For the seed sprouting of vegetables, firstly the seeds themselves have the ability to germinate, and secondly, they require suitable environmental conditions, including temperature, oxygen, and moisture.
Two conditions must be met for seed sprouting
1.The internal conditions of seed sprouting
The internal conditions of seed sprouting mainly refer to two aspects.
- The seed itself has sprouting ability (sprouting potential), that is, the seed is alive rather than dead.
- The seed can germinate when given the conditions required for its sprouting. Therefore, whether it is direct seeding or seedling cultivation, it must be a viable seed. However, many vegetable crop seeds (such as onions, leeks, etc.) have a short seed life and almost lose their ability to germinate when stored indoors for more than one year.
Therefore, for vegetable crops with short seed life, use new seeds for sowing, and try not to use stale seeds. Even for vegetable crops with a long seed life, such as tomatoes and cabbage, it is best to check the sprouting rate before planting.
On the other hand, even if some vegetable seeds are vigorous and given suitable sprouting conditions, they sometimes still do not germinate. This situation is called dormancy. In order to make the seeds germinate and emerge smoothly after sowing, the seeds with dormant characteristics are Measures should be taken to relieve their dormancy before sowing.
2.External conditions of seed sprouting
During the sprouting process, the seeds have high requirements for environmental conditions. Under suitable conditions, the seeds can germinate quickly and grow strong seedlings in a short period of time.
If it cannot be satisfied, it will affect the quality of seed sprouting to varying degrees.
Adequate moisture, suitable temperature, and sufficient oxygen are the three basic conditions (that is, the three elements of sprouting) essential for seed sprouting. In addition, light, carbon dioxide, and other factors also affect seed sprouting.
The 4 conditions for seed sprouting
Moisture is the most basic condition for seed sprouting. Only after the seeds have absorbed a large amount of water, can the stored nutrients be transformed into substances necessary for life activities.
Water can also soften the seed coat, increase air permeability, and accelerate the water-absorbing sprouting of seeds.
Before the seeds germinate, they must absorb a certain amount of water. However, the water absorption and water absorption speed are different depending on the type of vegetable, which mainly depends on the structure of the seed coat and the nutrient composition of the seed storage.
Generally, seeds with more protein absorb water faster and more, seeds with more starch absorb water slowly and less, and seeds with more fat are somewhere in between.
Seeds with good seed coats will absorb water faster, while seed coats will be dense, but seeds with poor water permeability will absorb water slowly.
The seed coats of cruciferous, leguminous, tomato, cucumber, and other vegetable seeds have good water permeability; the seed coats of vegetable seeds such as Umbelliferae, eggplant, pepper, watermelon, wax gourd, bitter gourd, onion, and spinach are more difficult to permeate.
Therefore, the time should be reasonably controlled according to these characteristics when soaking seeds; if the swelling time is too long, it will cause the nutrient extravasation of the seed and the decline of seed vigor.
In addition, after sowing, the sprouting rate of vegetable seeds is closely related to the soil water content, and the soil water content should be controlled according to the type of vegetable.
The seeds require an appropriate temperature during sprouting. The lowest, highest, and most suitable temperatures for seed sprouting of different vegetable species are different.
Generally, temperature-loving vegetables (melons, solanaceous fruits, and some beans) require a higher temperature, the suitable temperature is 20-30℃, the highest temperature is 35-40℃, and the lowest temperature is 10℃.
The suitable temperature for sprouting of cold-tolerant and semi-cold-resistant vegetables (cabbage, cabbage, mustard greens, etc.) is 15-25°C, the highest temperature is about 30-35°C, and the lowest temperature is 0-4°C.
However, most vegetable seeds can germinate well within the range of 15-30°C. Among them, some vegetable seeds have a wider temperature range suitable for germinating, such as cabbage vegetables; some are narrower, such as lettuce.
Under normal circumstances, within a suitable temperature range, the seed sprouting rate is higher and the sprouting time is shorter.
If the temperature is higher than the suitable temperature, although the seeds germinate faster, the quality of the buds is poor (some vegetable seeds cannot germinate when the temperature is higher than the suitable temperature, especially lettuce and celery seeds);
However, if the temperature is lower than the appropriate temperature, the sprouting time of the seeds will be prolonged and the sprouting rate will be lower (even causing the seed to rotten when the humidity is high), and the seedling growth will be relatively weak.
Some kinds of seeds do not germinate well under constant temperature conditions as well as under variable temperature conditions. For example, eggplant is a typical vegetable crop that needs to change the temperature to germinate well. The best sprouting is when the temperature difference between day and night is 8～10℃, that is, day temperature. 30°C/night temperature 20°C variable temperature. In fact, after sowing, vegetable seeds are always under a certain temperature difference between day and night.
Oxygen is an extremely important condition for seed sprouting. During the storage of the seeds, the respiration is extremely weak and the oxygen demand is small, but when the seeds absorb water to germinate, the respiration is gradually vigorous, so the oxygen requirement increases sharply.
If there is no oxygen or insufficient oxygen when the seeds germinate, the seeds will not germinate or even fail to germinate.
If the air permeability is poor during soaking and accelerating sprouting or the soil is too thick after sowing, especially if the seedbed is too wet, hypoxia will cause the seeds to germinate poorly and even cause rotten seeds. Special attention should be paid to this problem after sowing legume vegetables and some melon vegetables.
The effect of light on the sprouting of vegetable seeds varies from species to species, but most vegetable seeds are not sensitive to light response during sprouting.
According to the sensitivity of seed sprouting to light, vegetable seeds can be divided into three categories:
The first type is light-demanding seeds, that is, seeds need a certain amount of light when they germinate, and they cannot germinate or germinate poorly under dark conditions. Such as cabbage, lettuce, celery, carrots, etc.
The second type is phobia seeds, which means that the seeds can only germinate under dark conditions, and the seeds cannot germinate if there is light. Such as melons, amaranth, green onions, leeks, etc.
The third type is medium-light seeds, which can germinate normally under light or dark conditions.
Most vegetable seeds, such as beans, fall into this category. To understand the effect of light on seed sprouting, corresponding measures can be taken in the process of sowing or accelerating sprouting to improve the sprouting rate and emergence rate of seeds.