Exogenous spermidine improved drought tolerance in Ilex verticillata seedlings

Winterberry (Ilex verticillata (L.) A. Gray) is a recently introduced ornamental tree species in China that has not been closely investigated for its drought resistance. In this study, we used two-year-old cuttings from I. verticillata (L.) A. Gray and two representative varieties derived from it, I. verticillata ‘Oosterwijk’ and I. verticillata ‘Jim Dandy’, as materials to investigate how this plant responds to drought stress and whether exogenous spermidine (SPD) can alleviate the negative effects caused by drought stress. The results showed that as the degree of drought stress increased, the leaves of winterberry seedlings became chlorotic, and their edges became dry. Similarly, the relative water content, specific leaf weight, chlorophyll content, leaf nitrogen content, net photosynthetic rate, stomatal conductance and transpiration rate were significantly reduced, whereas the content of malondialdehyde continuously increased with the degree of drought stress. The activities of superoxide dismutase, peroxidase, and catalase increased under moderate drought stress and then decreased under severe drought stress. The levels of soluble sugar and abscisic acid continued to increase, while those of auxin and gibberellic acid decreased. When compared with individual drought stress, an increase in the amount of external SPD clearly alleviated the effect of drought stress on winterberry seedlings. The combined phenotypes and physiological indices of the winterberry leaves under drought stress conditions revealed that the drought resistance of the native species was significantly higher than its two varieties. This finding serves as an important theoretical foundation for the popularization and application of I. verticillata (L.) A. Gray and the two varieties

Radiation-Induced c-Jun Activation Depends on MEK1-ERK1/2 Signaling Pathway in Microglial Cells

Radiation-induced normal brain injury is associated with acute and/or chronic inflammatory responses, and has been a major concern in radiotherapy. Recent studies suggest that microglial activation is a potential contributor to chronic inflammatory responses following irradiation; however, the molecular mechanism underlying the response of microglia to radiation is poorly understood. c-Jun, a component of AP-1 transcription factors, potentially regulates neural cell death and neuroinflammation. We observed a rapid increase in phosphorylation of N-terminal c-Jun (on serine 63 and 73) and MAPK kinases ERK1/2, but not JNKs, in irradiated murine microglial BV2 cells. Radiation-induced c-Jun phosphorylation is dependent on the canonical MEK-ERK signaling pathway and required for both ERK1 and ERK2 function. ERK1/2 directly interact with c-Jun in vitro and in cells; meanwhile, the JNK binding domain on c-Jun is not required for its interaction with ERK kinases. Radiation-induced reactive oxygen species (ROS) potentially contribute to c-Jun phosphorylation through activating the ERK pathway. Radiation stimulates c-Jun transcriptional activity and upregulates c-Jun-regulated proinflammatory genes, such as tumor necrosis factor-α, interleukin-1β, and cyclooxygenase-2. Pharmacologic blockade of the ERK signaling pathway interferes with c-Jun activity and inhibits radiation-stimulated expression of c-Jun target genes. Overall, our study reveals that the MEK-ERK1/2 signaling pathway, but not the JNK pathway, contributes to the c-Jun-dependent microglial inflammatory response following irradiation

Robust Transient Stability Emergency Control Considering Wind Power Uncertainties

Transient stability emergency control (TSEC) enhances power system transient stability during large disturbances but faces challenges in the high-penetration wind power grid where the wind power forecast error still cannot be ignored even with state-of-the-art forecasting methods. In this paper, the TSEC problem is modeled as robust nonlinear programming with the objective of maintaining rotor angle stability by generator tripping and load shedding while the uncertain wind power outputs are regarded as intervals. Interval programming is employed to solve the robust TSEC problem where the trajectory sensitivity analysis is applied to approximate the bounds of transient stability constraints. Numerical results on two test systems demonstrate that the proposed method improves computational efficiency and shows good performance on robustness

Biomechanical properties of ready-to-harvest rapeseed plants: Measurement and analysis

A large loss occurs in the combine harvesting of rapeseeds due to the fragility of rapeseed pods, and all the more so with the vibration of the combine header and the collision between the header and plants. Seed loss is greatly affected by the biomechanical properties of ready-to-harvest rapeseed plants. To understand the mechanism of pod cracking and seed loss and to propose measures for alleviating them, it is needed to study the biomechanical properties of ready-to-harvest rapeseed plants. To this end, “Huayouza 62”, a widely planted rapeseed variety in central China, was selected to study the biomechanical properties, including pod-cracking resistance, main stem-shearing resistance and resonant frequencies, of whole plants. The results showed that the distribution of pod-cracking resistance forces was 1.333–6.100 N in the mature stage, and the pod width and thickness had a significant influence on the cracking resistance. The main influencing factor of the main stem-shearing resistance was the stem diameter. A thicker main stem resulted in a larger shearing resistance force but a smaller shear stress. The moisture contents of the main stems varied from 47.71% to 76.13%. However, the varying moisture contents did not show a significant impact on the shearing resistance. The resonant frequencies of whole rapeseed plants ready for harvest ranged from 6.5 Hz to 7.5 Hz, which was close to the excitation frequency of the cutter bar on the 4LL-1.5Y harvester. This study lays a foundation for improving the design and construction of harvesting devices for rapeseed plants to reduce seed loss

Synthesis And Bioevaluation Of N-(Arylalkyl)-Homospermidine Conjugates

N1-(Arylalkyl)homospermidines (1c-1f) and terminally piperazine-substituted homospermidine conjugates (2a-2e) were synthesized and evaluated for cytotoxicity in mouse leukemia L1210, α-difluoromethylornithine (DFMO)-treated L1210, melanoma B16, spermidine (SPD)-treated B16, and HeLa cell lines. Results demonstrated that homospermidine was a more effective vector than piperazine-substituted homospermidine in ferrying diverse arenes into cells via the polyamine transporter. The leading compound, 9-anthracenemethyl-homospermidine (1a), was shown to induce apoptosis in B16 cells and IL-3 dependent FL5.12A pro-B cells. The novel conjugate 4-biphenylmethyl-homospermidine (1e) could also induce apoptosis. However, it exhibited different effect on the cell cycle of B16 cells compared to 1a. © 2007 Elsevier Ltd. All rights reserved

Study on the Vibration Characteristics of Rape Plants Based on High-Speed Photography and Image Recognition

The transmission characteristics of the vibration excitation of rape plants are of great significance to the study of the harvesting loss and threshing mechanism of rape during harvesting. Aiming to examine the problem that the existing vibration measurement method cannot be well adapted to the vibration measurement of small plants such as rape, this article proposes a vibration measurement method based on high-speed photography and image recognition and uses this measurement method to study the vibration characteristics of rape plants in the three states, i.e., sweep frequency, standing frequency, and free attenuation, with a default hydraulic shaker. The results showed that the average measurement error of the vibration amplitude of this method was 0.0068 mm, and the relative measurement error of the amplitude at 20 Hz was 0.45%, which met the test requirements. Based on this measurement method, a sweep frequency test of rape plants was carried out. It was found that the first-order and second-order vibration modes of rape plants were concentrated in the first 15 Hz. The resonance range of rape plants mainly occurred at 6–7 Hz and 11–12 Hz. The standing frequency vibration test showed that rape plants had strong resonance at 6 Hz and 11 Hz, and grain falling was 1.192% and 0.992%, respectively, which was greater than those of other frequencies. The free attenuation vibration of the rape plant showed that the average attenuation coefficients of the mark points on the lateral branch at 20 cm, 30 cm, and 40 cm from the branch node were 0.542, 0.475, and 0.441, respectively, and the attenuation coefficient decreased as the distance between the mark point and the branch node increased. The amplitude attenuation coefficient of the main branch had little difference, and the average value was 0.797. This research can provide some reference for exploring the threshing mechanism of the rape drum and optimizing the header structure and parameters

Potential Sources, Pollution, and Ecological Risk Assessment of Potentially Toxic Elements in Surface Soils on the North-Eastern Margin of the Tibetan Plateau

Due to increased levels of human activity, various pollutants are frequently detected on the Tibetan Plateau, where the environment is extremely fragile and sensitive. Therefore, this study investigated the sources, pollution, and ecological risks of soil potentially toxic elements (PTEs) in different landscape areas within the Qaidam Basin in the northeastern part of the Qinghai–Tibet Plateau. The contents of seven PTEs (Cd, Cu, Pb, Zn, As, Cr, and Ni) in 32 topsoil samples (0–2 cm) were analyzed in different regions of the Qaidam Basin. The concentrations of As, Cd, Cr, Cu, Ni, Pb, and Zn were 10.4–29.9 mg/kg, 0.08–4.45 mg/kg, 19–66 mg/kg, 8.2–40 mg/kg, 11.7–30.8 mg/kg, 11.1–31.2 mg/kg, and 32–213 mg/kg, respectively. The correlation between Pb and Cd in unpopulated areas was 0.896 (p < 0.01). The correlations among Pb, Cd, and Zn in agricultural areas, among As, Cd, Cr, and Zn in saline lake areas, and among As, Cd, Cr, Cu, Ni, Pb, and Zn in residential areas were all greater than 0.65 (p < 0.05). The principal component analysis results showed that Pb and Cd in unpopulated areas, Pb, Cd, and Zn in agricultural areas, As, Cd, Cr, Zn, and Pb in saline lake areas, and As, Cd, Cr, Cu, Ni, Pb, and Zn in residential areas were affected by human activities (significant factor >0.70). Based on the geological accumulation index and single-factor pollution index results, the maximum Cd values were found to be 4.93 and 45.88, respectively; Cd was thus the most serious PTE pollutant. The comprehensive pollution index of Nemero showed that moderately and severely polluted areas accounted for 18.89% and 18.46% of the total area, respectively. The results of the potential risk index showed that very strong and strong ecological risk points together accounted for 18.8% of the total points. The spatial variations in PTE pollution and the potential ecological risk index had similar patterns; both increased from the unpopulated areas in the northeastern Qaidam Basin to Golmud city in the south-western Qaidam Basin. These results indicate that human activities negatively impacted the soil ecological environment in the Qaidam Basin during the rapid development of the economy and urbanization and that these negative impacts tended to spread to unpopulated areas. Therefore, it is necessary to emphasize the significant impacts of human activities on environmental quality and formulate preventive measures to reduce PTE pollution in the Qinghai–Tibet Plateau