Comparative transcriptome and microbial community sequencing provide insight into yellow-leaf phenotype of Camellia japonica

Background Leaf color variation is a common trait in plants and widely distributed in many plants. In this study, a leaf color mutation in Camellia japonica (cultivar named as Maguxianzi, M) was used as material, and the mechanism of leaf color variation was revealed by physiological, cytological, transcriptome and microbiome analyses. Results The yellowing C. japonica (M) exhibits lower pigment content than its parent (cultivar named as Huafurong, H), especially chlorophyll (Chl) and carotenoid, and leaves of M have weaker photosynthesis. Subsequently, the results of transmission electron microscopy(TEM) exhibited that M chloroplast was accompanied by broken thylakoid membrane, degraded thylakoid grana, and filled with many vesicles. Furthermore, comparative transcriptome sequencing identified 3,298 differentially expressed genes (DEGs). KEGG annotation analysis results showed that 69 significantly enriched DEGs were involved in Chl biosynthesis, carotenoid biosynthesis, photosynthesis, and plant-pathogen interaction. On this basis, we sequenced the microbial diversity of the H and M leaves. The sequencing results suggested that the abundance of Didymella in the M leaves was significantly higher than that in the H leaves, which meant that M leaves might be infected by Didymella. Conclusions Therefore, we speculated that Didymella infected M leaves while reduced Chl and carotenoid content by damaging chloroplast structures, and altered the intensity of photosynthesis, thereby causing the leaf yellowing phenomenon of C. japonica (M). This research will provide new insights into the leaf color variation mechanism and lay a theoretical foundation for plant breeding and molecular markers.

The Spatial Variation Mechanism of Size, Velocity, and the Landing Angle of Throughfall Droplets under Maize Canopy

Larger diameter and velocity and smaller landing angle of sprinkler irrigation droplets are more likely to cause soil splash and erosion. However, the mechanism of crop canopy influence on the physical parameters of sprinkler droplets is unknown. In this study, with the landing angle of sprinkler irrigation droplets as the independent variable and maize plants (Zea mays L.) as the research object, an indoor sprinkler irrigation experiment was carried out. The effects of maize canopy and variation in sprinkler irrigation droplets landing angle on the value and spatial distribution pattern of size, the velocity, and the landing angle of throughfall droplets was analyzed. In addition, the spatial variation patterns of throughfall droplets size, velocities’ distribution, and individual droplet’s speed, kinetic energy were also explored. The results showed that maize canopy and the decreasing of the sprinkler irrigation droplet landing angle had a positive and obvious effect on reducing the size and velocity of penetrating rain droplets. However, the throughfall droplets’ landing angles were only small variations. When the landing angle of sprinkler irrigation droplets was >45°, the spatial distribution of throughfall droplets size and velocity corresponded well with the canopy structure and leaf projection area of maize, i.e., the further away from the maize stalk, the larger the size and velocity of throughfall droplets. Nevertheless, if the landing angle of sprinkler irrigation droplets was <45°, the spatial distribution mentioned above was mainly affected by droplets landing angle. The spatial variation of throughfall droplets’ size and velocities at different measurement points was attributed to the change of the larger droplets’ volume proportion and the equivalent velocity. Although the maize leaves had a certain degree of perturbation effect on the velocities and kinetic energy of the larger kinetic energy droplets, the flight path of these drops did not alter significantly. The results of this research will be of practical value in guiding the development of a new sprayer and the optimum selection of sprinkler heads.

The Variation Mechanism of Thermal Properties of Loess with Different Water Contents during Freezing

The thermal properties of soils are affected by many factors, such as temperature, water content, and structure. Based on the transient plane source method of thermal physics, the thermal properties of loess with different water content during the freezing process were tested. We analyzed the variation mechanism of thermal properties from the perspective of phase change. Based on the Pore/Particle and Crack Analysis System (PCAS) and theory of heat transfer, we then analyzed the microstructure and heat conduction process of loess. And a calculation model of volumetric heat capacity of frozen soil was presented. The results show that, in the major phase transition zone, the variation of the thermal properties of loess with temperature is the most significant. And the thermal diffusivity increases sharply with the significant increase of thermal conductivity and the rapid decrease of volumetric heat capacity. Moisture content not only increases the thermal conductivity and volume heat capacity of loess but also makes the influence of temperature on the thermophysical parameters more significant. The effect of temperature on thermal properties is mainly due to the change of heat transfer media caused by phase transition of water-ice, followed by the change of thermal properties of heat transfer media such as soil particles, water, ice, and air with temperature. Increasing the water content reduces the contact thermal resistance between soil particles because of the increase in the thickness of the water film on the surface of soil particles and the thermal conductivity of the heat transfer medium between particles, thus changing the thermal properties of soils.

Correlation between Dielectric Loss and Partial Discharge of Oil-Pressboard Insulation

Dielectric loss tand and partial discharge (PD) are important indicators for status assessment of oil-pressboard insulation. The correlation characteristics between these two parameters has significance for understanding the material’s degradation and helps to eliminate the information asymmetry for diagnostics. In this paper, the symmetric experimental platform is set up to measure the dielectric loss tand and PD for oil-pressboard insulation following the designed testing procedure consisted of raised and rested voltages. Three sets of samples with different water content were tested. The variation mechanism of tand with voltage is explained by proposed equivalent circuit, which introduced an asymmetric component representing defect part. PDs are found to be symmetric in the sinusoidal voltage cycles and their statistical parameters are calculated. Besides, the correlation between dielectric loss difference from raised voltage to rested voltage and PD is researched. Strong correlation is observed between dielectric loss and PD, which offers degradation insight for oil-pressboard insulation and helps to eliminate information asymmetry for material status diagnostics.