What door is moss?

Bryophytes are green autotrophic terrestrial plants, and plants are gametophytes, which germinate from spores into protonema and then develop from protonema. Bryophytes are generally small, and the plants (gametophytes) that are usually seen can be roughly divided into two types: one is liverworts, which keep the shape of leaflike bodies; The other is moss, which begins to differentiate like stems and leaves. Bryophytes have no real roots, only pseudoroots (filaments composed of single cells or a series of cells with epidermal processes). The differentiation level of tissue in stem is not high, only the differentiation of bark and axis, and there is no real vascular bundle structure Most leaves are composed of a layer of cells, which can not only carry out photosynthesis, but also directly absorb water and nutrients.

Bryophytes produce multicellular sperm cells and sperm organs on the gametophyte during sexual reproduction. The archegonium is bottle-shaped, the upper part is narrow and called the neck, with 1 groove in the middle, the lower part is enlarged and called the abdomen, and there are 1 large cells in the middle of the abdomen called the egg. Sperm is good at making. Sperm has two flagella, which swim from water into the archegonium and combine with the egg. After fertilization, the egg cell becomes a zygote (2n), and the zygote develops into an embryo in the archegonium. Embryo develops into sporophyte (2n) according to the nutrition of gametophyte. Spores cannot live independently, but can only parasitize on gametophytes. The most important part of sporophyte is spore cover. The sporogenous tissue cells in the spore capsule undergo multiple divisions, and then undergo meiosis to form spores (N), which expand in a suitable environment and germinate into new gametophytes.

In the life history of bryophytes, from spore germination to gametophyte formation, gametophyte produces male and female gametes, which is a sexual generation, from fertilized egg to embryo, from embryo to sporophyte is called asexual generation. Sexual generation and asexual generation alternate with each other, forming generation alternation.