胎花

她一出生，那殷红的胎记就如一帖狗皮膏药贴在她的脸上。上帝用这样一种方式，将她搁在母亲面前，似乎是在考验她：“这样一个孩子，你还要不要？”母亲拭干脸上的泪水，还是欣喜地抱起了她。

Simulation of vehicle braking behavior on wet asphalt pavement based on tire hydroplaning and frictional energy dissipation

To investigate the influence of wet conditions on vehicle braking behavior,a numerical-analytical method was proposed for the simulation of tire hydroplaning and frictional energy dissipation. First, a finite element model of tire hydroplaning was established using the coupled EulerianLagrangian method,including a pneumatic tire model and a textured asphalt pavement model. Then,the frictional force on the tire-pavement interface at different speeds was calculated by the model. Based on vehicle braking mechanism and frictional energy dissipation,a calculation method for braking distance was proposed based on a three-stage braking process. The proposed method was verified by comparing the calculated hydroplaning speed and braking distance with field test results.Then,vehicle braking distances and wet friction coefficients were calculated under different conditions. The results show that thinner water film,a more complex tread pattern and higher tire inflation pressure all contribute to the vehicle braking performance; moreover, the pavement texture has obvious influence on vehicle braking behavior,especially at a high speed. The proposed method shows great effectiveness in predicting vehicle braking behavior on wet asphalt pavements.

Pollen-embryogenesis and chromosomal variability in anther culture of Brassica hirta Moench (Sinapis alba L)

The anther cultures of Brassica hirta underwent pollenembryogenesis and callusing,which showed a wide range of chromosome numbers varying from 9 (n=12) to a highly polyploid.For embryogenesis,pretreatment of floral buds in 0.4 M sucrose solution for 72 hrs at 4℃ was superior to freshly cultured anthers.Culture temperature of 30℃ for 14 days before maintenance of cultures at 25℃ was significantly beneficial for embryo yield in comparison to cultures continuously incubated at 25℃.Dark treatment during culture was more effective for pollen-embryo yield.

Anther Culture of Chinese Radish(Raphanus sativus L. var. Longinnatus Bailey):Response of Different Genotypes to the Embryogenesis and the Traits of Regenerated Plantlets

[Objective] The aims were to ① conduct anther culture of Chinese radish varieties; ② observe the development of embryos from anther culture; ③ study the response of different genotypes to embryogenesis in anther culture; ④ observe the morphology of regenerated plantlets; ⑤ analyze the ploidy level of regenerated plantlets arising from the anther culture process. [Method]Anthers of 15 genotypes with diverse genetic backgrounds of Chinese radish have been cultured in vitro and induced to undergo embryogenesis and plant formation. [Result] Of 15 genotypes evaluated,four produced embryos. The genotype was the main factor to influence the embryogenesis. The morphology and the ploidy of the regenerated plantlets were observed,and the anther-derived plantlets included a mix of haploids,diploids and hexaploids. Of the plants that regenerated from anther embryos 60% were diploid. [Conclusion] The plantlets had the high ability to double spontaneously.

An Arabidopsis embryonic lethal mutant with reducedexpression of alanyl-tRNA synthetase gene

In present paper, one of the T-DNA insertional embryonic lethal mutant of Arabidopsis is identifled and designated as acd mutant. The embryo development of this mutant is arrested in globular stage. The cell division pattern is abnormal during early embryogenesis and results in disturbed cellular differentiation. Most of mutant embryos are finally degenerated and aborted in globular stage. However, a few of them still can germinate in agar plate and produce seedlings with shorter hypocotyl and distorted shoot meristem. To understand the molecular basis of the phenotype of this mutant, the joint fragment of T-DNA/plant DNA is isolated by plasmid rescue and Dig-labeled as probe for cDNA library screening. According to the sequence analysis and similarity searching, a 936bp cDNA sequence (EMBL accession#: Y12555) from selected positive clone shows a 99.8 % (923/925bp) sequence homology with Alanyl-tRNA Synthetase (A1aRS) gene of Arabidopsis thaliana. Furthermore, the data of in sitll hybridization experiment indicate that the expression of AlaRS gene is weak in early embryogenesis and declines along with globular embryo ’development’ in this mutant.Accordingly, the reduced expression of AlaRS gene maybe closely related to the morphological changes in early embryogenesis of this lethal mutant.

Effect of Different Hormone Combinations on Somatic Embryogenesis in Cotton Cultivar Xinluzao 33(Gossypium hirsutum L.)

[Objective] This study was conducted to evaluate the efficiency of somatic embryogenesis and plant regeneration for an upland cotton cultivar Xinluzao33 under the induction of different hormone combinations and thus to determine the optimal hormone combination. [Method] Calli of Xinluzao33(Gossypium hirsutum L.) were induced from seedling hypocotyl tissue by a range of DK and BK combinations. Embryogenic calli and embryos were induced on callus-inducing medium(CIM) without any hormones. Callus appearance and quality were compared to determine which medium was the optimal for callus induction. Embryogenesis ratio was calculated to determine which medium was the best for somatic embryogenesis and plant regeneration. [Result] Callus induction rate was 100% in all the 12 hormone combinations.The calli were yellow or kelly, and their texture was loose or soft under low concentrations of DK combinations, green or white, variably compact under high concentrations of DK combinations. The calli induced by BK combinations were kelly or green, covering creamy white substance. The best medium for callus induction was DK6(0.05 mg/L 2, 4-D and 0.10 mg/L KT). Embryogenic calli were successfully induced from all the combinations. The efficiency of embryogenic callus induction,embryogenesis, and plantlet regeneration were significantly different among the 12 combinations. The result showed that the embryogenesis ratio was the highest in BK3 combination(0.50 mg/L IBA and 0.50 mg/L KT), 72.86% of embryogenic calli differentiated into somatic embryos after being cultured on CIM for 80 d, and80.93% of the somatic embryos finally regenerated into plants on SEM(somatic embryo induction medium). [Conclusion] These results indicate that hormone combination BK3(0.50 mg/LIBA and 0.50 mg/L KT) was the best medium for somatic embryogenesis and plant regeneration from Xinluzao33.