Plasma Treatment – A Tool to Improve Seed Quality – A Review

Abstract

Plasma is a partially ionized gas composed of positive and negative ions, electrons, neutrals, molecules, photons and UV-light. It is the “fourth state of matter”. There are number of pre-sowing treatments that are employed to enhance seed quality viz., seed priming, coating and biological seed treatments, etc. In recent times, a new technique namely plasma treatment is evolved for this purpose. The plasma can be generated in many ways however for seed treatment the glow discharge method is commonly used due to its properties like seed quality improvement, seed enhancement and decontamination of pathogens present on seed coat surface. In glow discharge method plasma is formed by passage of electric current through a low pressure gas (argon). It is created by applying a voltage between two electrodes in a glass tube containing argon gas. A glow discharge is plasma formed by the passage of electric current through a gas. It is often created by applying a voltage between two electrodes in a glass tube containing a low-pressure gas. When the voltage exceeds a value called the striking voltage, the gas ionization becomes self-sustaining, and the tube glows with a colored light. The color depends on the gas used. Glow discharges are used as a source of light in devices such as neon lights, fluorescent lamps, and plasma-screen televisions. Analyzing the light produced with spectroscopy can reveal information about the atomic interactions in the gas, so glow discharges are used in plasma physics and analytical chemistry. They are also used in the surface treatment technique called sputtering. When the voltage exceeds a certain value, the gas in the tube ionizes, transforms into plasma. The ionized gas begins the conducting of electricity, causing it to glow. Plasma can be generated either under low pressure or at atmospheric pressure. However, the electric current is just the result of plasma formation; furthermore, the description is more adequate for capacitive plasma, however plasma can be induced – one of the upmost examples is ICP, Inductively Coupled Plasma. Plasma pre-treatment of seeds stimulates their germination and leads to suppression of fungal and bacterial plant pathogens. Crop yields are improved by treating the seeds in a low temperature plasma discharge generated between spaced electrodes connected to a source of high frequency electrical power.