Plant science maintains a firm position in major fields related to the environment and life on earth. The crucial role of plants is in food production and nurture environment balance and biodiversity. To fulfill the role it is important to have healthy plants. The growth and development are influenced by many components such as, environmental changes, like drought, cold, heat, salinity, presence of adequate amount of nutrients. In addition, the plants can be affected by various types of pathogens and may cause diseases which disturbs further growth. Large amounts of pesticides are used in order to overcome the pathogen attacks. Also, fertilizers are employed to deal with the nutrient deficit. However, inefficient use of these may result in contamination in plants. Conventional methods are available for the accurate determination of all these, though they are limited in applications due to the cost, time and man resources connected with these techniques. Progress in nanotechnology productively replaced these by nano sensors. Those are sensors in nano range and are capable of real-time monitoring with high-resolution and accuracy in less time. These provide micro-scale information, sometimes even at single molecule level, regarding the physiological processes and are able to interpret the same. This leap assists agricultural production and related areas. A brief overview of the application of nano sensors in detecting environmental stress, drought conditions, monitoring of nutrients, pathogens, plant metabolism is presented in this chapter.