1. Plants are the main source of human food. Humans need a large number of plants as food, including food provided by crops; Edible oil provided by cash crops; Fruits provided by fruit trees and economic plants.

Second, plants provide important raw material resources for human life. Cotton and hemp plants provide textile raw materials for human wear; Wood provides building materials for human habitation, building houses and bridges.

Thirdly, plants provide a lot of feed for livestock and poultry products needed by human beings, and the main energy supply of animals lies in plants. Animals without plants will die because of lack of energy.

Fourth, plants form forest scale, which is to purify the air. The sulfur dioxide in the air of forest plants is less than that of open space 15-50%. If it is in high temperature and high humidity summer, with the vigorous physiological activity function of forest trees, the absorption rate of sulfur dioxide by forest plants will accelerate. When the relative humidity is above 85%, the speed of sulfur dioxide absorption by forest plants is 5- 10 times of the relative humidity 15%. Humans need to breathe oxygen, but plants can absorb carbon dioxide and exhale oxygen. Oxygen released by plant photosynthesis is supplied to human beings.

5. Forest plants can adjust the climate. The dense crown of forest plants can absorb, scatter and reflect some solar radiation energy in summer, thus reducing ground warming. Because the roots of trees go deep into the ground, they constantly absorb the water in the deep soil for trees to transpiration, which makes the forest form fog normally and increases precipitation. Without plants, there will be soil erosion, water resources will be more scarce and cultivated land will be less and less. Plants also regulate the global environment.

Six, the plant itself has the function of water conservation. In addition, the decaying layer of plant litter on the surface is increasing, forming a thick sapropelic layer, which has strong functions of absorbing water, delaying runoff and weakening flood peak. Canopy can intercept rainwater, reduce the impact of rainwater on the ground, and maintain soil and water. Canopy can block 10-20% of precipitation, most of which evaporates into the atmosphere, and the rest falls to the ground or seeps into the soil along the trunk to become groundwater.

As producers, plants support the existence of various biological chains in complex ecosystems. Plants are the main source of energy, an important link of energy cycle and the main body to maintain the balance of ecosystem.

The emergence and development of human beings have always been accompanied by plants; People's understanding of plants has gone through a constantly changing process. Humans rely on the minimum living conditions provided by plants, such as shelter, food, labor and so on. Plants will soon be fatal if they lack the needs of human survival, and both survival and living environment restrict human safety.