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Generally, Pistacia species are dioecious, but monoecious strains in several populations have been found, providing excellent models for studying sex differentiation and sex determination mechanisms. Although the mechanisms of sex determination and sex evolution have been extensively studied, related research on heterozygous woody plants is limited. Here, we discuss the expressions of various sex types, which showed broad diversity and complex instability. We have also reviewed the sex determination systems in the plant kingdom and the morphological, cytological, physiological, and molecular aspects of the sex-linked markers in Pistacia trees. Moreover, hypotheses to explain the origin of monoecy are discussed, which is more likely to be the interaction between sex-related genes and environment factors in female plants. Besides, further prospects for the utilization of monoecious resources and the research directions of sex determination mechanism are proposed. This study provides important information on sex expression and provides more insights into sex differentiation and determination.

Syringa species are important ornamentals with strong floral scent, of which monoterpenes are the main component. In this study, a new monoterpene synthase gene, named SoLIM, was collected from the flowers of Syringa oblata and S.oblata var. alba using a homologous cloning method. The full-length cDNA of SoLIM was 1746 bp and encoded 581 amino acids. Sequence analysis showed that SoLIM contained the DDxxD and RRx8W motifs, which are two typical conserved monoterpene synthase motifs, and was thus classified as belonging to the Tpsb subfamily. Using quantitative reverse-transcription PCR, SoLIM was significantly expressed in the petals and pistils of S. oblata and S. oblata var. alba, respectively. SoLIM expression peaked earlier than the D-limonene emissions in the diurnal experiments, but occurred later when D-limonene had peaked during the flowering phase, indicating that differences in SoLIM gene expression and D-limonene emissions existed. The synthesis of floral scent is thus associated with diverse regulatory mechanisms that require further investigation.

Soil salinization is one of the main stress factors that affect both growth and development of plants. Hylotelephium erythrostictum exhibits strong resistance to salt, but the underlying genetic mechanisms remain unclear. In this study, hydroponically cultured seedlings of H. erythrostictum were exposed to 200 mM NaCl. RNA-Seq was used to determine root transcriptomes at 0, 5, and 10 days, and potential candidate genes with differential expression were analyzed. Transcriptome sequencing generated 89.413 Gb of raw data, which were assembled into 111,341 unigenes, 82,081 of which were annotated. Differentially expressed genes associated to Na+ and K+ transport, Ca2+ channel, calcium binding protein, and nitric oxide (NO) biosynthesis had high expression levels in response to salt stress. An increased fluorescence intensity of NO indicated that it played an important role in the regulation of the cytosolic K+/Na+ balance in response to salt stress. Exogenous NO donor and NO biosynthesis inhibitors significantly increased and decreased the Na+ efflux, respectively, thus causing the opposite effect for K+ efflux. Moreover, under salt stress, exogenous NO donors and NO biosynthesis inhibitors enhanced and reduced Ca2+ influx, respectively. Combined with Ca2+ reagent regulation of Na+ and K+ fluxes, this study identifies how NaCl-induced NO may function as a signaling messenger that modulates the K+/Na+ balance in the cytoplasm via the Ca2+ signaling pathway. This enhances the salt resistance in H. erythrostictum roots.

Pistacia chinensis Bunge is a pioneer tree for afforestation, and of high value as an ornament and for timber and medicine. It has also become the preferred biofuel tree in northern China in current years, with a broader development prospect. However, this development is seriously limited due to its dioecious character (separate sexes), because the male (nonfruit) trees are indispensable for pollination, and this leads to a waste of field and low yields. Fortunately, this bottleneck can be broken with the emergence of rare monoecious (having both female and male flowers, and even bisexual flowers) resources in Hebei Province, China. To determine their cultivation characteristics, the variation characteristics and blooming phenophase of local Pistacia were recorded with text, data, and images, by germplasm resources survey, telephone interviews, and field visits. Results showed that 1) 23 monoecious Pistacia were found, with very complex morphological features. 2) The branches of different gender types, ordered by inflorescence length were female > female on monoecious trees > bisexual flowers > inflorescence with male and female > male on monoecious trees > male. Ordered by inflorescence width: female > bisexual flower > female on monoecious trees > inflorescence with male and female > male on monoecious trees > male. Among these, the inflorescence length, inflorescence width, floret diameter, and floret spacing of bisexual flowers were significantly greater than that of male flowers, providing a basis to judge gender type without destructive sampling. 3) Gender types were unstable in successive years—female, male, mixed, or bisexual flowers could convert to another gender within 1 year, except that no female became male, and the overall trend was from male to mixed or bisexual gender in recent years. 4) The blooming phenophase changed a lot among different strains and sex types, which could enlarge the blooming period.

Pistacia chinensis Bunge is widely acknowledged to be dioecious, but rare monoecious individuals have been found. However, the origin of monoecism and the sex differentiation of different sex types remain intriguing questions. Here, sex expressions were explored by identification of sex-associated DNA markers, determination of the sex stability after grafting, and histological characterization of inflorescence bud development using anatomical analysis. The results showed that (1) although polymorphisms among individuals existed, the banding patterns of Polymerase Chain Reaction (PCR) products for different sex types on the same monoecious tree were consistent, (2) the sex expressions of grafted trees were not consistent with those of scions, indicating that monoecism probably did not originate from a stable bud mutation, and (3) both males and females underwent a bisexual period, then the stamen primordia in female buds degenerated into the second round tepals, while the pistil primordia in male buds gradually disappeared. During the sex differentiation phase, female buds were spindle-shaped, while the male buds were full teardrop-shaped, and male buds were bigger than female buds. Taken together, no sex-associated DNA marker was found, sex expressions were unstable after grafting, and the alternative sex organs appeared in the early stage of sex differentiation, suggesting that sex determination occurred during floral development instead of the early vegetative period. These results indicated that the sex expressions may be affected by environmental factors, increasing the understanding of sex determination mechanisms in P. chinensis and other species.

In order to seek a safe, sustainable, and low-cost method for reuse of municipal sewage sludge, four species of native plants, i.e., Forsythia suspensa, Sophora japonica, Cotinus coggygria, and Ailanthus altissima were planted in flowerpots containing 4 growth substrates consisting of raw sludge and fly ash at volume/volume ratios of 20:80, 40:60, 60:40, and 80:20, respectively. The results showed that the physiochemical characteristics of the sewage sludge and fly ash were complementary. The sludge supplied the nutrients and the fly ash maintained air permeability in the mixed substrate. The mixed substrates containing 40-60% sewage sludge that belonged to sand clay loam were suitable for the seedling growth of the four species. After the end of the growing season, the electrical conductivity, pH, and contents of organic matter, nitrogen, potassium, and heavy metals in the four growth substrates decreased significantly. Moreover, most of the heavy metals were removed from the substrates by seedling root system. A. altissima grew best, and heavy metal enrichments of F. suspense and C. coggygria were stronger than other two species. The results indicate that the new substrates containing 40-60% sludge exhibiting good physiochemical properties, are environmentally friendly, and suitable for landscape planting.

To investigate the influence of exogenous paclobutrazol (PBZ) application on the natural cold acclimation of Ligustrum lucidum, 1-year-old L. lucidum seedlings were conducted with PBZ at four concentrations (0, 100, 300, and 500 mg L−1) from September to December 2016, and leaves were collected to measure physiological and biochemical parameters. Results showed that 500 mg L−1 was the optimum concentration, which led to stronger freezing tolerance during natural cold acclimation. The enhanced freezing tolerance induced by exogenous PBZ application was attributed to the accumulation of chlorophyll, proline, soluble protein, and soluble sugar, and the regulation of gibberellic acid and abscisic acid. PBZ treatments initiated a cascade of steps for advancing the cold acclimation of L. lucidum. It appears that exogenous PBZ application may be applied to L. lucidum grown in northern China, where the growing periods are short and there are early fall frost events and low mid-winter temperatures.

Salinity is a major abiotic stress that impacts plant growth and development. Hylotelephium erythrostictum exhibits high salt resistance, but the mechanisms are largely unknown. In this study, we used iTRAQ technique to study the proteomic changes in leaves of H. erythrostictum under salt stress. On the basis of GO and KEGG analysis, we concluded that most DEPs were enriched in carbon metabolism, photosynthesis, plant hormone signal transduction, and energy metabolism including glycolysis/gluconeogenesis, pyruvate metabolism, and gyoxylate and dicarboxylate metabolism. Most DEPs that participate in photosynthesis were down-regulated in response to salt stress, but DEPs in energy metabolism were more up-regulated than down-regulated. In this study, changes in key proteins were analyzed to elucidate the response mechanisms of H. erythrostictum to salt stress.

Syringa is an important aromatic woody angiosperm that is widely planted in gardens. Its dry flowers are traditionally used to manufacture infusions and spices in China. In this study, the floral volatiles emitted from nine different Syringa species and varieties, viz. S. chinensis, S. p rotolaciniata, S. o blata, S. o blata var. giraldii, S. o blata var. plena, S. v ulgaris ‘Mrs Harry Bickle’, S. v ulgaris ‘Bright Centennial’, S. v ulgaris ‘White Spires’, and S. v ulgaris ‘President Lincoln’ were collected by the dynamic headspace technique, and then identified by automated thermal desorption–gas chromatography/mass spectrometry. There were significant differences in components and corresponding contents of floral scent emitted from the nine Syringa species and varieties. Among the detected components, β-ocimene exhibited the highest content, accounting for more than 70 % of the floral scent of S. p rotolaciniata, S. o blata var. giraldii, and S. v ulgaris ‘Bright Centennial’. A significant daytime variation of floral scent emitted from S. p ekinensis was recorded, especially for benzaldehyde, whose content first increased and then decreased. We studied the scent emitted from the in vitro flowers of S. v ulgaris ‘Pres Lincoln’ during the process of natural drying. Alcohol compounds were released in the greatest content, and the content of 2-ethyl-1-hexanol accounted for about 40 % of the total release amount. The results described the emission pattern and mechanisms of floral scent in Syringa.

This study aims to investigate the antioxidant effect of aromatic volatiles of three common aromatic plants, Lavandula dentata, Mentha spicata, and M. piperita. In this study, kunming mice subjected to low oxygen condition were treated with the volatiles emitted from these aromatic plants through inhalation administration. Then the blood cell counts, and the activities and gene expressions of antioxidant enzymes in different tissues were tested. The results showed that low oxygen increased the counts of red blood cells, white blood cells, and blood platelets of mice, and aromatic volatiles decreased their counts. Exposure to aromatic volatiles resulted in decreases in the malonaldehyde contents, and increases in the activities and gene expressions of superoxide dismutase, glutathione peroxidase, and catalase in different tissues under low oxygen. In addition, as the main component of aromatic volatiles, eucalyptol was the potential source that imparted positive antioxidant effect.

Lilium is a world famous fragrant bulb flower with high ornamental and economic values, and significant differences in fragrance are found among different Lilium genotypes. In order to explore the mechanism underlying the different fragrances, the floral scents of Lilium 'Siberia', with a strong fragrance, and Lilium 'Novano', with very little fragrance, were collected in vivo using a dynamic headspace technique. These scents were identified using automated thermal desorption - gas chromatography / mass spectrometry (ATD-GC/MS) at different flowering periods. We used RNA-Seq technology to determine the petal transcriptome at the full-bloom stage and analyzed differentially expressed genes to investigate the molecular mechanism of floral scent biosynthesis. The results showed that a significantly higher amount of Lilium 'Siberia' floral scent was released compared with Lilium 'Novano'. Moreover, monoterpenes played a dominant role in the floral scent of Lilium 'Siberia'; therefore, it is believed that the different emissions of monoterpenes mainly contributed to the difference in the floral scent between the two Lilium genotypes. Transcriptome sequencing analysis indicated that approximately 29.24 Gb of raw data were generated and assembled into 124,233 unigenes, of which 35,749 unigenes were annotated. Through a comparison of gene expression between these two Lilium genotypes, 6,496 differentially expressed genes (DEGs) were identified. The genes in the terpenoid backbone biosynthesis pathway showed significantly different expression levels. The gene expressions of 1-deoxy-D-xylulose 5-phosphate synthase (DXS), 1-deoxy-D-xylulose-5-phosphate reductoisomerase (DXR), 4-hydroxy-3-methylbut-2-enyl diphosphate synthase (HDS), 4-hydroxy-3-methylbut-2-enyl diphosphate reductase (HDR), isopentenyl diphosphate isomerase (IDI), and geranyl diphosphate synthase (GPS/GGPS), were upregulated in Lilium 'Siberia' compared to Lilium 'Novano', and two monoterpene synthase genes, ocimene synthase gene (OCS) and myrcene synthase gene (MYS), were also expressed at higher levels in the tepals of Lilium 'Siberia', which is consistent with the monoterpene emissions. We demonstrated that the high activation levels of the pathways involved in monoterpene biosynthesis in Lilium 'Siberia' resulted in higher accumulations and emissions of monoterpenes, which led to the difference in fragrance between these two Lilium genotypes.