Effect of artificially accelerated aging on the vigor of Metasequoia glyptostroboides seeds

Metasequoia glyptostroboides is an endangered relict plant native to China that has been widely introduced into many countries and areas around the world. However,its seeds germinate at a very low percentage. Consequently,population regeneration by seed is low under natural conditions, which probably contributes to the endangered status of this plant species. The present study aimed to describe the aging mechanism of M. glyptostroboides seeds. Our objective was to elucidate causes of the low germination rate in an effort to enhance potential for conservation of the species. We used germination tests,relative electrical conductivity and malondialdehyde content determination, ultrastructural observation of embryo cells, and analysis of superoxide dismutase, catalase,ascorbate peroxidase, and dehydroascorbate reductase activities during accelerated aging treatment. We found that M. glyptostroboides seeds have a low level of vigorand poor ability to maintain vigor, which is probably associated with the inefficiency of its enzymatic antioxidative system.

Effects of Sucrose on Total RNA Concentration during Formation of Microtubers of Pinellia ternata in vitro

[ Objective] This study aimed to investigate the variation rule of total RNA concentration during formation of microtubers of PineUia ternata induced by sucrose. [ Method ] Plantlets of P. ternata were used as experimental materials. Total RNA concentration was determined with spectrophotometer, and the variation of total RNA was analyzed before and after formation of P. ternata microtubers treated with different concentrations of sucrose using DDRT-PCR technology. [ Result] Total RNA concentration of P. ternata treated with different concentrations of sucrose varied greatly, which showed an upward trend in the first 15 d, de- clined from 15~ d to 25th d, and slightly raised from 25＇h d to 30＇8 d. Microtubers formed under various sucrose treatments showed an increase in RNA concentration after induction, and it was assumed that the treatment of high concentrations of sucrose might have activated the expression of development-related＇ genes in P. ter- nata microtubers. [ Conclusion] This study provides the basis for revealing the related gene expression information and molecular mechanism during formation of P. ternata microtubers induced by sucrose.

Research on Rapid Propagation of Gongshui Pomelo by Tissue Culture

[Objective] This study aimed to investigate the optimal medium and hor-mone combinations for efficient rapid propagation of Gongshui pomelo and analyze key technical measures in the tissue culture process. [Method] Stem tips and stem segments with buds were col ected from four varieties of pomelo adult trees as explants, to investigate the main effect and key regulatory factors of vegetative organs and tissue culture explants and to propose a series of measures to prevent and control microbial contamination. Final y, an efficient rapid propagation technology system of Gongshui pomelo was established. [Result] Spring shoot explants contained large amounts of auxin, cytokinins, gibberel ins and other growth regulators, which could be used for tissue culture with high bud generation rate and rapid growth. Different conditions led to various culture results. Specifical y, mature pomelo seeds should be generated on semisolid 1/2MS medium and transferred to solid MS medium for incubation. The propagation coefficient of stem segments with axillary buds was greater than that of stem tips, exhibiting significant differences. In ad-dition, the optimal hormone combination was 6-BA 0.5 mg/L ＋ NAA 0.5 mg/L, which significantly promoted the induction and differentiation of adventitious buds. [Conclusion] This study provided basis for basic research, production and application of pomelo germplasm resources.

Elastohydrodynamic Lubrication Interface Stiffness and Damping Considering Asperity Lateral Contact

Elastohydrodynamic lubrication(EHL)point contact occurs between two rough surfaces at the mesoscopic level,while the interaction of rough surfaces involves contact between asperities at the microscale level.In most cases,the contact between asperities within an interface takes the form of lateral contact rather than peak contact.Regions devoid of contact asperities are filled with lubricating oil.However,conventional models often oversimplify lateral contact forms as interactions between asperities and a smooth,rigid plane.These simplifications fail to accurately represent the true contact conditions and can lead to inaccuracies in the analysis of EHL’s contact performance.To address this issue,we have developed a novel EHL interface model comprising two rough surfaces.This model allows us to explore the influence of asperity height,contact angle,and contact azimuth angle on EHL interface performance.