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The relationship between plants and the environment is a core area of research in ecology. Owing to differences in plant sensitivity to the environment at different life history stages, the adaptive strategies of plants are a cumulative result of both their life history and environment. Previous research on plant adaptation strategies has focused on adult plants, neglecting saplings or seedlings, which are more sensitive to the environment and largely affect the growth strategy of subsequent life stages. We compared leaf N and P stoichiometric traits of the seedlings, saplings, and adult trees of Acer mono Maxim and different altitudes and found significant linear trends for both life history stages and altitude. Leaf N and P content by unit mass were greatly affected by environmental change, and the leaf N and P content by unit area varied greatly by life history stage. Acer mono leaf N‐P utilization showed a significant allometric growth trend in all life history stages and at low altitudes. The adult stage had higher N‐use efficiency than the seedling stage and exhibited an isometric growth trend at high altitudes. The N‐P utilization strategies of A. mono leaves are affected by changing environmental conditions, but their response is further dependent upon the life history stage of the plant. Thus, this study provides novel insights into the nutrient use strategies of A. mono and how they respond to the environmental temperature, soil moisture content along altitude and how these changes differ among different life history stages, which further provide the scientific basis for the study of plant nutrient utilization strategy on regional scale. The researchers investigated leaf nutrient utilization strategies during the seedling, sapling, and adult stages of A. mono under different moisture and temperature conditions.

The cuttage rooting method for Acer species is difficult to achieve a good efficacy as trees maintain good characteristics at the rejuvenation stage, thus improving the rooting of Acer species. The addition of exogenous hormones and rejuvenation can improve the rooting effect of cuttings; however, the specific regulatory mechanism is still unclear. Here, Acer mono Maxim rejuvenation and non-rejuvenation cuttings were used as test subjects, to investigate the effects of exogenous hormones on the activities of endogenous hormones and antioxidant enzymes in the rooting process of young cuttings. The results showed that exogenous growth-regulating substances significantly improved the rooting rate of A. mono. Exogenous hormones naphthylacetic acid (NAA) + indolebutyric acid (IBA) increased the initial levels of the endogenous hormones, indoleacetic acid (IAA) and abscisic acid (ABA), and the enzyme activities of peroxidase (POD) and polyphenol oxidase (PPO). Rejuvenation treatment prolonged the time of increase in ABA content and indoleacetic acid oxidase (IAAO) activity at the root primordium induction stage, while increasing trans-zeatin riboside (ZR) content and decreasing POD enzyme activity in cuttings. These results demonstrate that A. mono cuttings can achieve the purpose of improving the rooting rate by adding the exogenous hormone (NAA + IBA), which is closely related to the changes of endogenous hormone content and enzyme activity, and these changes of A. mono rejuvenation cuttings are different from non-rejuvenation cuttings.

In response to increasing timber demands, the natural secondary forest (NSF) is largely converted to larch plantation (LP) in Northeast China. However, it causes a series of problems such as mono-species composition, declined soil fertility and unsustainable productivity. On the other hand, it brings a great challenge for the forest managers to answer how to keep the LP with higher natural regeneration capability and how to change the pure plantations into mixed forests with more complex stand structures. Two typical spatial distribution patterns of LP within the NSF ecosystem, i.e., the Contour Type (CT, NSF and LP locating at the same slope position and aspect) and the Up-and-Down Type (UDT, LP locating at the down slope of adjacent NSF in the same aspect) were selected. The objectives of this study were to find out the optimal spatial distribution type of the LP to improve the regeneration potential (i.e., seeds in the soil stock) and the possibility inducing them into larch-broadleaved mixed forests. The spatial patterns of seed bank along the transects with the NSF-boundary-LP gradient were compared between CT and UDT. We found that in the CT stands, seed density of all species varied as a quadratic curve from NSF to LP and the largest seed density occurred at the boundary; for the dominant tree species in NSF, seed density of Fraxinus rhynchophylla tended to decrease logarithmically from NSF to LP and the seeds could only appear at 4 m away from the boundary in LP; litter depth was closely correlated with seed density and species richness in seed bank. In the UDT stands, seed density of all species tended to increase linearly from NSF to LP, and seed density in LP was 1.95 times higher than that in NSF significantly; seed densities of F. rhynchophylla and Acer mono increased as a quadratic curve from NSF to LP; the canopy openness was linearly correlated with seed density. Our results indicated that the establishment of the Up (NSF)-and-Down (LP) Type of stands could be more feasible for seed invasion. Comparative studies on the patterns of seed banks across the two spatial distribution types of larch plantations within the secondary forest ecosystem may provide some new insights into the tending measures on the LP management.

BACKGROUND AND AIMS: In spatially heterogeneous environments, a trade-off between seedling survival and relative growth rate may promote the coexistence of plant species. In temperate forests, however, little support for this hypothesis has been found under field conditions, as compared with shade-house experiments. Performance trade-offs were examined over a large resource gradient in a temperate hardwood forest. METHODS: The relationship between seedling survival and seedling relative growth rate in mass (RGRM) or height (RGRH) was examined at three levels of canopy cover (forest understorey, FU; small gap, SG; and large gap, LG) and at two microsites within each level of canopy cover (presence or absence of leaf litter) for five deciduous broad-leaved tree species with different seed sizes. KEY RESULTS: Within each species, both RGRM and RGRH usually increased with increasing light levels (in the order FU < SG < LG), whereas little difference was observed based on the presence or absence of litter. Seedling survival in FU was negatively correlated with both RGRM and RGRH in both LG and SG. The trade-off between high-light growth and low-light survival was more evident in the relationship with LG as compared with SG. An intraspecific trade-off between survival and RGR was observed along environmental gradients in Acer mono, whereas seedlings of Betula platyphylla var. japonica survived and grew better in LG. CONCLUSIONS: The results presented here strongly support the idea of light gradient partitioning (i.e. species coexistence) in spatially heterogeneous light environments in temperate forests, and that further species diversity would be promoted by increased spatial heterogeneity. The intraspecific trade-off between survival and RGR in Acer suggests that it has broad habitat requirements, whereas Betula has narrow habitat requirements and specializes in high-light environments.

BACKGROUND AND AIMS: Leaf life span, photosynthetic parameters and defensive traits were compared across seven species of deciduous broad-leaved tree seedlings native to northern Japan to test the 'cost-benefit hypothesis' that more productive leaves are more susceptible to herbivore attack than less productive leaves. METHODS: Studies were made on three early successional species, Alnus hirsuta, Betula maximowicziana and Betula platyphylla 'japonica'; one mid-successional species, Ostrya japonica, and three late-successional species, Carpinus cordata, Quercus mongolica 'grosseserrata' and Acer mono. Photosynthetic parameters and defensive traits (total phenolics, condensed tannin and toughness) of leaves were measured for each species, and a bioassay test with Eri silkmoth larvae (Samia cynthia ricini) was undertaken to evaluate differences between species in susceptibility to herbivore attack. KEY RESULTS: Early successional species have a shorter leaf life span (62-88 d) than late successional species (155-187 d). Leaf nitrogen content and light-saturated photosynthetic rate per unit leaf area (P[subscript sat]-area) and per unit leaf mass (P[subscript sat]-mass) were negatively correlated with leaf life span. The nitrogen content of early successional species was about 30 mg g⁻¹ and that of late successional species was about 16 mg g⁻¹. Leaf toughness and the C/N ratio were positively correlated with leaf life span, although condensed tannin was not correlated with leaf life span. The bioassay test showed that the number of days the larvae survived was negatively correlated with leaf life span. Average survival of larvae feeding on leaves of A. hirsuta, which has the shortest leaf life span, was 14·4 d and that of Q. mongolica, which has the longest leaf life span, was 6·6 d. The number of days of larval survival was positively correlated with leaf nitrogen content. There was no correlation between days of larval survival and defensive traits. CONCLUSIONS: These results indicate that species with a shorter leaf life span have higher photosynthetic productivity and are more susceptible to herbivore attack than species with a longer leaf life span. This supports the 'cost-benefit hypothesis'.

Royal jelly is a specific product secreted by honeybees, and has been sought after to maintain health because of its valuable bioactive substances, e.g., lipids and vitamins. The lipids in royal jelly come from the bee pollen consumed by honeybees, and different plant source of bee pollen affects the lipid composition of royal jelly. However, the effect of bee pollen consumption on the lipid composition of royal jelly remains unclear. Herein, we examined the influence of two factors on the lipid composition of royal jelly: first, two plant sources of bee pollen, i.e., Acer mono Maxim. (BP-Am) and Phellodendron amurense Rupr. (BP-Pa); secondly, different feeding times. Lipidomic analyses were conducted on the royal jelly produced by honeybees fed BP-Am or BP-Pa using ultra-high performance liquid chromatography (UPLC)-Q-Exactive Orbitrap mass spectrometry. The results showed that the phospholipid and fatty acid contents differed in royal jelly produced by honeybees fed BP-Am compared to those fed BP-Pa. There were also differences between timepoints, with many lipid compounds decreasing in abundance soon after single-pollen feeding began, slowly increasing over time, then decreasing again after 30 days of single-pollen feeding. The single bee pollen diet destroyed the nutritional balance of bee colonies and affected the development of hypopharyngeal and maxillary glands, resulting in differences in royal jelly quality. This study provides guidance for optimal selection of honeybee feed for the production of high-quality royal jelly.

The seedlings of Acer mono Maxim. were exposed to two watering regimes (well watered (100% of field capacity) and drought (30% of field capacity)) and two light levels (high light (100% of full sunlight) and low light (15% of full sunlight)) in a greenhouse to assess growth, photosynthesis, and foliar nutrient traits of woody plants under drought and low light. Drought significantly reduced growth and gas exchange characteristics of A. mono, including net photosynthetic rate (P N), stomatal conductance (g s), intercellular CO₂ concentration (Ci), and photosynthetic nitrogen use efficiency (PNUE). Also, drought reduced relative water content (RWC) and foliar C and N concentrations, but increased the C/N ratio. P N and C concentration were lower under drought and low light than in any other treatment, indicating that deep shade might seriously decrease C assimilation. However, the negative effect induced by drought was alleviated by improving RWC and maintaining C balance, and therefore low-light seedlings accumulated more biomass than those under high light when they were exposed to drought. Our results showed that trade-off and facilitation effects of drought and low light might be complementary and alter in different species.

To test the effects of elevated CO2 and soil N deficiency on N resorption efficiency (NRE) from senescing leaves in two non-N2-fixing deciduous broadleaved tree species, Japanese oak (Quercus mongolica var. grosseserrata Blume) and Painted maple (Acer mono Maxim. var. glabrum (Lév. Et Van’t.) Hara), potted seedlings were grown in a natural daylight phytotron with either ambient or elevated CO2 conditions (36 Pa and 72 Pa CO2) and with two levels of N (52.5 and 5.25 mg N pot−1 week−1 for high N and low N, respectively). We examined the N content (Nmass) of mature and senescent leaves, as well as photosynthesis and the growth of plants, and calculated both the mass-based NRE (NREmass) and leaf area-based NRE (NREarea). In both species, the Nmass of mature leaves decreased with high CO2 and low N, whereas the leaf mass per area (LMA) increased under elevated CO2, regardless of N treatments. In Q. mongolica, both the maximum rate of carboxylation (Vcmax) and the maximum electron transport rate (Jmax) were reduced by elevated CO2 and low N, but Vcmax exhibited an interactive effect of N and CO2 treatments. However, in A. mono, both the Vcmax and Jmax decreased under elevated CO2, regardless of N treatments. The partitioning of N for the photosynthetic function within leaves was also significantly decreased by elevated CO2 in both species and increased under low N in A. mono. The Nmass of senesced leaves decreased under low N in both species and exhibited an increase (Q. mongolica) or no effect (A. mono) by elevated CO2. The NREarea of Q. mongolica was affected by CO2 and N treatments, with a decrease under elevated CO2 compared to ambient CO2 and under low N compared to high N. The NREarea of A. mono was also affected by CO2 and N treatments and decreased under elevated CO2; however, unlike in the case of Q. mongolica, it increased under low N. We speculate that these interspecific differences in the responses of leaf N allocation, indicated by the photosynthetic (Vcmax and Jmax) and morphological (LMA) responses to elevated CO2, may have affected the NRE during defoliation under high CO2 and soil N-deficient conditions.

We isolated eight known secondary metabolites, including two isocoumarins and six coumarins, from the stems and branches of Acer mono Maxim. Their structures were confirmed using nuclear magnetic resonance spectroscopy and by comparing the data to published reports. The inhibitory effects of all compounds (1−8) on Escherichia coli β-glucuronidase were evaluated for the first time using in vitro assays. 3-(3,4-Dihydroxyphenyl)-8-hydroxyisocoumarin (1) displayed an inhibitory effect against β-glucuronidase (IC50 = 58.83 ± 1.36 μM). According to the findings of kinetic studies, compound 1 could function as a non-competitive inhibitor. Molecular docking indicated that compound 1 binds to the allosteric binding site of β-glucuronidase, and the results corroborated those from kinetic studies. Furthermore, molecular dynamics simulations of compound 1 were performed to identify the behavioral and dynamic properties of the protein–ligand complex. Our results reveal that compound 1 could be a lead metabolite for designing new β-glucuronidase inhibitors.

Heterodichogamy is a form of sex expression in which protandrous and protogynous individuals coexist, and is considered to be a mechanism that avoids selfing and promotes disassortative mating. We examined mating patterns in a heterodichogamous maple, Acer mono, using microsatellite markers. Parentage analysis revealed a selfing rate of only 9.8%. Disassortative mating between flowering types significantly exceeded within-type mating, but the mating patterns were better explained by flowering phenology (i.e., the temporal overlap between the female and male stages). Heterodichogamy in A. mono thus appears to promote outcrossing without requiring obligate self- or cross-incompatibility systems, although it did not guarantee disassortative mating. Multiple-regression analysis suggested that successful reproduction of pollen parents significantly increased with increased flower production and reciprocal flowering synchrony, but decreased only marginally with mating distance, although the distribution of mating distances suggested leptokurtic dispersal of pollen.