Gibberellin (GA) 20-oxidase (GA20ox) catalyses consecutive steps of oxidation in the late part of the GA biosynthetic pathway. A T-DNA insertion mutant (17S-14) in rice, with an elongated phenotype, was isolated. Analysis of the flanking sequences of the T-DNA insertion site revealed that an incomplete T-DNA integration resulted in enhanced constitutively expression of downstream OsGA20ox3 in the mutant. The accumulation of bioactive GA(1) and GA(4) were increased in the mutant in comparison with the wild-type plant. Transgenic plants overexpressing OsGA20ox3 showed phenotypes similar to those of the 17S-14 mutant, and the RNA interference (RNAi) lines that had decreased OsGA20ox3 expression exhibited a semidwarf phenotype. Expression of OsGA20ox3 was detected in the leaves and roots of young seedlings, immature panicles, anthers, and pollens, based on β-glucuronidase (GUS) activity staining in transgenic plants expressing the OsGA20ox3 promoter fused to the GUS gene. The OsGA20ox3 RNAi lines showed enhanced resistance against rice pathogens Magnaporthe oryzae (causing rice blast) and Xanthomonas oryzae pv. oryzae (causing bacterial blight) and increased expression of defense-related genes. Conversely, OsGA20ox3-overexpressing plants were more susceptible to these pathogens comparing with the wild-type plants. The susceptibility of wild-type plants to X. oryzae pv. oryzae was increased by exogenous application of GA(3) and decreased by S-3307 treatment. Together, the results provide direct evidence for a critical role of OsGA20ox3 in regulating not only plant stature but also disease resistance in rice.
Many studies have focused on the flexural behavior of conventional reinforced concrete (RC) beams strengthened with fiber reinforced polymer (FRP) bonded on the bottom surface; however, rare attempt is made to strengthen RC beams with FRP bonded on the side surface, furthermore, as for the comparative study of the both is even more scarce.Based on the existing bending experimental data of RC beams externally strengthened with FRP, the flexural capacity calculation formula of normal section of RC beams strengthened with FRP bonded on the side or bottom surface was deduced in the paper. In addition, a comparative analysis on the strengthening effect between bottom bonded FRP and side bonded FRP was made. The results indicated that the ultimate load-carrying capacity of the former was slightly lower than the later.
Based on the calculation method of cracking load for reinforced concrete beam, the formula to calculate cracking load of normal section for concrete beams strengthened with BFRP sheet is established. The cracking load experiment of seven concrete beams strengthened with BFRP and three concrete beams strengthened with CFRP is conducted, and the results showed that fiber sheet layers and fiber sheet types have little effect on cracking load of concrete beams strengthened, the cracking load of beams strengthened mainly depends on the strength of concrete. The comparison between estimated values and test values of concrete beams strengthened indicates that the estimated values are slightly smaller, the formula can be used to calculate the cracking load of concrete beams strengthened.
The fatigue failure modes of reinforced concrete beams externally strengthened with basalt fiber reinforced polymer(BFRP) sheets was examined in an experimental and analytical study. One strengthened beam failed due to the debonding and fracture of U-wraps FRP sheet at the anchors,and the others failed the fatigue fracture of the longitudinal tensile reinforcements. Based onCode for Design of strengthening concrete structure, the fatigue failure of RC bending members strengthened with FRP was analysed,and the indicate that with reinforcement ratio of 0.612% and fatigue stress ratio of 0.3, only the fatigue fracture of steel bars occured rather than the crushing of concrete in the compression zone.
An optimum reticulated shell structure is selected and its dynamic properties are analyzed. In this paper analyses the dynamic feature and gains the elementary parameters from the analysis of free vibration. The frequencies and modes are compared by two finite element methods. The paper analyzes the dynamic responses of the reticulated shell structure subjected to two-dimensional and three-dimensional earthquake waves respectively. Simultaneously analyses the linear,geometric nonlinear and both geometric and material nonlinear dynamic responses in two situations. The nodal displacements and stresses of members are compared and analyzed. The characteristics of elastoplastic seismic responses of the structure are revealed and the basic rules are obtained.
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