289
16.5 Mechanism of Germination
Germination processing can be conducted in different simple steps like sterilization,
steeping and sprouting. Germination can be activated in controlled environment
having optimum range of temperature, light and moisture factors. Before soaking
the seeds in water, sterilization is carried out to reduce the microbial load. Many
sterilization solutions available but solution of sodium hypochlorite (NaClO) with
various concentration proved to be promising and is commonly used to reduce to
microbial load before seed germination (0.07% NaClO solution) (Limón et al.
2014). By using above mentioned solution usually sterilization is carried out at
room temperature for 15–30-min duration in the ratio of 1:5 or 1:6 with 85 (g) seed
weight/solution volume. Beside sodium hypochlorite pure ethanol or ethanol 70%
solution and 0.2% formaldehyde solution also successfully used in literature for
3-min time duration (Nour et al. 2015; Pająk et al. 2014). Results of few research
shows effect of sterilization process on seed germination. While in few research
sterilization, process is omitted (Guo et al. 2012; Guajardo-Flores et al. 2013),
researcher claim that sterilization process can cause potential hazardous effects and
create seed food safety risks. So, sterilization of seeds is not compulsory before seed
germination, it depends upon many factors including seed condition, water changing frequency during germination process and germination purpose.
Before carrying germination, seed is usually soaked in water to re-hydrate the
seed and during this process temperature, time of soaking, ratio of seed weight and
water volume should be considered. Soaking the seed at room temperature from few
to 24 h and seed weight/volume ratio of 1:1.5 to 1:20 is a frequent practice which
carried out before seed germination. The variation in seed soaking depends upon
inherent characteristics of seeds for example water absorbing capacity of seeds,
seed coat thickness and seed size. After carrying out soaking process seeds could be
placed in incubators for proper germination (Gan et al. 2017). The metabolic activity of dry grains boosts rapidly as it is hydrated during soaking. For proper seed
germination process several processes should be note such as the light, temperature,
humidity, watering and time. Successful germination usually performed in dark and
temperature for germination is kept 20 to 30 °C. Proper care is required during germination process, for example watering to should be done every day to provide seed
optimum humidity for growth, water should be replaced periodically (twice a day),
it will help to eliminate metabolites of sprouted seed and stop the growth of microorganisms (Kandil et al. 2015). To start germination in the grains presence of water
is compulsory which initiates extensive biochemical and physiological process
which provides support to growing baby plant and this process ceased after elongation of embryonic axis. Emergence of radical round the embryo of the grain is the
visible sign that germination had completed (Bewley and Black 1994). Water penetration enhances seed rehydration which stimulates gibberellin synthesis in embryo
which leads to gene expression of hydrolytic enzyme (Nelson et al. 2013).
16 Effect of Germination Processing on Bioactive Compounds of Cereals and Legumes
16.5 Mechanism of Germination
Germination processing can be conducted in different simple steps like sterilization,
steeping and sprouting. Germination can be activated in controlled environment
having optimum range of temperature, light and moisture factors. Before soaking
the seeds in water, sterilization is carried out to reduce the microbial load. Many
sterilization solutions available but solution of sodium hypochlorite (NaClO) with
various concentration proved to be promising and is commonly used to reduce to
microbial load before seed germination (0.07% NaClO solution) (Limón et al.
2014). By using above mentioned solution usually sterilization is carried out at
room temperature for 15–30-min duration in the ratio of 1:5 or 1:6 with 85 (g) seed
weight/solution volume. Beside sodium hypochlorite pure ethanol or ethanol 70%
solution and 0.2% formaldehyde solution also successfully used in literature for
3-min time duration (Nour et al. 2015; Pająk et al. 2014). Results of few research
shows effect of sterilization process on seed germination. While in few research
sterilization, process is omitted (Guo et al. 2012; Guajardo-Flores et al. 2013),
researcher claim that sterilization process can cause potential hazardous effects and
create seed food safety risks. So, sterilization of seeds is not compulsory before seed
germination, it depends upon many factors including seed condition, water changing frequency during germination process and germination purpose.
Before carrying germination, seed is usually soaked in water to re-hydrate the
seed and during this process temperature, time of soaking, ratio of seed weight and
water volume should be considered. Soaking the seed at room temperature from few
to 24 h and seed weight/volume ratio of 1:1.5 to 1:20 is a frequent practice which
carried out before seed germination. The variation in seed soaking depends upon
inherent characteristics of seeds for example water absorbing capacity of seeds,
seed coat thickness and seed size. After carrying out soaking process seeds could be
placed in incubators for proper germination (Gan et al. 2017). The metabolic activity of dry grains boosts rapidly as it is hydrated during soaking. For proper seed
germination process several processes should be note such as the light, temperature,
humidity, watering and time. Successful germination usually performed in dark and
temperature for germination is kept 20 to 30 °C. Proper care is required during germination process, for example watering to should be done every day to provide seed
optimum humidity for growth, water should be replaced periodically (twice a day),
it will help to eliminate metabolites of sprouted seed and stop the growth of microorganisms (Kandil et al. 2015). To start germination in the grains presence of water
is compulsory which initiates extensive biochemical and physiological process
which provides support to growing baby plant and this process ceased after elongation of embryonic axis. Emergence of radical round the embryo of the grain is the
visible sign that germination had completed (Bewley and Black 1994). Water penetration enhances seed rehydration which stimulates gibberellin synthesis in embryo
which leads to gene expression of hydrolytic enzyme (Nelson et al. 2013).
16 Effect of Germination Processing on Bioactive Compounds of Cereals and Legumes