Why should rice seeds be sun-dried before sowing?

Sun-drying rice seeds before sowing can effectively improve the germination rate and germination vigor of the seeds. The main reasons are:

1. Sun-drying seeds can promote after-ripening of the seeds and increase enzyme activity. After rice seeds are harvested, although they are sun-dried, winnowed and cleaned before being stored, because maturity and dryness vary, the air humidity and temperature during storage will also change. If the seeds absorb moisture, respiration becomes vigorous, and nutrients inside the seeds are consumed heavily, which often leads to weakened germination ability and reduced germination vigor. Sun-drying the seeds can enhance the permeability of the seed coat, so that they absorb water evenly during soaking and enzyme activity is increased.

2. Sun-drying seeds can promote the entry of oxygen into the interior of the seeds. Seed germination requires free oxygen. Oxygen is the primary condition for the seed embryo to form gibberellin or to convert bound gibberellin into free gibberellin. Gibberellin can induce the formation of a-amylase, catalyzing the degradation of starch into soluble sugar, for use by the seed embryo in respiration and by the young roots and young shoots in forming new cells.

3. Sun-drying seeds can reduce the concentration of substances such as amine A in the husk, amine B in the husk, abscisic acid and vanillic acid. When the concentration of these substances is high, they inhibit germination.

4. Short-wave light in the solar spectrum, such as ultraviolet light, has sterilizing ability, so sun-drying seeds has a certain sterilizing effect.

Method of sun-drying seeds: spread the seeds thinly on a drying mat or cement ground, dry for 1-2 days, and turn them frequently so that the seeds dry evenly.