Accurate assessment of forest ecosystems requires choosing appropriate sampling scales that capture spatial heterogeneity. To determine the minimum sampling scale needed to assess key forest structural indices, we applied a moving window approach across twenty 1-ha primary broad-leaved Korean pine forest plots in Heilongjiang, China, systematically increasing window sizes from 5 m & times; 5 m to 95 m & times; 95 m and sliding them at 5 m intervals within each plot. At each window, we calculated seven indices representing three ecological dimensions: spatial structure (neighborhood comparison, angular scale, mingling), productivity (biomass, basal area), and species diversity (Simpson and Shannon indices). These values were compared to plot means to identify the minimum spatial scale at which index values stabilized within deviation thresholds of 10% or 20%. Then, we used a random forest model to investigate the drivers of variability in minimum sampling scale, incorporating plot-level means of each index and their coefficients of variation across 5 m & times; 5 m windows as explanatory variables. Results revealed varying scale sensitivities across indices. At the 10% deviation threshold, neighborhood comparison and angular scale stabilized at <= 50 m, species diversity at <= 75 m, and mingling and productivity at <= 85 m, which was identified as the minimum scale capturing all structural indices. Random forest analysis showed that while influencing factors varied across indices, the coefficient of variation was consistently the most important. This study provides a framework for tailored sampling strategies, supports forest inventory enhancements, and guides large-scale monitoring and conservation in temperate mixed forests.

Based on the survey data of nine primitive broad-leaved Korean pine forest plots ranging from 1 to 10.4 ha in Heilongjiang Province, this study used the moving window method and GIS technology to analyze the variation characteristics of the spatial distribution pattern of forest biomass in each plot. We explored the minimum area that can reflect the structural and functional characteristics of the primitive broad-leaved Korean pine forest, and used computer simulation random sampling method to verify the accuracy of the minimum area. The results showed that: (1) Through the analysis of the spatial distribution raster map of biomass deviation in the plots at various scales of 10 − 100 m, there is a minimum area (0.64 ha) for the critical range of biomass density variation in the primitive broad-leaved Korean pine forest. This minimum area based on biomass density can indirectly reflect the comprehensive characteristics of productivity level per unit area, structure, function, and environmental quality of the primitive broad-leaved Korean pine forest community. (2) Using computer simulation random sampling, it was found that only by sampling in a specific plot larger than or equal to the minimum area can equivalent or similar results be achieved as random sampling within the plot, indicating that the minimum area determined by the moving window method is accurate. (3) The minimum area determined in this paper is an excellent indicator reflecting the complexity of community structure, which can be used for comparing changes in community structure and function before and after external disturbances, and has a good evaluation effect. This minimum area can also be used as a basis for scientific and reasonable setting of plot size in the investigation and monitoring work of broad-leaved Korean pine forests in this region, thereby achieving the goals of improving work efficiency and saving work costs.

The multidimensionality of leaf traits allows plants to have diverse survival strategies to adapt to complex living environments. Whether the anatomical traits of leaves are associated with leaf economic traits and which group of traits are more strongly correlated with soil fertility factors remains unclear. We measured four leaf economic traits, four anatomical traits, and five soil fertility factors of eight coexisting broadleaf species distributed in mixed broadleaved-Korean pine (Pinus koraiensis) forests located in Northeast China. Results show a strong interdependence between economic and anatomical traits (p < 0.05). The range of variation between economic and anatomical traits were almost equal, but the causes of variation were different. Specific leaf area was positively correlated with the abaxial epidermis, negatively correlated with the ratio of spongy tissue to leaf thickness (ST/LT), and not correlated with adaxial epidermis. Leaf dry matter content was negatively correlated with the abaxial epidermis and adaxial epidermis, positively correlated with ST/LT. Specific leaf area, palisade tissue, and ST/LT showed stronger correlation with soil fertility factors than other traits. Soil fertility factors dominating trait variation were dependent upon the trait. Our results suggest anatomical traits can be considered in economic trait dimension. The coupled relationship between anatomical and economic traits is potentially a cost-effective adaptation strategy for species to improve efficiency in resource utilization. Our results provide evidence for the complex soil-trait relationship and suggest that future studies should emphasize the role of anatomic traits in predicting soil fertility changes.

天然林林下光质对乔木幼苗以及灌草的组成与更新具有重要的生态学意义.但目前对于林下光质的研究仍然有限.以吉林东部地区天然林为例,通过调查乔木数据和林下光质数据,基于移动窗口法分析不同空间尺度森林冠层结构与林下光质的关系.结果表明:不同林型下红光光子通量密度(R)与蓝光光子通量密度(B)存在差异.其中沙松-千金榆-花楷槭混交林林下蓝光光子通量密度最小,而沙松-紫椴-臭冷杉混交林和长白落叶松纯林林下最大.随着尺度的增大,天然林乔木胸高断面积与R/PFD(红光/光子通量密度比值)和B/PFD(蓝光/光子通量密度比值)的比值呈显著正相关(P＜0.05).并且随着尺度的增加,相关系数总体逐渐增大,在35m处达到峰值.在此基础上在南向、东向和西向各延伸10m时呈现显著正相关(P＜0.05).在该尺度下分析优势树种对林下R/PFD和B/PFD比值的影响时发现:R/PFD与B/PFD比值随着针叶林胸高断面积的增加而增加.相对于阔叶林来说,多数林型针叶林下的冠层结构与林下R/PFD和B/PFD比值之间显著正相关(P＜0.05).在不同树种下,乔木冠层结构对R/PFD和B/PFD比值的影响不同.总体而言,冠层结构在尺度以及树种组成上存在的差异能在一定程度上影响林下R/PFD和B/PFD比值的分布.本研究结果将有助于我们了解冠层结构对林下光质分布的影响机制,从而为天然林的更新、演替、恢复以及合理经营提供理论依据.

The variation and correlation of leaf economics and vein traits are crucial for predicting plant ecological strategies under different environmental changes. However, correlations between these two suites of traits and abiotic factors such as soil water and nitrogen content remain ambiguous. We measured leaf economics and vein traits as well as soil water and nitrogen content for two different shade-tolerant species (Betula platyphylla and Acer mono) in four mixed broadleaved-Korean pine (Pinus koraiensis) forests along a latitudinal gradient in Northeast China. We found that leaf economics traits and vein traits were decoupled in shade-intolerant species, Betula platphylla, but significantly coupled in a shade-tolerant species, A. mono. We found stronger correlations among leaf traits in the shade tolerant species than in the shade intolerant species. Furthermore, leaf economic traits were positively correlated with the soil water gradient for both species, whereas vein traits were positively correlated with soil water gradient for the shade intolerant species but negatively correlated in the shade tolerant species. Although economic traits were positively correlated with soil nitrogen gradient in shade intolerant species but not correlated in shade tolerant species, vein traits were negatively correlated with soil nitrogen gradient in shade tolerant species but not correlated in shade intolerant species. Our study provides evidence for distinct correlations between leaf economics and vein traits and local abiotic factors of species differing in light demands. We recommend that the ecological significance of shade tolerance be considered for species when evaluating ecosystem functions and predicting plant responses to environmental changes.

Investigating the spatial distributions and associations of tree populations provides better insights into the dynamics and processes that shape the forest community. Korean pine (Pinus koraiensis) is one of the most important tree species in broad-leaved Korean pine mixed forests (BKMFs), and little is known about the spatial point patterns of and associations between Korean pine and community-level woody species groups such as coniferous and deciduous trees in different developmental stages. This study investigated the spatial patterns of Korean pine (KP) trees and then analyzed how the spatial associations between KP trees and other tree species at the community level vary in different BKMFs. Extensive data collected from five relatively large sample plots, covering a substantial area within the natural distribution range of KP in northeastern China, were utilized. Uni- and bivariate pair correlation functions and mark correlation functions were applied to analyze spatial distribution patterns and spatial associations. The DBH (diameter at breast height) histogram of KP trees in northeastern China revealed that the regeneration process was very poor in the Changbai Mountain (CBS) plot, while the other four plots exhibited moderate or expanding population structures. KP trees were significantly aggregated at scales up to 10 m under the HPP null model, and the aggregation scales decreased with the increase in size classes. Positive or negative spatial associations were observed among different life stages of KP trees in different plots. The life history stages of the coniferous tree group showed positive spatial associations with KP saplings and juvenile trees at small scales, and spatial independence or negative correlations with larger KP trees at greater scales. All broad-leaved tree groups (canopy, middle, and understory layers) exhibited only slightly positive associations with KP trees at small scales, and dominant negative associations were observed at most scales. Our results demonstrate that mature KP trees have strong importance in the spatial patterns of KP populations, and site heterogeneity, limited seed dispersal, and interspecific competition characterize the spatial patterns of KP trees and community-level spatial associations with respect to KP trees, which can serve as a theoretical basis for the management and restoration of BKMFs in northeastern China.

Dynamic Global Vegetation Models (DGVM) are powerful tools for studying complicated ecosystem processes and global changes. This review article synthesizes the developments and applications of the Integrated Biosphere Simulator (IBIS), a DGVM, over the past two decades. IBIS has been used to evaluate carbon, nitrogen, and water cycling in terrestrial ecosystems, vegetation changes, land-atmosphere interactions, land-aquatic system integration, and climate change impacts. Here we summarize model development work since IBIS v2.5, covering hydrology (evapotranspiration, groundwater, lateral routing), vegetation dynamics (plant functional type, land cover change), plant physiology (phenology, photosynthesis, carbon allocation, growth), biogeochemistry (soil carbon and nitrogen processes, greenhouse gas emissions), impacts of natural disturbances (drought, insect damage, fire) and human induced land use changes, and computational improvements. We also summarize IBIS model applications around the world in evaluating ecosystem productivity, carbon and water budgets, water use efficiency, natural disturbance effects, and impacts of climate change and land use change on the carbon cycle. Based on this review, visions of future cross-scale, cross-landscape and cross-system model development and applications are dis-cussed.

Subcanopy tree species are an important component of temperate secondary forests. However, their biomass equations are rarely reported, which forms a “vertical gap” between canopy tree species and understory shrub species. In this study, we destructively sampled six common subcanopy species ( Syringa reticulate var. amurensis (Rupr.) Pringle, Padus racemosa (Lam.) Gilib., Acer ginnala Maxim., Malus baccata (Linn.) Borkh., Rhamnus davurica Pall., and Maackia amurensis Rupr. et Maxim.) to establish biomass equations in a temperate forest of Northeast China. The mixed-species and species-specific biomass allometric equations were well fitted against diameter at breast height (DBH). Adding tree height (H) as the second predictor increased the R 2 of the models compared with the DBH-only models by –1% to + 3%. The R 2 of DBH-only and DBH-H equations for the total biomass of mixed-species were 0.985 and 0.986, respectively. On average, the biomass allocation proportions for the six species were in the order of stem (45.5%) > branch (30.1%) > belowground (19.5%) > foliage (4.9%), with a mean root: shoot ratio of 0.24. Biomass allocation to each specific component differed among species, which affected the performance of the mixed-species model for particular biomass component. When estimating the biomass of subcanopy species using the equations for canopy species (e.g., Betula platyphylla Suk., Ulmus davidiana var. japonica (Rehd.) Nakai, and Acer mono Maxim.), the errors in individual biomass estimation increased with tree size (up to 68.8% at 30 cm DBH), and the errors in stand biomass estimation (up to 19.2%) increased with increasing percentage of basal area shared by subcanopy species. The errors caused by selecting such inappropriate models could be removed by multiplying adjustment factors, which were usually power functions of DBH for biomass components. These results provide methodological support for accurate biomass estimation in temperate China and useful guidelines for biomass estimation for subcanopy species in other regions, which can help to improve estimates of forest biomass and carbon stocks.

Recent studies suggest that the mycorrhizal type associated with tree species is an important trait influencing ecological processes such as response to environmental conditions and conspecific negative density dependence (CNDD). However, we lack a general understanding of how tree mycorrhizal type influences CNDD strength and the resulting patterns of species abundance and richness at larger spatial scales. We assessed 305 species across 15 large, stem-mapped, temperate forest dynamics plots in Northeastern China and North America to explore the relationships between tree mycorrhizal type and CNDD, species abundance, and species richness at a regional scale. Tree species associated with arbuscular mycorrhizal (AM) fungi showed a stronger CNDD and a more positive relationship with species abundance than did tree species associated with ectomycorrhizal (ECM) fungi. For each plot, both basal area and stem abundance of AM tree species was lower than that of ECM tree species, suggesting that AM tree species were rarer than ECM tree species. Finally, ECM tree dominance showed a negative effect on plant richness across plots. These results provide evidence that tree mycorrhizal type plays an important role in influencing CNDD and species richness, highlighting this trait as an important factor in structuring plant communities in temperate forests.

Large trees have been found to directly affect spatial patterns in forests and understanding forest spatial structure is important for developing effective forest management practices. We examined two primary broad-leaved Korean pine forests in Heilongjiang Province, China, to investigate the effects of large-diameter trees on the distribution of adjacent conspecific trees and to assess whether the effect is related to the conspecific negative density dependence hypothesis in temperate forest. We classified the tree with the widest diameter (diameter at breast height ? 50 cm) as the central tree and then surveyed the distribution of adjacent trees around each central tree. The degree of mingling between the central tree and adjacent trees was the lowest at 5?7 m. As the diameter of the adjacent trees increased the degree of mingling declined. This revealed that around the central tree, there was a ring of small trees conspecific to the central tree. The ring-like structure around large-diameter trees is consistent with the conspecific negative density dependence hypothesis. Thus, we propose that a ring-like structure promotes the succession and regeneration of the temperate forest.

The development and physiological status of pest insects are important factors that affect the effectiveness of biological control. Current knowledge reveals that heavy metals can be transferred to phytophagous insects through food chains and cause various chronic toxicological effects on the growth and physiology of phytophagous insects. These findings potentially attribute heavy metal contamination to an environmental factor governing biocontrol efficiency against pest insects, pointing to an urgent demand to better understand the effects of heavy metal exposure on insect susceptibility to entomopathogenic microorganisms. Here we discuss the transfer characteristics of heavy metals along the food chains to phytophagous insects and conclude that heavy metal exposure may promote insect susceptibility to entomopathogenic microorganisms in the heavy metal-contaminated regions. Furthermore, we propose a 'combined effect' hypothesis that combination of entomopathogenic agent and heavy metal stress can cause a much higher overall insect mortality than does the entomopathogenic agent or the heavy metal stress alone. This is a new and relatively unexplored area in the microbial-based biocontrol research, which might have great potential for future optimization of biocontrol strategies against economically and ecologically important agricultural or forest pests in the heavy metal polluted areas. (c) 2020 Society of Chemical Industry

Forest spatial structure has always been an important topic of ecological research. Large trees directly affect the spatial patterns in forest stands. In this study, we used the data from seven sample plots in natural mixed forests of Korean pine (Pinus koraiensis Siebold & Zucc.) and broad-leaved trees in Heilongjiang Province, China, to examine the effect of large trees on the spatial distribution of adjacent trees and to explore whether this effect is related to the gap dynamics theory. We classified trees with wide diameter (diameter at breast height (DBH) ≥ 50 cm) as central trees and then surveyed the distribution of adjacent trees around each central tree. The results revealed a ring structure of small trees (size class 2 (5.0 ≤ DBH < 10.0 cm) and size class 3 (10.0 ≤ DBH < 30.0 cm)) surrounding large trees. In the two northern sample plots, the trees formed the ring structures with radii of 4–7 m from the large-diameter trees. In the two central sample plots, the ring structures had the radii of 5–9 m and 5–8 m. Analogously, in the three southern sample plots, the ring structures had the radii of 7–11 m and 6–10 m. The formation of a ring structure is closely related to the competition among individuals, and there is an internal relationship between the formation of this structure and the dynamic theory.

Cadmium, a common environmental contaminant in both terrestrial and aquatic ecosystems, presented a serious hazard to growth and development of phytophagous insects. For better understanding the toxicology of Cd exposure on phytophagous insects, the physiological and molecular mechanisms underlying the energy metabolism disorder in midgut tissue of gypsy moth larvae fed on Cd-amended artificial diets (3.248 or 44.473 mg Cd/kg fresh food) were investigated. Our results showed that compared with control, Cd exposure at both two levels triggered detriment effects on growth indexes, and with the increase of exposure concentrations, the adverse effects were significantly exacerbated. Larval growth and nutritional indexes (except approximate digestibility) showed a strong positive correlation, indicating that growth retardation in the gypsy moth larvae under Cd stress was tightly related to the food utilization. The key genes at mRNA level in glycolysis/gluconeogenesis, citrate cycle pathway and starch/sucrose metabolism pathway also presented a significant and positive correlation with growth indexes, once again demonstrating that energy metabolism was the key factor that controls the growth and development of the gypsy moth larvae under Cd stress. Antioxidant system collapse and oxidative damage, a chief cause of histopathological alterations in midgut tissue, consist of the physiological basis of energy metabolism disorder in Cd-treated gypsy moth larvae. Together, these results suggest that histopathological alterations or oxidative damage of tissue structure significant disturbed physiological functions of midgut tissue in gypsy moth larvae exposed to Cd stress, as reflected via food utilization or energy metabolism disorder, and eventually resulted in larval growth retardation.

In the process of picking, actinidia arguta has difficulty in image recognition and occlusion problems, and there are few studies on kiwifruit recognition. Based on this, this study uses the color model to perform image basic processing and uses frequency domain enhancement to process the image. Simultaneously, in the frequency domain of the image, this study applied filtering to the original image of kiwifruit orchard, used homomorphic filtering to enhance the image of actinidia arguta orchard, highlighted the characteristics of actinidia arguta trunk, and reduced the influence of background noise on the recognition of actinidia arguta trunk. In addition, this study used a binocular stereo vision system for fruit location recognition to improve recognition accuracy. Finally, the effectiveness of the research method is verified by experimental research. The results show that the proposed algorithm performs well and can provide theoretical references for subsequent related research.

利用小兴安岭凉水自然保护区内10.4 hm~2样地的调查数据,统计并分析样地内乔木树种的组成与分布,借助混交度计算方法探究大径级个体周围同种邻木分布情况,并分析其产生的原因及大径级个体在其中发挥的作用,研究结果表明:（1）大径级个体（DBH≥50.0 cm）与其周围5—6 m范围内的邻木的混交程度最低,易形成围绕大径级个体（以下简称中央木）的同种邻木环形结构,该环形结构在一定程度上推动着未来的森林演替与更新;（2）距离中央木15 m范围内的中小径级个体（1级木（1.0 cm≤DBH＜5.0 cm）、2级木（5.0 cm≤DBH＜10.0 cm）、3级木（10.0 cm≤DBH＜30.0 cm））与中央木均保持较高的混交程度,而4级木（30.0 cm≤DBH＜50.0 cm）、5级木（DBH≥50.0 cm）与中央木的混交程度明显下降,以5级木最低,这种现象的产生与密度制约及物种共存机制存在密切关系。通过研究不同物种及不同生长阶段（不同径级）的林木分布,揭示了凉水地区阔叶红松林中大径级个体周围邻木分布格局特征及其成因,论证了大径级个体在控制周围林分结构、维持物种多样性及推动森林演替中的重要作用,为阔叶红松林的经营及管理提供了数据支撑。

The mechanical wound is one of the unavoidable threats to survival of plants. More researchers focus on the effect of mechanical wound to the over-ground tissues. And the effects of wound to roots were frequently ignored, although it is an important organ for plant growth. In our studies, the metabolomics study was performed to reveal the mechanical wound effects in Catharanthus roseus on roots and leaves by combining gas chromatography-mass spectrometer (GC-MS), liquid chromatograph-mass spectrometer (LC-MS) and statistical analyses. The metabolic response of TIAs and PCs in plants to wound was most active at 0.5 h after treatment via Q value analysis. At this time point, then significantly responsive primary metabolites and specific secondary compounds (TIAs and PCs) were screened by PLS-DA score plot. In this case, the treatments of CK, LT (wound to leaves) and RT (wound to roots) were clearly distinguished. The targeted compounds include 8 sugars, 4 TIAs and 12 PCs and they displayed specific responses to CK, LT and RT treatments. Under RT group, plants invest more resources on the local responses using TIAs and the color reactions to regulate wound close using PCs. Whereas, LT group might lay emphasis on systemic responses via TIAs induced by SA (salicylic acid) and gallic acid. Our studies provide some basic data for further investigations of the defensive mechanism on roots treated by mechanical wound.

Cd(II) is one of the most widespread and toxic heavy metals and seriously threatens plant growth, furthermore negatively affecting human health. For survival from this metal stress, plants always fight with Cd(II) toxicity by themselves or using other external factors. The effects of second metals copper (Cu(II)), zinc (Zn(II)) and calcium (Ca(II)) on the Cd(II)-affected root morphology, Cd(II) translocation and metabolic responses in Catharanthus roseus were investigated under hydroponic conditions. We found that the Cd-stressed plants displayed the browning and rot root symptom, excess H2O2 content, lipid peroxidation and Cd(II) accumulation in plants. However, the supplement with second metals largely alleviated Cd-induced toxicity, including browning and rot roots, oxidative stress and internal Cd(II) accumulation. The amended effects at metabolic and transcriptional levels involved in different second metals share either common or divergent strategies. They commonly repressed Cd uptake and promoted Cd(II) translocation from roots to shoots with divergent mechanisms. High Zn(II) could activate MTs expression in roots, while Cu(II) or Ca(II) did not under Cd(II) stress condition. The presence of Ca(II) under Cd stress condition largely initiated occurrence of lateral roots. We then grouped a metabolic diagram integrating terpenoid indole alkaloid (TIA) accumulation and TIA pathway gene expression to elucidate the metabolic response of C. roseus to Cd(II) alone or combined with second metals. The treatment with 100 Cd(II) alone largely promoted accumulation of vinblastine, vindoline, catharanthine and loganin, whereas depressed or little changed the expression levels of genes detected here, compared to 0 Cd(II) control. In the presence of Cd(II), the supplement with second metals displayed specific effect on different alkaloid. Among them, the metal Ca(II) is especially beneficial for serpentine accumulation, Zn(II) mainly promoted tabersonine production. However, the addition of Cu(II) commonly depressed accumulation of most alkaloids detected here. Generally, we presented different mechanisms by which the second metals used to alleviate Cd (II) toxicity. This plant has potential application in phytoremediation of Cd(II), due to relatively substantial accumulation of biomass, as well as secondary metabolites TIAs used as pharmaceutical materials when facing Cd stress.

对森林空间结构的研究一直是生态学重要研究内容之一,林分中大径级个体直接影响周围林分的空间格局,当大径级个体成为倒木或枯立木时会造成较大林隙,这也将导致周围空间格局发生变化.利用小兴安岭凉水自然保护区内10.4 hm2样地的调查数据,统计了样地内乔木树种组成,分析计算样地内树木个体间的分布规律,探究大径级个体对周围邻木空间分布的影响.研究结果表明:样地中共有乔木24种,共计7412株(去除分株),隶属于11科18属,林分中大径级个体周围存在由小径级树木聚集生长形成的环形结构,该环形结构随着邻木径级的变化而变化,2级邻木(5.0 cm≤DBH＜ 10.0 cm)主要在距离大径级个体3-7m范围内形成环形结构,3级邻木(10.0 cm≤DBH＜30.0 cm)主要在距离大径级个体3-6 m范围内形成环形结构,而1级邻木(1.0 cm≤DBH＜5.0cm)与4级邻木(30.0 cm≤DBH＜50.0 cm)并未形成环形结构,经分析环形结构的产生与林分内个体间的竞争存在密切关系,并且该结构与林隙斑块动态理论间存在内在联系,该结构是森林动态变化的一种表现形式,会伴随林木的生长产生或消失.研究表明大径级个体胸径的变化对邻木的环形结构分布范围也有一定影响,当大径级个体胸径增加时邻木的聚集范围有收缩的趋势.

Catharanthus roseus (C. roseus) and Vinca minor (V. minor) are two common important medical plants belonging to the family Apocynaceae. In this study, we used non-targeted GC-MS and targeted LC-MS metabolomics to dissect the metabolic profile of two plants with comparable phenotypic and metabolic differences. A total of 58 significantly different metabolites were present in different quantities according to PCA and PLS-DA score plots of the GC-MS analysis. The 58 identified compounds comprised 16 sugars, eight amino acids, nine alcohols and 18 organic acids. We subjected these metabolites into KEGG pathway enrichment analysis and highlighted 27 metabolic pathways, concentrated on the TCA cycle, glycometabolism, oligosaccharides, and polyol and lipid transporter (RFOS). Among the primary metabolites, trehalose, raffinose, digalacturonic acid and gallic acid were revealed to be the most significant marker compounds between the two plants, presumably contributing to species-specific phenotypic and metabolic discrepancy. The profiling of nine typical alkaloids in both plants using LC-MS method highlighted higher levels of crucial terpenoid indole alkaloid (TIA) intermediates of loganin, serpentine, and tabersonine in V. minor than in C. roseus. The possible underlying process of the metabolic flux from primary metabolism pathways to TIA synthesis was discussed and proposed. Generally speaking, this work provides a full-scale comparison of primary and secondary metabolites between two medical plants and a metabolic explanation of their TIA accumulation and phenotype differences.

Cadmium (Cd) is not an essential nutrition element to plants and high concentration of Cd in the environment causes severe damage to plants. It is reported that the gas phytohormone ethylene plays important roles in plant responses to Cd stress. However, whether plant secondary metabolism is involved in this process remains to be investigated. Here, the regulations of exogenous ethylene on internal Cd accumulation and terpenoid indole alkaloids (TIAs) biosynthesis in the medicinal plant Catharanthus roseus (L.) G. Don (C. roseus) under Cd stress condition were explored. Our results showed that Cd treatment inhibited biomass accumulation, increased Cd accumulation and H2O2 and malondialdehyde (MDA) productions. Simultaneously, Cd treatment enhanced yields of vindoline, catharanthine and vinblastine, as well as the gene expressions of TIAs pathway enzymes at transcriptional level. Exogenous ethylene application significantly reduced the Cd content in whole plants and the H2O2 and MDA productions in roots and leaves, indicating that Cd stress in C. roseus was effectively alleviated by the ethylene application. It was interesting to find that exogenous ethylene promoted the Cd transport from roots to leaves and the value of Cd TF (transfer factor) was increased from 0.41 to 0.53. In leaves, the transcriptional expression of metallothionein (MT) was up-regulated by exogenous ethylene application, together with the increase of Cd accumulation. Additionally, exogenous ethylene reduced the TIAs productions, with an exception of catharanthine in leaves. The transcriptional expressions of alkaloid transporters, triose phosphate translocator (MDR) and multidrug resistance (TPT) were also up-regulated in leaves by exogenous ethylene, in accordance with the change of catharanthine biosynthesis. All of our results showed that exogenous ethylene could elevate the Cd resistance of C. roseus and effectively influence TIAs biosynthesis in C. roseus. Regulations of ethylene on the transcriptional expressions of MT, pathway enzymes and alkaloid transporters might be involved in this process.