In the past decade, there are significant challenges in agriculture because of the rapidly growing global population. Meanwhile, microfluidic devices or lab-on-a-chip devices, which are a set of micro-structure etch or molded into glass, silicon wafer, PDMS, or other materials, have been rapidly developed to achieve features, such as mix, separate, sort, sense, and control biochemical environment. The advantages of microfluidic technologies include high-throughput, low cost, precision control, and highly sensitive. In particular, they have offered promising potential for applications in medical diagnosis, drug discovery, and gene sequencing. However, the potential of microfluidic technologies for application in agriculture is far from being developed. This thesis focuses on the application of microfluidic technologies in agriculture. In this thesis, three different types of microfluidic systems were developed to present three approaches in agriculture investigation.

Firstly, this report a high throughput approach to build a steady-state discrete relative humidity gradient using a modified multi-well plate. The customized device was applied to generate a set of humidity conditions to study the plant-pathogen interaction for two types of soybean beans, Williams and Williams 82.

Next, a microfluidic microalgal bioreactor is presented to culture and screen microalgae strains growth under a set of CO2 concentration conditions. C. reinhardtii strains CC620 were cultured and screened in the customized bioreactor to validate the workability of the system. Growth rates of the cultured strain cells were analyzed under different CO2 concentrations. In addition, a multi-well-plate-based microalgal bioreactor array was also developed to do long-term culturing and screening. This work showed a promising microfluidic bioreactor for in-line screening based on microalgal culture under different CO2 concentrations.

Finally, this report presents a microchip sensor system for ions separation and detection basing electrophoresis. It is a system owning high potential in various ions concentration analysis with high specificity and sensitivity. In addition, a solution sampling system was developed to extract solution from the soil.

All those presented technologies not only have advantages including high-throughput, low cost, and highly sensitive but also have good extensibility and robustness. With a simple modification, those technologies can be expanded to different application areas due to experimental purposes. Thus, those presented microfluidic technologies provide new approaches and powerful tools in agriculture investigation. Furthermore, they have great potential to accelerate the development of agriculture.