——  Plant intelligence is presented by phytochemicals  ——

Plant has no feet but can escape from harsh survival environment, while phytochemicals is the survival tool which plants have evolved through thousands of years for protecting themselves. It is a generic term for various biochemical substances synthesized in plants, also known as secondary plant metabolites, phytochemical factor, phytonutrients, plant actives, plant medicinal ingredients. Phytochemicals are the source of plant colors and flavors, and they are also the immune system of plants, enabling plants to protect themselves against insects and animals’ attack, bacterial infections and other external environmental threat.

Phytochemicals are present in the entire plant body, including roots, stems, leaves, as well as pericarps, flesh, kernels, and seeds. Currently, nearly 200,000 phytochemicals have been discovered. Researches have confirmed that phytochemicals containing diverse biological actives and can help humans in various ways, including anti-oxidation, tumor inhibition, anti-inflammation, cardiovascular improvement, microorganism inhibition, immunity regulation, whitening, and wrinkle elimination, etc., and can prevent many chronic diseases. For example, lycopene can prevent prostate disease; resveratrol can resist cell mutation; paclitaxel can inhibit cancer cell growth; anthocyanins can resist oxidation and anti-aging; carotene can prevent cardiovascular and cerebrovascular diseases, etc. There are still many functions of phytochemicals being explored. It can be seen that phytochemicals are of great significance to human health, and many experts and scholars even call them the 'seventh largest nutrients' other than the six nutrients. 

Although the types of phytochemicals are still being discovered and confirmed by research, they can be roughly divided into six categories according to their chemical structure. The first category is flavonoids, which belong to polyphenols, the largest species in the family of phytochemicals. It has about 4000 species which has been confirmed by the study. They mainly have antioxidant function, prevent cells from being oxidized and protect plants from parasites or microorganisms. As well as anti-allergic, anti-inflammatory and other functions, commonly known as anthocyanins, catechins and limonin. The second category is carotenoids, a fat-soluble pigment in yellow, red and orange. Mainly to help plants carry out photosynthesis, energy transfer and protection. Human beings usually use it as a food dye. β-carotene in the human body can be converted into vitamin A, which can protect the skin and eyes, there are common β-carotene, lycopene, capsaicin and so on. The third category is phenolic acids, which are also polyphenols. They are similar to flavonoids, but they have different structures and have antioxidant and free radical trapping effects. Common are chlorogenic acid, ellagic acid, p-coumaric acid and so on. The fourth category is organic sulfides. They usually have a strong taste which can drive away insects, or microorganisms and parasites such as allicin, glutathione, sulforaphane and so on. The fifth category is phytoestrogens, such as isoflavones rich in soybeans, potato soap rich in yam, and lignans rich in flaxseed and sesame. The sixth category is other remaining phytochemicals, such as chlorophyll, curcumin in ginger and curry, limonene in oranges and lemons, limonin, etc. 

Phytochemicals are closely related to plant intelligence. In order to resist the attack of insects, camphor tree reflects its own survival intelligence. It can release a kind of aromatic phytochemicals, this chemical has the characteristics of insect protection, anti-corrosion and so on. Therefore, the life of camphor tree is long, the crown is huge, and it is not easy to be harmed by pests and diseases. Camphor is very popular among the people. It has been regarded as a precious timber tree species since ancient times. People make camphor trees into suitcases, wardrobes and so on. It can play a natural insect repellent effect and enjoy a reputation internationally. The aroma of citrus fruits not only produces appetite, but contains the main volatile chemicals such as limonene and citral, which are also chemical defense tools for sterilization and insect repellent. Barley can resistant to grasshopper by synthesizing the phytochemicals carnitine and maltoalkali; Cruciferous vegetables can produce phytochemicals glucosinolates, the degradation products of this chemical has a unique smell which can cause harm to pests. In order to resist high temperature and reduce water loss, some plants using the synthesis of phytochemicals to make the surface of the leaves attached with the wax layer , reduce plant transpiration, control leaf temperature, and can protect plants from external mechanical damage at the same time. We can see that plants using the synthesis of phytochemicals, so as to better adapt to a variety of complex environment and show their survival intelligence.