Chlorophyll Fluorescence Parameters Research Articles

Optimum Plant Density Improved Cotton (Gossypium hirsutum L.) Root Production Capacity and Photosynthesis for High Cotton Yield under Plastic Film Mulching

Optimum Plant Density Improved Cotton (Gossypium hirsutum L.) Root Production Capacity and Photosynthesis for High Cotton Yield under Plastic Film Mulching

Involvement of BcERF109 in 1-MCP-delayed yellowing of pak choi (Brassica rapa subsp. Chinensis) via mitigation of major chlorophyll-degrading gene expression during storage

Leaf yellowing is a typical senescence symptom in postharvest pak choi (Brassica rapa subsp. Chinensis). Ethylene response factors (ERFs) are considered important regulators of leaf senescence. This study explored the likely regulatory effects of BcERF on pak choi yellowing via 1-methylcyclopropene (1-MCP) treatments. We identified an ERF transcription factor (TF), BcERF109, which may be involved in ethylene-induced pak choi yellowing. Treatment with 5.0 µL L–1 1-MCP suppressed the transcripts of chlorophyll catabolism genes (BcPPH1, BcRCCR, BcSGR2, and BcNYC1), inhibited decreases in chlorophyll content and chlorophyll fluorescence parameters, delayed chloroplast disintegration, and eventually mitigated yellowing. The treatment also blocked ethylene production and impeded the activities and transcripts of ethylene synthesis enzymes (ACC oxidase [ACO] and 1-aminocyclopropene-1-carboxylate [ACC] synthase [ACS]). In contrast, treatment with 10.0 µL L–1 ethylene accelerated pak choi yellowing, as indicated by greater ethylene production, activities and transcripts of ACO and ACS, and expression of chlorophyll catabolism genes, as well as reductions in chlorophyll content and fluorescence parameters. BcERF109 was identified as a nuclear-localised protein; its transcription levels were downregulated by 1-MCP and upregulated by ethylene. Molecular biology assays revealed that BcERF109 enhanced the transcriptional capacities of BcPPH1, BcRCCR, BcNYC1, and BcSGR2 by binding to their promoters. The transient overexpressing of BcERF109 in tobacco leaves stimulated the expression of endogenous genes (BcPPH1, BcRCCR, BcNYC1, BcSGR2, and BcERF109), leading to accelerated chlorophyll degradation and leaf yellowing. The application of 1-MCP mitigated pak choi yellowing by influencing ethylene synthesis and modulating the regulatory effects of BcERF019 on genes associated with chlorophyll catabolism. These results revealed a new regulatory mechanism involving ERF TFs in 1-MCP-induced delayed yellowing of green vegetables.

Effects of different light conditions on morphological, anatomical, photosynthetic and biochemical parameters of Cypripedium macranthos Sw.

In this study, the morphological (plant height, leaf length and width, stem diameter and leaf number), anatomical (epidermal cell density and thickness, Stomatal length and width), photosynthetic (net photosynthetic rate, transpiration rate, stomatal conductance, intercellular CO2 concentration, relative humidity, leaf temperature and chlorophyll fluorescence parameters) and biochemical parameters (the content of soluble sugar, soluble protein, proline, malondialdehyde and electrical conductivity) of Cypripedium macranthos Sw. in Changbai Mountain were determined under different light conditions (L10, L30, L50, L100). The results showed that morphological values including plant height, leaf area, stem diameter and leaf number of C. macranthos were smaller under the condition of full light at L100. The epidermal cell density and epidermal thickness of C. macranthos were the highest under L30 and L50 treatments, respectively. It had the highest net photosynthetic rate (Pn) and chlorophyll content under L50 treatment. Meanwhile, correlation analysis indicated that photosynthetically active radiation (PAR) and water use efficiency (WUE) were the main factors influencing Pn. C. macranthos accumulated more soluble sugars and soluble proteins under L100 treatment, while the degree of membrane peroxidation was the highest and the plant was severely damaged. In summary, the adaptability of C. macranthos to light conditions is ranked as follows L50 > L30 > L10 > L100. Appropriate light conditions for C. macranthos are 30%-50% of full light, which should be taken into account in protection and cultivation.

Early diagnosis of greenhouse cucumber downy mildew in seedling stage using chlorophyll fluorescence imaging technology

Cucumber downy mildew, caused by Pseudoperonospora cubensis, typically remains hidden from view during its initial infection stage. To address this issue, this study proposed an early diagnosis model for greenhouse cucumber downy mildew. This study was conducted under controlled conditions, utilising a large-scale mobile chlorophyll fluorescence imaging system to monitor the samples during their seedling stage on a daily basis from the first day of inoculation. A total of 98 sets of fluorescence parameter values and corresponding fluorescence images were collected. Machine learning methods, such as recursive feature elimination (RFE) and Least Absolute Shrinkage and Selection Operator (LASSO) regression with L1 regularisation, were used to screen the chlorophyll fluorescence parameter Ft_D3, whose corresponding the chlorophyll fluorescence images were used as inputs to the proposed model, following by employing a convolutional neural network (CNN) transfer learning method to the early detection task of cucumber downy mildew in fluorescence images. The study improved the topology structure of ResNet50, the network model with a learning rate of 0.001 and 16 cycles as the optimal feature extractor. The results indicated that the enhanced network displayed improved performance in early detection of cucumber downy mildew compared with other CNNs. Infected leaves were distinguished from healthy leaves in the early stages of infection, specifically 3 days before the appearance of symptoms. The accuracy of the model in the task of early diagnosis of downy mildew was 94.76%. This study presents an efficient approach for the photosynthetic characterisation and early identification of cucumber downy mildew.

Mechanisms of hormetic effects of ofloxacin on Chlorella pyrenoidosa under environmental-relevant concentration and long-term exposure

Antibiotics are frequently detected in surface water and pose potential threats to organisms in aquatic ecosystem such as microalgae. The occurrence of biphasic dose responses raised the possibility of stimulation of microalgal biomass by antibiotics at environmental-relevant concentration and caused potential ecological risk such as algal bloom. However, the underlying mechanisms of low concentration-induced hormetic effects are not well understood. In this study, we evaluated the hormesis of ofloxacin on Chlorella pyrenoidosa under environmental-relevant concentration and long-term exposure. Results showed the hormetic effects of ofloxacin on cell density and carbon fixation rate (RC). The predicted maximum promotion was 17.45 % by 16.84 μg/L and 20.08 % by 15.78 μg/L at 21 d, respectively. The predicted maximum concentration of non-effect on cell density and RC at 21 d was 3.24 mg/L and 1.44 mg/L, respectively. Ofloxacin induced the mobilization of pigments and antioxidant enzymes to deal with oxidative stress. PCA analysis revealed Chl-a/Chl-b could act as a more sensitive biomarker under acute exposure while chlorophyll fluorescence parameters were in favor of monitoring long-term implication. The hormesis in increased secretion of extracellular organic matters was regarded as a defensive mechanism and accelerated indirect photodegradation of ofloxacin. Bioremoval was dominant and related to biomass accumulation in the total dissipation while abiotic removal appeared slight contributions. This study provided new insights into the understanding of hormesis of microalgae induced by antibiotics.

Transcriptomic profiling reveals the contribution of Nitric Oxide to maintaining photosynthesis and antioxidant ability in Hylotelephium erythrostictum leaves under salt stress

Hylotelephium erythrostictum is a plant species with high garden value and notable salt tolerance, yet the salt tolerance mechanism is poorly understood. In this study, we treated the plants under salt stress with exogenous nitric oxide (NO) and discovered that the content of malondialdehyde (MDA) decreased, while soluble sugar increased. The chlorophyll fluorescence parameters, such as the maximum photochemical efficiency of PS II (Fv/Fm), actual quantum yield Y(II), and the photochemical quenching coefficient (qP) increased, whereas the non-photochemical quenching coefficient (NPQ) decreased. Afterthat, we performed transcriptome sequencing on leaves treated with 200 mM NaCl after 0, 5, and 10 d. A total of 124,008 unigenes were identified and functionally annotated. Transcripts related to NO synthase exhibited increased expression levels, and transcripts related to superoxide dismutase (SOD) and catalase (CAT) were also significantly upregulated. In contrast, the majority of the differently expressed genes (DEGs) associated with photosynthesis and photosynthesis-antenna protein metabolic pathways were downregulated. Furthermore, the expression levels of HeSOD2, HeCAT2, HeCab1, and HepsaA were significantly upregulated. These results suggest that NO enhances the photosynthetic and antioxidant capacity of H. erythrostictum and improves salt tolerance. Our study will lead to a better understanding of how this plant responds to stressful conditions and potentially develop ways to enhance its salt tolerance by identifying salt-tolerance genes.

The application potential of mepiquat chloride in soybean: improvement of yield characteristics and drought resistance

BackgroundDrought can result in yield losses, the application of plant growth regulators is an effective measure to improve drought resistance and yield. The objective of the study was to explore the application potential of mepiquat chloride (MC) in regulating soybean yield and drought resistance.MethodsIn this study, a three-year field experiment was designed and combined with drought experiments to measure the yield of popularized varieties during 2021–2022 and drought-resistant and drought-sensitive varieties were selected, and planted in the field in 2023.ResultsMC increased the yield of HN84 and HN87 for two consecutive years from 2021 to 2022 and improved their physiological characteristics under field conditions. Under M200 treatment, the yield of HN84 increased by 6.93% and 9.46%, and HN87 increased by 11.11% and 15.72%. Different concentrations of MC have different effects on soybeans. The maximum increase of SOD, POD and proline in HN84 under M400 treatment reached 71.92%, 63.26% and 71.54%, respectively; the maximum increase of SOD, POD and proline in HN87 under M200 treatment reached 21.96%, 93.49% and 40.45%, respectively. In 2023, the foliar application of MC improved the physiological characteristics of HN44 and HN65 under drought-stress conditions. On the eighth day of drought treatment, compared to the drought treatment, the leaf and root dry weight of HN44 under M100 treatment increased by 17.91% and 32.76%, respectively; the dry weight of leaves and roots of HN65 increased by 20.74% and 29.29% under M200 treatment, respectively. MC also reduced malondialdehyde (MDA) content, decreased antioxidant enzyme activity and proline content. In addition, different concentrations of MC increased the chlorophyll fluorescence parameters (Fs, Fv/Fm, YII, and SPAD). In the field, the plant height of the two varieties decreased significantly, the yield increased, the number of two-grain and three-grain pods increased, and the stem length at the bottom and middle decreased with MC induction.ConclusionsThe application of 100–200 mg/L MC effectively improved drought resistance and increased yield. This study provided support for the rational application of MC in soybean production.

Regulation of photosynthetic function and reactive oxygen species metabolism in sugar beet (Beta vulgaris L.) cultivars under waterlogging stress and associated tolerance mechanisms

Sugar beet (Beta vulgaris L.) is an economically important sugar crop worldwide that is susceptible to sudden waterlogging stress during seedling cultivation, which poses a major threat to sugar beet development and production. Our understanding of the physiological basis of waterlogging tolerance in sugar beet is limited. To investigate the photosynthetic adaptation strategies of sugar beet to waterlogging stress conditions, the tolerant cultivar KUHN1260 (KU) and sensitive cultivar SV1433 (SV) were grown under waterlogging stress, and their photosynthetic function and reactive oxygen species (ROS) metabolism were assessed. Our results showed that waterlogging stress significantly reduced the photosynthetic pigment content, rubisco activity, and expression level of the photosynthetic enzyme genes SvRuBP, SvGAPDH, and SvPRK, gas exchange parameters, and chlorophyll fluorescence parameters, induced damage to the ultrastructure of the chloroplast of the two sugar beet cultivars, inhibited the photosynthetic carbon assimilation capacity of sugar beet leaves, damaged the structural stability of photosystem II (PSII), and disturbed the equilibrium between electrons at the acceptor and donor sides of PSII, which was the result of stomatal and non-stomatal limiting factors. Moreover, the level of ROS, H2O2, and O2▪−, antioxidant enzyme activity, and gene expression levels in the leaves of the two sugar beet cultivars increased over time under waterlogging stress; ROS accumulation was lower and antioxidant enzyme activities and gene expression levels were higher in the waterlogging-tolerant cultivar (KU) than the waterlogging-sensitive cultivar (SV). In sum, these responses in the more tolerant cultivars are associated with their resistance to waterlogging stress. Our findings will aid the breeding of waterlogging-tolerant sugar beet cultivars.

Comparative Studies on Effects of Simulated Microgravity on Growth and Photosynthetic Parameters in Rice and Mungbean

Microgravity or low gravity environment of space can be simulated on Earth by using clinorotation with appropriate speed of rotation. Previous reports show that microgravity environment (real or simulated) affects growth, chlorophyll content and photosynthetic performance in different plants. However, most of the reports showed variation in results. Earlier studies carried out on simulated microgravity (SMG) using clinorotation in our laboratory showed increase in growth, chlorophyll content and various yield attributes in case of laboratory and field grown rice. Subsequent studies were carried out on mungbean seedlings. In the present work, comparative aspects of these studies are reported. Results of the present study showed increase in growth, chlorophyll content and chlorophyll fluorescence parameters in SMG samples as compared to control samples in rice and mungbean seedlings. Interestingly, percentage of enhancement in growth, chlorophyll content and chlorophyll fluorescence parameters of SMG samples is significantly higher in rice (monocotyledonous) seedlings as compared to mungbean (dicotyledonous).

Estimating of chlorophyll fluorescence parameter Fv/Fm for plant stress detection at peatlands under Ramsar Convention with Sentinel-2 satellite imagery

Monitoring vegetation is essential in Earth Observation (EO) due to its link with the global carbon cycle, playing a crucial role in ecosystem management. The fluorescence of chlorophyll (ChF) is a reliable indicator of plants' photosynthetic activity and growth, especially when they are experiencing unfavourable conditions, particularly in terrestrial wetlands. These wetlands are integral components of the landscape, contributing significantly to climate mitigation, adaptation, biodiversity, and the well-being of both the environment and humanity. We conducted a research study using the XGBoost machine learning algorithm to map the chlorophyll fluorescence parameter Fv/Fm in the Biebrza River Valley, which is known for its marshes, peatlands, and diverse flora and fauna. Our study highlights the benefits of using ensemble classifiers derived from EO Sentinel-2 satellite imagery for accurately mapping Fv/Fm across terrestrial landscapes under the Ramsar Convention at Narew River Valley (Poland) and Čepkeliai Marsh (Lithuania). The XGBoost algorithm provides an accurate estimate of ChF with a robust determination coefficient of 0.747 and minimal bias at 0.013, as validated using in situ data. The precision of Fv/Fm chlorophyll fluorescence parameter estimation from remote sensing sensors depends on the growth stage, emphasizing the importance of identifying the optimal overpass time for S-2 observations. Our study found that biophysical factors, as denoted by spectral indices related to greenness and leaf pigments, were highly impactful variables among the top classifiers. However, incorporating soil, vegetation and meteorological indicators from remote sensing data could further increase the accuracy of chlorophyll fluorescence mapping.

Environmental effects and their impact on yield in adjacent experimental plots of high-stem and short-stem wheat varieties

BackgroundIn regional wheat trials, when short-stem wheat varieties and high-stem wheat varieties are planted adjacent to each other in small plots, changes in their marginal plot environment can lead to bias in yield evaluation. Currently, there is no relevant research revealing the degree of their mutual influence.ResultsIn a regional wheat experiment, when high-stem wheat varieties and short-stem wheat varieties were planted adjacent to one another, there was no significant change in soil temperature or humidity in the high-stem wheat variety experimental plot from November to May compared to the control plot, while the soil humidity in the short-stem wheat variety experimental plot was greater than that in the control plot. In May, the soil temperature of the short-stem wheat varieties in the experimental plot was lower than that in the control plot. Illumination of the wheat canopy in the high-stem wheat variety experimental plot had a significant positive effect in April and May, while illumination of the wheat canopy in the short-stem wheat variety experimental plot had a negative effect. The chlorophyll fluorescence parameters of flag leaves in the high-stem wheat variety experimental plots showed an overall increasing trend, while the chlorophyll fluorescence parameters of flag leaves in the experimental plots of short-stem wheat varieties showed a decreasing trend. The analysis of the economic yield, biological yield, and yield factors in each experimental plot revealed that the marginal effects of the economic yield and 1000-grain weight were particularly significant and manifested as positive effects in the high-stem wheat variety experimental plot and as negative effects in the short-stem wheat variety experimental plot. The economic yield of the high-stem wheat variety experimental plot was significantly greater than that of the control plot, the economic yield of the short-stem wheat variety experimental plot was significantly lower than that of the control plot, and the economic yield of the high-stem experimental plot was significantly greater than that of the short-stem experimental plot. When the yield of the control plot of the high-stem wheat varieties was compared to that of the control plot of the short-stem wheat varieties, the yield of the control plot of the short-stem wheat varieties was significantly greater than that of the control plot of the high-stem wheat varieties.ConclusionsBased on these findings, it is concluded that plots with high-stem and short-stem wheat varieties are adjacent in regional wheat trials, the plots of high-stem wheat varieties are subject to marginal positive effects, resulting in a significant increase in economic yield; the plots of short-stem wheat varieties are subject to marginal negative effects, resulting in a decrease in economic yield. This study reveals the mutual influence mechanism of environment and yield with adjacent planting of high-stem and short-stem wheat varieties in regional wheat trials, providing a useful reference and guidance for optimizing the layout of regional wheat trials.

The responses of pepper plants to nitrogen form and dissolved oxygen concentration of nutrient solution in hydroponics

BackgroundThe presence of oxygen in the growth medium is absolutely essential for root development and the overall metabolic processes of plants. When plants do not have an adequate oxygen supply for respiration, they can experience a condition known as hypoxia. In order to investigate the impact of different nitrogen forms and varying oxygen levels in nutrient solutions on the growth, photosynthesis, and chlorophyll fluorescence parameters of bell pepper plants, a comprehensive study was conducted. The experiment was designed as a factorial experiment, considering two main factors: nitrogen forms (calcium nitrate and ammonium sulfate) with a fixed nitrogen concentration of 5 mM, and the oxygen levels of the nutrient solutions (ranging from 1.8 ± 0.2 to 5.3 ± 0.2 mg. L-1).ResultsThe study examined the effects of nitrogen (NH4+ and NO3−) application on various parameters of vegetative growth. The results demonstrated that the use of ammonium (NH4+) led to a reduction in the most measured parameters, including the fresh and dry mass of both the root and shoot, at low O2 concentrations of 1.8 ± 0.2; 2.6 ± 0.2 and 3.8 ± 0.2 mg. L-1. However, an interesting observation was made regarding the impact of oxygen levels on root growth in plants grown with nitrate (NO3−). Specifically, the highest levels of oxygen significantly increased root growth in NO3−-fed plants. Additionally, the application of NH4+ resulted in an increase in chlorophyll concentration in the leaves, particularly when combined with high oxygen levels in the nutrient solution. On the other hand, leaves of plants fed with NO3− exhibited higher photosynthetic rate (A), intrinsic water use efficiency (iWUE), and instantaneous carboxylation efficiency (A/Ci) compared to those fed with NH4+. Furthermore, it was found that NO3−-fed plants displayed the highest instantaneous carboxylation efficiency at oxygen levels of 3.8 and 5.3 mg. L-1, while the lowest efficiency was observed at oxygen levels of 1.8 and 2.6 mg. L-1. In contrast, NH4+-grown plants exhibited a higher maximal quantum yield of PSII photochemistry (Fv/Fm), as well as increased variable fluorescence (Fv) and maximum fluorescence (Fm), compared to NO3−-grown plants. Interestingly, the NO3−-fed plants showed an increase in Fv/Fm, Fv, and Fm with the elevation of oxygen concentration in the nutrient solution up to 5.3 mg. L-1.ConclusionThis study showed that, the growth and photosynthesis parameters in bell pepper plants are sensitive to oxygen stress in floating hydroponic culture. Therefore, the oxygen level in the nutrient solution must not be lower than 3.8 and 5.3 mg. L-1 in NH4+ and NO3− –supplied culture media or nutrient solutions, respectively.

Genetic dissection of ten photosynthesis-related traits based on InDel- and SNP-GWAS in soybean.

A total of 416 InDels and 112 SNPs were significantly associated with soybean photosynthesis-related traits. GmIWS1 and GmCDC48 might be related to chlorophyll fluorescence and gas-exchange parameters, respectively. Photosynthesis is one of the main factors determining crop yield. A better understanding of the genetic architecture for photosynthesis is of great significance for soybean yield improvement. Our previous studies identified 5,410,112 single nucleotide polymorphisms (SNPs) from the resequencing data of 219 natural soybean accessions. Here, we identified 634,106 insertions and deletions (InDels) from these 219 accessions and used these InDel variations to perform principal component and linkage disequilibrium analysis of this population. The genome-wide association study (GWAS) were conducted on six chlorophyll fluorescence parameters (chlorophyll content, light energy absorbed per reaction center, quantum yield for electron transport, probability that a trapped exciton moves an electron into the electron transport chain beyond primary quinone acceptor, maximum quantum yield of photosystem II primary photochemistry in the dark-adapted state, performance index on absorption basis) and four gas-exchange parameters (intercellular carbon dioxide concentration, stomatal conductance, net photosynthesis rate, transpiration rate) and revealed 416 significant InDels and 112 significant SNPs. Based on GWAS results, GmIWS1 (encoding a transcription elongation factor) and GmCDC48 (encoding a cell division cycle protein) with the highest expression in the mapping region were determined as the candidate genes responsible for chlorophyll fluorescence and gas-exchange parameters, respectively. Further identification of favorable haplotypes with higher photosynthesis, seed weight and seed yield were carried out for GmIWS1 and GmCDC48. Overall, this study revealed the natural variations and candidate genes underlying the photosynthesis-related traits based on abundant phenotypic and genetic data, providing valuable insights into the genetic mechanisms controlling photosynthesis and yield in soybean.

Photosynthetic response of Chlamydomonas reinhardtii and Chlamydomonas sp. 1710 to zinc toxicity.

Zinc (Zn) is an essential trace element but can lead to water contamination and ecological deterioration when present in excessive amounts. Therefore, investigating the photosynthetic response of microalgae to Zn stress is of great significance. In this study, we assessed the photosynthetic responses of neutrophilic Chlamydomonas reinhardtii and acidophilic Chlamydomonas sp. 1710 to Zn exposure for 96 h. The specific growth rate (μ), chlorophyll-a (Chl-a) content, and chlorophyll fluorescence parameters were determined. The results demonstrated that Chlamydomonas sp. 1710 was much more tolerant to Zn than C. reinhardtii, with the half-maximal inhibitory concentration (IC50) values of 225.4 mg/L and 23.4 mg/L, respectively. The μ and Chl-a content of C. reinhardtii decreased in the presence of 15 mg/L Zn, whereas those of Chlamydomonas sp. 1710 were unaffected by as high as 100 mg/L Zn. Chlorophyll fluorescence parameters indicated that the regulation of energy dissipation, including non-photochemical quenching, played a crucial role in Zn stress resistance for both Chlamydomonas strains. However, in the case of C. reinhardtii, non-photochemical quenching was inhibited by 5 mg/L Zn in the first 48 h, whereas for Chlamydomonas sp. 1710, it remained unaffected under 100 mg/L Zn. Chlamydomonas sp. 1710 also exhibited a 20 times stronger capacity for regulating the electron transfer rate than C. reinhardtii under Zn stress. The light energy utilization efficiency (α) of Chlamydomonas sp. 1710 had the most highly non-linear correlation with μ, indicating the energy utilization and regulation process of Chlamydomonas sp. 1710 was well protected under Zn stress. Collectively, our findings demonstrate that the photosystem of Chlamydomonas sp. 1710 is much more resilient and tolerant than that of C. reinhardtii under Zn stress.

Adventitious root formation confers waterlogging tolerance in cowpea (Vigna unguiculata (L.) Walp.)

Crop adaptation to waterlogging stress necessitates alterations in their morpho-physiological and biochemical characteristics. Cowpeas, which serve as a dual-purpose legume crop (food and fodder), are sensitive to waterlogging stress, especially when exposed to extended periods of water stagnation during the early growth stage. In this study, we subjected five distinct and superior cowpea varieties to 10 days of waterlogging stress at the early seedling stage (V2, 15 days post emergence for 10 days) under controlled conditions. The aim was to comprehend the response of these varieties and identify the ideal trait for screening a large collection of cowpea genetic resources for waterlogging tolerance. We measured and analyzed changes in morpho-physiological and root parameters to gain a deeper understanding of the mechanism underlying waterlogging tolerance. The treatment (waterlogging and control), genotype, and their interactions had a significant impact on the most studied traits (p < 0.05). The results indicated a significant reduction in morpho-physiological parameters such as plant height, leaf area, leaf number, Normalized Difference Vegetation Index (NDVI), chlorophyll content, and chlorophyll fluorescence parameters under stress treatment than control conditions. However, root parameters like the number of adventitious roots (AR) and their length (ARL) significantly increased under waterlogging stress in tolerant cowpea varieties like DC15 and PL4. Correlation and PCA analyses further revealed a positive and significant association between cowpeas’ waterlogging tolerance and AR formation and its AR length. Therefore, the current study reveals that swift development of AR and ARL may serve as potential traits conferring waterlogging tolerance in cowpeas. Using suitable mapping populations, these traits could reveal genomic regions associated with waterlogging tolerance in cowpeas. The tolerant varieties and key traits identified in this study could be beneficial in breeding programs aimed at enhancing waterlogging tolerance in cowpeas.

Effect of ethylene production by four pathogenic fungi on the postharvest diseases of green pepper (Capsicum annuum L.)

Ethylene produced by plants generally induces ripening and promotes decay, whereas the effect of ethylene produced by pathogens on plant diseases remains unclear. In this study, four ethylene-producing fungi including Alternaria alternata (A. alternata, Aa), Fusarium verticilliodes (F. verticillioides, Fv), Fusarium fujikuroi 1 (F. fujikuroi 1, Ff-1) and Fusarium fujikuroi 2 (F. fujikuroi 2, Ff-2) were severally inoculated in potato dextrose broth (PDB) media and postharvest green peppers, the ethylene production rates, disease indexes and chlorophyll fluorescence parameters were determined. The results showed that Ff-2 and Fv in the PDB media had the highest and almost the same ethylene production rates. After inoculation with green peppers, Ff-2 treated group still exhibited the highest ethylene production rate, whereas Aa treated group had a weak promotion effect on ethylene production. Moreover, the ethylene production rate of green peppers with mechanical injury was twice that without mechanical injury, and the ethylene production rates of green peppers treated with Aa, Ff-1, Ff-2 and Fv were 1.2, 2.6, 3.8 and 2.8 folds than those of green peppers without treatment, respectively. These results indicated that pathogen infection stimulated the synthesis of ethylene in green peppers. Correlation analysis indicated that the degreening of Fusarium-infected green pepper was significantly positively correlated with the ethylene production rate of green pepper, whereas the disease spot of Aa-infected green pepper had a significant positive correlations with the ethylene production rate of green peppers. Chlorophyll fluorescence results showed that the green peppers already suffered from severe disease after being infected with fungi for 4 days, and Fusarium infection caused early and serious stress, while the harm caused by A. alternata was relatively mild at the early stage. Our results clearly showed that α-keto-γ-methylthiobutyric acid (KMBA)-mediated ethylene synthesis was the major ethylene synthesis pathway in the four postharvest pathogenic fungi. All the results obtained suggested that ethylene might be the main infection factor of Fusarium spp. in green peppers. For pathogenic fungi, stimulating green peppers to produce high level of ethylene played a key role in the degreening of green peppers.

Toxic effect of ciprofloxacin on the photosynthesis reactions in microalga Scenedesmus quadricauda (Turp.) Bréb.

Ciprofloxacin (CIP) is widely used broad-spectrum antimicrobial drug of fluoroquinolone family. The widespread use of ciprofloxacin increases its release into the environment. Ciprofloxacin is detected in aquatic ecosystems potentially harming aquatic organisms. The CIP effect on photosynthetic organisms is not fully studied. In this study we examined the CIP effect on green freshwater microalgae Scenedesmus quadricauda (Turp.) Bréb. using chlorophyll fluorescence methods (JIP test parameters and rapid light curves). A significant decrease in the cell number was observed at ≥10 mg/L of сiprofloxacin in comparison with control. Analysis of chlorophyll fluorescence parameters obtained from OJIP transients revealed the changes in photosynthetic reactions in сiprofloxacin treatment. Ciprofloxacin was found to inhibit electron transport rate in photosystem II (PSII). The decrease in the quantum yield of electron transport in photosystem II (φEo) was accompanied by the decrease in performance index (PIABS) and an increase in energy dissipation (DI0/RC). Ciprofloxacin enhanced the photosensitivity of microalgae but did not inhibit the recovery of photosynthetic activity after the photooxidative stress. In this regard the effect of CIP differs from that of the well-known antibiotic chloramphenicol that inhibits the resynthesis of plastid proteins and, accordingly, the recovery of photosynthetic activity associated with the resynthesis of PSII protein D1. Among the fluorescence parameters, PIABS was found to be the most stress-specific; therefore it can be proposed to detect an early toxic CIP effect in microalgae.

Response of photosynthetic pigments, gas exchange and chlorophyll fluorescence parameters to light quality in Phoebe bournei seedlings

Response of photosynthetic pigments, gas exchange and chlorophyll fluorescence parameters to light quality in Phoebe bournei seedlings

Responses of leaf traits to altitude in Quercus aquifolioides and Sorbus rehderiana on the eastern edge of the Qinghai-Tibet Plateau, China.

As the most senstitive plant organs to environmental changes, leaves serve as crucial indicators of plant survival strategies. We measured the morphology, anatomical traits, gas exchange parameters, and chlorophyll fluorescence parameters of Quercus aquifolioides (evergreen broad-leaved) and Sorbus rehderiana (deciduous broad-leaved) at altitudes of 2600, 2800, 3000, 3200 and 3400 m on the eastern edge of the Qinghai-Tibet Plateau, China. We explored the similarity and difference in their responses to altitude change and the ecological adaptation strategy. The results showed that as the altitude increased, leaf dry matter content of Q. aquifolioides decreased, that of S. rehderiana increased, leaf size for both species gradually decreased, and the palisade coefficient of Q. aquifolioides showed a decreasing trend, contrasting with the increasing trend in S. rehderiana. As the altitude increased, the thickness of leaves, palisade tissue, spongy tissue, upper epidermis, and lower epidermis of both species increased significantly, with the increment of 22.4%, 4.9%, 45.1%, 23.3%, 19.6%, and 28.2%, 46.9%, 8.9%, 25.9%, 20.8% at altitude of 3400 m, respectively, compared with the altitude of 2600 m. The gas exchange and chlorophyll fluorescence parameters of S. rehderiana significantly increased with increasing altitude, while Q. aquifolioides showed the opposite trend. Leaf anatomical traits, gas exchange, and chlorophyll fluorescence parameters of both species displayed considerable plasticity. There were significant correlations among most leaf traits and between leaf traits and altitude. The survival strategy of Q. aquifolioides was more conservative in response to altitude changes, while that of S. rehderiana was more active. Both species adapted to different altitudes by adjusting their own traits.

Comparative physiological and anatomical responses of Tagetes erecta L. and Zinnia elegans Jacq. seedlings to AgNO3 and ZnSO4 metals and their nanoparticles

Heavy metals (HMs) pose a significant ecological risk due to their enduring presence in the ecosystem. They become more prevalent as a result of urbanization and industrialization, disrupting critical functions of plant life such as photosynthesis, seedling growth, and germination. Understanding the impact of HMs and nanoparticle exposure on plants is crucial for developing effective strategies to mitigate their potential hazards. Therefore, an effort was made to elucidate the impact of biosynthesized Ag NPs (nanoparticles) and ZnO NPs versus their precursor metal salts, AgNO3 and ZnSO4, respectively on two Asteraceous plants, Mexican marigold (Tagetes erecta L.) and Zinnia (Zinnia elegans Jacq.) in hydroponic solution by monitoring the changes in photosynthetic pigments and their associated photochemistry of photosystem II along with the anatomical attributes. In the present study, two concentrations (50 μM and 100 μM) for each treatments viz., AgNO3, Ag NPs, ZnSO4 and ZnO NPs were given to the seedlings. Metal salts were found to be more toxic than their nanoparticles, and this was manifested in terms of reduction in photosynthetic pigments, especially chlorophylla content (by 32% in marigold and 27% in Zinnia upon exposure to 100 µM of AgNO3, respectively) in both test seedlings. Reduction in chlorophyll fluorescence parameters was also found under metal as well as nanoparticle toxicity. In contrast, energy flux parameters such as absorption of photon per active reaction centre (ABS/RC), trapped energy flux per active reaction centre (TR0/RC), electron transport flux per active reaction centre (ET0/RC) and energy dissipation flux per active reaction centre (DI0/RC) increased significantly to cope with stress toxicity. Similarly, metals and nanoparticles also distorted the anatomy of the root and leaf, and the effect was more intense under AgNO3 treatment than with ZnSO4 in Zinnia. In conclusion, Zinnia seedlings were more resilient towards all the tested conditions, which might be attributed to their adaptability to various environmental factors, indicating their potential for thriving in diverse climates.