First, the budding period
The germination period of Chinese cabbage is from sowing to "cross-pulling", which usually takes about 6 days under suitable environmental conditions. The "pull cross" is called "pull cross" because two true leaves and two cotyledons are similar in size and interact to form a cross. When Chinese cabbage seeds absorb water and swell, the temperature is appropriate, water and oxygen are sufficient, and the seeds germinate quickly and turn white. Generally, about 3 days after sowing, cotyledons flatten, the fifth leaf expands, and 1 true leaf is exposed at the same time. By the seventh day or so, a "pull cross" was formed, and the germination period was over. Before cotyledons turn green, seedlings are mainly supplied by nutrients stored in seed cotyledons. With the increase of chlorophyll in cotyledons, the seedlings gradually changed from autotrophic to heterotrophic, that is, the seedlings had formed an assimilating organ capable of photosynthesis and began to live independently, relying entirely on nutrients in cotyledons to absorb water and nutrients for photosynthesis.
Second, the seedling stage
The seedling stage is usually a true leaf from cross to 10, and at the end of the seedling stage, the plant is disc-shaped, commonly known as "clump tree" or "small spread disk". The growth period is about 16 ~ 18 days. If the early-maturing variety produces five true leaves during this period, it will take about 12 ~ 14 days. The root system developed in depth at seedling stage. At the end of the seedling stage, the taproot is 40-50 cm long, and the lateral root grows rapidly, with the third to fourth branches. The diameter of the root system can reach about 40 cm, and the main root system is distributed 5-20 cm from the ground. The cultivation goal in production is that the seedlings are neat and healthy, and there are no diseased seedlings and insect seedlings. The cultivation measures are timely thinning and replenishing seedlings, ensuring that the seedlings are neat and consistent, thinning diseased seedlings and insect-damaged seedlings, and pouring dilute fertilizer twice to promote the healthy growth of seedlings.
Third, the rosette period
From the end of seedling stage to the beginning of plant "hook heart", it is called rosette stage. Generally, the growth period needs 23 ~ 28 days, and the early-maturing varieties generally need 18 ~ 22 days. By the end of the rosette period, the outer leaves of all varieties had been flattened, the green leaf area of the whole plant reached the maximum, and the outer leaves formed a vigorous rosette shape, which created good conditions for the formation of yield. Generally, the number of outer leaves of early-maturing varieties is 16 ~ 20, and that of middle-late-maturing varieties is 22 ~ 26. During this period, the seepage velocity of taproot slowed down, with the longest taproot reaching more than 1 m, the distribution diameter of the root system being about 60 cm, and the taproot group being distributed 5-30 cm from the ground. The heading stage is an important period in the growth of Chinese cabbage, and the cultivation goal in production is to establish a high-yield shed to provide a rich material basis for the fruiting stage. The cultivation measure is to promote before and control after, and harvest the line at the late stage of the rosette or at the beginning of the hook. If the growth potential of the rosette is not strong in the early and middle stages, it is necessary to strengthen fertilizer and water management and promote growth. If the rosette grows vigorously in the early and middle stages, it is necessary to control the water and length in time, which is called promoting before and controlling after.
Fourth, the nodulation stage.
The nodulation period is from the "hook" to the formation of compact lobules. When a plant gives birth to a certain number of outer leaves, the regenerated leaves begin to curl inward, which is called "hook heart". "Gouxin" is an important physiological sign, which is not only the end of the growth period of outer leaves, but also the beginning of the growth period of bulbous leaves. The growth status of the whole field during the "hook heart" period can be used as an important diagnosis period, and the cultivation measures can be formulated in time according to the field production situation.
Generally, the heading period is about 40 ~ 60 days, the early-maturing variety is 25 ~ 30 days, and the heat-resistant Chinese cabbage 18 ~ 22 days. According to the growth dynamics of nodulation stage, it can be divided into prophase, metaphase and anaphase. In the early heading stage, it is commonly known as "tube pulling", which shows that the outer bulb leaves grow rapidly and the outline of bulb leaves forms rapidly. For heavy Chinese cabbage varieties, this period is the growth peak of the 1 ~ 5 bulb leaves, and the root system is no longer deep, but the number of lateral root classifications and root hairs increases sharply, with a diameter range of 80 ~ 120 cm. The taproot is distributed in the soil layer from the surface to 30 cm, which can absorb water and fertilizer. The middle stage of nodulation, commonly known as "filling stage", is the fastest growing stage of bulbous leaves, and the 6 ~ 7 leaves of bulbous leaves grow vigorously. At this time, the leaves stopped differentiating and entered flower bud differentiation, and the number of leaves no longer increased. When the bulb expands to a certain size, the volume does not increase, that is, it enters the late stage of nodulation. With the increase of the number of blades, the density of the blade ball is constantly filled.