Detailed Explanation of the Biological Characteristics of Angelica sinensis (Part One)
Angelica sinensis seeds lose their germination rate after being stored at room temperature for 1 year, but can be stored for more than 3 years under low-temperature dry conditions. Mature seeds can germinate and grow under suitable conditions of moisture, temperature, oxygen, etc. Seed germination goes through three processes:
(1) The water absorption and swelling process. The components that make up Angelica sinensis seeds, such as starch, fat, protein, and cellulose, are all hydrophilic colloids, which exist in a gel state under dry conditions. When the seeds absorb water, water penetrates into the colloidal network structure inside the seeds, causing the gel state to become a sol state, and the volume increases accordingly. This process is a physicochemical phenomenon called the seed water absorption and swelling process.
(2) The substance transformation process. As the amount of water absorbed by the seeds increases, the activity of various enzymes is strengthened, and respiratory activity also proceeds vigorously. The complex substances inside the seeds (starch, protein, fat, cellulose, etc.) are hydrolyzed under the action of enzymes into simple soluble substances that are easily absorbed by the embryo - monosaccharides, amino acids, etc. These are the energy and material sources for seed germination. The above changes in the seed contents promote embryo germination. These are biochemical phenomena, called the seed substance transformation process.
(3) The biological process. When the water absorbed by the seeds reaches about 45-50% of their own weight, water absorption and swelling end. With the transformation of the seed contents, the seeds then begin to germinate and grow. First, the radicle begins to elongate and break through the seed coat, then the coleoptile also breaks through the coat, and then one or two pairs of seminal roots grow. Under normal circumstances, the radicle grows faster than the plumule. When the plumule reaches half the length of the seed and the radicle is equal in length to the seed, it is called germination.
After the seeds germinate, the radicle rapidly elongates and grows downward in a curved manner, entering the soil. At the same time, the hypocotyl elongates, causing the curved cotyledons to carry the fruit coat and break through the surface soil, extending above the ground. The two long lanceolate cotyledons unfold, forming a seedling. When the cotyledons grow to about 2 cm in length, the first primary leaf grows from the center of the cotyledons. Seed germination and seedling emergence are not only related to seed quality, but are also closely related to external conditions.
Moisture: During seed germination, all internal physiological changes must involve water. However, if the soil moisture is too high, oxygen will be insufficient, which is also unfavorable for Angelica sinensis germination and may even cause the seeds to rot. Even if seedlings emerge, their growth will be very weak. Therefore, when sowing Angelica sinensis, the soil water content should be maintained at 22-28%. To make Angelica sinensis seeds germinate quickly and emerge uniformly, seed soaking treatment is generally carried out before sowing, so that the seed water content reaches about 40%.
Temperature: The minimum temperature for Angelica sinensis seed germination is 6°C, the optimum temperature is about 20°C, and the maximum temperature is 34-36°C. Within a certain range, the speed of seed germination accelerates as temperature increases, but above 24°C, the germination process is inhibited due to increased respiratory intensity; below 10°C, germination is slow and uneven, and the seeds are prone to disease infection. Generally, an average daily temperature of about 16°C is favorable for cultivating strong seedlings. Under normal sowing period conditions, it takes about 10-16 days from sowing to emergence; when sown at an average daily temperature of 10-12°C, emergence occurs in 16-20 days; at an average daily temperature of 20-24°C, emergence occurs 7-14 days after sowing.
Oxygen: During germination, Angelica sinensis seeds respire quite vigorously and need sufficient oxygen. If the soil is clayey, soil moisture is too high, the soil is compacted, or sowing is too deep, the seeds cannot germinate due to lack of oxygen, or may even rot, and even if seedlings emerge, their growth is very weak.