Plants provide food for humans and animals. People can directly enjoy the seeds of plants, such as wheat seeds ground into flour, rice seeds hulled and processed into rice, soybean seeds made into tofu, sesame seeds squeezed out of edible oil, pepper seeds squeezed into pepper as seasoning, etc. You can also directly appreciate the stems and leaves of plants, such as cabbage, rape, lettuce, sugar cane, etc. Or appreciate the roots of plants, such as potatoes, sweet potatoes, radishes, beets, etc. There are also flowers of plants, such as cauliflower and broccoli; Or the fruits of plants, such as tomatoes, cucumbers, apples, peaches, strawberries and so on. People can also use plants to raise livestock and provide food such as meat, eggs and milk for human beings. People grow cotton and hemp for textile, mulberry and sericulture to obtain silk products. People grow herbs to obtain medicinal materials. Grow tobacco, coffee and cocoa to get stimulants. Afforestation can obtain wood and papermaking raw materials, and forests can also prevent wind and fix sand and protect the earth's ecological environment. In the final analysis, human beings can't live without plants, and plants feed the whole human race.

All kinds of plants in the world are generally developed from small seeds. Under suitable external conditions, cells divide and embryos develop into plumule and radicle. Under the nutrition provided by endosperm, the seedlings broke through the soil and survived by absorbing the nutrients decomposed in endosperm before the trilobal stage, forming stems, branches, leaves and roots, forming plants. Later, it continuously absorbed carbon dioxide from air and water, and absorbed 13 mineral nutrients necessary for human body from soil, which grew stronger and stronger. When you reach a certain age, you will transition from vegetative growth stage to reproductive growth stage, flowering, fruiting, maturity, aging and death, leaving seeds for a new round of life process.

This plant is a natural chemical plant. Since the birth of plant life, complex and subtle chemical reactions have been taking place in its body. Using the simplest inorganic substances as raw materials, various complex organic substances are synthesized.

In the daytime or under the illumination, plants inhale carbon dioxide from the atmosphere through the stomata on the leaves, and generate carbohydrates, namely sugars, with the water absorbed by the roots, and release oxygen and heat. This process is called photosynthesis.

At night or in the dark, some carbohydrates are consumed in the process of breathing to provide energy, while others are further synthesized into starch, fat, cellulose or amino acids, protein, protoplasm or nucleic acid, chlorophyll, vitamins and other essential substances, and plants are made of these substances.