Eucommia ulmoides Oliver is widely distributed in China. This species has been used mainly in medicine due to the high concentration of chlorogenic acid (CGA), flavonoids, lignans, and other compounds in the leaves and barks. However, the categories of metabolites, dynamic changes in metabolite accumulation and overall molecular mechanisms involved in metabolite biosynthesis during E. ulmoides leaf growth and development remain unknown. Here, a total of 515 analytes, including 127 flavonoids, 46 organic acids, 44 amino acid derivatives, 9 phenolamides, and 16 vitamins, were identified from four E. ulmoides samples using ultraperformance liquid chromatography–mass spectrometry (UPLC-MS) (for widely targeted metabolites). The accumulation of most flavonoids peaked in growing leaves, followed by old leaves. UPLC-MS analysis indicated that CGA accumulation increased steadily to a high concentration during leaf growth and development, and rutin showed a high accumulation level in leaf buds and growing leaves. Based on single-molecule long-read sequencing technology, 69,020 transcripts and 2880 novel loci were identified in E. ulmoides. Expression analysis indicated that isoforms in the flavonoid biosynthetic pathway and flavonoid metabolic pathway were highly expressed in growing leaves and old leaves. Co-expression network analysis suggested a potential direct link between the flavonoid and phenylpropanoid biosynthetic pathways via the regulation of transcription factors, including MYB (v-myb avian myeloblastosis viral oncogene homolog) and bHLH (basic/helix-loop-helix). Our study predicts dynamic metabolic models during leaf growth and development and will support further molecular biological studies of metabolite biosynthesis in E. ulmoides. In addition, our results significantly improve the annotation of the E. ulmoides genome.

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Eucommia ulmoides Oliver (EUO), an economic tree grown specifically in China, is widely used in various fields. To satisfy the requirements of industrial development, superior varieties need to be selected for different uses. However, there is no unified standard for breeders to reference. In this study, leaf-related traits were classified by a probability grading method. The results indicated there were significant differences between different planting models for the studied traits, and the traits in the Arbor forest model showed more abundant variation. Compared with genotype, the planting model accounted for relatively bigger variance, indicating that the standard should be divided according to planting models. Furthermore, the optimum planting model for different traits would be obtained by analyzing the variation range. Association analyses were conducted among traits to select the crucial evaluation indexes. The indexes were divided into three grades in different planting models. The evaluation system on leaf-related traits of EUO germplasm was established preliminarily, which considered planting models and stability across years for the first time. It can be treated as a reference to identify and evaluate EUO germplasm resources. Additionally, the study served as an example for the classification of quantitative traits in other economically important perennial plants.

Natural rubber latex (NRL) preserved by high ammonia (HA) presents substantial pollution issues despite its good all-around properties. Cleaning preservation of NRL is critical in the modern rubber industry. In this study, NRL was preserved using N,N ′ -methylene-bis-morpholine (MBM), and the impact of MBM on the preservation and characteristics of NRL was investigated. The results showed that when the MBM dose was greater than 0.15 wt%, the volatile fatty acid value (VFA No.) and viscosity value of fresh NRL were lower, and it could be stored for longer than 5 days without losing stability. Furthermore, MBM demonstrated a favorable preservation effect on concentrated NRL (CNRL). To be effective, MBM must be administered at a dosage greater than 0.3 wt%. The mechanical stability test (MST) and VFA No. of the low-ammonia (LA)-CNRL prepared by MBM combined with ammonia were somewhat lower, whereas the viscosity value was greater. The research showed that the dose of lauric acid soap needs to be increased to improve the stability of ultra-LA-CNRL made by MBM–ammonia composite preservation. After pre-vulcanization treatment, the stability of LA-CNRL preserved by MBM–ammonia composite was drastically reduced. As the stabilizer dose was increased, the CNRL viscosity value decreased, whereas the MST and heat stability improved. The LA-CNRL vulcanized film has excellent mechanical properties similar to HA-CNRL. Furthermore, the infrared spectrum of the LA-CNRL raw rubber film was similar to that of the HA-CNRL film. The thermal degradation curve and characteristic temperature were also similar to that of the HA film. The study indicates that MBM has an outstanding preservation effect on fresh NRL and LA-CNRL, and the findings constitute a significant step forward in the development of the CNRL sector.