Coordination of root growth with root morphology, physiology and defense functions in response to root pruning in Platycladus orientalis.

Introduction: Root pruning is commonly used to facilitate seedling transplantation for the restoration of degraded or damaged ecosystems. However, little is known about how root growth coordinates morphology, physiology and defense functions following root pruning. Objectives: We aim to elucidate whether and how root growth trades off with defense functioning after pruning. Methods: Seedlings of Platycladus orientalis, a tree species widely used in forest restoration, were subjected to root pruning treatment. A suite of root growth, morphological and physiological traits were measured after pruning in combination with proteomic analysis. Results: Root growth was insensitive to pruning until at 504 h with a significant increase of 16.8%, whereas root physiology was activated rapidly after pruning. Key root morphological traits, such as root diameter, specific root length and root tissue density, showed no response to the pruning treatment. Plant defense syndromes such as reactive oxygen species-scavenging enzymes and defensive phytohormones such as jasmonic acid and abscisic acid, were recruited at six hours after pruning and recovered to the unpruned levels at 504 h. Compared with the controls, 271, 360 and 106 proteins were differentially expressed at 6, 72 and 504 h after root pruning, respectively. These proteins, associated with defense function, showed temporal patterns similar to the above defense syndromes. Conclusion: Our results suggest a root growth-defense tradeoff following root pruning in P. orientalis. This tradeoff was potentially due to the significant increase of indole-3-acetic acid, the phytohormone stimulating root branching, which occurred soon after pruning. Together, these results provide a holistic understanding of how root growth is coordinated with root morphology, physiology, and defense in response to root pruning.

[Spatial variations and its influencing factors of soil carbon and nitrogen on the southern foot of Taihang Mountains, China]. / å¤ªè¡Œå±±å—éº“å¡é¢åœŸå£¤ç¢³æ°®ç©ºé—´å˜å¼‚æ€§åŠå ¶å½±å“å› ç´ .

As an important ecological barrier for the North China Plain, research on the spatial variations of soil nutrients in the southern foot of the Taihang Mountains is of great significance for the forestry ecological construction in this rocky mountainous area. With the typical slopes (the artificial forestland and the natural wild slope) of the southern foot of the Taihang Mountains as the research objects, we used the grid method to arrange sampling points, and combined classical statistics, geostatistics and constrained sorting methods to analyze the spatial variations of soil nutrients. The results showed that: 1) soil total carbon (TC) contents were 6.80-57.05 g·kg-1, and the total nitrogen (TN) contents were 0.74-3.93 g·kg-1. The coefficients of variation of both soil TC and TN were 25.0%-52.8%, belonging to the moderate degree of variation, which were caused by the combination of random and structural factors. The spatial aggregation of soil nutrients decreased with increasing lag distances. 2) The contents of soil nutrients had increasing trends from the top to the bottom of the slopes, with high nutrient values appearing at the bottom of the slopes. 3) The soil bulk density, gravel content, vegetation coverage, and soil water content were the main factors affecting the spatial variability of soil TC and TN on the southern foot of the Taihang Mountains. 4) Soil water content was the main factor affecting soil nutrients at the natural wild slope, but not at the artificial forestland.

Using Spectral Reflectance to Estimate the Leaf Chlorophyll Content of Maize Inoculated With Arbuscular Mycorrhizal Fungi Under Water Stress.

Leaf chlorophyll content is an important indicator of the growth and photosynthesis of maize under water stress. The promotion of maize physiological growth by (AMF) has been studied. However, studies of the effects of AMF on the leaf chlorophyll content of maize under water stress as observed through spectral information are rare. In this study, a pot experiment was carried out to spectrally estimate the leaf chlorophyll content of maize subjected to different durations (20, 35, and 55 days); degrees of water stress (75%, 55% and 35% water supply) and two inoculation treatments (inoculation with Funneliformis mosseae and no inoculation). Three machine learning algorithms, including the back propagation (BP) method, least square support vector machine (LSSVM) and random forest (RF) method, were used to estimate the leaf chlorophyll content of maize. The results showed that AMF increased the leaf chlorophyll content, net photosynthetic rate (A), stomatal conductance (gs), transpiration rate (E), and water use efficiency (WUE) of maize but decreased the intercellular carbon dioxide concentration (Ci) of maize and atmospheric vapor pressure deficit (VPD) regardless of the water stress duration and degree. The first-order differential spectral data can better reflect the correlation between leaf chlorophyll content and spectrum of inoculated maize when compared with original spectral data. The BP model performed bestin modeling the maize leaf chlorophyll content, yielding the largest R 2-values and smallest root mean square error (RMSE) values, regardless of stress duration. These results provide a reliable basis for the effective monitoring of the leaf chlorophyll content of maize under water stress.

The quality of wild Salvia miltiorrhiza from Dao Di area in China and its correlation with soil parameters and climate factors.

INTRODUCTION: Salvia miltiorrhiza is a frequently used herb in traditional Chinese medicine, and tanshinone IIA (Tan IIA) and salvianolic acid B (Sal Acid B) are two major extracts obtained from its dried root. The quality of herbal ingredients can be affected by environmental factors. OBJECTIVE: To evaluate the quality of wild S. miltiorrhiza and investigate the influence of soil constituents and parameters as well as climatic conditions and factors on the content of Tan IIA and Sal Acid B. METHODOLOGY: We collected samples in 12 natural locations in the Dao Di area in China, the area in which S. miltiorrhiza grows, that results in a distinctive higher quality of medicinal materials from the harvested plant. The concentrations of Tan IIA and Sal Acid B were measured by high-performance liquid chromatography (HPLC). Soil total carbon, total nitrogen, available nitrogen, available phosphorus, available potassium, and particle size distribution were determined. We also collected climate data using ArcGIS from the WorldClim database, and correlation tests, redundancy, and regression analyses were conducted to analyse the relationship and cluster the samples according to their chemical profile. RESULTS: The content of Tan IIA and Sal Acid B in most of the samples was significantly different (P < 0.05). Soil available phosphorus was considered as a key factor that influenced the quality of wild S. miltiorrhiza, and we found a significant negative association between the concentration of Tan IIA in roots and soil available phosphorus. Moreover, the accumulation of Tan IIA in S. miltiorrhiza was also significantly associated with precipitation in April, May, and October, maximum temperature in January, and standard deviation of temperature seasonality. There was no significant correlation between the content of Sal Acid B and ecological factors. In addition, samples collected from Mengshan, Hexian, and Lushi locations were rich in Tan IIA and tended to cluster together, whereas samples collected from Longquan and Huoshan locations tended to cluster and were poor in Tan IIA. CONCLUSION: The Tan IIA content in samples collected from southern Anhui was significantly lower than that in other Dao Di locations. The content of Tan IIA was related more to the soil than the temperature. Compared with Tan IIA, Sal Acid B was less influenced by soil and climate factors. The findings of this study may provide helpful references for quality control of medicinal plants that exert pharmacological effects in humans.

[Spatial distribution of plant diversity in shrub layer of Quercus variabilis plantation and its relationship with light environment]. / æ “çš®æ Žäººå·¥æž—çŒæœ¨å±‚æ¤ç‰©å¤šæ ·æ€§çš„ç©ºé—´åˆ†å¸ƒåŠå ¶ä¸Žå ‰çŽ¯å¢ƒçš„å ³ç³».

We analyzed the spatial heterogeneity of plant species diversity in shrub layers and its relationship with light environment in Quercus variabilis plantation and Q. variabilis-Platycladus orientali mixed forest, following the method of geostatistics. The results showed that plant species diversity indices (Shannon H, Simpson Ds, Margalef Ma) of shrub layers in Q. variabilis plantation were significantly lower than that in Q. variabilis-P. orientalis mixed forest. The variation ranges and spatial autocorrelation distances of plant species diversity index in Q. variabilis plantation were higher than that in Q. variabilis-P. orientalis mixed forest, with lower spatial homogeneity but stronger spatial dependence. The plant species diversity indices of H, Ds and Ma structural ratios of shrub layers in Q. variabilis pure forest were 44.2%-49.7%, with moderate spatial autocorrelation. The structure ratios of H, Ds and Ma in Q. variabilis-P. orientalis mixed forest were 1.5%-3.3%, with strong spatial autocorrelation. The spatial distribution of biodiversity showed obvious strip-like gradient trend in Q. variabilis plantation and patchy gradient change in Q. variabilis-P. orientalis mixed forest, suggesting that the spatial continuity of plant species of shrub layers was worse in Q. variabilis-P. orientalis mixed forest and that the spatial variation was stronger than that in Q. variabilis pure forest. Results of correlation analysis and stepwise regression analysis showed that the total light and plant canopy openness were the most significant factors affecting plant species diversity of shrub layers in both forest types. Light environment formed by plant canopy structure played a crucial part in maintaining plant diversity in shrub layer.

Examining CO2 and N2O pollution and reduction from forestry application of pure and mixture forest.

Greenhouse gases (GHGs) carbon dioxide (CO2) and nitrous oxide (N2O), contribute significantly to global warming, and they have increased substantially over the years. Reforestation is considered as an important forestry application for carbon sequestration and GHGs emission reduction, however, it remains unknown whether reforestation may instead produce too much CO2 and N2O contibuting to GHGs pollution. This study was performed to characterize and examine the CO2 and N2O emissions and their controlling factors in different species and types of pure and mixture forest used for reforestation. Five soil layers from pure forest Platycladus orientalis (PO), Robinia pseudoacacia (RP), and their mixed forest P-R in the Taihang mountains of central China were sampled and incubated aerobically for 11 days. The P-R soil showed lower CO2 and N2O production potentials than those of the PO soils (P < 0.01). The average reduction rate of cumulative CO2 and N2O was 31.63% and 14.07%, respectively. If the mixed planting pattern is implemented for reforestation, the annual CO2 reduction amounts of China's plantation can be achieved at 8.79 million tonnes. With the increase of soil depths, cumulative CO2 production in PO and RP soils decreased, whereas CO2 and N2O production in P-R soil did not show similar pattern. Soil particle size fraction was the main factor influencing GHGs emissions, and the clay fraction showed negative correlation with cumulative CO2 and N2O production. In summary, compared with PO pure artificial forests, the mixture plantation mode can not only reduce GHGs pollution but also improve soil fertility, which is conducive to sustainable management of artificial forests.

The responses of soil bacterial communities and enzyme activities to the edaphic properties of coal mining areas in Central China.

Soil physicochemical properties, bacterial communities and enzyme activities change with land subsidence resulting from coal mining. However, research on the responses of bacterial communities and enzyme activities to the soil properties in different degree of subsidence areas is limited. As such, we collected soil samples from a control area (C area), a moderate mining subsidence area (M area) and a severe mining subsidence area (S area) in Central China. Soil properties, such as the pH, total nitrogen (TN) content, total phosphorus (TP) content, available phosphorus (AP) content, organic matter (OM) content, and soil enzyme (urease, invertase, catalase and alkaline phosphatase) activities were measured in each sampling area at depths of 0-20 cm, 20-40 cm, and 40-60 cm. The results indicated that the soil physiochemical properties, soil urease activity, soil alkaline phosphatase activity and soil bacterial richness and diversity in the topsoil (0-20 cm) of the mining subsidence area were significantly lower than those in the C area. However, the soil enzyme activities within the deepest layer of the subsidence area were significantly greater than those of the C area. The bacterial communities within the depth of 0-20 cm were dominated by RB41, Pseudomonas, MND1, Nitrospira, Trichococcus, Sphingomonas and Dongia, whereas RB41 and Pseudomonas were the dominant species in the C area and subsidence area, respectively. Using correlation analysis, we found that the soil pH value, soil AP content and activities of the four enzymes were the main factors affecting the soil bacterial community structure. In addition, the soil nutrient contents, enzyme activities and bacterial richness and evenness decreased with increasing subsidence degree (classified by geological hazards, groundwater and landscape damage degree of coal mining subsidence). These results provide a reliable basis for environmental management of mining areas.

Low population genetic differentiation in two Tamarix species (Tamarix austromongolica and Tamarix chinensis) along the Yellow River.

Geological events have been shown to be the main factors affecting the distributions and population genetic structure of species. However, the impact of the Yellow River, the second longest river in China, on the distribution and genetic structure of the endemic flora remains largely unknown. Here, we used microsatellites to evaluate the genetic structure of Tamarix austromongolica and Tamarix chinensis (343 individuals in total), two endemic tree species widely distributed along the Yellow River, as well as the role of river drainages in shaping the structure. We found that frequent gene flow resulted in low genetic differentiation among populations within species (T. austromongolica: Fst = 0.144, Nm = 1.486; T. chinensis: Fst = 0.103, Nm = 2.177); and low levels of genetic differentiation were detected between populations within species on the north and south banks. Also, high gene flow was found between populations in the upper reaches and those in the middle reaches, and middle reaches and lower reaches of the Yellow River (T. austromongolica: Fst = 0.023, Nm = 10.619; T. chinensis: Fst = 0.045, Nm = 5.306). Additionally, discriminant analysis of principal components (DAPC) and Bayesian analysis revealed a weak population structure in T. austromongolica and T. chinensis. Therefore, the Yellow River does not act as a barrier to dispersal and gene flow for Tamarix. Our findings provide support for the role of the river in shaping the spatial distribution and the genetic structure of species.

Demographic expansion of two Tamarix species along the Yellow River caused by geological events and climate change in the Pleistocene.

The geological events and climatic fluctuations during the Pleistocene played important roles in shaping patterns of species distribution. However, few studies have evaluated the patterns of species distribution that were influenced by the Yellow River. The present work analyzed the demography of two endemic tree species that are widely distributed along the Yellow River, Tamarix austromongolica and Tamarix chinensis, to understand the role of the Yellow River and Pleistocene climate in shaping their distribution patterns. The most common chlorotype, chlorotype 1, was found in all populations, and its divergence time could be dated back to 0.19 million years ago (Ma). This dating coincides well with the formation of the modern Yellow River and the timing of Marine Isotope Stages 5e-6 (MIS 5e-6). Bayesian reconstructions along with models of paleodistribution revealed that these two species experienced a demographic expansion in population size during the Quaternary period. Approximate Bayesian computation analyses supported a scenario of expansion approximately from the upper to lower reaches of the Yellow River. Our results provide support for the roles of the Yellow River and the Pleistocene climate in driving demographic expansion of the populations of T. austromongolica and T. chinensis. These findings are useful for understanding the effects of geological events and past climatic fluctuations on species distribution patterns.

De novo sequencing and comparative transcriptome analysis of adventitious root development induced by exogenous indole-3-butyric acid in cuttings of tetraploid black locust.

BACKGROUND: Indole-3-butyric acid (IBA) is applied to the cuttings of various plant species to induce formation of adventitious roots (ARs) in commercial settings. Tetraploid black locust is an attractive ornamental tree that is drought resistant, sand tolerant, can prevent sand erosion and has various commercial uses. To further elucidate the mechanisms of AR formation, we used Illumina sequencing to analyze transcriptome dynamics and differential gene expression at four developmental stages in control (CK) and IBA-treated groups. RESULTS: The short reads were assembled into 127,038 unitranscripts and 101,209 unigenes, with average lengths of 986 and 852 bp. In total, 10,181 and 14,924 differentially expressed genes (DEGs) were detected in the CK and IBA-treated groups, respectively. Comparison of the four consecutive developmental stages showed that 282 and 260 DEGs were shared between IBA-treated and CK, suggesting that IBA treatment increased the number of DEGs. We observed 1,721 up-regulated and 849 down-regulated genes in CI vs. II, 849 up-regulated and 836 down-regulated genes in CC vs. IC, 881 up-regulated and 631 down-regulated genes in CRP vs. IRP, and 5,626 up-regulated and 4,932 down-regulated genes in CAR vs. IAR, of which 25 up-regulated DEGs were common to four pairs, and these DEGs were significantly up-regulated at AR. These results suggest that substantial changes in gene expression are associated with adventitious rooting. GO functional category analysis indicated that IBA significantly up- or down-regulated processes associated with regulation of transcription, transcription of DNA dependent, integral to membrane and ATP binding during the development process. KEGG pathway enrichment indicated that glycolysis/gluconeogenesis, cysteine and methionine metabolism, photosynthesis, nucleotide sugar metabolism, and lysosome were the pathways most highly regulated by IBA. We identified a number of differentially regulated unigenes, including 12 methionine-related genes and 12 ethylene-related genes, associated with the KEGG pathway cysteine and methionine metabolism. The GO enrichment, pathway mapping, and gene expression profile analyses revealed molecular traits for root induction and initiation. CONCLUSION: Our study presents a global view of the transcriptomic profiles of tetraploid black locust cuttings in response to IBA treatment and provides new insights into the fundamental mechanisms associated with auxin-induced adventitious rooting.

Improvement of tolerance to lead by filamentous fungus Pleurotus ostreatus HAU-2 and its oxidative responses.

Wastewater contaminated with heavy metals is a world-wide concern. One biological treatment strategy includes filamentous fungi capable of extracellular adsorption and intracellular bioaccumulation. Here we report that an acclimated strain of filamentous fungus Pleurotus ostreatus HAU-2 can withstand Pb up to 1500 mg L(-1) Pb, conditions in which the wildtype strain cannot grow. The acclimated strain grew in liquid culture under 500 mg L(-1) Pb without significant abnormity in biomass and morphology, and was able to remove significant amounts of heavy metals with rate of 99.1% at 200 mg L(-1) and 63.3% at 1500 mg L(-1). Intracellular bioaccumulation as well as extracellular adsorption both contributed the Pb reduction. Pb induced levels of H2O2, and its concentration reached 72.9-100.9 µmol g(-1) under 200-1000 mg L(-1) Pb. A relatively higher malonaldehyde (MDA) concentration (8.06-7.59 nmol g(-1)) was also observed at 500-1500 mg L(-1) Pb, indicating that Pb exposure resulted in oxidative damage. The fungal cells also defended against the attack of reactive oxygen species by producing antioxidants. Of the three antioxidant enzymes superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT), CAT was the most responsive and the maximal enzyme activity was 15.8 U mg(-1) protein. Additionally, glutathione (GSH) might also play a role (3.16-3.21 mg g(-1) protein) in detoxification under relatively low Pb concentration (100-200 mg L(-1)). Our findings suggested that filamentous fungus could be selected for increased tolerance to heavy metals and that CAT and GSH might be important components of this tolerance.

Natural regeneration of trees in three types of afforested stands in the Taihang Mountains, China.

Natural regeneration is the natural process by which plants replace themselves. It is a cost-effective way to re-establish vegetation, and it helps to preserve genetic identity and diversity. In this study, we investigated the natural regeneration of trees in three types of afforested stands in the Taihang Mountains, China, which were dominated by Robinia pseudoacacia (black locust), Quercus variabilis (Chinese cork oak) and Platycladus orientalis (Chinese arborvitae) respectively. A consistent pattern was found among the three types of stands, being that the density of seedlings was positively correlated with the overstory canopy cover and negatively correlated with the covers of shrub, herb and litter layers. While a positive correlation between the density of seedlings and stand age was found for the conifer stands, negative correlations were found for the two types of broadleaf stands. Correlations between the density of saplings and the stand attributes were not consistent among the three types of stands. The two types of broadleaf stands had higher densities of seedlings and saplings than the conifer stands. While the broadleaf stands had adequate recruits for regeneration, the conifer stands did not have enough recruits. Our findings suggest that the overstory canopy should be prevented from being disturbed, any reduction of the canopy cover will decrease the recruits and affect the regeneration.

Influence of iron and copper oxides on polychlorinated diphenyl ether formation in heterogeneous reactions.

Polychlorinated diphenyl ether (PCDE) has attracted great attention recently as an important type of environmental pollutant. The influence of iron and copper oxides on formation of PCDEs was investigated using laboratory-scale flow reactors under air and under nitrogen at 350 °C, a temperature corresponding to the post-combustion zone of a municipal solid waste incinerator. The results show that the 2,2',3,4,4',5,5',6-otachlorodiphenyl ether (OCDE) formed from the condensation of pentachlorophenol (PCP) and 1,2,4,5-tetrachlorobenzene (Cl4Bz) is the predominant congener formed on the SiO2/Fe2O3 surface with and without oxygen. This indicated that HCl elimination between PCP and 1,2,4,5-Cl4Bz molecules formed 2,2',3,4,4',5,5',6-OCDE in the presence of Fe2O3. On the other hand, decachlorodiphenyl ether, nonachlorodiphenyl ether, and OCDE were the dominant products on the SiO2/CuO surface without oxygen, although the 2,2',3,4,4',5,5',6-OCDE was the dominant product on the SiO2/CuO surface with oxygen. Therefore, the presence of Fe2O3 and CuO influences the formation and homologue distribution of PCDEs, which shifted towards the lower chlorinated species. Fe2O3 can promote both the condensation and dechlorination reaction without oxygen. On the contrary, with oxygen, Fe2O3 suppresses the condensation of chlorobenzene and chlorophenol to form PCDEs and polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/Fs). CuO can increase the formation of lower chlorinated PCDEs and PCDDs without oxygen. In conclusion, the different fly ash components have a major influence on PCDE emissions.

[Soil microbial characters under different vegetation communities in taihang mountain area].

This paper measured the numbers and biomass of soil microbes as well as the soil respiration rate under mixed coniferous--broadleaved forest, mixed coniferous forest, pure coniferous forest, pure deciduous broadleaved forest, shrubs, and bare land in Taihang Mountain area, aimed to evaluate the soil microbial characters under different vegetation communities in this area. The results showed that shrub land had the greatest numbers and biomass of soil microbes, followed by deciduous broadleaved forestland, mixed coniferous--broadleaved forestland, pure coniferous forestland, and bare land. Soil respiration rate had the similar trend. When restoring the vegetations on degraded mountain land, more attention should be paid to the natural restoration capability of forest ecosystems.