Discussion on the principle of absorbing Fertilizer by Plant leaves

The main function of leaves is to use solar energy for photosynthesis, at the same time, the synthetic products are biochemically transformed and transferred to other organs. At the same time, the leaves can also constantly exchange materials with the outside world. The shape and mechanism of nutrient absorption of leaves is similar to that of roots, which accords with the five basic principles of rational fertilization, namely, the theory of nutrient return, the law of minimum nutrients, the law of optimal factors, the law of diminishing returns and the law of comprehensive action of factors. But the structure of the leaf is different from the root. From the structure of crop leaves, there is a stratum corneum on the surface of the leaf, a waxy layer on the outside of the stratum corneum, leaf epidermis cells under the cuticle and mesophyll cells under the epidermis cells. The epidermis cells of the leaves are arranged neatly, with palisade cells near the upper epidermis and sponge cells near the lower epidermis. There is also a structure called stomata on the upper and lower surface of the blade, which is the channel of communication between the interior of the leaf and the outside world. Leaves have three ways to exchange matter with the outside world, one is through the stomata mainly distributed on the leaf surface, generally, the stomata on the back of the leaves are more than the stomata on the leaf surface. The number of stomata on the leaf surface of most annual crops is 100,200 per square millimeter. These pores can absorb not only CO2 in the atmosphere, but also H2O, NH3, NO2, SO2 and other gases. Stomata can also release O2, H2O, NH3 and H2S to the atmosphere. Another way for the material exchange between the leaf and the outside world is the hydrophilic pore of the cuticle on the leaf surface. These holes have a large number of apertures.