Higher plants: spore and seminal

Higher plants are those kinds of plants that have emerged on land and adapted to their new habitat. They number more than 300 thousand species. Higher plants are distinguished by the presence of vegetative organs, such as root and shoot, and have the same photosynthetic pigments: chlorophyll and carotenoids.

Higher plants in their majority have a complex transport system of substances, can regulate the evaporation of water with the help of leaves. Cells of higher plants form tissues. Sporophyte prevails in the life cycle (except bryophytes).

The gametophyte is reduced in a post-penny manner to several cells. The organs of sexual and asexual reproduction are multicellular. Fertilization with complication of species ceases to depend on water. The zygote gives rise to a multicellular embryo.

Higher terrestrial plants make up the bulk of the Earth's biomass - about 90%.

Systematics of higher plants

Higher plants include higher spore and higher seed plants.

Higher spore: rhiniform (exceptionally fossil), psilotoid (about 20 species), bryophytes (23-27 thousand species), moss-like (about 1300 species), horsetail (about 30 species), fern-shaped (of the order of 12,000 species).

Higher plants, which reproduce by spores, botanists are united by a common name - higher spore. These include both existing and extinct species. The body of the higher spore is divided into aboveground and underground parts, vegetative organs are developed. The life cycle consists of alternation of generations: sporophyte and gametophyte. The sporophyte is well developed, lives for a long time (the exception is the bryophytes). Multicellular sporangia develop on it, after which meiosis immovable haploid spores are formed. They are single-celled, small in size, spread mainly by the wind and germinate into the gametophyte.

Fertilization of higher spore occurs only in the presence of water. According to the arrangement of the reproductive organs , there are two-sexed plants (in which there are both male and female cells) and same-sex (there are either male or female cells).

Spores can be different and equal in size. Higher spore plants, which have the same spores, are called equisporous, and those with different spores have different spores. Depending on the size, microspores (small in size) and megaspores (large) are distinguished.

It is believed that the seed plants occurred directly from the spore, in particular from the ferns.

Higher seed plants: Pinophytes (gymnosperms) - about 800 species, magnoliofits (angiosperms) - 300 thousand species.

Higher seed plants reached their heyday in the Mesozoic era, when the climate became more arid and cold, a change of seasons appeared. At present, angiosperms are most common.

Seed plants have a number of advantages over higher spore plants. They consist of the same organs: root, shoot, seed. The trunk is much stronger than the spore, since it grows wood cells. With this, the bulk of the wood cells is dead.

Seed plants are exceptionally sporadic. The gametophyte develops on the sporophyte and feeds at its expense.

Reproduction occurs with the help of seeds, which are multicellular formed embryos, which include a supply of nutrients. Fertilization of higher seeds is preceded by pollination - the transfer of pollen grains into seed germs with the egg. Pollination is carried out with the help of wind, water, animals, insects. Fertilization ceases to depend only on water, as in higher spore. It occurs due to a vegetative cell of pollen, which grows into a pollen tube.