The Influence of Cadmium on Fountain Grass Performance Correlates Closely with Metabolite Profiles.

The relationship between metabolite changes and biological endpoints in response to cadmium (Cd) stress remains unclear. Fountain grass has good Cd enrichment and tolerance abilities and is widely used in agriculture and landscaping. We analyzed the metabolic responses by detecting the metabolites through UPLC-MS and examined the relationships between metabolite changes and the characteristics of morphology and physiology to different Cd stress in fountain grass. Our results showed that under Cd stress, 102 differential metabolites in roots and 48 differential metabolites in leaves were detected, with 20 shared metabolites. Under Cd stress, most of the carbohydrates in leaves and roots decreased, which contributed to the lowered leaf/root length and fresh weight. In comparison, most of the differential amino acids and lipids decreased in the leaves but increased in the roots. Almost all the differential amino acids in the roots were negatively correlated with root length and root fresh weight, while they were positively correlated with malondialdehyde content. However, most of the differential amino acids in the leaves were positively correlated with leaf length and leaf fresh weight but negatively correlated with malondialdehyde content. Metabolic pathway analysis showed that Cd significantly affects seven and eight metabolic pathways in the leaves and roots, respectively, with only purine metabolism co-existing in the roots and leaves. Our study is the first statement on metabolic responses to Cd stress and the relationships between differential metabolites and biological endpoints in fountain grass. The coordination between various metabolic pathways in fountain grass enables plants to adapt to Cd stress. This study provides a comprehensive framework by explaining the metabolic plasticity and Cd tolerance mechanisms of plants.

Optimization of culture medium for in vitro germination and storage conditions of Exochorda racemosa pollen.

Pollen morphology, pollen vigor, and long-term pollen storage are critical for plant cross-breeding and genetic improvement of Exochorda racemosa. We developed a protocol for viability determination and storage of E. racemosa pollen for breeding new varieties. The medium components for E. racemosa pollen germination was optimized by using an Orthogonal Assay Test Strategy (OATS). The germination rates of E. racemosa pollen were investigated after storing at different temperatures and different storage periods. The size of E. racemosa pollen was medium with three germination ditches, and the sculptural type of pollen was striate. Red ink and 2,3,5-triphenyl tetrazolium chloride (TTC) can effectively distinguish viable pollen from the unviable pollen of E. racemosa. The most suitable medium (CK2) for E. racemosa was composed of 150 g· L-1 sucrose, 100 mg·L-1 boric acid, 150 mg· L-1 Ca(NO3)2 and 50 mg· L-1 GA3. Low-temperature stress produced the greater inhibition of pollen tube growth compared with high-temperature conditions. The CK2 medium at pH 6.5 resulted in the highest pollen germination rate and most extended pollen tube length. The optimal temperature for storage of dried pollen was -80°C (P < 0.01), and the germination rate was 53.60% after storage for 390 days. Thawing in a 35°C water bath produced the best viability of E. racemosa pollen after storage at -20°C and -80°C. The short-term storage of E. racemosa fresh pollen at 4°C was better than that at -20°C and -80°C (P < 0.01). It is possible to evaluate pollen quality and store pollen grains for E. racemosa by the parameters defined in this study.

First Report of Colletotrichum aenigma Causing Anthracnose of tree peony in China.

Tree peonies (Paeonia suffruticosa Andr. and hybrids) are well-known ornamental and medicinal plants cultivated in temperate and subtropical regions around the world. From June to September 2021, severe leaf spot disease was observed on 3 tree peony cultivars ('Luoyanghong', 'Moyushenghui', 'Roufurong') in Xinxiang (35º29´N, 113º95´E) and Luoyang (34º64´N, 112º49´E), Henan Province, China. Leaf spot incidence was as high as 28% ('Luoyanghong'), 45% ('Moyushenghui') and 67% ('Roufurong'), respectively. Symptoms appeared initially as small purple spots less than 1 mm in diameter in the middle and upper parts of the leaves, and then evolved to coalescent lesions, causing brown scorch ultimately. From each cultivar, 5 diseased leaves were collected. Leaflet tissues (3-4 mm2) cut from spot margins were surface sterilized in 75% alcohol for 45 s, washed 5 times with sterile distilled water, and then cultivated on potato dextrose agar (PDA) medium at 28 °C in the dark. Eleven isolates were obtained, and colonies grown from single conidia on PDA were 80-85 mm in diameter after 10 d, with scattered small, dark-based spikes on the surface of the colonies. The aerial mycelium was cottony, dense, and dark gray near the center on the reverse side. Conidia were cylindrical to clavate, with rounded apex and rounded base, and the conidia contents were granular, 8.44-14.06×3.60-4.31 µm (mean=11.28×3.69 µm, n=40). Appressoria were mostly subglobose or with a few broad lobes, pale to medium brown, 3.36-6.72×3.35-5.60 µm (mean=5.02×4.55 µm, n=20). Based on the culture representation and conidial morphology, the isolates were characterized as Colletotrichum gloeosporioides species complex (Weir et al. 2012; Fu et al. 2019). To further identity the species, the actin (ACT), calmodulin (CAL), chitin synthase (CHS-1), glyceraldehyde-3-phosphate dehydrogenase (GAPDH), and the ribosomal internal transcribed spacers (ITS) loci of isolates PSW0002, PSW0008 and PSW0009 were amplified using ACT-512F/ACT-783R, CL1C/CL2C, CHS-79F/CHS-345R, GDF/GDR, and ITS1/ITS4, primers (Weir et al. 2012; Schena et al; 2014; Kim et al. 2021; Li et al. 2021). Fifteen sequences were deposited in GenBank (ACT for OP225605, OP225606, and OP225607, CAL for OP225608, OP225609 and OP225610, CHS for OP225611, OP225612 and OP225613, GAPDH for ON321897, OP225614, and OP225615, and ITS for ON323473, OP214349 and OP214350 ), which showed 100% sequence similarity to Colletotrichum aenigma (JX009443 and JX009519 for ACT, JX009683 and JX009684 for CAL, JX009774 and JX009903 for CHS-1, JX010244 and JX009913 for GAPDH, JX010243 and JX010148 for ITS). Three isolates clustered with C. aenigma (ex-holotype culture ICMP 18608) in the multi-locus phylogenetic tree with a bootstrap value of 100%. To achieve Koch's postulates, pathogenicity was tested on 5-year-old healthy potted plants ('Luoyanghong'). Thirty leaves were inoculated with 10 µL conidial suspension (isolate PSW0002, 1×106 conidia/mL) and the controls were inoculated with sterile water. Plants were placed in a greenhouse at 28°C under conditions with 12 h photoperiod and 90% relative humidity. After 5 to 10 days, distinct spots were observed on the inoculated leaves, while the control leaves showed no symptoms. C. aenigma was reisolated from all inoculated leaves, but not from the control. C. aenigma has been reported to cause anthracnose on Pyrus pyrifolia (Weir et al. 2012), Camellia sasanqua (Chen et al. 2019), Juglans regia (Wang et al. 2020), Paeonia ostii (Ren et al. 2020), and Capsicum annuum (Sharma et al. 2022). A previous study reported C. gloeosporioides as a pathogen of anthracnose in tree peonies in China (Xuan et al. 2017), the typical symptoms were big necrotic lesions (5-10 mm diam) on leaves，which were significantly different from those caused by C. aenigma. To our knowledge, this is the first report of C. aenigma causing anthracnose in tree peonies in China. This finding may help to take effective control of anthracnose in tree peonies.

Combining Metabolic Analysis With Biological Endpoints Provides a View Into the Drought Resistance Mechanism of Carex breviculmis.

Metabolomics is an effective tool to test the response of plants to environmental stress; however, the relationships between metabolites and biological endpoints remained obscure in response to drought stress. Carex breviculmis is widely used in forage production, turf management, and landscape application and it is particularly resistant to drought stress. We investigated the metabolomic responses of C. breviculmis to drought stress by imposing a 22-day natural soil water loss. The results showed that water-deficit restrained plant growth, reducing plant height, leaf fresh weight, and total weight, however, increasing soluble protein content and malondialdehyde content. In total, 129 differential metabolites in the leaves were detected between drought and control using the Ultrahigh Performance Liquid Chromatography-Mass Spectrometer (UPLC-MS) method. Drought enhanced most of the primary and secondary metabolites in the differential metabolites. Almost all the sugars, amino acids, organic acids, phytohormones, nucleotides, phenylpropanoids and polyketides in the differential metabolites were negatively correlated with plant height and leaf fresh weight, while they were positively correlated with soluble protein content and malondialdehyde content. Metabolic pathway analysis showed that drought stress significantly affected aminoacyl-tRNA biosynthesis, TCA cycling, starch and sucrose metabolism. Our study is the first statement on metabolomic responses to drought stress in the drought-enduring plant C. breviculmis. According to the result, the coordination between diverse metabolic pathways in C. breviculmis enables the plant to adapt to a drought environment. This study will provide a systematic framework for explaining the metabolic plasticity and drought tolerance mechanisms of C. breviculmis under drought stress.

Multi-omics analysis reveals the influence of tetracycline on the growth of ryegrass root.

Environmental factors, including antibiotics such as tetracycline, can alter biological processes in plants. To ascertain how cell/tissue response to tetracycline, a multi-omic analysis was implemented to explore the molecular mechanism of tetracycline influencing the growth of ryegrass root. Tetracycline induced extensive changes in the root metabolome in plants, particularly impacting metabolites of flavonoid metabolic pathways, which were supported through consistent differences between transcriptome and proteome. Cross-comparison between mRNA and protein contents considered the authentication of congruence with related metabolites and revealed changes of several biological processes under tetracycline stress. Overall, we present an undemanding multi-omic strategy to survey the significant influence on the root under tetracycline stress.

Biochar-Stimulated Pumpkin Performance Under Cadmium Stress Is Strongly Linked to Metabolite Pattern.

In this study, pumpkin seedlings were subjected to cadmium stress (100 mg/L cadmium ion solution, 10 days) without or with wheat straw biochar at different concentrations (0%, 0.5%, 1%, and 2% w/v). As the biochar concentration increased, the amount of cadmium accumulated in the root and stem of pumpkin seedlings decreased and the fresh weight of root, stem and leaf increased. The highest cadmium concentration was in the root, followed by the stem and then the leaf. 1% and 2% biochar treatments reduced the oxidative stress of cadmium to seedlings, and added the contents of fatty acid, carbohydrate, amino acid and indoleacetic acid in the root. With the increase of biochar concentration, the metabolites promoting root growth increased. These results provide new information about how biochar alleviates cadmium stress by affecting the metabolic response.

Providing a view for toxicity mechanism of tetracycline by analysis of the connections between metabolites and biologic endpoints of wheat.

Metabolomics is an implement for testing the toxicity of antibiotics, and provides a comprehensive view of the overall response to stress; however, the connections between metabolites and biologic endpoints keep unclear in response to antibiotics. In this study, wheat seeds were exposed to tetracycline for 5 days. The results proved that tetracycline restrained growth, reduced chlorophyl and carotinoid contents and cell permeability, and increased reactive oxygen species (ROS) levels and malondialdehyde (MDA) content. Orthogonal partial least squares (OPLS) was used to analyze the connections between metabolites and biologic endpoints, which discovered that 11 metabolic pathways were significantly affected by tetracycline, and amino acid metabolism could largely apply to root growth and ROS accumulation, while carbohydrate metabolism could have a ruling effect on tetracycline-induced cell permeability. 13 metabolites all played active roles in mediating tetracycline's effects on root length, root fresh weight and cell permeability but had no significant effects on ROS levels. The majority of metabolites with passive effects on root length, root fresh weight and cell permeability had active effects on ROS levels. These results offer a view about stress reaction of wheat to tetracycline.

Effects of tetracycline on growth, oxidative stress response, and metabolite pattern of ryegrass.

Tetracycline is an antibiotic that frequently contaminates the environment. In this study, the growth and metabolites of ryegrass seedlings treated with tetracycline (0, 1, 10 or 100 mg/L) for 5 days were investigated. The results showed that the growth of ryegrass and the concentrations of carotenoid and chlorophyll decreased as the tetracycline concentration increased. Tetracycline increased the production of reactive oxygen species (ROS) and cell permeability and triggered mitochondrial membrane potential loss in the roots of ryegrass. The metabolic profiles of ryegrass differed between the control and tetracycline-treated groups. The contents of glucose, shikimic acid, aconitic acid, serine, lactose, phenylalanine, mannitol, galactose, gluconic acid, asparagine, and glucopyranose were positively correlated with root length and had high variable importance projection values. These compounds may have crucial functions in root extension. Tetracycline also affected aminoacyl-tRNA biosynthesis, nitrogen metabolism, and alanine, aspartate and glutamate metabolism in the roots. Tetracycline may affect root extension by regulating the synthesis/degradation of these metabolites or the activity of their biosynthetic pathways. These results provide an insight into the stress response of ryegrass to tetracycline.

Responses of soil enzymatic activities to transgenic Bacillus thuringiensis (Bt) crops - A global meta-analysis.

Transgenic Bacillus thuringiensis (Bt) crops have been widely planted, and the resulting environmental risks have attracted extensive attention. To foresee the impacts of Bt crops on soil quality, it is essential to understand how Bt crops alter the soil enzymatic activities and what the important influencing factors are. We compiled data from 41 published papers that studied soil enzymatic activities with Bt crops and their non-Bt counterparts. The results showed that dehydrogenase and urease significantly increased, but neutral phosphatase significantly decreased under Bt crop cultivations without Bt residues incorporation. The activities of dehydrogenase, ß-glucosidase, urease, nitrate reductase, alkaline phosphatase, and aryl sulfatase significantly increased under Bt crop cultivation with Bt residues incorporation. The response ratios of other enzymes were not significantly changed. Generally, the response ratios of soil enzymes were greater with Bt residues incorporation than those of Bt crop cultivations without Bt residues incorporation. Further, the response ratios of soil enzymes varied with Bt crop types and growth periods. It was the strongest under Bt cotton among Bt crops, and the significant responses usually appeared in the middle growth stages. The responses of soil enzymes ascribed more to the properties of Bt crops than to soil properties across sites. Given - significant responses of some soil enzymes to Bt crops, we recommended that soil environmental risks should be carefully evaluated over the transgenic crops.

Shifting plant species composition in response to climate change stabilizes grassland primary production.

The structure and function of alpine grassland ecosystems, including their extensive soil carbon stocks, are largely shaped by temperature. The Tibetan Plateau in particular has experienced significant warming over the past 50 y, and this warming trend is projected to intensify in the future. Such climate change will likely alter plant species composition and net primary production (NPP). Here we combined 32 y of observations and monitoring with a manipulative experiment of temperature and precipitation to explore the effects of changing climate on plant community structure and ecosystem function. First, long-term climate warming from 1983 to 2014, which occurred without systematic changes in precipitation, led to higher grass abundance and lower sedge abundance, but did not affect aboveground NPP. Second, an experimental warming experiment conducted over 4 y had no effects on any aspect of NPP, whereas drought manipulation (reducing precipitation by 50%), shifted NPP allocation belowground without affecting total NPP. Third, both experimental warming and drought treatments, supported by a meta-analysis at nine sites across the plateau, increased grass abundance at the expense of biomass of sedges and forbs. This shift in functional group composition led to deeper root systems, which may have enabled plant communities to acquire more water and thus stabilize ecosystem primary production even with a changing climate. Overall, our study demonstrates that shifting plant species composition in response to climate change may have stabilized primary production in this high-elevation ecosystem, but it also caused a shift from aboveground to belowground productivity.

Climate warming reduces the temporal stability of plant community biomass production.

Anthropogenic climate change has emerged as a critical environmental problem, prompting frequent investigations into its consequences for various ecological systems. Few studies, however, have explored the effect of climate change on ecological stability and the underlying mechanisms. We conduct a field experiment to assess the influence of warming and altered precipitation on the temporal stability of plant community biomass in an alpine grassland located on the Tibetan Plateau. We find that whereas precipitation alteration does not influence biomass temporal stability, warming lowers stability through reducing the degree of species asynchrony. Importantly, biomass temporal stability is not influenced by plant species diversity, but is largely determined by the temporal stability of dominant species and asynchronous population dynamics among the coexisting species. Our findings suggest that ongoing and future climate change may alter stability properties of ecological communities, potentially hindering their ability to provide ecosystem services for humanity.

Estimation of nutrient discharge from the Yangtze River to the East China Sea and the identification of nutrient sources.

Based on a time-series dataset and the mass balance method, the contributions of various sources to the nutrient discharges from the Yangtze River to the East China Sea are identified. The results indicate that the nutrient concentrations vary considerably among different sections of the Yangtze River. Non-point sources are an important source of nutrients to the Yangtze River, contributing about 36% and 63% of the nitrogen and phosphorus discharged into the East China Sea, respectively. Nutrient inputs from non-point sources vary among the sections of the Yangtze River, and the contributions of non-point sources increase from upstream to downstream. Considering the rice growing patterns in the Yangtze River Basin, the synchrony of rice tillering and the wet seasons might be an important cause of the high nutrient discharge from the non-point sources. Based on our calculations, a reduction of 0.99Tg per year in total nitrogen discharges from the Yangtze River would be needed to limit the occurrences of harmful algal blooms in the East China Sea to 15 times per year. The extensive construction of sewage treatment plants in urban areas may have only a limited effect on reducing the occurrences of harmful algal blooms in the future.

Leaf P increase outpaces leaf N in an Inner Mongolia grassland over 27 years.

The dynamics of leaf nitrogen (N) and phosphorus (P) have been intensively explored in short-term experiments, but rarely at longer timescales. Here, we investigated leaf N : P stoichiometry over a 27-year interval in an Inner Mongolia grassland by comparing leaf N : P concentration of 2006 with that of 1979. Across 80 species, both leaf N and P increased, but the increase in leaf N lagged behind that of leaf P, leading to a significant decrease in the N : P ratio. These changes in leaf N : P stoichiometry varied among functional groups. For leaf N, grasses increased, woody species tended to increase, whereas forbs showed no change. Unlike leaf N, leaf P of grasses and forbs increased, whereas woody species showed no change. Such changes may reflect N deposition and P release induced by soil acidification over the past decades. The interannual effect of precipitation may somewhat have reduced the soil available N, leading to the more modest increase of leaf N than of leaf P. Thus, leaf N : P stoichiometry significantly responded to long-term environmental changes in this temperate steppe, but different functional groups responded differently. Our results indicate that conclusions of plant stoichiometry under short-term N fertilization should be treated with caution when extrapolating to longer timescales.

UV radiation is the primary factor driving the variation in leaf phenolics across Chinese grasslands.

Due to the role leaf phenolics in defending against ultraviolet B (UVB) under previously controlled conditions, we hypothesize that ultraviolet radiation (UVR) could be a primary factor driving the variation in leaf phenolics in plants over a large geographic scale. We measured leaf total phenolics, ultraviolet-absorbing compounds (UVAC), and corresponding leaf N, P, and specific leaf area (SLA) in 151 common species. These species were from 84 sites across the Tibetan Plateau and Inner Mongolian grasslands of China with contrasting UVR (354 vs. 161 mW/cm(2) on average). Overall, leaf phenolics and UVAC were all significantly higher on the Tibetan Plateau than in the Inner Mongolian grasslands, independent of phylogenetic relationships between species. Regression analyses showed that the variation in leaf phenolics was strongly affected by climatic factors, particularly UVR, and soil attributes across all sites. Structural equation modeling (SEM) identified the primary role of UVR in determining leaf phenolic concentrations, after accounting for colinearities with altitude, climatic, and edaphic factors. In addition, phenolics correlated positively with UVAC and SLA, and negatively with leaf N and N: P. These relationships were steeper in the lower-elevation Inner Mongolian than on the Tibetan Plateau grasslands. Our data support that the variation in leaf phenolics is controlled mainly by UV radiation, implying high leaf phenolics facilitates the adaptation of plants to strong irradiation via its UV-screening and/or antioxidation functions, particularly on the Tibetan Plateau. Importantly, our results also suggest that leaf phenolics may influence on vegetation attributes and indirectly affect ecosystem processes by covarying with leaf functional traits.