, when grown under long day conditions, the level of AAIR expression declined very rapidly after flowering. This variation of AAIR expression is consistent with the change of enzymatic activity of acetohydroxy acid isomeroreductase. Functional complementation experiments carried out using an acetohydroxy acid isomeroreductase deficient E. coli strain showed that these cells could not grow on M9 medium without addition of branched-chain amino acids unless they were transformed with the AAIR expression vector. Further study revealed that overexpression of the pea AAIR cDNA in acetohydroxy acid isomeroreductase deficient E. coli strain enhanced significantly its branched-chain amino acid biosynthetic capacity. Results from gel shift experiments showed that fractions of pea nuclear protein extracts could bind specifically to some A/T rich regions present in introns of the AAIR gene. The A/T-rich-region-binding proteins remained at a steady level in the non-senescing apical buds of short-day grown G2 pea. In the rapid-senescing apical buds of long-day grown G2 pea, the levels of these proteins declined rapidly after flower initiation. Therefore, the nuclear protein binding capacities to endogenous promoter regions may constitute an important mechanism to regulate AAIR gene expression.

Screen, Design and Enzymatic Activity Determination of Artificial Microperoxidases

Peroxidase activity greatly impacts the maintenance of flee radical homeostasis, and can prevent or treat diseases related to free radicals. Microperoxidase-11（MP-11 ） is created via hydrolysis of cytochrome c iron-porphyrin complexes. In these complexes, the heme iron is penta-coordinate with histidine and exhibits excellent antioxidant activity when decomposing hydrogen peroxide. In this study, we screened the Ph.D.-7 and Ph.D.-12 phage display＇ peptide libraries and obtained ten small peptide ligands of deuterohemin（the vinyl groups of oxidized heme）. Among these polypeptides, DhHP-7P1, 12P1, 12P2 and 12P6 have good enzymatic activity compared with MP-11, and exhibit activities up to 50% of MP-11. Based on the screened sequences, we designed a series of artificial microperoxidases and determined that a higher peroxidase activity could be achieved with an enzymatic active site containing a second site of histidine residue spaced between two arginine residues with an interval of two amino acids（Dh-XHRXXR）.

Irrigation regimes modulate non-structural carbohydrate remobilization and improve grain filling in rice(Oryza sativa L.)by regulating starch metabolism

Recently developed ‘super’ rice cultivars with greater yield potentials often suffer from the problem of poor grain filling, especially in inferior spikelets. Here, we studied the activities of enzymes related to starch metabolism in rice stems and grains, and the microstructures related to carbohydrate accumulation and transportation to investigate the effects of different water regimes on grain filling. Two ‘super’ rice cultivars were grown under two irrigation regimes of well-watered(WW) and alternate wetting and moderate soil drying(AWMD). Compared with the WW treatment,the activities of ADP glucose pyrophosphorylase(AGPase), starch synthase(StSase) and starch branching enzyme(SBE), and the accumulation of non-structural carbohydrates(NSCs) in the stems before heading were significantly improved, and more starch granules were stored in the stems in the AWMD treatment. After heading, the activities of α-amylase, β-amylase, sucrose phosphate synthase(SPS) and sucrose synthase in the synthetic direction(SSs)were increased in the stems to promote the remobilization of NSCs for grain filling under AWMD. During grain filling, the enzymatic activities of sucrose synthase in the cleavage direction(SSc), AGPase, StSase and SBE in the inferior spikelets were increased, which promoted grain filling, especially for the inferior spikelets under AWMD.However, there were no significant differences in vascular microstructures. The grain yield and grain weight could be improved by 13.1 and 7.5%, respectively, by optimizing of the irrigation regime. We concluded that the low activities of key enzymes in carbon metabolism is the key limitation for the poor grain filling, as opposed to the vascular microstructures, and AWMD can increase the amount of NSC accumulation in the stems before heading, improve the utilization rate of NSCs after heading, and increase the grain filling, especially in the inferior spikelets, by altering the activities of key enzymes in carbon metabolism.

Chitosan Nanoparticles as Biostimulant in Lettuce (Lactuca sativa L.) Plants

Biodegradable nanoparticles such as chitosan nanoparticles (CSNPs) are used in sustainable agriculture since theyavoid damage to the environment;CSNPs have positive effects such as the accumulation of bioactive compoundsand increased productivity in plants. This study aimed to investigate the impact of applying CSNPs on lettuce,specifically focusing on enzymatic activity, bioactive compounds, and yield. The trial was conducted using a completelyrandomized design, incorporating CSNPs: 0, 0.05, 0.1, 0.2, 0.4, and 0.8 mg mL−1. The doses of 0.4 mg mL−1improve yields up to 24.6% increases and 0.1 mg mL−1 of CSNPs increases total phenols by 31.2% and antioxidantcapacity by 34.6%. In addition, when low concentrations of CSNPs (0.05 and 0.1 mg L−1) were applied, anincrease in catalase was determined. The CSNPs represent a good alternative to be used as a biostimulant in sustainableagriculture because they improve the yield and quality of lettuce by increasing the bioactive compounds.

Soil enzymatic activities and microbial community structure with different application rates of Cd and Pb

This study focused on the changes of soil microbial diversity and potential inhibitory effects of heavy metals on soil enzymatic activities at different application rates of Cd and/or Pb. The soil used for experiments was collected from Beijing and classified as endoaquepts. Pots containing 500 g of the soil with different Cd and/or Pb application rates were incubated for a period of 0, 2, 9, 12 weeks in a glasshouse and the soil samples were analyzed for individual enzymes, including catalase, alkaline phosphatase and dehydrogenase, and the changes of microbial community structure. Results showed that heavy metals slightly inhibited the enzymatic activities in all the samples spiked with heavy metals. The extent of inhibition increased significantly with increasing level of heavy metals, and varied with the incubation periods. The soil bacterial community structure, as determined by polymerase chain reaction- denaturing gradient gel electrophoresis techniques, was different in the contaminated samples as compared to the control. The highest community change was observed in the samples amended with high level of Cd. Positive correlations were observed among the three enzymatic activities, but negative correlations were found between the amounts of the heavy metals and the enzymatic activities.

Response of soil catalase activity to chromium contamination

The impact of chromium（Ⅲ） and （Ⅵ） forms on soil catalase activity was presented. The Orthic Podzol, Haplic Phaeozem and Mollic Gleysol from different depths were used in the experiment. The soil samples were amended with solution of Cr（Ⅲ） using CrCl3, and with Cr（Ⅵ） using K2Cr2O7 in the concentration range from 0 to 20 mg/kg, whereas the samples without the addition of chromium served as control. Catalase activity was assayed by one of the commonly used spectrophotometric methods. As it was demonstrated in the experiment, both Cr（Ⅲ） and Cr（Ⅵ） have an ability to reduce soil catalase activity. A chromium dosage of 20 mg/kg caused the inhibition of catalase activity and the corresponding contamination levels ranged from 75% to 92% for Cr（Ⅲ） and 68% to 76% for Cr（Ⅵ）, with relation to the control. Catalase activity reached maximum in the soil material from surface layers （0-25 cm）, typically characterized by the highest content of organic matter creating favorable conditions for microorganisms.

Dynamic changes in microbial activity and community structure during biodegradation of petroleum compounds:A laboratory experiment

With 110-d incubation experiment in laboratory, the responses of microbial quantity, soil enzymatic activity, and bacterial community structure to different amounts of diesel fuel amendments were studied to reveal whether certain biological and biochemical characteristics could serve as reliable indicators of petroleum hydrocarbon contamination in meadow-brown soil, and use these indicators to evaluate the actual ecological impacts of 50-year petroleum-refining wastewater irrigation on soil function in Shenfu irrigation area. Results showed that amendments of ~ 1000 mg/kg diesel fuel stimulated the growth of aerobic heterotrophic bacteria, and increased the activity of soil dehydrogenase, hydrogenperoxidase, polyphenol oxidase and substrate-induced respiration. Soil bacterial diversity decreased slightly during the first 15 d of incubation and recovered to the control level on day 30. The significant decrease of the colony forming units of soil actinomyces and filamentous fungi can be taken as the sensitive biological indicators of petroleum contamination when soil was amended with 〉15000 mg/kg diesel fuel. The sharp decrease in urease activity was recommended as the most sensitive biochemical indicator of heavy diesel fuel contamination. The shifts in community structure to a community documented by Sphingomonadaceae within a-subgroup of Proteobacteria could be served as a sensitive and precise indicator of diesel fuel contamination. Based on the results described in this paper, the soil function in Shenfu irrigation area was disturbed to some extent.

Analytical methodologies for sensing catechol-O-methyltransferase activity and their applications

Mammalian catechol-O-methyltransferases(COMT)are an important class of conjugative enzymes,which play a key role in the metabolism and inactivation of catechol neurotransmitters,catechol estrogens and a wide range of endobiotics and xenobiotics that bear the catechol group.Currently,COMT inhibitors are used in combination with levodopa for the treatment of Parkinson’s disease in clinical practice.The crucial role of COMT in human health has raised great interest in the development of more practical assays for highly selective and sensitive detection of COMT activity in real samples,as well as for rapid screening and characterization of COMT inhibitors as drug candidates.This review summarizes recent advances in analytical methodologies for sensing COMT activity and their applications.Several lists of biochemical assays for measuring COMT activity,including the probe substrates,along with their analytical conditions and kinetic parameters,are presented.Finally,the challenges and future perspectives in the field,such as visualization of COMT activity in vivo and in situ,are highlighted.Collectively,this review article overviews the practical assays for measuring COMT activities in complex biological samples,which will strongly facilitate the investigations on the relevance of COMT to human diseases and promote the discovery of COMT inhibitors via high-throughput screening.

Irradiation Injury Temporarily Induces Enhancement of APN/CD13 Peptidase Activity on Aorta-gonads-mesonephros (AGM)-derived Stromal Cells

This study was designed to investigate the expression of aminopeptidase N （APN）/CD13 on intraembryonic AGM stromal cells, and the change of its enzymatic activity after irradiation injury. The expression of APN/CD13 on AGM stromal cells was assayed by RT-PCR and immunihistochemistry. After the stromal cells in AGM region were irradiated with 8.0 Gy of ^60Co T-rays, APN/CD13 enzymatic activity was measured by spectrophotometer at different time points. The result showed that AGM stromal cells strongly expressed APN/CD13. The enzymatic activity of APN/CD13 decreased temporarily after irradiation injury, then increased to higher level 4 h after irradiation, and it returned to the pre-irradiation level 24 to 48 h after the irradiation. The enzymatic activity of APN/CD13 was temporarily enhanced after irradiation injury, which might be one of the compensatory mechanisms that promote the hematopoietic recovery after irradiation.

Microbial Function, Enzymatic Activities and Diversity in an Anaerobic-Anoxic-Aerobic Reactor System

Enzymatic activities of beta-gincosidase （ β-GLC ）, （ LAP）, and alkaline phosphatase （ APA）, corresponding to nutrient eliminations, and the microbial community structures were analyzed in an anaerobic-anoxic-aerobic reactor system. Results showed that most activity of β-GLC （64.2 μmoi/（ L · h ）） associated with the largest fraction of small- molecular-weight carbohydrates was found in the aerobic reactor, indicating the existence of coupled hydrolysis-uptake mechanism in the aerobic bacteria. Similar activities of LAP presented in the anoxic and aerobic environments, whose increases accompanied by increments in nitrogen uptake rates greatly accelerated the processes of aerobic nitrification and anoxic denitrification. The highest APA activity displayed in the anaerobic reactor, however, dephosphorization performance was mainly achieved under aerobic condition. Microbial community fingerprints generated by polymerase chain reaction amplification and denaturing gradient gel dectrophoresls （ PCR-DGGE ） revealed that Proteobacterium, Actinobacterium, and Nitrosplra were the predominant classes in the activated sindge and there was no evidence of community variations among each function reactor in the system with biomass recycling.

Effect of Different Bioassay Methods on Enzymatic Characteristics of Cotton Aphid, Aphis gossypfi Glover （Hemiptera：Aphididae）

In this study, the susceptibility of three populations of cotton aphid, Aph＆ gossypii Glover （Hemiptera：Aphididae） was assayed to imidacloprid （35SC） and thiametoxam （50WG）. The involvement of metabolic enzymes in the resistance strain of cotton aphid to the neonicotinoids was determined by the biochemical biomarkers and the resistance mechanism was determined as CaE. In another study, three different bioassay experiments were designed for detecting the susceptibility of cotton aphid to imidacloprid and thiametoxam and the effect of these two insecticides on the enzymatic activity of cotton aphid was assessed in the adult aphids treated with three different bioassay methods using a modified version of the FAO dip test, residue bioassay procedure and starvation method. Our findings suggested that the type of bioassay methods is very important when aphids＇ populations assess for the resistance against the neonicotinod insecticides. It has shown the starvation method is the most reliable method compared with other methods.

Thinning intensity affects microbial functional diversity and enzymatic activities associated with litter decomposition in a Chinese fir plantation

Microbial functional diversity and enzymatic activities are critical to maintaining material circulation during litter decomposition in forests.Thinning,an important and widely used silvicultural treatment,changes the microclimate and promotes forest renewal.However,how thinning affects microbial functional diversity and enzymatic activities during litter decomposition remains poorly understood.We conducted thinning treatments in a Chinese fir plantation in a subtropical region of China with four levels of tree stem removal（0,30,50,and 70%）,each with three replicates,and the effects of thinning on microbial functional diversity and enzymatic activities were studied 7 years after treatment by collecting litter samples four times over a 1-year period.Microbial functional diversity and enzymatic activities were analyzed using Biolog Ecoplates（Biolog Inc.,Hayward,CA,USA）based on the utilization of 31 carbon substrates.Total microbial abundance during litter decomposition was lower after the thinning treatments than without thinning.Microbial functional diversity did not differ significantly during litter decomposition,but the types of microbial carbon-source utilization did differ significantly with the thinning treatments.Microbial cellulase and invertase activities during litter decomposition were significantly higher under the thinning treatments due to changes in the litter carbon concentration and the ratios of carbon and lignin to nitrogen.The present study demonstrated the important influence of thinning on microbial activities during litter decomposition.Moderate-intensity thinning may maximize vegetation diversity and,in turn,increase the available substrate sources for microbial organisms in litter and promote nutrient cycling in forest ecosystems.

Relationships between leaf color changes,pigment levels,enzyme activity,photosynthetic fluorescence characteristics and chloroplast ultrastructure of Liquidambar formosana Hance

Liquidambar formosana Hance is an attractive landscape tree species because its leaves gradually change from green to red,purple or orange in autumn.In this study,the red variety of L.formosana was used to establish a quantitative model of leaf color.Physiological changes in leaf color,pigment levels,enzyme activity,photosynthetic fluorescence characteristics and chloroplast ultrastructure were monitored.The relationship between leaf color and physiological structure indices was quantitatively analyzed to systematically explore the mechanisms behind leaf color.Our data showed that with a decrease in external temperatures,chloroplast numbers and sizes gradually decreased,thylakoid membranes became distorted,and chlorophyll synthesis was blocked and gradually decreased.As a result,chloroplast membranes could not be biosynthesized normally;net photosynthesis,maximum and actual photochemical efficiency,and rate of electron transfer decreased rapidly.Excess light energy caused leaf photoinhibition.With intensification of photoinhibition,leaves protected themselves using two mechanisms.In the first,anthocyanin synthesis was promoted by increasing chalcone isomerase and flavonoid glycosyltransferase activities and soluble sugar content so as to increase anthocyanin to filter light and eliminate reactive oxygen species to reduce photoinhibition.In the second,excessive light energy was consumed in the form of heat energy by increasing the non-photochemical quenching coefficient.These processes tuned the leaves red.

Improvement of Selected Morphological, Physiological, and Biochemical Parameters of Banana (Musa acuminata L.) Using Potassium Silicate under Drought Stress Condition Grown in vitro

Drought stress has become more common in recent years as a result of climate change impacts on the production of banana crops and other fruit trees.The growth and productivity of Musa spp are severely impacted by the gradual degradation of water resources and the erratic distribution pattern of annual precipitation amount.The aim of the work includes increased drought tolerance in light of water scarcity in the world as a result of the bananas’being gluttonous for water needs.This investigation was carried out from 2019 to 2020 to study the effect of potassium silicate on morphological growth and biochemical parameters of Musa acuminata L under drought stress by PEG.As a result,drought stress reduced the morphological characteristics such as shoots number,shoot length,roots number,and survival percentage and biochemical characteristics such as chlorophyll a,b,carotenoids,stomatal status,and RWC.While proline content increased in the leaf of M.acuminata L.Media complemented with K2SiO3(2 to 6 mM)either individually or in combination with PEG led to an improvement in all morphological and biochemical characteristics.The activities of CAT,POD,and PPO enzymes increased significantly compared to control.Furthermore,the lowest PPO,CAT,and POD activity were achieved.Additionally,K2SiO3 treatments under drought stress successfully enhanced the leaf stomatal behavior.Our results suggest that K2SiO3 can help to maintain plant integrity in the tested cultivar under drought stress.