Enumerating physiological property of bacterial exopolysaccharide by neutron radiography

Neutron imaging is a non-destructive and non-invasive technique which is complementary to other radiation imaging techniques like X-ray and gamma imaging. Neutron radiography measures the attenuation of a neutron beam due to absorption and scattering within a sample using a two-dimensional position-sensitive detector that measures the transmitted neutron intensity. Neutron imaging is ideal for agricultural research applications because neutrons are sensitive to hydrogen, which the plants or roots contain in abundance. In contrast, the soil does not contain a lot of hydrogen. That means the plant roots show up as dark, clear, and distinct regions in the radiographic images. Neutrons are ideally suited for this task since they readily penetrate most common materials but are strongly attenuated by those containing hydrogen such as water. Also, water distribution in soil and roots can be easily imaged and quantified. One of the leading concerns in agriculture is the decreasing availability of water for irrigation leading to drought-like conditions. After the subsequent water losses and deep percolation, the water thereafter which remains in the soil for uptake by plants and soil microbiota is termed green water. The cumulative amount of productive green water flow depends on the correlation between the growth of plants in the root section and soil microbiota and transpiration rate. Various biotic movements in the soil ecosystem involve Plant Growth Promoting Rhizobacteria mechanism to increase yield and feasible growth of crop management. One such mechanism is the biosynthesis of exopolysaccharides. It plays a major role in conserving the water content of plant and maintains soil moisture. Bacteria like Azotobacter vinelandii, Bacillus drentensis, Enterobacter cloacae, Agrobacterium sp,. Xanthomonas sp. are EPS producing PGPR which is vital in the renewal of soil fertility. Various methods are being devised to increase the soil water retention. One such method is the use of EPS producing bacteria which is the subject of this work. The high neutron attenuation coefficient of hydrogen (in water) makes neutron radiography an excellent candidate for studying or measuring soil water dynamics. The objective of the present experiment is to use neutron radiography to directly visualize water retention/distribution in soil during evaporation in the presence or absence of EPS producing bacteria. The physical property of extracted EPS was analysed in the sand with the help of a novel method, neutron radiography at Bhabha Atomic Research Centre. The evaporation process of the sandy soil treated with different EPS and control samples were imaged to show the neutron radiographs at t=0 (start of the experiment) and t = 24 hrs. After 24 hours of evaporation, 90% of water loss was observed for M5a1 and water having RWC 8.542% and 10.463%. The highest RWC was maintained by SSN1 29.7% compared to SGM81 (19.06%). EPS producing PGPR has many practical applications in agriculture as well as industrial sector. (author)