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This paper reports a description of the theory of contact angle measurement and its use for the determination of surface energy of solids. The main objective of the work is to present a convenient approach to explain wetting phenomenon using contact angle theory. A brief review of Young’s equation and Young- Dupre equation is also presented followed by an extended Fowke’s equation widely used for the calculation of surface energy of solids. The two liquid model has been applied to determine the surface energy of polycarbonate and low density polyethylene.Key words: Contact angle; Surface energy; Surface characterization; Wettability; Young’s equation; Fowke’s modelThe Himalayan Physics Vol.2, No.2, May, 2011Page:1-4Uploaded Date: 31 July, 2011

The extensive use of chemical fertilizers to increase crop yields in agricultural fields has had a negative impact on the environment. To produce more food on less land and fulfill the growing global demand for food, farmers will need innovative and environmentally friendly technology. Several studies have cited the positive effects of plasma-activated water (PAW) on seeds in their research findings. This study investigates the effects of PAW on four distinct seed species: phapar (Fagopyrum esculentum), barley (Hordeum vulgare), mustard (Brassica nigra), and rayo (Brassica juncea). Deionized (DI) water was treated for 5 or 10 min using the gliding arc discharge (GAD) system, which was operated by line frequency in the air. Water analysis indicates that the physiochemical parameters (electrical conductivity, pH, nitrate, nitrite, and ammonia concentration) of PAW were significantly different from DI water. Despite exposure to GAD for a certain period of time, the temperature of DI water did not alter significantly. All calculated germination parameters were significantly enhanced for seeds treated with PAW compared to the control. In addition, they displayed a significant increase in total seedling length and exhibited greater vigor. Seeds immersed in PAW absorbed significantly more water than seeds soaked in DI water, enabling rapid water penetration into the seed and early seedling emergence. This puts plasma agriculture ahead of conventional farming methods.

The present work is focused on investigating the effect of plasma-activated water (PAW) on the seed germination and seedling growth of radish, fenugreek, and pea seeds. A home-made gliding arc discharge (GAD) reactor generated in air under atmospheric pressure and operating at 50 Hz line frequency is used for water activation. PAW was prepared by exposing deionized water to GAD for 5, 10, 15, and 20 min. As a result of plasma treatment, deionized water showed substantial changes in physical characteristics such as pH and electrical conductivity along with chemical parameters such as nitrites, nitrates, and ammonia. The effect on germination was evaluated based on the fraction of germinated seeds and their length at 7 and 12 days after treatment. Seeds irrigated with PAW resulted in a higher imbibition rate than those irrigated by deionized water. When the seeds were irrigated with PAW, the germination parameters such as final germination rate, mean germination rate, coefficient of velocity of germination, germination index, and growth parameters such as shoot/seedling length and vigor index increased. In conclusion, PAW may be utilized to increase the germination rate of seeds.

The present study reports the generation of plasma-activated water (PAW) using dielectric barrier discharge (DBD), its physicochemical properties, and its potential impact on the seed germination and seedling growth of soybean. The results revealed significant changes in physical parameters, such as pH, total dissolved solids, total suspended solids, turbidity, conductivity, dissolved oxygen, and chemical parameters, such as calcium, chromium, sodium, manganese, nitrate, nitrites, phosphorus, and sulfur and biological parameter such as E. coli in water after plasma treatment. The concentration of dissolved oxygen, conductivity, nitrate, nitrite, and sulfur was increased with an increase in water treatment time, and the amounts of the other analyzed parameters decreased with the increase in water treatment time. The effects of untreated water and plasma-activated water treated for 20 minutes on soybean germination and growth were studied. The germination rate was found to be higher with plasma-treated water. Shoot lengths, seedlings length, vigor index, and germination rates were increased as compared to those germinated by normal water irrigation. The seedlings irrigated with PAW responded to the abundance of nitrogen by producing intensely green leaves because of their increased chlorophyll a as compared to seedlings irrigated with normal water. However, the content of chlorophyll b and carotenoids was found to decrease in the case of seedlings irrigated with PAW. Based on this report, we conclude that PAW could be used to substantially enhance seed germination and seedling growth.