Causes and Control methods of early bolting of Angelica sinensis

Perennial herb Angelica sinensis, 0.4-1 m tall. The florescence is from June to July and the fruiting period is from July to September. Its root can be used in medicine and is one of the most commonly used traditional Chinese medicines. It has the effects of tonifying blood and blood, regulating menstruation and relieving pain, moistening dryness and smooth intestines, anti-cancer, anti-aging and immunity. Angelica often bolts and blossoms in June and July in the second year of cultivation, with a bolting rate of 10% in normal years and more than 80% in serious cases. In bolting and flowering plants, the parenchyma cells of secondary xylem are lignified, the ratio of secondary phloem to secondary xylem changes from the normal 2:1 to 1:10, the fleshy root is gradually xylem and hollow, firewood is large, lack of oil and gas, and can not be used medicinally. Therefore, preventing and controlling early bolting is an important technical measure to improve the yield and quality of Angelica sinensis. The following analysis and put forward Angelica bolting reasons and prevention and control methods.

[bolting reason]

1. Genetic factors: with bolting Angelica sinensis seeds, the bolting rate of seedlings bred by normal main bolting or overripe seeds and aged seeds will be very high, reaching more than 80-90%.

2. Ecological factors: at low altitude, high temperature, sunny slope. Raising seedlings or transplanting in arid areas is easy to cause early bolting of Angelica sinensis. The correlation degree between early bolting of Angelica sinensis and various factors from large to small is altitude, annual precipitation, density, organic fertilizer and nitrogen. The bolting rate of seedlings stored in shade is about 50% lower than that in sunny land; the soil water content in storage period is 50-60g/kg, the bolting rate decreases by 60% when shading 50% after transplanting, and the bolting rate reaches its peak when sunshine is more than 14 hours.

3. Nutrition level: the early bolting rate of Angelica sinensis was positively correlated with seedling weight and size. The seedlings whose diameter is less than 0.5cm are suitable for transplanting, but the seedling size should correspond to the seedling age. If the seedling weight is very small, but the seedling age is old, the bolting rate of the seedlings is still very high, on the contrary, the large seedlings with large seedlings and young seedlings rarely bolting. For Angelica sinensis seedlings with the same seedling age, the greater the seedling weight, not only the bolting process was accelerated, the earlier the bolting time, but also the bolting ratio was significantly increased. Early bolting rate was also related to nitrogen content and sugar content of Angelica sinensis seedlings, and there was a significant negative correlation between nitrogen content and early bolting rate.

4. Cultivation measures

The main results are as follows: (1) when the seed maturity is sown with the seeds of full maturity or the head and ear of the main stem, the seedling grows strongly, the sugar content in the root accumulates quickly, and the early bolting rate increases obviously.

(2) when the weight of Angelica sinensis seedlings is the same, the earlier the sowing is, the longer the seedling age is, and the higher the early bolting rate is. The growth period of Angelica sinensis seedlings is generally 90-110days, and the fresh weight of one hundred roots is 40g-70g. Generally, sowing and raising seedlings are from the middle of June to the middle of July, that is, it is more suitable for sowing between the Summer Solstice and Greater Heat. In general, when Cold Dew and Frosts Descent are in the first and middle of October, the temperature drops to zero. If the seedlings are raised too late or get up early, the seedlings are not nutritious enough and are easy to rot.

(3) the sowing density of Angelica sinensis seeds is generally 60kg-75kg/hm2, sometimes as much as 112.5kg/hm2.

(4) for the seedlings stored under the same conditions of transplanting time, bolting easily occurred early after transplanting, the rate of early bolting decreased and the bolting period was delayed. Seedlings with forked roots are also easy to bolt early.

(5) the bolting rate of chemical fertilizer was increased, among which diammonium phosphate was the highest. P fertilizer had a significant effect on the bolting rate of Angelica sinensis, and the application of NP fertilizer would accelerate the bolting process. When the application of NK fertilizer was high, the early bolting rate of Angelica sinensis was significantly increased.

(6) the climate and environment of Angelica sinensis likes cool, shady and humid climate. From May to July, if Angelica sinensis meets high temperature and drought climate during vegetative growth period, the bolting rate is generally on the high side.

[prevention and control methods]

1. Select and retain improved varieties. Under the same cultivation conditions, the seeds of early bolting and flowering plants generally have the character of early maturity and are easy to bolting and flowering. According to the experiment, under the same conditions of seedlings and cultivation and management measures, the seedlings were raised with seeds flowering and fruiting in the second year and the third year, respectively. as a result, the early bolting rate of the seedlings cultivated with the seeds of flowering and fruiting in the second year was 30% higher than that of the seeds in the third year, and the bolting time was 10% and 15 days earlier. At the same time, the seed bolting rate of Angelica sinensis is also related to the seed maturity, the fully mature seeds have strong vitality, the growth is exuberant after planting, the bolting rate is high, and the vitality of tender seeds is weak. Although it will not bolt early after sowing, it has low survival rate, weak growth and low yield. it is also difficult to adopt in production. Therefore, in order to improve the seedling quality and reduce the early bolting rate, the seedlings must be planted in the current three-year-old field with large roots, strong growth, late flowering, moderate seed maturity (fish belly white) and uniform seeds. Due to the inconsistent development of the main stem and lateral branches of Angelica sinensis, the main stem must be cut off at the early stage of bolting, so as to promote the uniform development of each branch in order to obtain seeds that meet the requirements of production.

2. Sowing at the right time, fertilizing reasonably, controlling seedling age and seedling weight. According to the production practice: Angelica seedlings not only need a certain low temperature, but also need enough sugar, so the tall seedlings are easy to bolting and flowering, but the early bolting rate of seedlings is very low. At the same time, the seedling age also had a great effect on bolting, and the early bolting rate of older seedlings was higher when the same batch of seeds were raised at the same time and the root weight was the same. According to the data of Taibai County, Shaanxi Province, using seeds harvested in three years to raise seedlings, the seedling age is more than 130 days, the early bolting rate is more than 90%, and there is almost no early bolting phenomenon when the seedling age is less than 70 days. But the seedling age is too small, the seedling root weight is small, the survival rate is low, the growth is weak, the yield is low and the benefit is poor. In order to control large seedlings and old seedlings and reduce the rate of early bolting and flowering, the sowing date should be postponed appropriately, the seedling age should be controlled within 110 days, the weight of 100 seedlings should be less than 40 grams, and nitrogen fertilizer should be applied properly in the later stage of seedling raising to increase the total nitrogen content of plants so as to reduce the total sugar content of plants. inhibit bolting and flowering.