Analysis of floral scent emitted from Syringa plants

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. protolaciniata, S. oblata, S. oblata var. giraldii, S. oblata var. plena, S. vulgaris ＇Mrs Harry Bickle＇, S. vulgaris ＇Bright Centennial＇, S. vulgaris ＇White Spires＇, and S. vulgaris ＇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. protolaciniata, S. oblata var. giraldii, and S. vulgaris ＇Bright Centennial＇. A significant daytime variation of floral scent emitted from S. pekinensis was recorded, especially for benzaldehyde, whose content first increased and then decreased. We studied the scent emitted from the in vitro flowers of S. vulgaris ＇Pres Lincoln＇ during the process of natural drying. Alcohol compounds were released in the greatest content, and the content of 2-ethyl-l-hexanol accounted for about 40 % of the total release amount. The results described the emission pattern and mechanisms of floral scent in Syringa.

Gene cloning and expression analysis of limonene synthase in Syringa oblata and S.oblata var.alba

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 was1746 bp and encoded 581 amino acids.Sequence analysis showed that SoLIM contained the DDxxD and RRx8 W 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.

The Comparison of Cold tolerance of Three Species of Evergreen Broad-leaved Woody Plants

[Objectives]This study aimed to select evergreen broad-leaved woody plants with higher ornamental value and stronger cold tolerance for introduction from the south to the north,and to apply them to urban greening,so as to enrich the plant community structure of the landscape in the northern region.[Methods]Three species of evergreen broad-leaved woody plants,i.e.,Ligustrum lucidum,Ilex cornuta and Eriobotrya japonica,were selected as the experimental materials.The morphological performances and the changes of the physiological indexes were observed and measured during the overwintering period in the open field in Beijing.The relationship between the indexes and the low temperature was also analyzed.The strength of cold tolerance of the three species was compared.[Results]The electrical conductivity,the contents of MDA and proline were negatively correlated with the corresponding low temperature.The contents of soluble sugar and soluble protein increased with the dropping temperature,but they had little response to the short-term temperature rise.[Conclusions]Combined with morphological and physiological indexes,it was found that the changes of the contents of proline and soluble sugar among the physiological indexes were closely related to the cold tolerances of the three tree species of broad-leaved woody plants.The cold tolerance of I.cornuta was the strongest,E.japonica was the second,and that of L.lucidum was the worst.

Cloning and Expression Analysis of Allene Oxide Synthase Gene Ls AOS in Lilium‘Siberia'

[Objectives]Allene oxide synthase(AOS),the first specific enzyme in the biosynthetic pathway of jasmonate(JA),has an important role in regulating JA accumulation in plants.This study was conducted to amplify full-length AOS gene from Lilium‘Siberia'(LsAOS)and to explore the spatiotemporal expression of this gene.[Methods]LsAOS was cloned by rapid amplification of c DNA ends(RACE)and analyzed bioinformatically.LsAOS expression level in nine organs/tissues and at four flowering stages was determined by quantitative PCR(q-PCR).[Results]LsAOS gene has an open reading frame of 1542 bp,encoding a protein of 514 amino acids.The LsAOS protein sequence was more homologous with the AOS protein of Musa acuminata Colla than that in any other plant species.The LsAOS expression reached the maximum level at bud stage,and then gradually decreased over time during the flowering period.The LsAOS expression level in leaves was the highest,followed by in inner petals,roots,stems,etc.[Conclusions]JA participates in the whole process of plant development,and is closely related to stress resistance and secondary metabolism.AOS is one of the key genes in JA pathway and plays an important role in regulating the biosynthesis of JA.

Comparison of Cold Tolerance in Three Ground-cover Chrysanthemum Cultivars during Wintering in the Open Field

[Objectives]Among many chrysanthemum types,the ground-cover chrysanthemum cultivar group has the characteristics of dwarf plant,long flowering period,rich color and strong resistance to stress.This study aimed to screen out cultivars with strong cold tolerance in order that they can be used for planting in urban green space and economic forests in northern cold areas,so as to enrich the plant community structures of landscape in cold regions.[Methods]Three ground-cover chrysanthemum cultivars,i.e.,‘Meiaihuang’,‘Xinhong’and‘Zixunzhang’,were selected as the experimental materials.During the wintering period in the field in Beijing,they were observed and measured for the changes of the morphological manifestations and the physiological indices,and the relationship between the indices and low temperature was analyzed.The cold tolerance of the three ground-cover chrysanthemum cultivars was also comprehensively evaluated.[Results]During the open-field overwintering period,the root activity of the three ground-cover chrysanthemum cultivars increased slowly with cooling,decreased at the freezing low temperature,and then increased again in early spring.With natural cooling,the membrane injury percentages(MIPs)of the leaves and foot shoots increased significantly,and the contents of malondialdehyde(MDA)increased;the contents of soluble sugar(SS)and proline(Pro)gradually accumulated,and the contents of SS and Pro in foot shoots increased significantly in late winter;and the superoxide dismutase(SOD)activity showed a similar trend of rising slowly at first and then increasing significantly.There were correlations between MIPs in the leaves and foot shoots of the three cultivars and other physiological indices:a significant negative correlation with MDA content,and a significant positive correlation with SS content,Pro content and SOD activity.[Conclusions]Combining the morphological manifestations and physiological indices,the cold tolerance of the three ground-cover chrysanthemum cultivars was evaluated by the subordinate function method.The results showed that the cold tolerance of the three ground-cover chrysanthemum cultivars ranked as‘Meiaihuang’>‘Xinhong’>‘Zixunzhang’.The strong cold tolerance of foot shoots and roots was the main reason that the three ground-cover chrysanthemum cultivars could overwinter in the open field.