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Dioecious plants display sexual dimorphism in functional traits, which influences sex-specific interactions. Intersexual interactions in belowground facilitation processes and mechanisms remain poorly understood, necessitating further studies. Belowground facilitation involves resource complementarity, mycorrhizal fungal networks, root exudate-mediated belowground chemical communication, and plant–soil feedback. Spatial segregation of sexes may not necessarily reflect the outcomes of sex-specific interactions, but could be associated with sex-specific reproductive strategies. Dioecious plant species exhibit sexual dimorphism in various aspects, including morphology, physiology, life history, and behavior, potentially influencing sex-specific interactions. While it is generally accepted that intersexual interactions in dioecious species are less intense compared with intrasexual interactions, the mechanisms underlying belowground facilitation in intersexual combinations remain less understood. Here, we explore these mechanisms, which encompass resource complementarity, mycorrhizal fungal networks, root exudate-mediated belowground chemical communication, as well as plant–soil feedback. We address the reason for the lack of consistency in the strength of inter- and intrasexual interactions. We also propose that a comprehensive understanding of the potential positive consequences of sex-specific interactions can contribute to maintaining ecological equilibrium, conserving biodiversity, and enhancing the productivity of agroforestry. [ABSTRACT FROM AUTHOR]

There are significant differences in the morphological and physiological responses of larch species with contrasting growth rates under fertilization. However, little is known about species-specific differences in responses to nutrient imbalance caused by fertilization. Therefore, in this study, the effects of nitrogen (N) and phosphorus (P) fertilization on the morphological, physiological and chloroplast ultrastructural traits of two contrasting larch species, fast-growing Larix kaempferi and slowly-growing L. olgensis , grown in larch plantation soil, were investigated during two growth seasons. It was shown that N and combined N and P (NP) fertilization increased plant photosynthesis, foliar N contents, chlorophyll contents, and dry mass accumulation and partitioning in aboveground organs in both larch species. Although P fertilization enhanced P accumulation, its presence reduced the N content in soluble proteins in the foliage of both larch species. Yet, P fertilization exhibited some differences in the two species: P fertilization increased photosynthesis, chlorophyll content and biomass accumulation of L. olgensis , while it decreased these parameters dramatically in L. kaempferi. P fertilization increased foliar N content in L. olgensis , while it reduced it in L. kaempferi . P fertilized L. kaempferi had more damaged chloroplast ultrastructure than L. olgensis . In addition, L. kaempferi exhibited lower acid phosphatase activities, and higher photosynthesis and biomass accumulation than L. olgensis , except under P fertilization. L. kaempferi allocated more biomass into needles, except under P fertilization, while L. olgensis allocated more into stems under fertilization. In conclusion, it was shown that nutrient imbalance caused by P fertilization has greater negative effects on a fast-growing species than on a slowly-growing one, and the negative effects are related to differences in acclimation strategies, N partitioning to photosynthetic components, and P transportation and metabolism in the foliage. [ABSTRACT FROM AUTHOR]

Non-structural carbohydrates (NSC) are critical to plant signaling, gene transcription, physiological processes, survival and growth. Previous studies have demonstrated that species differing in NSC contents have various responses to stressful environments. However, effects of intra- and interspecific competition or N fertilization on NSC have not been previously studied. We employed two coniferous tree species, Larix kaempferi and Larix olgensis , to investigate the effects of intra- and interspecific competition on NSC under two N supply levels, with and without N fertilization. N fertilization significantly promoted the growth rates, biomass accumulation, carbon isotope composition and N concentration of leaves of the two species. Competition patterns significantly affected the average root diameter. Interspecific competition tended to increase the specific root length and specific root tip density. Also, interspecific competition significantly increased the N concentration of leaves but declined their C:N ratio under no N fertilization (N−) treatments. L. kaempferi greatly benefited from the presence of L. olgensis , particularly under N fertilization (N+) treatments. Competition patterns, N fertilization and their interactions promoted N and carbohydrate storage. Our results demonstrated that N was a crucial factor to drive and regulate carbon balance. Differences between species in carbohydrate metabolism may contribute to their coexistence or niche differentiation. [ABSTRACT FROM AUTHOR]

Males and females of dioecious plant species are different in morphology, physiology, and immunity. Male and female plants differently regulate microbial communities in the rhizosphere, phyllosphere, and endosphere along the soil–plant continuum. Sexual dimorphism in root exudates is the major force in regulating sex-specific microbial communities in the rhizosphere. Deterministic processes in sex-specific microbial assembly in the plant endosphere are caused by different physical–chemical traits like cell wall and phytohormones. Males can alleviate stress-caused damage in females by recruiting stress-tolerant microorganisms under intersexual interactions. Plant microbiota can greatly impact plant growth, defense, and health in different environments. Thus, it might be evolutionarily beneficial for plants to be able to control processes related to microbiota assembly. Dioecious plant species display sexual dimorphism in morphology, physiology, and immunity. These differences imply that male and female individuals might differently regulate their microbiota, but the role of sex in microbiota assembly has been largely neglected so far. Here, we introduce the mechanism of how sex controls microbiota in plants analogically to the sex regulation of gut microbiota in animals, in particular in humans. We argue that plant sex imposes selective pressure on filtering and constructing microbiota in the rhizosphere, phyllosphere, and endosphere along the soil–plant continuum. Since male plants are more resistant than female plants to environmental stresses, we suggest that a male host forms more stable and resistant plant microbiota that cooperate more effectively with the host to resist stresses. Male and female plants can distinguish whether a plant is of the same or different sex, and males can alleviate stress-caused damage in females. The impact of a male host on microbiota would protect female plants from unfavorable environments. [ABSTRACT FROM AUTHOR]

Highlights: [•] A four-year field experiment was conducted in a fir forest using the OTC method. [•] Soil warming accelerated labile C decay and increased recalcitrant C pools. [•] Soil warming did not influence the respiration quotient at either elevation. [•] Altitude significantly affected soil C fractions. [•] The high altitude was more responsive to soil warming than the low altitude. [Copyright &y& Elsevier]

Abstract: Dioecious plants show sexually different responses to environmental stresses. However, little is known about the dimorphic morphological and physiological responses to soil pollution. To investigate sex-related adaptive responses of Populus yunnanensis seedlings when exposed to excess zinc (Zn), acid rain (AR) and their combination (Zn+AR), we analyzed growth parameters, Zn accumulation and allocation, photosynthetic capacity and biochemical responses under different treatments. Results revealed that both excess Zn and Zn+AR have a negative effect on plant growth. Males have a greater potential than females to enrich Zn. The photosynthesis limitation could be attributable to a lower stomatal conductance, photosynthetic nitrogen use efficiency and nitrate reductase activity induced by Zn accumulation. Overproduction of reactive oxygen species was detected, and females showed higher levels of H2O2 and than did males under excess Zn and Zn+AR. In addition, indicators related to plant injury showed expected increases and exhibited sexual differences. Males synthesized more biochemical molecules, such as proline and non-protein thiol, showing a stronger defense capacity in responses to either excess Zn or Zn+AR. Taking into account the Zn accumulation and the resulting injuries in plants, we suggest that excess Zn causes sex-related adaptive responses and males possess a more effective self-protection mechanism, Zn-stressed individuals suffering from AR did not show notable aggravation or alleviation when compared to damages induced by excess Zn alone. [Copyright &y& Elsevier]

Abstract: To examine whether deciduous and evergreen tree species differ in their performance and plastic responses to elevated atmospheric CO2 and temperature, we investigated growth, leaf area ratio (LAR), specific root length (SRL), nitrogen uptake efficiency (NUpE) and nitrogen use efficiency (NUE) of Populus yunnanensis and Abies faxoniana grown in environment-controlled chambers. Our results showed that temperature stimulated growth more than did CO2 in both species. The magnitude of temperature and CO2 effects varied between the species, as greater stimulation was detected in A. faxoniana than in P. yunnanensis. Greater responses of A. faxoniana were associated with higher LAR and higher NUE. However, NUpE did not differ between species and could not explain this advantage. On the other hand, the studied species did not differ in their mean overall plasticity (calculated for each species by averaging the indices of plasticity obtained for each of the 17 variables), which, however, was achieved in different ways. Across CO2 and temperature treatments, A. faxoniana exhibited greater plasticity in stomatal conductance, LAR, SRL and NUE, whereas P. yunnanensis exhibited greater plasticity in net photosynthesis rate, leaf respiration and root/shoot ratio. Our results suggested that plasticity of key traits, such as LAR, SRL and NUE, may have important implications for the superiority of A. faxoniana in the response to climate change. Our results highlight the importance of exploring the functional significance of traits rather than the extent of plasticity as potential determinants of interspecific differences in responses to climate change. [Copyright &y& Elsevier]

Abstract: Elodea canadensis is an aquatic angiosperm native to North America. It has attracted great attention due to its invasive nature when transported to new areas in its non-native range. We have determined the complete nucleotide sequence of the chloroplast (cp) genome of Elodea. Taxonomically Elodea is a basal monocot, and only few monocot cp genomes representing early lineages of monocots have been sequenced so far. The genome is a circular double-stranded DNA molecule 156,700bp in length, and has a typical structure with large (LSC 86,194bp) and small (SSC 17,810bp) single-copy regions separated by a pair of inverted repeats (IRs 26,348bp each). The Elodea cp genome contains 113 unique genes and 16 duplicated genes in the IR regions. A comparative analysis showed that the gene order and organization of the Elodea cp genome is almost identical to that of Amborella trichopoda, a basal angiosperm. The structure of IRs in Elodea is unique among monocot species with the whole cp genome sequenced. In Elodea and another monocot Lemna minor the borders between IRs and LSC are located upstream of rps19 gene and downstream of trnH-GUG gene, while in most monocots, IR has extended to include both trnH and rps19 genes. A phylogenetic analysis conducted using Bayesian method, based on the DNA sequences of 81 chloroplast genes from 17 monocot taxa provided support for the placement of Elodea together with Lemna as a basal monocot and the next diverging lineage of monocots after Acorales. In comparison with other monocots, the Elodea cp genome has gone through only few rearrangements or gene losses. IR of Elodea has a unique structure among the monocot species studied so far as its structure is similar to that of a basal angiosperm Amborella. This result together with phylogenetic analyses supports the placement of Elodea as a basal monocot to the next diverging lineage of monocots after Acorales. So far, only few cp genomes representing early lineages of monocots have been sequenced and, therefore, this study provides valuable information about the course of evolution in divergence of monocot lineages. [Copyright &y& Elsevier]

Abstract: The effects of three watering regimes (100%, 50% and 25% of field capacity, FC) on photosynthetic traits and leaves’ self-protective systems were investigated in Populus cathayana Rehd. males and females. The results showed that drought (25% of FC) caused disorder in photosynthesis, increased the amounts of osmotically active substances (soluble sugars, proteins and proline), accumulation of reactive oxygen species (ROS), changes in antioxidant enzyme activities and damage in the integrity of cellular membranes and chloroplasts in both males and females. However, compared with drought-stressed females, drought-stressed males showed (1) higher values of net photosynthetic rate (P n), maximum rate of electron transport driving RuBP regeneration (J max), maximum rate of RuBP carboxylation (V cmax), carboxylation efficiency (CE) and non-photochemical quenching coefficient (qP); (2) higher contents of soluble proteins and proline; (3) higher activities of superoxide dismutase (SOD), ascorbate peroxidase (APX), peroxidase (POD) and polyphenoloxidase (PPO); (4) less negative effects on cellular membranes and chloroplasts. These results indicate that P. cathayana males have a better self-protection of the photosynthetic system, greater accumulation of substances for osmotic adjustment and a more efficient enzymatic detoxification cycle for eliminating the negative effects caused by ROS under drought stress than do females. [Copyright &y& Elsevier]

Abstract: In all, 48 sites of subalpine coniferous forest that had undergone natural regeneration for 5–310 years were selected as study locations in the Southwest China. We compared species richness (S), plant diversity (Shannon–Wiener index, H′; Margalef index, R), and above- and below-ground ecosystem carbon (C) pools of six plant communities along a chronosequence of vegetation restoration, and we also examined evidence for a functional relationship between plant diversity and C storage. Our results showed that above-ground C increased significantly (over 52-fold), mainly due to the increase of C in aboveground living plants and surface litter. Soil organic carbon (SOC) content increased from the herb community type (dominated by Deyeuxia scabrescens, P1) to mixed forest type (dominated by Betula spp. and Abies faxoniana, P4), which constituted the main C pool of the system (63–89%), but decreased thereafter (communities P5–P6). The mean C stock in the whole ecosystem – trees, litter layer and mineral soil – ranged from 105 to 730MgCha−1 and was especially high in the spruce forest community type (dominated by Picea purpurea, P6). On the other hand, the relationships between C stocks (soil, aboveground) and mean annual temperature or altitude were generally weak (P >0.05). Moreover, we did not detect a relationship between S and aboveground C storage, while we found a significant negative relationship between H′, R and aboveground C storage. In addition, our experiment demonstrated that total root biomass and litter C/N ratio were significant functional traits influencing SOC, while S, R, and H′ had little effect. Path analysis also revealed that litter C/N ratio predominantly regulated SOC through changes in the quantity of microorganisms and soil invertase enzyme activity. [Copyright &y& Elsevier]

• Sexual dimorphism was present in phenolic metabolites of roots. • Females showed greater biochemical plasticity in response to different-sex neighbors. • Mixed-sex plantations had more diverse microbial communities in rhizosphere. • Phenolic metabolites may cause selective pressure that shapes microbial communities. We assessed root phenolics and rhizosphere microbiomes of Populus cathayana females and males in the replicated 30-year-old plantations, including pure female plantations (PF), pure male plantations (PM), and mixed female and male plantations (MS) to reveal sex and neighbor effects, and associations between root phenolic metabolites and root-related microbes. The phenolic composition of females varied more between intrasexual and intersexual interactions compared to that of males. Thus, sexual dimorphism was present in the metabolic composition and biochemical plasticity. MS plantations enhanced the bacterial and fungal alpha diversity of both females and males. The composition of fungal communities of females and males in MS plantations was different from that in PF and PM, while such differences were not found in the composition of bacterial communities. Bacterial and fungal diversities were correlated with concentrations of specific phenolic metabolites and were most positively responsive to root benzoic acid and pinoresinol production, respectively. Our findings indicate that sex-specific interactions affect the system of plant sex - root phenolics - rhizosphere microbes, and they may contribute to sex-specific resource utilization patterns. Knowledge of such mechanisms would be helpful when establishing plantations of dioecious plants. [ABSTRACT FROM AUTHOR]

We studied the genetic diversity, gene flow and population structure among 18 populations of the clonal bryophyte Trichocolea tomentella located in Finland, Lithuania, the UK and Canada using DNA fingerprinting methods. T. tomentella is a habitat-limited, unisexual hepatic, which occupies spring and mesic habitats in woodland. The relatively small populations are increasingly fragmented with a high risk for extinction for extrinsic reasons. The presence of relatively high levels of genetic diversity regardless of population size highlights the role of even small remnant populations as important sources of genetic diversity in T. tomentella. The long-term accumulation of genotypes and somatic mutations may explain the observed levels of diversity. Gene flow among populations seems to be infrequent indicating dispersal limitation also on the relatively small spatial scale. Colonization within populations is not affected by isolation by distance suggesting the occurrence of random short-range dispersal of detached vegetative fragments. The population structure study confirmed the low mortality rates of shoots indicating a long life span of the clones in favourable conditions. Efficient ramet production by branching is likely to operate against interspecific competition. To conclude, T. tomentella appears to persist well in undisturbed habitats due to clonal regeneration, although restricted dispersal capacity is likely to prevent successful (re-)colonization in the potential habitat patches of recovering forest landscapes. The implications of the results for conservation are introduced. [Copyright &y& Elsevier]

Abstract: Birch (Betula albosinensis Burk.) seedlings were grown under two CO2 concentrations, 350μmolmol−1 (ambient CO2) and 700μmolmol−1 (elevated CO2), and in two planting densities, 32plants/m2 (low density, LD) and 72plants/m2 (high density, HD). The objectives were to characterize the responses of leaf photosynthesis to long-term elevated CO2 in birch seedlings in different planting densities, and to assess whether elevated CO2 regulates the photosynthetic capacity of leaves, in terms of nitrogen concentration (N), the activity of ribulose bisphosphate carboxygenase (Rubisco), the photosynthetic efficiency of Rubisco and the concentration of nonstructural carbohydrates (TNC). In both planting densities, the leaves of birch seedlings grown under elevated CO2 but measured at 350μmolmol−1 CO2 had a lower leaf N concentration, net CO2 assimilation rate (A), transpiration (E) and stomatal conductance (g s), and a higher water use efficiency (WUE) than those of birch seedlings both grown and measured under ambient CO2 concentration. On the other hand, the values of A, E, g s and WUE were significantly affected by planting density under ambient CO2, whereas these parameters were not affected by planting density under elevated CO2. In contrast, the levels of sucrose, soluble sugars, starch and TNC in the leaves were not significantly affected by planting density under ambient CO2, whereas these parameters were significantly affected by planting density under elevated CO2. Our results demonstrated that there are different acclimations of leaf photosynthesis in birch seedlings, as affected by elevated CO2 and planting density, and they highlighted the importance of the CO2 level and planting density for the physiological ecology of woody plants. [Copyright &y& Elsevier]

We exposed the cuttings of Populus cathayana to Hoagland’s solution containing four different manganese (Mn) concentrations (0, 0. 1, 0. 5 and 1mM) in a greenhouse to characterize the physiological and biochemical basis of Mn resistance in woody plants. Two contrasting populations of P. Cathayana were used in our study, which were from the wet and dry climate regions in western China, respectively. The results showed that Mn treatments significantly decreased chlorophyll content and growth characteristics, including shoot height, basal diameter, biomass accumulation and total leaf area in the two populations. Mn treatments also significantly increased the levels of abscisic acid (ABA), polyamines and free amino acids especially proline (Pro), histidine (His) and phenylalanine (Phe) available for cellular signaling and heavy metal chelation. In addition, high Mn concentrations also caused oxidative stress indicated as the accumulation of hydrogen peroxide (H2O2) and malondialdehyde (MDA) contents. On the other hand, there were different responses to Mn stress between the two contrasting populations. Compared with the dry climate population, the wet climate population accumulated more Mn in plant tissues especially in leaves; it showed lower tolerance index and more pronounced decrease in growth and chlorophyll contents. The wet climate population not only accumulated less ABA, putrescine and free amino acids, but also exhibited lower activities of superoxide dismutase (SOD) and ascorbate peroxidase (APX), thus suffering from more serious oxidative damage. Therefore, our results showed that the wet climate population was more susceptible to Mn stress than the dry climate population. [Copyright &y& Elsevier]

Abstract: Cuttings of Populus kangdingensis and P. cathayana originating from high and low altitudes in south-west China, respectively, were used to determine the effect of drought and enhanced UV-B radiation and their combination on plant growth and physiological traits in a greenhouse during one growing season. In both species, cuttings grown under drought conditions exhibited reduced growth and more abscisic acid (ABA) accumulation than did plants kept under well-watered conditions. Enhanced UV-B radiation significantly reduced plant growth and influenced ascorbate peroxidase (APX) activity, proline concentration, the amount of UV-B absorbing compounds and carbon isotope composition (δ 13C) in both species, while it hardly affected ABA accumulation. However, partial differences in responses to each stress were observed between the two species. In P. cathayana, the additive effect of both stresses on plant height and leaf area was observed, and drought significantly increased the free proline concentration. In contrast, distinctly higher APX activity, and ABA and δ 13C levels were observed in P. kangdingensis when compared to P. cathayana. Moreover, an increase in the amount of UV-B absorbing compounds was detected in P. kangdingensis both after the treatment with UV-B alone as well as after its application to drought-stressed plants. In P. cathayana, superoxide dismutase (SOD) activity showed a significant increase under enhanced UV-B, while a pronounced increase in the amount of UV-B absorbing compounds was observed only under the combination of the two stresses. Our results suggest that P. kangdingensis, originating from high altitude and being apparently adapted to drought and high levels of UV-B, exhibits greater tolerance to drought and enhanced UV-B radiation than does P. cathayana originating from lower altitude. [Copyright &y& Elsevier]

• Sex significantly affects water content, NO 3 −, total N and total P of rhizosphere. • Bacteria in bulk and rhizosphere are more strongly affected by sex than fungi. • Higher soil moisture in female rhizosphere promotes N-cycling related bacteria. • More Actinobacteria in rhizosphere contribute to higher N use efficiency of male. Plant-soil microbe interactions are determined by plant characters. Sexual dimorphism in root development, nitrogen (N) assimilation and resource allocation have been studied in different environments. However, how dioecious plants affect soil microbial communities in natural forests, particularly in low precipitation regions, is still poorly known. In this study, natural Populus euphratica forests were investigated in three arid regions. We hypothesized that males and females impose sex-specific impacts on physiochemical traits of soil, microbial communities and N-cycling processes. We discovered only little sex effect on most physiochemical traits, and bacterial and fungal communities in top soil (0–20 cm) in the three studied forests. However, the sex effect was greater in deep soil. Compared with fungi, the structure and composition of bacterial communities were affected more by plant sex in the rhizosphere and bulk soil. Sex indirectly affected N-cycling processes through a negative impact on the soil water content. Expressions of AOA, AOB, nifH , nirS and nirK in the rhizosphere soil were significantly affected by sex, forest site and their interactions. Proteobacteri a, Actinobacteria and Firmicutes in the rhizosphere and bulk soils of P. euphratica males showed more significant effects on ammoxidation, N fixation, denitrification and protease activities when compared to females. The results suggest that sexual differences in shaping bacterial communities and affecting N-cycling processes are greater when the soil becomes drier. Thus, low precipitation causes intense sex differences in the nitrogen uptake and use efficiency. Our study highlights the importance of sexual effects on shaping specific microbial communities and N-cycling processes. [ABSTRACT FROM AUTHOR]

• Inter- and intra-sexual competition patterns affected eco-physiological responses of P. cathayana to EC, ET and ETC. • Carbon-related metabolites of females were most strongly affected by ET under inter- and intra-sexual competition. • Males exhibited strongest responses of water and nitrogen use efficiencies to EC and ETC. • Competitive pressure of females on males was intensified by ET but alleviated by ETC. It remains unclear how global climate change affects dioecious plants that may be especially vulnerable to climate drivers, because they often exhibit skewed sex ratios and eco-physiological specialization in certain microhabitats. In this study, female and male saplings of Populus cathayana were employed to explore sex-specific responses and the effects of sexual competition under elevated temperature (ET), elevated CO 2 (EC) and combination of elevated temperature and CO 2 (ETC). The results demonstrated that elevated temperature and CO 2 interactively modulated sexual competition and responses of P. cathayana. Moreover, competition patterns affected the eco-physiological responses of P. cathayana to climate change treatments. Under both intra- and inter-sexual competition, biomass components, photosynthetic parameters and carbon-related metabolites of females were most strongly affected by ET, while males exhibited a higher photosynthesis and resource use efficiency, and a better biomass accumulation and carbon balance mechanism when compared to females when experiencing intra-sexual competition under EC. The competitive pressure of females on males in inter-sexual competition was intensified by ET, while it was alleviated by ETC. We conclude that climate change drivers and competition patterns differently regulate the sex-specific responses and competitive intensity of males and females, which may have a crucial effect on sex ratios, spatial sexual segregation, biomass production and carbon sequestration in dioecious species in the future. [ABSTRACT FROM AUTHOR]

Abstract: Two experiments were performed to test the relevance of bryophyte (Plantae, Bryophyta) material for forensic studies. The first experiment was conducted to reveal if, and how well, plant fragments attach to footwear in general. In the test, 16 persons walked outdoors wearing rubber boots or hiking boots. After 24h of use outdoors the boots were carefully cleaned, and all plant fragments were collected. Afterwards, all plant material was examined to identify the species. In the second experiment, fresh material of nine bryophyte species was kept in a shed in adverse conditions for 18 months, after which DNA was extracted and subjected to genotyping to test the quality of the material. Both experiments give support for the usability of bryophyte material in forensic studies. The bryophyte fragments become attached to shoes, where they remain even after the wearer walks on a dry road for several hours. Bryophyte DNA stays intact, allowing DNA profiling after lengthy periods following detachment from the original plant source. Based on these experiments, and considering the fact that many bryophytes are clonal plants, we propose that bryophytes are among the most usable plants to provide botanical evidence for forensic investigations. [Copyright &y& Elsevier]

• P application level and pattern affected the performance of P. deltoides clones. • Root traits and rhizosphere processes varied among P. deltoides genotypes. • Tradeoffs occurred between root morphology and root exudation in low-P soils. • High soil acid phosphatase activity alleviated negative effects of P shortage. • Higher SRL was associated with higher biomass under high/heterogeneous P supply. Soil phosphorus (P) availability and its distribution influence plant growth and productivity. To evaluate strategies that allow genotypes to be efficient under variable P environments, we planted six hybrid Populus deltoides clones belonging to the section Aigeiros (Aig), LL1, LL9, NL351, NL35, NL1388 and NL895, to three growth conditions in a greenhouse experiment, including low P, a high homogenous P supply and a high heterogeneous P supply. Functional traits, including foliar and root traits as well as rhizosphere processes, were measured. Large genotypic variation in shoot biomass and leaf P concentration was found in response to the P supply level and pattern. Compared with no P supply, LL1, LL9 and NL895 had a greater root length, biomass and P concentration in leaves under a homogenous P supply, while growth traits of NL351, NL35 and NL1388 were not significantly affected. A heterogeneous P supply enhanced the shoot biomass of LL1 and LL9. The root proliferation of LL1 and LL9 in P-rich patches was related to increased P acquisition in leaves. By contrast, a heterogeneous P supply did not enhance the biomass accumulation and the morphological plasticity of roots in other four genotypes, NL351, NL35, NL895 and NL1388, in P-rich patches. We found that functional traits or rhizosphere processes under low P could predict high P performance in Populus clones. Genotypes with a higher specific root length under low P can accumulate a larger biomass under a homogenous P supply. Conversely, high acid phosphatase concentrations decreased the positive impact of a heterogeneous P supply on a genotype's performance. Our results provide implications and applications for silviculture and forest management. [ABSTRACT FROM AUTHOR]

Nitrogen (N) deposition affects plant growth and interspecific interaction. This study aimed to explore the effect of N deposition on the growth and eco-physiological interactions between two tree species dominating in subtropical forests. A greenhouse experiment was conducted for 6 months in which the conifer Cunninghamia lanceolata and the broadleaved Phoebe chekiangensis were grown in monocultures and in a mixture under two levels of N addition: 0 and 45 kg ha−1 yr−1. The plant growth, root architecture, biomass distribution, element contents in plants and soil, and photosynthetic physiology were determined. The height and crown width of both seedlings tended to be higher in the mixture than in the monoculture when grown without N addition. P. chekiangensis was superior to C. lanceolata in resource acquisition and showed a greater net photosynthetic rate, plant height, crown width, total biomass, and belowground biomass distribution. In the mixture, N addition increased the net photosynthetic rate and decreased the height, ground diameter, and crown width of both species. Belowground biomass distribution was decreased in C. lanceolata but increased in P. chekiangensis under N addition. The P contents in both seedlings were higher in the mixture than in monocultures. Results showed N addition aggravated the competition and weakened the growth of both species in the mixture, largely determined by the competition for resources through the changing root architecture and biomass allocation. Our results provide new insights into the mechanisms of interspecific interaction in response to increasing N deposition in silvicultural practice. • N-addition enhances photosynthesis of both species in mixture. • N-addition increases greater belowground biomass of Phoebe chekiangensis than Cunninghamia lanceolata. • N-addition aggravates competition but declines growth of both species. [ABSTRACT FROM AUTHOR]

Drought stress influences the growth of plants and thus grafting has been widely used to improve tolerance to abiotic stresses. Poplars possess sex-specific responses to drought stress, but how male or female rootstock affect the grafted plant is little known. To explore the mechanisms underlying changes in drought tolerance caused by grafting, we investigated the changes in growth, leaf traits, gas exchange and antioxidant enzyme activities of reciprocally grafted seedlings between Populus euramericana cv. "Nanlin895" (NL-895) (female) and Populus deltiodes cv." 3412 " (NL-3412) (male) under water deficit stress with 30% field capacity for 30 d. Results showed that drought stress affected adversely growth, morphological, and physiological characteristics in all seedlings studied. Grafted seedlings with male roots can effectively alleviated the inhibition of growth induced by drought stress, as shown by higher WUE, activities of SOD, POD and CAT, and lower levels of lipid peroxidation. Male seedlings with female roots were found to be less tolerance to drought than non-grafted male clones and female scions with male roots, but more tolerance than non-grafted female clones. This results suggested that drought tolerance of grafted seedlings is primarily caused by the rootstock, although the scion also affects the grafted plant. Thus, paying attention on the root genotype can provide an important means of improving the drought tolerance of poplars. • Grafted poplars with male roots can effectively alleviated the inhibition of growth induced by drought stress. • Both scion and rootstock can influence the drought tolerance of grafted poplars. • Drought tolerance of poplars is primarily caused by the root. [ABSTRACT FROM AUTHOR]

Abstract The impact of conspecific and heterospecific neighboring plants on soil bacterial and fungal communities has never been explored in a forest ecosystem. In the present study, we first investigated soil microbial communities in three plantations: Larix kaempferi monoculture, L. olgensis monoculture and their mixture. Then, a two-year growth experiment was conducted to investigate the effects of intra- and inter-specific interactions of L. kaempferi and L. olgensis on rhizosphere microbial communities at two different nitrogen levels. The results demonstrated clear differences in the beta-diversity and composition of bacteria and fungi among the three plantations, which implied the presence of different effects of plant-plant interactions on soil microbial communities. The results of the pot experiment showed that L. kaempferi suffered from greater neighbor effects from its conspecific neighbor regardless of N fertilization, although the effect declined when L. kaempferi was grown with L. olgensis under N fertilization. Changes in intra- and inter-specific plant interactions significantly impacted the chemical and biological properties of soil under N fertilization, with lower concentrations of NH 4 +, and lower soil microbial biomass (C Mic) and soil carbon nitrogen biomass (N Mic) under intra-specific plant interactions of L. kaempferi (KK) compared to inter-specific interactions of L. kaempferi and L. olgensis (KO). N fertilization increased bacterial and fungal alpha diversities in the rhizosphere soil of KO. For the beta diversity, the PERMANOVA results demonstrated that there was a significant impact of intra- and inter-specific plant interactions on soil microbial communities, with KK significantly differing from intra-specific plant interactions of L. olgensis (OO) and KO. The two plant species and N fertilization showed specific effects on the soil microbial composition, particularly on the fungal community. Both L. olgensis and N fertilization increased the abundance of Ascomycota but reduced that of Basidiomycota , and even shifted the dominance from Basidiomycota to Ascomycota under KO combined with N fertilization. Highlights • Neighbor plant negatively affected plant growth, in particular for L. kaempferi. • Inter-specific plant interactions raised bacterial and fungal diversity in added N. • L. olgensis and N addition induced the dominance of the Basidiomycota community. • L. olgensis mainly affected microbial community in inter-specific associations. [ABSTRACT FROM AUTHOR]

Nitrogen (N) partitioning within a leaf affects leaf photosynthesis and adaptation to environmental fluctuations. However, how plant sex influences leaf N allocation and its tradeoffs in acclimation to drought, excess salt and their combination remains unknown. Here, leaf N allocation between the photosynthetic and non-photosynthetic apparatus and among the components of the photosynthesis in Populus cathayana Rehder females and males were investigated under drought, salt and their combination to clarify the underlying mechanism. We found that males with a lower leaf N allocation (N L) into non-protein N (N np), showed a greater leaf N allocation into photosynthetic apparatus, especially into the carboxylation component under all treatments, and a greater leaf N allocation into cell wall under drought and salt stress alone, consequently causing higher photosynthetic N use efficiency (PNUE) and tolerance to stresses. Conversely, females had a greater leaf N allocation into N np under all treatments than males and a lower leaf photosynthetic N (N P) allocation. There was a tradeoff in leaf N allocation among photosynthetic apparatus (N P / N L), cell wall (N CW / N L) and N np , which explained plant responses to drought, salt and their combination. Moreover, the leaf N allocation into the carboxylation component could explain the intersexual difference in responses to all treatments, while leaf cell wall N (N CW) and N np reflected intrasexual differences among treatments in both sexes. These findings indicate sex-specific strategies in coping with drought, salt and their combination that relate to leaf N allocation, which may contribute to sex-specific photosynthesis and niche segregation. [Display omitted] • The tradeoffs of leaf nitrogen allocation determined sex-specific responses. • Leaf N allocation into the carboxylation component explained the sexual difference. • Higher N allocation into photosynthesis in male determined its greater tolerance. • Higher N allocation into non-protein in female decreased photosynthetic N proportion. [ABSTRACT FROM AUTHOR]

Despite the ubiquitous distributions and critical ecological functions of microorganisms in pedogenesis and ecosystem development in recently deglaciated areas, there are contrasting successional trajectories among bacteria and fungi, but the driving forces of community assembly still remain poorly resolved. In this study, we analyzed both bacterial and fungal lineages associated with seven different stages in the Hailuogou Glacier Chronosequence , to quantify their taxonomic composition and successional dynamics, and to decipher the relative contribution from the bottom-up control of soil nutrients and altered vegetation as well as top-down pressures from nematode grazers. Co-occurrence networks showed that the community complexity for both bacteria and fungi typically peaked at the middle chronosequence stages. The overlapping nodes mainly belonged to Proteobacteria and Acidobacteria in bacteria, and Ascomycota and Basidiomycota in fungi, which was further supported by the indicator species analysis. Variation in partitioning and structural equation modeling suggested that edaphic properties were the primary agents shaping microbial community structures, especially at the early stages. The importance of biotic factors, including plant richness and nematode feeding, increased during the last two stages along with the establishment of a coniferous forest, eventually governing the turnover of fungal communities. Moreover, bacterial communities exhibited a more compact network topology during assembly, thus supporting determinism, whereas the looser clustering of fungal communities illustrated that they were determined more by stochastic processes. These pieces of evidence collectively reveal divergent successional trajectories and driving forces for soil bacterial and fungal communities along a glacier forefield chronosequence. [ABSTRACT FROM AUTHOR]

Soil salinity is usually accompanied by alkalization in northwest China, and they both negatively impact plant growth and result in severe ecological problems. Some studies have reported tree responses to salinity or alkali stress alone, however, the interactive salinity and alkali effects are still unclear, especially in dioecious trees. In this study, we measured growth, morphology, leaf stomata, gas exchange, carbon isotope composition (δ13C), total soluble sugar and starch contents, Na+ accumulation and allocation, oxidative stress, and antioxidants of female and male Populus euphratica seedlings in response to salinity, alkali and their interaction. Our study showed no significant sexual differences in studied traits under control conditions. In addition, P. euphratica females showed greater inhibitory and negative effects, such as bigger decreases in growth and gas exchange, lower stomatal density and water use efficiency (as described by δ13C), and lower levels of soluble sugars and antioxidant enzyme activities compared with males under salinity, alkali and interactive stress conditions. Furthermore, P. euphratica males had a greater ability of ion exclusion and Na + transport restriction. For example, males allocated more Na+ to stems and roots than females, whereas females had higher Na+ contents in leaves under stress conditions. In conclusion, our results indicated that P. euphratica males have superior resistance and they perform better than females under salinity, alkali and their interactive stress conditions. • Females had greater inhibitory and negative effects under salinity and alkali stress. • Males had greater ability of ion exclusion and Na + transport restriction. • Males had stronger resistance and better performance under salinity and alkali stress. [ABSTRACT FROM AUTHOR]

Abstract: An integrated physiological, biochemical and proteomic approach was used to systematically investigate the salt stress responses of Populus cathayana Rehder. Cuttings of a one-year-old female clone were used. Saline treatments had the NaCl concentrations of 0, 50 and 100mM added to full-strength Hoagland''s solution. Salinity significantly decreased the relative water content (RWC) of leaves, the contents of chlorophyll a and chlorophyll b, CO2 assimilation rate (A) and stomatal conductance (gs) in both salt stress treatments, which suggested that the chloroplast function was affected by salt stress. The observed increases of H2O2 and malondialdehyde (MDA) contents, and electrolyte leakage suggested that salinity caused cellular damage, whereas the increases in compatible solutes and in the activities of antioxidant enzymes enhanced the salt tolerance. Total proteins of the leaves were extracted by a combination of TCA–acetone and phenol, and separated by two-dimensional gel electrophoresis at pH 4–7. More than 1000 protein spots were reproducibly detected on each gel, and 38 salt-responsive proteins were successfully identified by peptide mass fingerprint (PMF). Although the proteins identified in this investigation represent only a very small part of poplar leaf proteins, some of the novel salt-responsive proteins identified here may be involved in physiological and biochemical responses to salt stress in P. cathayana, while the other identified proteins play a role in numerous cellular functions, including signal transduction, mRNA processing and the regulation of the cell cycle. The analysis of physiological and proteomic alterations, and the identification of stress-related proteins contribute to knowledge of salt acclimation in poplar. [Copyright &y& Elsevier]

Abstract: Although western Sichuan is regarded as a natural distribution and variation center for the Tacahamaca section of the Populus species in China, little is currently known about the majority of poplar species occurring in this region. In the present study, molecular data were utilized to determine the genetic relationships among Populus species in section Tacamahaca in western Sichuan. The chloroplast simple sequence repeat (cpSSR)- and nuclear SSR-based UPGMA analyses were performed for 7 Populus species, with 50 specimens representing 10 accessions. The results provided molecular evidence suggesting that P. schneideri is genetically highly similar to P. kangdingensis, as also indicated by previous studies based on their morphological characters. Similarly, the combination of cpSSR and nuclear SSR analyses indicated that P. trinervis and P. simonii have a close genetic affinity, which is supported by morphological traits and similarities in the range of natural habitats. Although, based on nuclear SSR analysis, P. yunnanensis is distinct from the other species, it shared the same cpSSR profiles with P. simonii and P. trinervis. This result reflects similar maternal phylogeny among the three species. In addition, the cluster analyses clearly showed a close relationship among accessions of the same species and suggested monophyly in P. przewalskii and P. cathayana. Our results demonstrated that the combination of cpSSR and nuclear SSR molecular markers enables a clear estimation of genetic relationships among Populus species and they provided information for preliminary conclusions that will be helpful in guiding future research. [Copyright &y& Elsevier]