As a highly valued and multiple function tree species, Cyclocarya paliurus is planted and managed for timber production and medical use. However, limited information is available on its genotype selection and cultivation for growth and phytochemicals. Responses of growth and secondary metabolites to light regimes and genotypes are useful information to determine suitable habitat conditions for the cultivation of medicinal plants. Both light regime and provenance significantly affected the leaf characteristics, leaf flavonoid contents, biomass production and flavonoid accumulation per plant. Leaf thickness, length of palisade cells and chlorophyll a/b decreased significantly under shading conditions, while leaf areas and total chlorophyll content increased obviously. In the full light condition, leaf flavonoid contents showed a bimodal temporal variation pattern with the maximum observed in August and the second peak in October, while shading treatment not only reduced the leaf content of flavonoids but also delayed the peak appearing of the flavonoid contents in the leaves of C. paliurus. Strong correlations were found between leaf thickness, palisade length, monthly light intensity and measured flavonoid contents in the leaves of C. paliurus. Muchuan provenance with full light achieved the highest leaf biomass and flavonoid accumulation per plant. Cyclocarya paliurus genotypes show diverse responses to different light regimes in leaf characteristics, biomass production and flavonoid accumulation, highlighting the opportunity for extensive selection in the leaf flavonoid production.

Cyclocarya paliurus (Batal.) Iljinskaja, as a woody tree species, has various health-promoting phytochemicals and is commonly used in tea production in China. A field trial for C. paliurus was conducted at two typical sites to evaluate genotype × environmental interaction (GEI) effects and identify the stability and adaptability of 13 families. The genotype main effects and genotype × environment interaction effects (GGE) were used to analyze the GEI effects for tree height, diameter at breast height (DBH), and leaf flavonoid and triterpenoid contents. Two-way analysis of variance indicated that the tree growth and leaf phytochemical contents were mainly affected by genotype and GEI. Based on the results of GGE, the JH1 family had high mean values and high stability in total flavonoid and total triterpenoid accumulations, while the KM4 family exhibited high means and high stability in tree height and DBH growth, as well as high means and medium stability in total triterpenoid content. Pearson’s correlation analysis indicated that the annual mean DBH was significantly and positively correlated with leaf phytochemical content in C. paliurus when all data for the 13 families at the two sites were used. Our results suggest that JH1 should be mainly extended as a superior genotype for the production of flavonoids and triterpenoids in the leaves, while KM4 could be spread for timber production or leaf triterpenoid production. This study provides useful information on the selection of C. paliurus genotypes in target sites and cultivation strategies for establishing oriented plantations.

Cyclocarya paliurus is an important rare and multipurpose tree species in China. In view of the difficulty of asexual propagation of Cyclocarya paliurus , this paper explores the technical system of Cyclocarya paliurus cutting propagation from the aspects of cutting collection position and time, tannin removal pretreatment, hormone treatment, sand storage treatment, cutting matrix, environmental factors and physical factors, and discusses its internal physiological changes in the process of cutting rooting. This paper attempts to clarify the physiological characteristics of Cyclocarya paliurus in the process of cutting propagation and rooting. The results of this study can provide technical support and theoretical basis for the cuttings propagation of Cyclocarya paliurus . The results show that the rooting rate of cuttings inserted on the mixture of perlite and vermiculite is up to 32.2 %. In summer, when the middle and upper parts of branches were treated with 300 mg/L rooting powder No. 1 and GGR-6 (Green Growth Regulator-6) mixture, the rooting rate was up to 44.4 %; in winter, the rooting rate of the base of branches was 36.7 % under the same treatment. During the rooting process of Cyclocarya paliurus , a large number of nutrients such as soluble sugar, starch and soluble protein were consumed. SOD (Superoxide Dismutase), POD (Peroxidase), and PPO (Polyphenol oxidase) are closely related to cutting and rooting. High activity SOD and POD are conducive to the expansion of cuttings, and high activity SOD and PPO are conducive to improving the stress resistance of cuttings. Hormone treatment can improve the enzyme activity and make the enzyme activity change in the direction conducive to rooting. The change of endogenous hormone content in cuttings reflects the rooting ability of Cyclocarya paliurus . Substrate heating and hormone treatment can regulate the content of endogenous hormone in cuttings during the rooting process, so as to affect the rooting effect, the stable total nitrogen content in cuttings was conducive to root formation.

To increase the yield of secondary metabolites, Arbuscular mycorrhiza fungi were used to improve cyclocarya paliurus. The experiment measured growth indicators, biomass, mineral nutrients, etc. The results showed that after inoculation with mycorrhizal fungi the nitrogen content in the leaves of the experimental group was 27.87 mg/g, K content was 7.48 mg/g, Ca content was 26.63 mg/g, and Mg content was 2.82 mg/g. Compared with the control group (Cg), mycorrhizal fungi can promote the absorption of mineral nutrients by C. paliurus seedlings. A. mycorrhizal fungi had a certain influence on the proportion of root, stem, leaf, and total biomass of C. paliurus seedlings, and their biomass distribution in various parts was relatively balanced. A. mycorrhizal fungi can significantly increase the biomass of willow seedlings’ stems and significantly increase their proportion in the total biomass (p < 0.05). After mycorrhizal inoculation, the secondary metabolic yields of quinic acid, quercetin, and kaempferol in C. paliurus leaves were 0.87 mg/g, 0.32 mg/g, and 0.65 mg/g, respectively, higher than those in the Cg. It is concluded that the use of A. mycorrhizal to improve the survival rate of medicinal materials and ensure the quality of medicinal materials is a new idea for the industrial production of C. paliurus.

To reveal the effects of genotype–herbivore interactions on leaf quality, foliar variations in phytochemicals, morphoanatomy, and herbivory damage ratio were investigated in a Cyclocarya paliurus (Batalin) Iljinsk. (Juglandaceae) germplasm resources bank. Results showed less herbivory damage in genotypes with a higher leaf thickness, but more herbivory damage in genotypes with a higher leaf stomatal density. Herbivory damage ratios were significantly correlated with the contents of leaf secondary metabolites, whereas the response of secondary metabolites to insect attack was type-specific and varied between intact leaves and damaged leaves. Based on key indicators of leaf quality (contents of triterpenoids, flavonoids, polyphenols, pterocaryoside A, pterocaryoside B, and cyclocaric acid B), the investigated genotypes were divided into three distinct groups by integrating TOPSIS and cluster analysis, while four genotypes with slight insect damage demonstrated the prioritization for future applications. Our findings lay a foundation for further selection of its superior varieties with both insect resistance and high leaf quality.