What are the changes in the growth of animals and plants? The growth rate of plants changes regularly with the change of day and night or seasons, and the process of plant growth and development has obvious seasonality and periodicity. Let's look at the periodic law of plant growth.
Periodic law of plant growth1i. Germination period
The first stage of plant growth is germination. The seed embryo consists of cotyledons, which become the first leaf of the seedling. When the temperature and soil are suitable, the seeds will expand and open, the radicle will extend to the main root, and the cotyledons will become leaves.
Second, the seedling stage
As the leaves open, plants will enter the seedling stage, when the root system of seedlings is very fragile, so be careful. The soil should be kept moist, and the seedlings should be gradually exposed to light to avoid direct sunlight.
Third, the growth period
Chlorophyll in plant leaves absorbs energy from light and contributes to photosynthesis. Plants will grow rapidly, which requires a lot of water and nutrients. Pay attention to replenish water, keep the soil moist, avoid water accumulation in the basin soil, apply fertilizer properly and apply thin fertilizer frequently. For foliage plants, nitrogen fertilizer is mainly supplemented to make roots and leaves grow healthily, and for flowering plants, phosphorus and potassium fertilizer are appropriately supplemented.
Fourth, the flowering period
After a vigorous growth period, a plant will enter the flowering period, and the flowering period of different plants is different. For seasonal flowering plants, fertilization should be suspended at flowering stage, and for plants with long and continuous flowering stage, phosphorus and potassium fertilizers can be supplemented appropriately at flowering stage.
Latency of verb (abbreviation for verb)
After flowering, plants usually go into dormancy, when their growth usually stops. Some plants shed their leaves during dormancy, while others have evergreen leaves all year round, even in winter.
Periodic law of plant growth 2 In the process of plant growth, the growth rate of cells, organs or the whole plant shows the law of slow-fast-slow. That is, the growth is slow at first, then gradually accelerates, and then slows down or even stops after reaching the highest point. These three stages of plant growth are collectively called the big growth period. If time is taken as the abscissa and growth as the ordinate, the growth of plants shows an "S" curve.
Why can the growth of organs show the cycle of birth and growth? This should be analyzed from the growth of cells. When organs begin to grow, most cells are in the stage of cell division. Because cell division is based on the increase of the number of protoplasts, the process of protoplast synthesis is slow, so the volume increase is slow. However, when cells enter the elongation growth period, the volume of cells will increase rapidly due to the entry of water. But after the cell elongation reaches the highest rate, it will gradually slow down and finally stop.
The life-long growth of plants presents an "S"-shaped growth curve for complex reasons, mainly related to the size of photosynthetic area and the strength of life activities. In the early stage of growth, the photosynthetic area of seedlings is small, the root system is underdeveloped and the growth rate is slow; In the middle stage, with the rapid expansion of photosynthetic area and the establishment of huge roots, the growth rate is obviously accelerated; In the later stage, the plants gradually aged, the photosynthetic rate slowed down, the root system grew slowly, and the growth slowed down or even stopped.
Generally speaking, the growth of plants is an irreversible process of increasing volume and weight. Dead seeds swell when exposed to water, and their volume and weight will also increase, but they can still be restored to their original state after drying. This reversible increase in volume and weight cannot be called growth. Growth is usually accompanied by an increase in plant dry matter.
However, it should be noted that when seeds germinate, the fresh weight and volume of seeds do increase obviously due to a large amount of water absorption, but before the formation of green leaves, the dry weight decreases due to the consumption of a large amount of organic matter by breathing. At this time, there is the growth of protoplasm and the formation of new cells in the embryo. Of course, this is still a growth phenomenon. So the growth defined above refers to majority and relative.
How to make use of the grand growth period of planting plants
According to the law of large growth period, corresponding measures can be taken to promote or inhibit the growth of organs and even the whole plant. For example, to promote the growth of rice and wheat plants, it is necessary to ensure adequate water and fertilizer supply at the beginning of the medium term, and it is too late to grow rapidly; For example, to prevent wheat lodging, it must be before ear differentiation, which will affect the growth of wheat ears.
The growth of plants can be expressed by the fresh weight, dry weight, length, area and diameter of plant organs. Growth is the amount of growth accumulation, that is, the actual amount of plant materials at the time of determination, which is equivalent to the appearance of plants. Growth rate is the speed of growth, which is equivalent to the growth of plants. There are two expressions: absolute growth rate and relative growth rate.
The former refers to the absolute growth in unit time, such as the number of diameters of fruits increased every day; The latter refers to the percentage of growth per unit time to the original plant. For example, in a certain growth period, the single plant weight is 10g, the daily gain is 1g, and the relative growth rate is10 {BF}; In another growth stage, each plant weighs 50g, and although it gains 2.5g every day, its relative growth rate is only 5 {BF}. This calculation is convenient to compare the actual effects of some agricultural measures on crop growth in different periods or on different plots, and has practical significance.
Periodic law of plant growth. Life cycle of garden plants
The life cycle of garden plants refers to the whole process from childhood, growth to youth, adulthood, and finally into old age until death. However, with different varieties, the' life stage' of plants will also show subtle differences. Generally speaking, the life cycle of plants can't escape the natural law of birth, aging, illness and death.
For woody plants, their life cycle can be divided into embryonic stage, juvenile stage, youth stage, mature stage and aging stage. For annual and biennial herbs, there are only four life stages, namely, embryonic stage, seedling stage, flowering stage and aging stage. The flowering period generally lasts 1~2 months. Compared with woody plants, herbaceous plants have a shorter life cycle.
Developmental characteristics of garden plant organs
Root system is the source of life for garden plants. Without roots, plants can't grow and develop. Generally speaking, the roots of plants are divided into main roots, lateral roots and adventitious roots. The taproot will be stronger and absorb more nutrients.
According to the growth mode of root system, root system can be divided into horizontal root system and vertical root system. Horizontal roots grow horizontally along the ground, and vertical roots grow vertically on the ground. In fact, the development of root system is regular. In order to make plants grow well, it is necessary to create a good environment for roots. For bud branches, species are also divided into trunk, central trunk, main bud, lateral bud and so on. Its growth modes include vertical, climbing and creeping.
Factors affecting the growth and development of rhizomes
Root system is the transport mechanism of plant nutrition, and the healthy growth of a plant depends not only on the root system, but also on the environment in which the root system is located. The factors that affect the growth of root system are soil nutrients, soil moisture, soil temperature, soil ventilation and organic components contained in plants themselves. The factors affecting the new shoots of branches and buds are external environmental factors, nutritional status of mother plants, rootstock selection and so on.