Why should vegetables and grain seeds be soaked before sowing? What are the specific methods?

Soaking the seeds of vegetables and grains is a method of soaking the seeds of vegetables and grains with clean water or various solutions.

The purpose of seed soaking is to make the grain absorb water quickly and reach the water content that can germinate normally. The moisture content of dried seeds is usually less than 15%, the physiological activity is very weak and is in a dormant state. After the seed absorbs water, the seed coat expands and softens, the oxygen dissolved in the water enters the cell with the water, and the enzymes in the seed begin to activate. Due to the action of enzymes, the respiration of the embryo was enhanced, and the insoluble substances stored in the endosperm were gradually transformed into soluble substances, which were transported to the embryo with water. The seed embryo obtains water, energy and nutrients, and the cells begin to divide, elongate and break through the glume (germination) under suitable temperature and oxygen conditions. It can be seen that in order to make the seed germinate, we must first make it absorb enough water. However, a seed does not germinate with water. It must absorb at least 15 percent of its weight before it can begin to germinate. It can only germinate normally when the amount of water absorbed reaches 40% of its own weight.

The time needed for seed soaking is related to the thickness of the hull, the permeability, the water content of the seed before soaking and the water temperature of the seed. Indica rice absorbs water faster than japonica rice; seeds with low water content absorb water faster and those with high water content absorb water more slowly; those with high temperature are faster and those with low temperature are slower. Whether the seed absorbs enough water can be judged from the appearance. The seed that absorbs enough water is translucent, and the embryo and endosperm can be vaguely distinguished through the husk, the endosperm expands, the endosperm becomes soft, and the rice grain can be crushed by hand when the husk is peeled, and there is no click when breaking.

Soaking vegetable seeds before sowing can make the seeds absorb enough water in a short time and germinate rapidly. at the same time, it can also play the role of sterilization, disease prevention and enhance seed resistance. This paper introduces four common seed soaking methods before sowing vegetable seeds: hot water soaking, warm water soaking, warm soup soaking, sodium hydroxide soaking.

1. Seed soaking in hot water

It helps to kill germs and eggs on the surface of the seed. It is required that the water temperature is 75 ℃ ~ 85 ℃ and the water consumption is about 4 to 5 times that of the seed. Soak and stir until the water temperature drops to 30 ℃ and the seed expands fully. This method is suitable for seeds with hard and thick seed coat and difficult to penetrate, such as leek, towel gourd, wax gourd and so on.

2. Seed soaking in warm water

The required water temperature is 20 ℃ ~ 30 ℃, which is suitable for seeds with thin seed coat and fast water absorption, such as Chinese cabbage, cabbage and so on. There is no hard heart to soak the seed.

3. Seed soaking method with warm soup

This method is effective in preventing tomato early blight, eggplant brown streak, sweet pepper anthracnose, cucumber corner spot, celery spot blight and so on. It is required that the water temperature and time should be accurate and cool immediately after soaking for enough time. For example, the water temperature of tomato seed soaking is 52 ℃ and the soaking time is 30 minutes; the water temperature of sweet pepper, cucumber and eggplant is 55 ℃ and the soaking time is 12 hours; the soaking temperature of celery seed is 48 ℃ and the soaking time is 30min.

4. Soaking seeds with sodium hydroxide

This method can kill most of the viruses and fungi inside and outside the vegetable seed, and can effectively prevent vegetable virus disease, anthrax, corner spot and early blight. First soak the vegetable seeds in clean water for 4 hours, then soak 15min in 25% sodium hydroxide solution, and finally rinse with clean water and dry for 18 hours.