The commercial products of seaweed and seaweed extract have been used in agriculture in many countries since 1950, and have produced many surprising results. Their action mechanism has also attracted the attention of scientific research and industry.

 

Although seaweed extract contains many mineral elements and trace elements unmatched by terrestrial plants, the simple dilution of these nutrients by 200 ~ 500 or even 1000 times can not fully explain its great effect, It was not until 1973 that brain, a scientist, first confirmed that seaweed extract contained many physiologically active plant hormones by biological detection, that people gradually realized the important role of active substances in plant growth.

 

What are the extracts of seaweed? These active substances are mainly: cytokinin, betaine, auxin, seaweed polyphenols, abscisic acid, gibberellin, ethylene and polyamines.

 

betaine

 

Betaine is a derivative of amino acid or sub amino acid, which contains fully methylated pentavalent nitrogen and exists in seaweed in open-loop or closed-loop structure. Betaine and its analogues participate in the transport of inorganic and organic substances in plants. They are also components of some macromolecules, and also ensure the osmotic balance of crops in various salt stresses. The diversity of algae determines the diversity of their structures and functions.

 

auxin

 

Plant auxin, referred to as auxin, is a general term for substances that can cause the same effect as indole acetic acid. As an endogenous plant hormone, auxin mainly plays the following four physiological roles in vivo: affecting the activity of cell cambium; Enhance the permeability of cell membrane; Induce the formation of ethylene; Affect the development of ovary.

 

Cytokinin

 

Cytokinin is an important endogenous plant hormone. It plays an important role in plant growth and development, and is widely used in agriculture and horticulture. The physiological functions of cytokinin mainly include the following aspects: promoting the development of plant flowers and buds and the growth of new organs; Enhance the development and growth of roots and promote the formation of adventitious roots; Promote plant fruit ripening; Inhibit the growth of plant lateral buds.

 

Seaweed polyphenols

 

Phenol compounds in algae are chemical defense substances in plants. Structurally, they can be divided into two categories: polyphloroglucinol (brown algae polyphenols) in brown algae and bromophenol in red algae. Phloroglucinol exists in most brown algae, and its molecular weight ranges from hundreds to tens of thousands or even hundreds of thousands. So far, it has been found that these compounds only exist in brown algae. Its basic structural unit is phloroglucinol, and has tannin like chemical properties, such as precipitated alkaloids and proteins.

                                                                 

Effect of seaweed extract on crops and its mechanism

 

The wonderful growth promoting and stress resisting effects of seaweed extract on crops have been continuously confirmed in a large number of practices. A large number of experiments show that seaweed extract can improve crop yield, improve the quality of agricultural products, enhance the ability of crop drought resistance, cold resistance and disease resistance, and significantly reduce the accumulation and residue of pesticides and chemical fertilizers in vegetables.

 

Mechanism of seaweed extract improving drought resistance of crops

 

Seaweed extract is rich in seaweed polysaccharides, which can be easily absorbed by crop leaves. After these seaweed polysaccharides are absorbed by crops, they can increase the viscosity and elasticity of cell protoplasm, increase the concentration of cell fluid, improve the water absorption capacity and water retention capacity, and maintain the stability of hydrolase, protease and lipase, so as to prevent the destruction of plasma membrane structure and improve the drought resistance of plants.

 

Mechanism of seaweed extract reducing nitrate accumulation in vegetables

 

The results showed that different concentrations of seaweed extract could significantly reduce the nitrate content and enhance the nitrate reductase activity of spinach, and the concentration had a linear negative correlation with nitrate content and a linear positive correlation with nitrate reductase activity. This shows that seaweed extract reduces the nitrate content of spinach by enhancing the activity of nitrate reductase. Under the action of nitrate reductase, it converts nitrate into amino acids or proteins, and promotes the transformation or metabolism of nitrate accumulated in spinach.

 

Seaweed extract significantly improved the quality of vegetables

 

The results showed that seaweed extract could increase the dry matter content of Pepper by 13.8%, soluble sugar content by 4.1% and Vc content by 23.3%; The soluble sugar content of carrot decreased by 1.3%, VC content decreased by 11.8%, carotene content increased by 45.0%, carotenoid content increased by 29.2% and Fe content decreased by 18.9%. Carotene and carotenoid mainly affected the color of meat root, which showed that seaweed extract mainly improved the appearance quality (color) of carrot; The crude fiber of celery decreased by 6.6% and the content of VC increased by 10.4%; The content of organic acid, soluble solid and VC increased by 11.3%, 26.7% and 12.2% respectively. Seaweed extract can significantly improve the quality of vegetables.

 

Control effect and mechanism of seaweed extract on tomato virus disease

 

Seaweed extract has significant control effect on tomato virus disease. At the same time, kelp extract can enhance SOD enzyme activity, chlorophyll content and strong seedling index, and the concentration has a significant positive correlation with SOD enzyme activity and strong seedling index. It shows that seaweed extract can control tomato virus disease by improving enzyme activity and plant resistance.