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Positive interspecific interactions in resource capture and soil property modification benefit the establishment of mixed plantations, contingent on environmental conditions. However, primary species frequently reject companion tree species frequently arises in forest management practices. To understand this contradiction, we investigated the effects of five planting patterns involving two local companion tree species (Phoebe chekiangensis and Torreya grandis) and Phyllostachys edulis on the soil nitrogen (N) and phosphorus (P) content, enzyme activities, net N mineralization rates, microbial composition, fungal functional groups, and the AMO gene abundance under both shade and full light conditions using a pot experiment. Under the full light condition, altered soil properties were predominantly influenced by interspecific interaction compared to intraspecific interactions, leading to an overall enhancement in nutrient availability and enzymatic activities. Under the shade condition, mixing with P. edulis similarly facilitated increased NH4+-N content, ammonification rate, and urease activity. However, P. edulis significantly decreased ammonia monooxygenase and its encoding gene, as evidence by the unbalanced ratio of net ammonification to net nitrification (2.2-fold) under the shade condition, resulting in high NH4+-N/NO3–-N ratios. Additionally, the shade condition induced soil microbial communities in the mixture to resemble those of monocultured dominant species (P. edulis). Our findings also indicated that specific plant-fungal associations in companion species were disrupted when intercropped with P. edulis. Therefore, this study highlights how the performance of companion species, linked to soil NH4+-N/NO3–-N ratios and plant-fungal associations, leads to their suppression by P. edulis under shade conditions.

Abstract Background KNOTTED1-like homeobox (KNOX) genes, plant-specific homologous box transcription factors (TFs), play a central role in regulating plant growth, development, organ formation, and response to biotic and abiotic stresses. However, a comprehensive genome-wide identification of the KNOX genes in Moso bamboo (Phyllostachys edulis), the fastest growing plant, has not yet been conducted, and the specific biological functions of this family remain unknown. Results The expression profiles of 24 KNOX genes, divided into two subfamilies, were determined by integrating Moso bamboo genome and its transcriptional data. The KNOX gene promoters were found to contain several light and stress-related cis-acting elements. Synteny analysis revealed stronger similarity with rice KNOX genes than with Arabidopsis KNOX genes. Additionally, several conserved structural domains and motifs were identified in the KNOX proteins. The expansion of the KNOX gene family was primarily regulated by tandem duplications. Furthermore, the KNOX genes were responsive to naphthaleneacetic acid (NAA) and gibberellin (GA) hormones, exhibiting distinct temporal expression patterns in four different organs of Moso bamboo. Short Time-series Expression Miner (STEM) analysis and quantitative real-time PCR (qRT-PCR) assays demonstrated that PeKNOX genes may play a role in promoting rapid shoot growth. Additionally, Gene Ontology (GO) and Protein–Protein Interaction (PPI) network enrichment analyses revealed several functional annotations for PeKNOXs. By regulating downstream target genes, PeKNOXs are involved in the synthesis of AUX /IAA, ultimately affecting cell division and elongation. Conclusions In the present study, we identified and characterized a total of 24 KNOX genes in Moso bamboo and investigated their physiological properties and conserved structural domains. To understand their functional roles, we conducted an analysis of gene expression profiles using STEM and RNA-seq data. This analysis successfully revealed regulatory networks of the KNOX genes, involving both upstream and downstream genes. Furthermore, the KNOX genes are involved in the AUX/IAA metabolic pathway, which accelerates shoot growth by influencing downstream target genes. These results provide a theoretical foundation for studying the molecular mechanisms underlying the rapid growth and establish the groundwork for future research into the functions and transcriptional regulatory networks of the KNOX gene family.

To address the issue of phosphorus limitation in agricultural and forestry production and to identify green and economical alternatives to chemical phosphorus fertilizers, this paper reviews the utilization of phosphorus in plant–soil systems and explores the considerable potential for exploiting endogenous phosphorus resources. The application of phosphate-solubilizing microorganisms (PSMs) is emphasized for their role in phosphorus activation and plant growth promotion. A focus is placed on microbial interactions as an entry point to regulate the functional rhizosphere microbiome, introducing the concept of synthetic communities. This approach aims to deepen the understanding of PSM interactions across plant root, soil, and microbial interfaces, providing a theoretical foundation for the development and application of biological regulation technologies to enhance phosphorus utilization efficiency.

Abstract Key message Short-term nitrogen (N) deposition stimulates phosphorus (P) demand owing to the growth improvment of Phyllostachys edulis seedlings. Increased N loads led to the acquisition and utilization of sufficient P, while the limitation of P starvation could be alleviated by the higher activity of soil acid phosphatase and P use efficiency rather than P resorption from senescent organs. Context Plants in most terrestrial ecosystems are usually subjected to natural phosphorus (P) deficiency or surplus by overfertilization associated with increasing global nitrogen (N) deposition. As the widely distributed gramineous plant in Southern China, moso bamboo (Phyllostachys edulis (Carrière) J. Houz) grows fast and it also shows a relatively good growth performance under the variable N and P conditions. However, few studies focus on the special mechanism of P mobilization and utilization of moso bamboo, especially with the N loads. Aims The objective of this study was to figure out the mechanisms of P mobilization and utilization in P. edulis seedlings under varying levels of soil P and N deposition conditions in the subtropical region of China. Methods We grew P. edulis seedlings under 3 experimental N deposition rates (0 (N −), 30 (N +), and 60 (N + +) kg N ha−1·a−1) and 3 levels of soil P (2.99 mg·kg−1, soil available P content under natural conditions, denoted as P1; 20 mg·kg−1, P2; and 40 mg·kg−1, P3). We measured growth traits and analyzed the related P use indices. Results Dry weight and P accumulation of new leaves and stems increased with increasing N loads under the 3 P treatments, with the positive effects of N deposition being stronger in the P2 and P3 treatments. Compared with N − , N + , and N + + significantly increased P use efficiency (PUE) (+ 15.54% and + 12.47%, respectively) regardless of soil P conditions. The P resorption efficiency showed a decreasing tendency under variable P conditions with increasing N, whereas PUE was further increased. Acid phosphatase (APase) activity and soil available P content were significantly improved by N loads in P1. Conclusion Phyllostachys edulis seedlings showed high growth plasticity and P mobilization mechanisms under different soil P availability with N loads. In general, N addition stimulated P demand of P. edulis seedlings owing to the growth promotion in the short period of experiment. A special P use mechanism in P deficiency conditions was that the limitation of P starvation was alleviated by the higher soil APase activity and PUE instead of P resorption from senescent organs. The long-term effect of N deposition on P mobilization and utilization in P. edulis forests requires further monitoring.

Summary Phosphate‐mobilizing bacteria (PMB) play a critical role in the regulation of phosphorus availability in the soil. The microbial genes pqqC and phoD encode pyrroloquinoline quinone synthase and bacterial alkaline phosphatase, respectively, which regulate inorganic and organic phosphorus mobilization, and are therefore used as PMB markers. We examined the effects of soil properties in three Moso bamboo forest sites on the PMB communities that were profiled using high‐throughput sequencing. We observed differentiated responses of pqqC‐ and phoD‐harbouring PMB communities to various soil conditions. There was significant variation among the sites in the diversity and structure of the phoD‐harbouring community, which correlated with variation in phosphorus levels and non‐capillary porosity; soil organic carbon and soil water content also affected the structure of the phoD‐harbouring community. However, no significant difference in the diversity of pqqC‐harbouring community was observed among different sites, while the structure of the pqqC‐harbouring bacteria community was affected by soil organic carbon and soil total nitrogen, but not soil phosphorus levels. Overall, changes in soil conditions affected the phoD‐harbouring community more than the pqqC‐harbouring community. These findings provide a new insight to explore the effects of soil conditions on microbial communities that solubilize inorganic phosphate and mineralize organic phosphate.

Breeding early maturing cultivars is one of the most important objectives in pear breeding. Very early maturing pears provide an excellent parental material for crossing, but the immature embryo and low seed germination of their hybrid progenies often limit the selection and breeding of new early maturing pear cultivars. In this study, we choose a very early maturing pear cultivar ‘Pearl Pear’ as the study object and investigate the effects of cold stratification, the culture medium, and the seed coat on the germination and growth of early maturing pear seeds. Our results show that cold stratification (4 °C) treatment could significantly improve the germination rates of early maturing pear seeds. A total of 100 days of cold-temperature treatment in 4 °C and in vitro germination on White medium increased the germination rate to 84.54%. We also observed that seed coat removal improved the germination of early maturing pear seeds, with middle seed coat removal representing the optimal method, with a high germination rate and low contamination. The results of our study led to the establishment of an improved protocol for the germination of early maturing pear, which will greatly facilitate the breeding of new very early maturing pear cultivars.

Moso bamboo (Phyllostachys edulis) is the most widely distributed bamboo species in the subtropical regions of China. Due to the fast-growing characteristics of P. edulis, its growth requires high nutrients, including phosphorus. Previous studies have shown that SPX proteins play key roles in phosphorus signaling and homeostasis. However, the systematic identification, molecular characterization, and functional characterization of the SPX gene family have rarely been reported in P. edulis. In this study, 23 SPXs were identified and phylogenetic analysis showed that they were classified into three groups and distributed on 13 chromosomes. The analysis of conserved domains indicated that there was a high similarity between PeSPXs among SPX proteins in other species. RNA sequencing and qRT-PCR analysis indicated that PeSPX6 and PeSPX-MFS2, which were highly expressed in roots, were clearly upregulated under low phosphorus. Co-expression network analysis and a dual luciferase experiment in tobacco showed that PeWRKY6 positively regulated the PeSPX6 expression, while PeCIGR1-2, PeMYB20, PeWRKY6, and PeWRKY53 positively regulated the PeSPX-MFS2 expression. Overall, these results provide a basis for the identification of SPX genes in P. edulis and further exploration of their functions in mediating low phosphorus responses.

Two types of bamboo shoots, high bamboo (Phyllostachys prominens) shoots (HBSes) and moso bamboo (Phyllostachys edulis) shoots (MBSes), underwent a fast post-harvest lignification process under room temperature storage. To explore the mechanism of lignification in two types of bamboo shoots after post-harvest during room temperature storage, the measurement of cell wall polymers (lignin and cellulose) and enzyme activities of phenylalanine ammonialyase (PAL) and peroxidase (POD), and relative expression of related transcription networks factors (TFs) were performed. The results suggested that the lignification process in HBSes is faster than that in MBSes because of incremental increase in lignin and cellulose contents within 6 days and the shorter shelf-life. Additionally, compared with the expression pattern of lignification-related TFs and correlation analysis of lignin and cellulose contents, MYB20, MYB43, MYB85 could function positively in the lignification process of two types of bamboo shoots. A negative regulator, KNAT7, could negatively regulate the lignin biosynthesis in two types of bamboo shoots. In addition, MYB63 could function positively in HBSes, and NST1 could function negatively in MBSes. Notably, MYB42 may function differently in the two types of bamboo shoots, that is, a positive regulator in HBSes, but a negative regulator in MBSes. Transcription networks provide a comprehensive analysis to explore the mechanism of lignification in two types of bamboo shoots after post-harvest during room temperature storage. These results suggest that the lignification of bamboo shoots was mainly due to the increased activity of POD, higher expression levels of MYB20, MYB43, MYB63, and MYB85 genes, and lower expression levels of KNAT7 and NST1 genes, and the lignification process of HBSes and MBSes had significant differences.

Atmospheric nitrogen (N) deposition can increase the susceptibility of vascular plants to other stresses, but the physiological basis of such a response remains poorly understood. This study was designed to clarify the physiological mechanisms and to evaluate bioindicators of N deposition impact on vascular plants. We evaluate multiple physiological responses to ~4 years of simulated additional N deposition (30–90 kg N ha−1 year−1) on three age-classes (1a, 3a, and 5a) of Moso bamboo. A saturating response to the additional N deposition was found both in foliar N concentration and in Pn. However, 3- and 5-year-old bamboo seemed to be less tolerant to extremely high N deposition than 1-year-old bamboo since they were saturated at a lower N addition. Furthermore, C/N/P stoichiometric ratios were very sensitive to N deposition in all three-age classes of bamboo, but the responses to N deposition in the various age-classes were diverse. We also found that the highest additional N deposition suppressed stomatal conductance and transpiration rate, suggesting an induced water stress. The stress induced by the high N load was also seen in photochemistry, where it reduced potential and actual photosynthetic use of light energy, diminished photo-protection capacity, and increased risk of the photo-damage. High additional N deposition contributed to a decrease in the foliar soluble protein contents and to an increase in the peroxidase activity (POD). Our study suggested, for the first time, that although the photosynthetic rate was enhanced by the increased N deposition in Moso bamboo, long-term high N load causes negative effects, such as damage to photosystem II. In Moso bamboo photochemical parameters are more sensitive to N deposition than photosynthetic rate or foliar N concentration. Furthermore, plant age should be taken into account when assessing plants' susceptibility to changes in global change drivers, such as N deposition. These findings facilitate the revealing of the risks potentially caused to vascular plants by increased N deposition before any visible symptoms of injury are seen.

Biochar amendment has been proposed as a strategy to improve acidic soils after overuse of nitrogen fertilizers. However, little is known of the role of biochar in soil microbial biomass carbon (MBC) and bacterial community structure and diversity after soil acidification induced by nitrogen (N) deposition. Using high-throughput sequencing of the 16S rRNA gene, we determined the effects of biochar amendment (BC0, 0 t bamboo biochar ha ^−1 ; BC20, 20 t bamboo biochar ha ^−1 ; and BC40, 40 t bamboo biochar ha ^−1 ) on the soil bacterial community structure and diversity in Moso bamboo plantations that had received simulated N deposition (N30, 30 kg N ha ^−1 yr ^−1 ; N60, 60 kg N ha ^−1 yr ^−1 ; N90, 90 kg N ha ^−1 yr ^−1 ; and N-free) for 21 months. After treatment of N-free plots, BC20 significantly increased soil MBC and bacterial diversity, while BC40 significantly decreased soil MBC but increased bacterial diversity. When used to amend N30 and N60 plots, biochar significantly decreased soil MBC and the reducing effect increased with biochar amendment amount. However, these significant effects were not observed in N90 plots. Under N deposition, biochar amendment largely increased soil bacterial diversity, and these effects depended on the rates of N deposition and biochar amendment. Soil bacterial diversity was significantly related to the soil C/N ratio, pH, and soil organic carbon content. These findings suggest an optimal approach for using biochar to offset the effects of N deposition in plantation soils and provide a new perspective for understanding the potential role of biochar amendments in plantation soil.