Are males and females of Populus cathayana differentially sensitive to Cd stress?

This study clarifies the mechanisms of Cd uptake, translocation and detoxification in Populus cathayana Rehder females and males, and reveals a novel strategy for dioecious plants to cope with Cd contamination. Females exhibited a high degree of Cd uptake and root-to-shoot translocation, while males showed extensive Cd accumulation in roots, elevated antioxidative capacity, and effective cellular and bark Cd sequestration. Our study also found that Cd is largely located in epidermal and cortical tissues of male roots and leaves, while in females, more Cd was present in vascular tissues of roots and leaves, as well as in leaf mesophyll. In addition, the distributions of sulphur (S) and phosphorus (P) were very similar as that of Cd in males, but the associations were weak in females. Scanning electron microscopy and energy spectroscopy analyses suggested that the amounts of tissue Cd were positively correlated with P and S amounts in males, but not in females (a weak correlation between S and Cd). Transcriptional data suggested that Cd stress promoted the upregulation of genes related to Cd uptake and translocation in females, and that of genes related to cell wall biosynthesis, metal tolerance and secondary metabolism in males. Our results indicated that coordinated physiological, microstructural and transcriptional responses to Cd stress endowed superior Cd tolerance in males compared with females, and provided new insights into mechanisms underlying sexually differential responses to Cd stress.Peer reviewe

Ecophysiological responses of two poplar species to intraspecific and interspecific competition under different nitrogen levels

Aims Populus deltoides and P. euramericana are widely used in China as major forestry species. At present, little is known about their responses to nitrogen (N) deficiency when grown in monocultures or mixed plantations. The aim of this investigation was to analyze the growth, and morphological and physiological responses of P. deltoides and P. euramericana to different N levels under competition conditions. Methods We employed two Populus species (P. deltoides and P. euramericana) to discover how N deficiency affects plant traits under different competition types (P. deltoides x P. deltoides, intraspecific competition; P. euramericana x P. euramericana, intraspecific competition; P. deltoides x P. euramericana, interspecific competition). Potted seedlings were exposed to two N levels (normal N, N deficiency), and nitrogen- and competition-driven differences in growth, morphology and physiology were examined. Important Findings Under normal N conditions, interspecific competition significantly decreased the total root weight, root mass fraction (RMF), root-shoot ratio (R/S) and carbon/nitrogen ratio (C/N), and increased the leaf dry weight, leaf mass fraction and total leaf area of P. euramericana compared with intraspecific competition. The same conditions significantly affected the growth and morphological variables of P. deltoides, except for the dry weight of fine roots, R/S, specific leaf area, RMF, total nitrogen content and C/N compared with intraspecific competition. In addition, chlorophyll a (Chla), total chlorophyll (Tchl), carotenoid contents (Caro) and the carbon isotope composition (delta C-13) of P. deltoides were significantly lower in interspecific competition than in intraspecific competition, but no difference was detected in P. euramericana. The effects of N deficiency on P. deltoides under intraspecific competition were stronger than under interspecific competition. In contrast, the effects of N deficiency on P. euramericana between intraspecific and interspecific competition were not significantly different. These results suggest that under normal N condition, P. deltoides is expected to gain an advantage in monocultures rather than in mixtures with P. euramericana. Under N deficiency, the growth performance of P. euramericana was more stable than that of P. deltoides under both cultivation modes.Peer reviewe

Different responses in leaf-level physiology to competition and facilitation under different soil types and N fertilization

Knowledge of how competition and facilitation affect photosynthetic traits and nitrogen metabolism contributes to understanding of plant-plant interaction mechanisms. We transplanted two larch species, Larix kaempferi and L. olgensis, to establish intra- and interspecific interaction experiments under different types of soil. Experiment 1: Two different soil types were selected, one from a c. twenty years old L. kaempferi plantation (named larch soil) and another from a secondary natural forest (named mixed forest soil). The experiment included three types of plant interactions (L kaempferi + L. kaempferi, L. olgensis + L. olgensis, and L. kaempferi + L. olgensis) and two soil types. Experiment 2: N fertilization was applied to larch soil. The experiment included the same three types of plant interactions as in Experiment 1 and two N treatments. The growth of L kaempferi was negatively affected by larch soil and accelerated by N fertilization, particularly under interspecific interaction. The effects of soil type combined with plant-plant interactions or N fertilization influenced the chlorophyll pigment content, net photosynthetic rate (Pn), photosynthetic N use efficiency (PNUE) and total non-structural carbohydrates of leaves (TNC). CM a/Chl b (ratio of chlorophyll a to chlorophyll b) was higher when the growth of L. kaempferi was facilitated by the presence of L olgensis in mixed forest soil. However, the ratio significantly declined when L. kaempferi confronted strong competition from L. olgensis in larch soil without N fertilization. Under N fertilization in larch soil, Chl a/Chl b of L. olgensis significantly increased by the presence of L. kaempferi. Plant-plant interactions and soil types affected the number of chloroplasts, especially in L. kaempferi, which had a greater number of chloroplasts under interspecific interactions than in monoculture when growing in mixed forest soil. L. olgensis enhanced its ability to absorb N-NO3- under interspecific interactions in larch N- soil, while L. kaempferi enhanced its ability to absorb N-NH4+ under interspecific competition in mixed forest soil. Competition or facilitation modified the photosynthetic traits and nitrogen metabolism depending on the type of soil. Differences in these physiological processes contribute to divergent performance among individuals growing under interspecific or intraspecific competition, or in isolation.Peer reviewe

Microstructural and physiological responses to cadmium stress under different nitrogen levels in Populus cathayana females and males

Although increasing attention has been paid to the relationships between heavy metal and nitrogen (N) availability, the mechanism underlying adaptation to cadmium (Cd) stress in dioecious plants has been largely overlooked. This study examined Cd accumulation, translocation and allocation among tissues and cellular compartments in Populus cathayana Rehder females and males. Both leaf Cd accumulation and root-to-shoot Cd translocation were significantly greater in females than in males under a normal N supply, but they were reduced in females and enhanced in males under N deficiency. The genes related to Cd uptake and translocation, HMA2, YSL2 and ZIP2, were strongly induced by Cd stress in female roots and in males under a normal N supply. Cadmium largely accumulated in the leaf blades of females and in the leaf veins of males under a normal N supply, while the contrary was true under N deficiency. Furthermore, Cd was mainly distributed in the leaf epidermis and spongy tissues of males, and in the leaf palisade tissues of females. Nitrogen deficiency increased Cd allocation to the spongy tissues of female leaves and to the palisade tissues of males. In roots, Cd was preferentially distributed to the epidermis and cortices in both sexes, and also to the vascular tissues of females under a normal N supply but not under N deficiency. These results suggested that males possess better Cd tolerance compared with females, even under N deficiency, which is associated with their reduced root-to-shoot Cd translocation, specific Cd distribution in organic and/or cellular compartments, and enhanced antioxidation and ion homeostasis. Our study also provides new insights into engineering woody plants for phytoremediation.Peer reviewe

Responses of dioecious Populus to heavy metals: a meta-analysis

A total of 946 sets of comparative data were collected from 20 publications and a meta-analysis performed to evaluate the responses of growth, photosynthetic capacity, oxidative stress and antioxidants in Populus females and males under exposure to heavy metals, like Cu, Mn, Zn, Pb and Cd. It was found that heavy metals have negative effects on Populus growth and photosynthetic capacity, as the average total biomass, leaf biomass, stem biomass, root biomass and height decreased by 29.78%, 33.41%, 27.22%, 35.30% and 34.83%, respectively. Furthermore, total chl, Pn, gs, E, Ci decreased by 23.30%, 26.03%, 40.49%, 23.76% and 18.24%, respectively. In addition, heavy metals increased oxidative stress and antioxidant enzyme activities: the average values of TBARS, H2O2, \begin{document}${\text{O}^-_2}$\end{document} and MDA increased by 51.39%, 55.79%, 64.67% and 48.92%, respectively, and proline, APX, NPT, POD, CAT and SOD increased by 68.91%, 64.81%, 68.40%, 57.34%, 77.30% and 49.01%, respectively. However, there were sex-specific responses to heavy metals: females suffered more negative effects, as they had significantly greater decreases in root biomass, R/S ratio, height and total chl, and significantly smaller increases in NPT and POD activities than males. The present meta-analysis shows the responses of Populus females and males to heavy metals on a regional scale, which is crucial for understanding the patterns of sexual dimorphism and sex ratio biases in Populus with increasing heavy metal pollution in the future

Mechanism for generating and promoting manufacturing project portfolio synergy

To explore the mechanism for generating and promoting project portfolio (PP) synergy, a model applying the causal loop diagram (CLD) is established. The efforts have been done include four parts. First, a sustainable objective system is determined through the improved balanced scorecard. Second, three categories of manufacturing projects are identified to illustrate the characteristics and objectives. Third, a CLD model is constructed based on the objective achievement process of PPs. Fourth, suggestions are made to promote the objective realization by synergy. The major result is that the generation and promotion mechanism are portrayed through the causal loops and feedbacks of CLD. CLD is adopted as the analytical approach for superiority in visualizing complex relationships. The main findings are: (1) The synergy generation mechanism is specified that PP synergy generates from the collaborative behaviors among PPs. (2) PP synergy promotes objective realization through additional effects arise from complex feedbacks among behaviors

A Simple Model to Predict Machined Depth and Surface Profile for Picosecond Laser Surface Texturing

A simple mathematical model was developed to predict the machined depth and surface profile in laser surface texturing of micro-channels using a picosecond laser. Fabrication of micro-craters with pulse trains of different numbers was initially performed. Two baseline values from the created micro-craters were used to calculate the estimated simulation parameters. Thereafter, the depths and profiles with various scanning speeds or adjacent intervals were simulated using the developed model and calculated parameters. Corresponding experiments were conducted to validate the developed mathematical model. An excellent agreement was obtained for the predicted and experimental depths and surface profiles. The machined depth decreased with the increase of scanning speed or adjacent interval

Power supply for on-line monitoring device of power lines based on double-half ring core

In order to solve the problem of insufficient energy supply of the on-line monitoring device of the transmission line, a sensor energy acquisition scheme directly installed on the transmission line is proposed. In the current power supply, induction power supply is a kind of energy extraction method with better practical applicability. Since the monitoring devices and electronic equipment on the transmission line are often in a strong magnetic field and high voltage environment, designing a stable and reliable power supply is the guarantee for the stable operation of the monitoring devices and electronic equipment. This paper presents a structure of energy-absorbing iron core with two semi-circular magnetic cores, and studies the magnetic saturation problem in the inductive power supply and the design of the DC output circuit

Community metagenomic assembly reveals microbes that contribute to the vertical stratification of nitrogen cycling in an aquaculture pond

The identities and functional capacities of the microbial populations within surface water (SW), bottom water (BW), surface sediment (SS) and deep sediment (DS) samples from a typical grass carp (Ctenopharyngodon idellus) culturing pond in central China were explored using metagenomics. In total, the community structure and microbial processes of the water columns was distinct from that of the SS and DS layers. Alphaproteobacteria, Actinobacteria, Cyanobacteria and Planctomycetes were abundant in the water, while Deltaproteobacteria, Gammaproteobacteria, Euryarchaeota (Archaea) and Nitrospirae were more abundant in the sediment (P < .05). The functional potential and microorganisms responsible for the N nutrient cycles were also reconstructed in silico. The high functional potential for N assimilation, protein synthesis and cell proliferation in pond water should be responsible for low ammonia concentration detected. Ammonia oxidation functional genes were present in very low abundances, and were mostly detected in the water columns and related to Nitrosomonas (100%). Denitrification were observed mostly in SS and the main taxon involved was Rhodocyclales. The potential for N fixation (nif genes) and dissimilatory nitrate reduction to ammonium was also observed mostly in sediment, which is a disadvantage for ammonia reduction in the pond ecosystem. Overall, these results offer a more detailed perspective on the microbial functional ecology of the aquaculture pond