Stevia sweeteners are derived from the leaves of the Stevia rebaudiana (Bertoni) plant, an herbal shrub native to South America. The stevia plant has been used for food and medicinal purposes for hundreds of years, and its leaves and crude extracts have been sold as dietary supplements. Purified extracts of the sweet substances found in the stevia leaf, called steviol glycosides, are considered to be generally recognized as safe (GRAS) by the U.S. Food and Drug Administration (FDA). However, whole stevia leaves and crude leaf extracts are not permitted to be sold as sweeteners in the U.S. because there is not enough toxicological information on these products, according to the FDA. Stevia sweeteners are made by extracting steviol glycosides from the leaves of the stevia plant and purifying them to remove some of the bitter attributes found in the crude extract. Stevia JINING USP INTERNATIONAL CO.,LTD. , https://www.uspintl.com
Preserved vegetables in early spring
After planting vegetables in greenhouses in the early spring, if they encounter cold weather, they are prone to frost damage and bring losses to production. In order to prevent the seedlings from freezing after being planted and to promote the robust growth of the seedlings, antifreeze measures should be taken actively. Increased light intensity, strong photosynthesis of seedlings, production of sugar and starch and other nutrients, and strong cold resistance. In order to allow the seedlings to receive more sunlight, the outer cover should be exposed as early as possible in the normal temperature range, and the outer cover should be opened on cloudy days and rainy days. It is best to use high light transmittance. The dripless or dustproof film should always keep the film surface clean and increase the light transmittance. Reducing the heat dissipation in the gaps should be sealed in the booth, and attention should be paid to the gaps in the various places that are blocked to minimize heat dissipation in the gaps. The humidity in the shed control room is high, the water content in the seedlings is high, and the cell fluid concentration is low, so that the seedlings are susceptible to freezing. In early spring, because the temperature is low and the light is weak, if the humidity in the greenhouse is too high, the seedlings will not only be susceptible to freezing damage, but they will also be susceptible to diseases. Therefore, the number of times of watering and watering should be strictly controlled in the early stage to prevent the soil and air humidity in the shed from being too high. When the humidity in the booth is too high, it is necessary to enhance ventilation and humidity. Ventilation must be carried out at a high temperature around noon to prevent cold air outside the shelter from directly blowing onto the seedlings and causing freezing damage. Scientific fertilization does not apply nitrogen fertilizer to avoid weakening the cold resistance of seedlings. Potassium fertilizer can increase the cold resistance of seedlings. The rice vinegar, sugar, and superphosphate are mixed and mixed into a 300-fold liquid, which is sprayed on the leaf surface to increase the sugar content and hardness of the leaf meat and improve the cold resistance. Strengthen the coverage of early spring season, the night outside the greenhouse should cover quilts, straw and other external insulation materials, and keep the external insulation cover is often in a dry state, the greenhouse should be used to hang two layers of curtain, buckle a small arch shed and so on. Plastic sheds should also be covered with multiple layers. Grass rakes are surrounded around the outside. Plastic film surrounds the sheds at the bottom of the shed. The sheds are suspended in two layers of curtains, buckled in small arches, covered with plastic film, and directly covered with non-woven fabrics. Seedlings are superior. It can also be used as a windbreak in the north of the greenhouse to protect the wind and cold. Temporary heating measures are adopted. When the temperature in the greenhouse is lower than 15°C during the daytime and the nighttime temperature is lower than 5°C, cold injury or freezing injury may occur. In case of cold weather, it is necessary to take necessary temporary warming measures at night to artificially supplement heat. Temporary heating equipment such as heaters and stoves can be installed in the sheds, but chimneys must be led to the outside of the sheds. It is not possible to heat them with open flames to prevent poisonous gases from damaging the seedlings when fuel is burned.