以往,不同季节有不同的蔬菜供人们食用。现在,由于有了大棚种植,大部分蔬菜一年四季都能吃到。不过,在不同季节生长的同种蔬菜,营养价值是不一样的。从植物的自然生长规律的角度来看,还是提倡食用时令蔬菜为主,反季节蔬菜为辅。蔬菜的营养变化主要原因就是反季节蔬菜大多在大棚或玻璃温室种植。蔬菜营养的高低与光合作用关系密切,自然生长的蔬菜光照充足,光合作用强,有利于维生素、糖类等营养素的积累和转化。同时,露天种植有利于促进植物的代谢和从土壤中吸收 In the past, different seasons have different vegetables for people to eat. Now, thanks to the greenhouses, most vegetables are eaten all year round. However, the same type of vegetables growing in different seasons, the nutritional value is not the same. From the perspective of the law of natural growth of plants, it is still advocated that seasonal vegetables should be used mainly for food and supplemented by seasonal vegetables. The main reason for the change in the nutrition of vegetables is that most of the seasonal vegetables are planted in greenhouses or glasshouses. The level of vegetable nutrition and photosynthesis are closely related to the natural growth of vegetables sufficient light, photosynthesis, is conducive to vitamins, carbohydrates and other nutrients accumulation and transformation. In the meantime, planting in the open air helps to promote plant metabolism and absorption from the soil