When pear trees encounter low temperatures and pollinating insects during flowering, artificial pollination must be carried out. Artificial pollination is suitable for early flowering. When pollination, the head of the stigma is to be fresh, and when the petals are water, the best pollination time is due to the color of the stigma during this period. Yellow, secreted mucilage is conducive to pollination.
Vitamin A is a fat-soluble vitamin, an organic compound whose chemical formula is C20H30O. It is stable to heat, acid, and alkali, and is easily oxidized. Ultraviolet rays can promote its oxidative damage. Vitamin A includes A1 and A2, and A1 is retinol. Vitamin A2 is 3-dehydroretinol, and its physiological activity is 40% of that of vitamin A1. [1]
Vitamin A has a variety of physiological functions such as promoting growth, reproduction, maintaining normal secretion of bones, epithelial tissue, vision and mucosal epithelium, and vitamin A and its analogs have the effect of preventing precancerous lesions. Deficiency manifests as growth retardation, impaired dark adaptation and night blindness. Dry eye disease occurs due to dryness, desquamation, hyperkeratosis, and decreased secretion of lacrimal glands of epidermal and mucosal epithelial cells. In severe cases, corneal softening, perforation and blindness occur. Respiratory epithelial cells become keratinized and lose their cilia, making them less resistant to infection. The recommended intake of vitamin A (RNI) for adults in my country is 800 μg retinol activity equivalent per day for men and 700 μg retinol activity equivalent per day for women. [2] Foods rich in vitamin A include liver, egg yolk, and milk powder of poultry and livestock. Carotene can be converted into vitamin A in the mucosa of the small intestine, red-yellow and dark green vegetables. Fruits contain more carotene.
Vitamins,Vitamin Powder,Vitamin K,Vitamin A
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