Compound minirhizotron device for root phenotype and water content near root zone

The study of phenotype plays a significant role in plant growth and development. In plant phenotype, the growth state and size distribution of roots are crucial to plant growth and development. Exploring the variation of root development and root zone water content is conducive to improving planting technology with efficiency. Whereas, commercial root phenotype monitoring devices on the market are expensive and sophisticated. This study aims to develop a compound minirhizotron device to acquire images of tomato root system and monitor water content near the root zone. The device mainly included core controller module, transmission module, image acquisition module and moisture monitoring module. The device could realize image acquisition of root system at multiple positions and monitoring of water content near root zone under the condition of less damage to root system. Through image processing, parameters such as root length and root diameter could be calculated. Results indicated that tomato roots at the depth of 6-10 cm from the substrate surface were more densely distributed, and root density decreased with increasing substrate depths. And furthermore, total root length showed a gradual downward trend with the downward movement of the substrate layer. In addition, the closer to the vertical downward straight line from the tomato cultivation site, the greater the root diameter within the monitoring range. In the monitoring results of water content near root zone, the closer to the ground, the higher monitored substrate water content. The overall results showed that the compound minirhizotron device could aquire both root system images and water content near root zone stablely and for a long-term, which could improve the efficiency of planting and irrigation technology.