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The taxonomic classification of Picea meyeri and P. mongolica has long been controversial. To investigate the genetic relatedness, evolutionary history, and population history dynamics of these species, genotyping-by-sequencing (GBS) technology was utilized to acquire whole-genome single nucleotide polymorphism (SNP) markers, which were subsequently used to assess population structure, population dynamics, and adaptive differentiation. Phylogenetic and population structural analyses at the genomic level indicated that although the ancestor of P. mongolica was a hybrid of P. meyeri and P. koraiensis, P. mongolica is an independent Picea species. Additionally, P. mongolica is more closely related to P. meyeri than to P. koraiensis, which is consistent with its geographic distribution. There were up to eight instances of interspecific and intraspecific gene flow between P. meyeri and P. mongolica. The P. meyeri and P. mongolica effective population sizes generally decreased, and Maxent modeling revealed that from the Last Glacial Maximum (LGM) to the present, their habitat areas decreased initially and then increased. However, under future climate scenarios, the habitat areas of both species were projected to decrease, especially under high-emission scenarios, which would place P. mongolica at risk of extinction and in urgent need of protection. Local adaptation has promoted differentiation between P. meyeri and P. mongolica. Genotype‒environment association analysis revealed 96,543 SNPs associated with environmental factors, mainly related to plant adaptations to moisture and temperature. Selective sweeps revealed that the selected genes among P. meyeri, P. mongolica and P. koraiensis are primarily associated in vascular plants with flowering, fruit development, and stress resistance. This research enhances our understanding of Picea species classification and provides a basis for future genetic improvement and species conservation efforts. [ABSTRACT FROM AUTHOR]

Investigating the mechanisms by which plants adapt to low phosphorus content in ecosystems is crucial for nutrient dynamics division. Our study investigated the growth adaptation strategies of Pinus massoniana seedlings to low phosphorus conditions, including nutrient and non-structural carbohydrate (NSC) allocation, nutrient stoichiometry, and changes in nutrient resorption efficiency along a fact-based gradient. Our results showed that the total biomass and aboveground biomass proportion increased with substrate phosphorus content, reaching maximum biomass in the one-time phosphorus treatment. The nutrient concentration of components remained relatively stable, with the allocating preference to roots and needles under low phosphorus conditions. NSC was allocated as starch in fine roots and as soluble sugar in needles. Seedlings did not show signs of phosphorus limitation, even in the non-phosphorus group. The nitrogen resorption efficiency to phosphorus resorption efficiency ratio (NRE: PRE) of needles significantly varied between the high and low phosphorus treatments. In response to phosphorus deficiency, seedlings demonstrated homeostatic adjustments to maintain the relative stability of nutrient concentration. Fine roots and needles were prioritized to ensure nutrient uptake and photosynthetic product production. Additionally, it was necessary to differentiate the indicative function of nitrogen/phosphorus for various species and components, and NRE: PRE potentially provides a sensitive indicator of nutrient limitation status. [ABSTRACT FROM AUTHOR]

Analyzing the molecular and physiological processes that govern the uptake and transport of nitrogen (N) in plants is central to efforts to fully understand the optimization of plant N use and the changes in the N-use efficiency in relation to changes in atmospheric N deposition changes. Here, a field experiment was conducted using the ectomycorrhizal fungi (EMF), Pisolithus tinctorius (Pt) and Suillus grevillei (Sg). The effects of N deposition were investigated using concentrations of 0 kg·N·hm−2a−1 (N0), a normal N deposition of 30 kg·N·hm−2a−1 (N30), a moderate N deposition of 60 kg·N·hm−2a−1 (N60), and a severe N deposition of 90 kg·N·hm−2a−1 (N90), with the goal of examining how these factors impacted root activity, root absorbing area, NH4+ and NO3− uptake kinetics, and the expression of ammonium and nitrate transporter genes in Pinus massoniana seedlings under different levels of N deposition. These data revealed that EMF inoculation led to increased root dry weight, activity, and absorbing area. The NH4+ and NO3− uptake kinetics in seedlings conformed to the Michaelis–Menten equation, and uptake rates declined with increasing levels of N addition, with NH4+ uptake rates remaining higher than NO3− uptake rates for all tested concentrations. EMF inoculation was associated with higher Vmax values than were observed for non-mycorrhizal plants. Nitrogen addition resulted in the upregulation of genes in the AMT1 family and the downregulation of genes in the NRT family. EMF inoculation under the N60 and N90 treatment conditions resulted in the increased expression of each of both these gene families. NH4+ and NO3− uptake kinetics were also positively correlated with associated transporter gene expression in P. massoniana roots. Together, these data offer a theoretical foundation for EMF inoculation under conditions of increased N deposition associated with climate change in an effort to improve N absorption and transport rates through the regulation of key nitrogen transporter genes, thereby enhancing N utilization efficiency and promoting plant growth. Synopsis: EMF could enhance the efficiency of N utilization and promote the growth of Pinus massoniana under conditions of increased N deposition. [ABSTRACT FROM AUTHOR]

The nutrient limitation due to increasing stand age is one of the reasons for affecting the growth of trees. However, non-structural carbohydrate (NSC) play an important role in plant adaptation to stress environment. Yet, little is known about the adaptation mechanism of NSC when faced with nutrient limitation caused by the increasing stand age. Here, we selected a chronosequence of Pinus massoniana Lamb. plantations with increasing age including 5-, 12-, 28-, 37- and 56-year old stand. We measured the radial growth from 2016 to 2021, branch length from 2017 to 2021, N, P and NSC in each organ (including current year leaves, 1-year leaves, current year branches, 1-year branches, trunk, fine roots and coarse roots). With the increase of stand age, radial growth increased first and then decreased, with the highest value in 37-year old stand. The N: P ratio was greater than 16 and P concentrations were lower than 1 g/kg except that in 5-year old stand, and the variation of N: P along age sequence was basically consistent with the variation of radial growth, indicating that the P limitation increased along the age sequence, but it had been alleviated after reaching 37-year old. The NSC concentrations in P. massoniana were almost significantly increased in leaves, branches and fine root along the age sequence, but were only increased to 37-year old stand in coarse root and trunk, and then decreased after reaching 37-year old. This reflected that less fixed carbon had been allocated to structural biomass growth (trunk) and more had been allocated to the function organ (fine root), which played a positive effect on alleviating P limitation, but was not conducive to trunk thickening growth. The branches growth decreased with the increase of stand age, but the branch P and NSC did increase, indicating that branches increased the storage of P and NSC to supply other organs by reducing growth consumption. It was concluded that with the increase of stand age, P limitation can be alleviated by reducing trunk growth and increasing carbohydrates allocation to the functional organ (fine roots) to support absorbing the limited nutrient. The study deepens our understanding of the need to enhance nutrient management in older age P. massoniana plantations. • Along the age sequence, the P limitation increased first and then decreased, and reaching a peak at 37-year old stand. • An internal P mobilization that the P would transfer from old organ to young organ. • The P limitation had been alleviated by increasing the allocation of NSC to functional organs (fine roots) and decreasing the trunk growth. [ABSTRACT FROM AUTHOR]

Pinus elliottii is an evergreen coniferous tree. It is considered a potential species for ecological restoration in the Three Gorges Reservoir Area (TGRA). To classify the effects of different degrees of flooding stress in winter on nutrient accumulation in Pinus elliottii after experiencing early drought stress in summer, simulated water treatments of deep submergence (DS) and moderate submergence (MS) were imposed after the summer drought period. The results indicated that the survival rate of seedlings was 95.3%, and the accumulation trend of the flooded plants was rapid at an average rate of 1.99 ± 0.33% in the early stage of flooding (stage I: 0–7 days), a rapid release rate in the second stage (stage II: 7–60 days), and an average rate of only 0.07 ± 0.04% in the later stage (stage III: 60–150 days). After 150 days of flooding, the leaves of Pinus elliottii released an average of 7.156 ± 0.4 g kg−1 of organic carbon, 8.839 ± 0.6 g kg−1 of nitrogen, 0.781 ± 0.1 g kg−1 of phosphorus, and 2.985 ± 0.3 g kg−1 of potassium of macroelement content, and an average of 0.201 ± 0.03 g kg−1 manganese, 0.147 ± 0.04 g kg−1 iron, 0.002 g kg−1 copper, and 0.023 g kg−1 of zinc of microelement contents. Our results also demonstrated that after 150 days of flooding, the C/N, N/P, and C/P ratios of the nutrient element content of Pinus elliottii in the water-level fluctuation zone of the TGRA were 0.810%, 11.32%, and 9.16%, respectively. The absorption and release of nutrients under water flooding are generally divided into three stages: first, the early storage stage (the first stage: 0 to 7 days, optional), then the rapid release (the second stage: 7 to 60 days), and the later stage slow release phase (third stage: 60 to 150 days). Water flooding reduced the contents of C, N, P, and K and affected the absorption of nutrient elements in the plant. At the same time, soluble Mn2 + and Fe2 + over absorbed during flooding could cause toxicity to leaf tissues. At the same time, Pinus elliottii selected to reduce Cu in leaves to ensure that the root has a strong redox capacity and improve nitrogen utilization, thereby preventing the long-term flooding of toxic cations and acid substances. Taken together, our results conclude that increased drought stress can reduce the ability of Pinus elliottii seedlings to withstand flooding stress; the seedlings of Pinus elliottii can maintain their growth by accumulating certain nutrient elements under submerged conditions, which implies that this species would be a suitable candidate for reforestation in the TGRA because of its tolerance to submergence. [ABSTRACT FROM AUTHOR]

Photosynthesis and the allocation of photosynthetic products are the two main factors that determine plant growth. To understand the growth and productivity of Pinus massoniana Lamb., the diurnal changes in photosynthetic rate were continuously monitored. Furthermore, the translocation and allocation of the photosynthetic products synthesized in the morning and afternoon were explored using 13C pulse labeling. The results showed that: (1) on sunny days, the diurnal variation of the net photosynthetic rate showed a "double peak" curve, with an obvious "a depression" when temperatures were highest and humidity lowest. On cloudy days, it showed an irregular "jagged" curve, which was curve consistent with the variations in photosynthetically active radiation (PAR). Meanwhile, the photosynthetic rate changed with the transient changes in environmental factors such as PAR, temperature, and humidity. (2) The mean value of the net photosynthetic rate in the morning was higher than in the afternoon, and the response of the net photosynthetic rate to environmental change (PAR, temperature, humidity, and CO2 concentration) in the morning was greater than that in the afternoon. (3) The translocation of photosynthetic products synthesized in the afternoon was faster than that in the morning. Shortly after synthesis of photosynthetic products, the translocation of products synthesized in the morning tended toward upper organs (including current-year leaves and 1-year leaves), while the translocation of products synthesized in the afternoon decreased in the upper organs. However, after 15 days of 13C pulse labeling, the allocation of the photosynthetic products synthesized in the morning and afternoon tended to be the same. These results indicate that the differences in the photosynthetic products synthesized and the temporal differences in the translocation rates did not affect the final allocation of the photosynthetic products in the various organs of the P. massoniana. These results improve our knowledge of the functional phases of P. massoniana during the diurnal cycle. [ABSTRACT FROM AUTHOR]

The physiological mechanisms driving treeline formation succession captured the attention of ecologists many years ago, yet they are still not fully understood. In this study, physiological parameters (soluble sugars, starch, and nitrogen) were investigated in combination with transcriptomic analysis in the treeline tree species Picea crassifolia. The study was conducted in the middle of Qilian Mountain Reserves, Gansu Province, China, within the elevation range of 2500–3300 m. The results showed that the concentrations of non-structural carbohydrates decreased with increasing elevation in the current-year needles and current-year branches, as well as in the coarse and fine roots. RNA-Seq demonstrated that 483 genes were upregulated and 681 were downregulated in the comparison of 2900 and 2500 m (2900 vs. 2500), 770 were upregulated and 1006 were downregulated in 3300 vs. 2500, and 282 were upregulated and 295 were downregulated in 3300 vs. 2900. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis revealed that the differentially expressed genes were highly enriched in photosynthesis-related processes, carbon fixation and metabolism, and nitrogen metabolism. Furthermore, almost all photosynthesis-related genes were downregulated, whereas many genes involved in cuticle lipids and flavonoid biosynthesis were upregulated, contributing to the survival of P. crassifolia under the treeline condition. Thus, our study provided not only molecular evidence for carbon limitation hypothesis in treeline formation, but also a better understanding of the molecular mechanisms of treeline tree survival under adverse conditions. [ABSTRACT FROM AUTHOR]

Background: Understanding the adaptive strategies of plants to phosphorus (P) deficiency, particularly the plasticity of structural and physiological responses, is crucial for predicting plant growth. Our study aimed to investigate the growth, root morphological and resistance trait responses of Pinus massoniana seedlings under a fact-based low-P range.A P manipulation experiment (0–9.299 mg·kg−1) was carried out to measure biomass, root morphological and resistance traits of P. massoniana seedlings.The root to shoot biomass ratio changed, however, the belowground biomass did not change in response to decreased P content of the growing substrate. Seedlings extended fine roots (0–2 mm in length) thus increased root surface area to enhance P uptake. The length of coarse root (> 5 mm) and root average diameter increased with P addition. A strong response was found in root resistance traits, which also exhibited higher plasticity and made greater contributions to growth. Antioxidant enzyme activities, malondialdehyde content, acid phosphatase activity, and organic acid content all decreased with P addition, but root vigor showed a more sensitive response, making it a potentially informative indicator for changes in P conditions.Physiological traits related to root resistance were more sensitive and important in plant growth regulation, while root morphological traits showed different adaptative strategies among root classes to regulate biomass and absorptive function. The combined effects of morphological and resistance traits alleviate the limitation of P on plant growth. Our findings will provide insights into the adaptive strategies of plantation growing in subtropical regions under limiting nutrient environment.Methods: Understanding the adaptive strategies of plants to phosphorus (P) deficiency, particularly the plasticity of structural and physiological responses, is crucial for predicting plant growth. Our study aimed to investigate the growth, root morphological and resistance trait responses of Pinus massoniana seedlings under a fact-based low-P range.A P manipulation experiment (0–9.299 mg·kg−1) was carried out to measure biomass, root morphological and resistance traits of P. massoniana seedlings.The root to shoot biomass ratio changed, however, the belowground biomass did not change in response to decreased P content of the growing substrate. Seedlings extended fine roots (0–2 mm in length) thus increased root surface area to enhance P uptake. The length of coarse root (> 5 mm) and root average diameter increased with P addition. A strong response was found in root resistance traits, which also exhibited higher plasticity and made greater contributions to growth. Antioxidant enzyme activities, malondialdehyde content, acid phosphatase activity, and organic acid content all decreased with P addition, but root vigor showed a more sensitive response, making it a potentially informative indicator for changes in P conditions.Physiological traits related to root resistance were more sensitive and important in plant growth regulation, while root morphological traits showed different adaptative strategies among root classes to regulate biomass and absorptive function. The combined effects of morphological and resistance traits alleviate the limitation of P on plant growth. Our findings will provide insights into the adaptive strategies of plantation growing in subtropical regions under limiting nutrient environment.Results: Understanding the adaptive strategies of plants to phosphorus (P) deficiency, particularly the plasticity of structural and physiological responses, is crucial for predicting plant growth. Our study aimed to investigate the growth, root morphological and resistance trait responses of Pinus massoniana seedlings under a fact-based low-P range.A P manipulation experiment (0–9.299 mg·kg−1) was carried out to measure biomass, root morphological and resistance traits of P. massoniana seedlings.The root to shoot biomass ratio changed, however, the belowground biomass did not change in response to decreased P content of the growing substrate. Seedlings extended fine roots (0–2 mm in length) thus increased root surface area to enhance P uptake. The length of coarse root (> 5 mm) and root average diameter increased with P addition. A strong response was found in root resistance traits, which also exhibited higher plasticity and made greater contributions to growth. Antioxidant enzyme activities, malondialdehyde content, acid phosphatase activity, and organic acid content all decreased with P addition, but root vigor showed a more sensitive response, making it a potentially informative indicator for changes in P conditions.Physiological traits related to root resistance were more sensitive and important in plant growth regulation, while root morphological traits showed different adaptative strategies among root classes to regulate biomass and absorptive function. The combined effects of morphological and resistance traits alleviate the limitation of P on plant growth. Our findings will provide insights into the adaptive strategies of plantation growing in subtropical regions under limiting nutrient environment.Conclusion: Understanding the adaptive strategies of plants to phosphorus (P) deficiency, particularly the plasticity of structural and physiological responses, is crucial for predicting plant growth. Our study aimed to investigate the growth, root morphological and resistance trait responses of Pinus massoniana seedlings under a fact-based low-P range.A P manipulation experiment (0–9.299 mg·kg−1) was carried out to measure biomass, root morphological and resistance traits of P. massoniana seedlings.The root to shoot biomass ratio changed, however, the belowground biomass did not change in response to decreased P content of the growing substrate. Seedlings extended fine roots (0–2 mm in length) thus increased root surface area to enhance P uptake. The length of coarse root (> 5 mm) and root average diameter increased with P addition. A strong response was found in root resistance traits, which also exhibited higher plasticity and made greater contributions to growth. Antioxidant enzyme activities, malondialdehyde content, acid phosphatase activity, and organic acid content all decreased with P addition, but root vigor showed a more sensitive response, making it a potentially informative indicator for changes in P conditions.Physiological traits related to root resistance were more sensitive and important in plant growth regulation, while root morphological traits showed different adaptative strategies among root classes to regulate biomass and absorptive function. The combined effects of morphological and resistance traits alleviate the limitation of P on plant growth. Our findings will provide insights into the adaptive strategies of plantation growing in subtropical regions under limiting nutrient environment. [ABSTRACT FROM AUTHOR]

The continuous input and degradation of organic matter is crucial for soil organic carbon (SOC) sequestration during stand development. However, it remains unclear how the relative contribution of plant residues and microbial necromass to SOC changes with stand age and what are the determinants of the change pattern. The space-for-time substitution (chronosequence) approach was used to establish plots of Pinus massoniana plantations at five stand ages (6, 13, 29, 38, and 57 years). Soil samples were collected in each plot to determine the relative contribution of plant residues and microbial necromass to SOC storage by using SOC-normalized content of lignin and microbial necromass carbon (MNC). Lignin increased initially from young to mature but then decreased in over-mature plantation (R 2 = 0.54, P < 0.01) and was dominated by vanillyl phenols (79 %–89 %). MNC decreased at first from young to mature but then increased in over-mature plantation (R 2 = 0.50, P < 0.05) and it was dominated by fungal necromass carbon (54–63 %). Partial least squares path modeling revealed that stand age directly positively affected lignin and MNC, and indirectly maintained their change patterns through tree growth and microbial attributes. Stand age had a total positive effect (0.57) on lignin and a total negative effect (−0.54) on MNC. Regression analysis showed that the ratio of SOC to total nitrogen (SOC/TN) was positively correlated with lignin (R 2 = 0.76, P < 0.01) yet negatively correlated with MNC (R 2 = 0.58, P < 0.01). Additionally, the diameter at breast height, pH, and the ratio of fungal to bacterial biomass together with SOC/TN regulated the patterns of lignin and MNC with stand age. Overall, this study highlights the opposite pattern of lignin and MNC and emphasizes the importance of considering both tree growth and microbial attributes when developing SOC sequestration strategies with stand age. [Display omitted] • Lignin is mainly dominated by vanillyl phenols with stand age. • Microbial necromass carbon is mainly dominated by the fungal necromass carbon with stand age. • Microbial necromass initially decreases but then increases as stand developed. • Lignin initially increase but then decrease as stand developed. • Tree growth and microbial attributes govern lignin and microbial necromass change with stand age. [ABSTRACT FROM AUTHOR]