Chapter 13 Section 3 Interrelationships between plants

There are not only contradictions between plants such as competition for light, fertilizer and space, but also because plants can release special chemical substances to the surrounding environment, changing the surrounding ecological environment, resulting in mutual growth and mutual restraint among plants and soil microorganisms.Our ancestors, in the long-term production practice, observed the phenomenon of biochemical heterogeneity among plants, and used it in production, and achieved many practical results.Jia Sixie talked about the benefits of mixing melons and soybeans in "Qi Min Yao Shu".Its method is, when sowing melon seeds, plant three soybean seeds next to it at the same time.When the melon has a few leaves, pinch off the stems and leaves on the ground of the bean tree and keep the bean root.Why do you want to do this?Jia Sixie said: "Melons are weak, and the seedlings are not alone, so soybeans are needed to raise the soil." It turns out that soybeans help the melon seedlings to emerge, which is one of the benefits.The root nodules of beans can fix nitrogen, so Jia Sixie said: "Don't pull them out, because pulling them out will make the soil empty and dry." It can be seen that people at that time had realized that beans could fertilize the soil and help other plants grow. The second benefit.In "Qi Min Yao Shu · Bamboo and Wood", Jia Sixie also talked about the mutual benefit of locust tree (bean family) and hemp.Ma depends on locust tree to support, and locust tree depends on hemp to support.When the hemp was ripe, it was mowed [yiyi], and the locust tree was kept, and the hemp field was hoeed to pine and sow the hemp seeds and then planted. After three consecutive years of planting, the hemp was nourished, and the locust tree became a straight seedling.

The Han Dynasty "Fan [fan] Shengzhi Shu" records: "The method of planting mulberries... each mu is planted with three liters of millet scorpion, and both millet and mulberry will grow."Yuan "Nong Sang Essentials" said: "The mulberry can be planted with crops, and there is a saying in the farm family: the mulberry grows millet, and the millet grows mulberry." This fully demonstrates the ancients' understanding of the relationship between mulberry and millet. Wang Hao (haohao) in the Qing Dynasty said in "Guang Qun Fang Pu": "Tea gardens should not be interspersed with evil trees, but osmanthus, plum, magnolia, magnolia, rose, pines, and green bamboos are planted between them, which are enough to cover the frost and snow. , to shade the autumn sun. Under it, you can plant fragrant orchids, secluded chrysanthemums and fragrant things, and it is most forbidden for vegetable borders to force each other, which will inevitably seep, and the dregs will be pure." The upper layer is interplanted with trees, and the lower layer is interplanted with herbs and aromatic plants. A fairly complete artificial plant community established using the phenomenon of plant mutualism.

Regarding the relationship between plants, there is a record in "Lu Shi Chunqiu" more than 2,000 years ago that "there are no miscellaneous trees under the osmanthus branches".It is also said: "The tree gets osmanthus and withers." These all show that the ancients have realized that osmanthus trees hinder the growth of other trees, and thus form a special ecological landscape.This is what was described in the "Guangzhi" of the Jin Dynasty, "Gui grows in Hepu and grows on the top of the mountain. It is evergreen in winter and summer, and its kind is self-evident. There are no miscellaneous trees in the forest." In the Tang Dynasty, in order to clear the weeds in front of the house, Xu Kai "made people use cinnamon crumbs to cloth the cracks in the bricks, and all the weeds died."Shen Kuo gave a scientific explanation for the above phenomenon. He said: "Gaigui tastes pungent and stings (shi Shi). However, the killing of osmanthus is true, not for stinging." "On" said: "Using osmanthus as a ding, nailing the wood, the wood will die", and further pointed out that "a ding to a small size may not be able to sting a big tree, and it will control the ear by its nature." Shen Kuo correctly pointed out The reason why osmanthus can inhibit the growth and development of other plants is that it can secrete a pungent gas that can kill other plants, and it is also pointed out that this is a natural phenomenon.What Shen Kuo summarized is actually what is called plant biochemical allergy in modern biology.That is, plants change the surrounding micro-ecological environment by excreting metabolites from the body, which leads to mutual growth or mutual restraint among plants.