Respiration, sorption and germination of seeds stored in controlled atmosphere

Most deleterious changes that occur during seed storage are associated with invasive forces such as moulds, bacteria, insects, mites and rodents. Even under most favourable conditions biochemical and physiological changes occur in seeds. Chemical Fumigation, Controlled Atmosphere (CA) and Air Conditioning and Dehumidification (ACD) are technologies that are used to protect stored products from attack by insects and pests and to restrict growth of micro-organisms. A laboratory study on the effects of varying CA conditions on seed quality was undertaken. Respiration rate was measured as CO2 produced by seeds in an airtight acrylic cylinder. Average CO2 production by sorghum and soybean seeds was between 1 to 4 mg/Kg in 24 hours, whereas the respiration quotient (RQ) varied between 0.06 to 1.18. The diffusion of gases into the pores of grains controls the sorption process. About 70% of the CO2 sorbed seems to be "chemisorbed". The results on germination and viability of soybean and sorghum seeds indicate that an atmosphere containing high CO2 does not have a detrimental effect on seeds as much as high storage temperature and higher moisture content. A locally built Pressure Swing Adsorption (PSA) N-2 generation plant (10 1/min) reduced the CA operating costs. CA technology can be a potent alternative for commercial long-term storage of seeds.