1。 A seed falls into the soil, and after a period of time, it begins to germinate when conditions are suitable (mostly in spring), and a seed grows radicle, embryo and hypocotyl. Then continue to develop, the embryo develops to the outside, the radicle develops to the underground, and the hypocotyl develops to the middle.

2。 Then, the leaves of plants begin to carry out photosynthesis and begin to synthesize sugar (glucose). Then, the sugar is converted into starch in the processing occasions of leaves, and further substances such as protein and fat are synthesized. Then it is transported to all parts of plants through sieve tubes for their growth and development, and the roots absorb water, minerals, N elements and trace elements from the soil. And then transported to various parts through conduits for synthesis.

3。 Year after year, day after day. The cell cambium, which plays the most critical role, is the main place for the division of plant filamentous cells. Through its division, more and more cells and plants become thicker and thicker.

In addition, plant growth mainly absorbs water through splinter cell and then grows.

4. Finally, the plants grow up. What kind of tree are you talking about? Every tree changes differently throughout the year. Did your school plant camphor trees? What is the answer? Trees are evergreen all year round and change leaves in autumn and winter. I can not help you with anything.

Analyze the factors affecting the growth of trees by expanding data;

1, temperature

Generally speaking, if the average temperature in the hottest month of the year is lower than 10℃, local trees cannot grow. The lower the temperature, the shorter the shrubs, so that only grass can grow. China is located in the middle and low latitudes. Even in the northernmost Mohe County of Heilongjiang Province, the hottest monthly average temperature is 18.4℃, and the forest is still vast. In China, the low temperature in summer only affects the growth of trees on high mountains, about 2000 meters in the northeast, 3000 meters in the north and 3500-4500 meters in the mountainous areas of Qinghai-Tibet Plateau.

Near this height, the average temperature in the hottest month is slightly higher than 10℃, and the trees are obviously shorter. I have seen this small and exquisite and very beautiful tree near the main peak of Wuyi Mountain and the top of Yunling Mountain in Hengduan Mountains of Yunnan Province.

The low temperature in summer determines whether trees can survive, and the low temperature in winter determines the kinds of trees that can survive. From Northeast China to South China, from high mountains to low altitude areas, due to the gradual increase of the lowest temperature in winter, tree species have evolved from cold-tolerant cold temperate coniferous forests to temperate broad-leaved deciduous forests, subtropical broad-leaved evergreen trees and even lush equatorial rainforests. The distribution of economic trees requires stricter temperature.

Generally, apple trees in temperate zone can't stand the cold below MINUS 30℃, so apples in northeast China are generally only distributed along the Bohai Sea and the Yellow Sea. Subtropical citrus is afraid of the low temperature of minus 7 ~ 9℃. If the lowest temperature is below-9 ~ 1 1℃, citrus orchards will suffer devastating freezing damage. Therefore, planting citrus in the north of the Yangtze River has no economic value; Rubber, a tropical crop, will be frozen when the temperature is 5℃, which is also the reason why tropical crops cannot be planted in tropical latitudes in China.

Observing the street trees in major cities in China, we can also find the relationship between many trees and climate. The north has a temperate climate, and broad-leaved and deciduous trees are mostly used as street trees, even in the middle and lower reaches of the subtropical Yangtze River. Because the height and temperature of the sun in these areas are relatively high and the sun is relatively hot in summer, street trees just play the role of shading passers-by at this time. By the time the cold wave rolled south in winter and the temperature plummeted, the trees had lost all their leaves and generously let the warm sunshine fill the sidewalk.

But in the tropics, the hot summer is very long, even in winter, the temperature is very high, so most street trees are evergreen and cool all year round. In Guangzhou, Nanning and other big cities in South China, the tree crowns on both sides of the road are often connected together, making the road a pavilion. There grows a kind of tree called banyan, which can survive in tropical and subtropical warm areas in winter. In the rainy season, due to the high temperature and humidity, the air roots hanging on the branches are full of vitality. Once they reach the ground, they take root in the soil and gradually become real trunks. Thanks to the support of these secondary trunks, the branches of banyan trees can continue to grow horizontally. After a few years, a big banyan tree can be unique and become a forest, even covering several acres.

Step 2 precipitate

If the temperature conditions can meet the needs of tree growth, then whether trees can grow and what they look like depends on the amount of precipitation. Here are a few examples.

First, the tropical, subtropical and temperate arid areas in the world are all deserts, and it is impossible to plant trees and grass because of extreme water shortage.

Secondly, in the tropics, there is only one rainy season (summer) a year. If there is little rainfall in rainy season, for example, the area with annual rainfall of 500 ~ 1000 mm in Africa is Savannah. There are some short trees scattered on the grassland, which generally have umbrella-shaped crowns, and the most famous is baobab. The trunk of this tree is thick and loose, and a lot of water is stored in the trunk. Fruit often weighs several kilograms, and starch pulp is edible, so it is called "monkey bread".

Third, the west coast of the mainland with a latitude of 30 ~ 40 degrees north has a Mediterranean climate. The winter here is still warm and the trees are still growing. The influence of precipitation on trees is mainly due to the improper seasonal matching of precipitation and heat. The rainy season in Mediterranean climate is in winter, but summer is dry season. In order to spend the long and dry summer, the trees are not dense, the trees are not tall, the leaves are hard and leathery, and some often have many fine hairs, which are called hard-leaf evergreen forests. Olives are the most important economic trees in the Mediterranean climate.

Fourthly, in mountainous areas with high altitude and large scope, vegetation landscape can change greatly. This is mainly due to the huge difference in precipitation caused by different topography and altitude. Rainfall usually increases with the elevation. Therefore, in the most typical cases, the miracle of the desert at the foot of the mountain and the forest on the mountain can appear, such as the northern slope of Tianshan Mountain and the northern slope of Qilian Mountain in China.

The rainfall on windward slopes is often much more than that on leeward slopes, so the vegetation landscape on windward slopes in mountainous areas can also be very different. For example, the annual rainfall on the south slope of Doukou Mountain, located in the southwest of Cambodia in the tropical monsoon region and facing the southwest monsoon, can reach more than 3,000 mm, and the rainy Buge Mountain can even exceed 5,000 mm. Therefore, the southwest slope is a tropical rainforest landscape, with layers of trees stacked on top of each other and a large number of vines and climbers in the forest.

However, due to the influence of topography, the annual rainfall on the leeward northeast slope (including the capital Phnom Penh) is greatly reduced, only 1000 ~ 2000mm, so the forest is sparse and the tree species are single. Moreover, in the late dry season, in order to protect themselves and reduce the huge evaporation under high temperature, all the leaves of the plants have fallen out (that is, the trees fall in spring instead of winter), but they are still trees! In Xishuangbanna, China, I have also seen that in the dry season of winter and spring, the leaves of rubber forest fall all over the ground, and the leaves on the branches are sparse. When the precipitation on the leeward slope decreases below the critical value, the vegetation landscape will also change qualitatively.

For example, Dongpo, Daxing 'anling, China, welcomes the knights of peace. Shu? Warm? 50 ~ 500 mm, the temperate forest is full of slopes, but the annual rainfall on the leeward west slope is reduced to 250 ~ 300 mm, so the grassland is boundless and drowns the cattle and sheep, so there is a landscape of "the sky is grey, the wild is boundless, the wind blows grass and the cattle and sheep are low". There are even windward slopes in the world that are forests, and leeward slopes are extreme situations of desert and semi-desert, such as the west coast mountains in North and South America.

References:

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