Biological characteristics of Angelica sinensis (2)

The main results are as follows: (1) the root growth of Angelica sinensis spans three years from sowing to physiological maturity, and the whole growth period is more than 500 days. After the seed germination, the radicle lengthens rapidly, bends downward and grows into the soil. When the main radicle extends to 3 cm, the primary lateral root begins to form, and then the secondary lateral root appears on the primary lateral root. The main root continues to thicken and elongate, and gradually becomes fleshy, forming a typical fleshy straight root with a length of 20 cm and a diameter of 0.3 cm. After transplanting in early April of the following year, a large amount of nutrients were used for the development of leaves, and the growth of the root system was slow. Because the root tip of the main root was damaged in the process of seedling emergence and transplanting, the development of the lateral root was inhibited, thus promoting the development of a large number of lateral roots. after closing in July, the diameter of the main root began to thicken, resulting in new lateral roots, and the first lateral roots began to be fleshy. In the early and middle of August, the temperature began to decrease and the leaf extension reached the maximum, at this time, the assimilation products of the leaves were mainly transported to the roots, the diameters of the main roots and lateral roots increased rapidly and became fleshy, and the growth was slow after the air temperature turned cold, but the rate of matter accumulation in the roots accelerated. In the early and middle of October, when the aboveground part began to wither, the root growth reached the maximum, with a total length of 30cm to 50cm and a diameter of 3cm to 5cm. This is the harvest period of Angelica sinensis. If it is not harvested in time, the third year of overwintering Angelica sinensis (some Angelica sinensis entered the bolting and flowering stage in the second year) changed from vegetative growth to reproductive growth, and a lot of nutrients were consumed due to bolting, flowering and fruiting. The root becomes hard and thin, gradually Lignification becomes hollow, becomes firewood, and loses its medicinal value.

(2) the growing stem is the organ that connects the underground root with the aboveground branches, leaves, flowers and fruits. It plays an important role in transporting and regulating water and nutrients between organs. The stem of Angelica sinensis is divided into vegetative stem and flower stem. The vegetative stem only exists during the vegetative growth period (before bolting), the stem is extremely shortened, there is neither differentiation of stem nodes, nor obvious stem extending to the ground, the appearance is in a stemless state, only a few leaves grow from the base, clustered at the top of the vegetative stem, in the shape of a rosette. In the middle and late March of the third year, Angelica began to turn green, and then the growth point began to change from vegetative growth to reproductive growth, forming a reproductive growth point. In mid-and late May, the aboveground stem began to shoot out and quickly extended to the ground, that is, bolting, forming an erect multi-node (usually 5o-8 nodes), a multi-branched stem up to 1.5 meters, and at the same time, a large compound inflorescence was formed at the top of the main stem and branches.

(3) the growing leaf is an important vegetative organ of Angelica sinensis, and its main functions are photosynthesis, transpiration and gas exchange. Angelica sinensis leaves are divided into basal leaves and cauline leaves, which are 2-3 odd-pinnate leaves, which are composed of leaves, petioles and leaf sheaths. The main function of leaves is photosynthesis. Under light conditions, green leaves can synthesize organic matter from water and carbon dioxide absorbed by plants. In general, the larger the leaf area per plant, the higher the single root weight. In a certain range, the larger the leaf area coefficient, the higher the yield per mu. Therefore, improving cultivation and management measures and increasing leaf area coefficient is an important measure to obtain high yield of Angelica sinensis, but at the same time, we should guard against plant growth. The structure of leaf is divided into three parts: epidermis, mesophyll and vein. The epidermis is in the outermost layer of the leaf, with hairs and stomata on it. The opening and closing of stomata controls the gas exchange and water transpiration inside and outside Angelica sinensis. The epidermis is mesophyll, which is composed of palisade tissue and spongy tissue, and contains many chloroplasts. It is an important place for Angelica sinensis to carry out photosynthesis and synthesize organic nutrients. The main vein of the leaf vein is located in the middle of the leaf, distributed between the palisade tissue and the spongy tissue. Leaf veins communicate with petiole, stem and root vascular system, which constitute a complete system of water and nutrient transportation in Angelica sinensis plant. During the vegetative growth period of the first year, the growing points successively produced leaf primordia, forming 5-7 basal leaves, clustered at the top of the vegetative stem, showing a rosette, with larger leaves and longer petioles. After turning green in the second year, the growth accelerated gradually with the increase of air temperature, and new cauline leaves were produced one after another. the average temperature was higher than 14 ℃. At this time, not only the number of leaves increased rapidly, but also the leaf area increased rapidly. From June to July, the aboveground part entered the period of vigorous growth, and most of the large compound leaves were formed. The leaf area coefficient reached 3 to 4, which laid the foundation for high yield. The plants with remaining seeds were not picked in the second year, stayed in the field for the winter, turned green in the middle and late March of the third year, re-issued new leaves, and then transferred to reproductive growth, and the growth point differentiated into stem nodes and elongated to form flower stalks. At this time, the basal leaves stopped differentiation and produced cauline leaves at the nodes of the flower stem, alternate, smaller leaves, shorter petioles, sheath-shaped base expansion and clasping.