1, fission reproduction, also known as fission, is a reproductive mode in which an organism splits from its mother to produce new offspring. The new individuals produced by division and reproduction are roughly the same in size and shape. In single-celled organisms, this mode of reproduction is more common. For example, paramecium, amoeba and bacteria all divide and reproduce.

The division and reproduction of amoeba is shown in the upper right picture.

2. Bud reproduction Bud reproduction is also called bud reproduction, which is a reproductive mode in which the mother gives birth to buds in a certain part. The bud gradually grows up, forms the same individual as the mother, falls off from the mother and becomes a complete new individual. Yeast and hydra (when the environment is bad, hydra also has sexual reproduction. ) often bud and reproduce.

3. Spore reproduction Some organisms can produce a kind of cell when they grow up, which can directly form a new individual without pairing. This cell is called spore, and this reproduction is called spore reproduction. For example, Rhizopus forms sporangia at the top of its upright mycelium, producing spores. Spores can develop into new rhizopus when they fall in a humid and warm environment rich in organic matter. Generally speaking, lower plants and fungi reproduce in this way. Such as Adiantum, Penicillium and Aspergillus.

4, vegetative reproduction by the vegetative organs of plants (roots, leaves, stems) to produce a new way of individual reproduction, called vegetative reproduction. For example, the tubers of potatoes, the roots of thistles, the creeping branches of strawberries and the leaves of begonia can all germinate, and these buds can form new individuals.

Nutritional reproduction can make offspring keep their parents' traits, so people often use artificial methods such as rooting, cutting and grafting to propagate flowers and trees.

The vegetative propagation in the natural state is called natural vegetative propagation. Such as strawberry creeping branches, begonia leaves and potato tubers; Artificial assisted vegetative propagation is called artificial vegetative propagation. Such as cutting and grafting

Cutting: Cut branches into small pieces, insert them into the soil, and take root and sprout into new plants.

Grafting: Grafting the branches (or buds) of one plant to the branches of another plant, so that the cambium of the two plants is aligned, so that they can heal each other and grow into a plant.

Scion: a grafted bud or branch.

Rootstock: a grafted plant

Survival principle: use the regenerative ability of cambium.

The key to survival: pay attention to make the cambium of scion and rootstock close together. In this way, the cells split from the cambium combine the scion with the rootstock.

The conditions for asexual propagation of plants such as cuttings are as follows: 1. Stem segments (keep two segments), the upper incision is horizontal and the lower incision is inclined, except for environmental conditions such as light, moisture, temperature and humidity; 2. Blade: the last section is removed, and the next section is completely removed.

5. Tissue culture

Plant cells are omnipotent. According to this theory, plant propagation can be completed by using plant tissue culture technology. The general process of plant tissue culture is as follows: under aseptic conditions, plant organs or tissues are cut off and cultured on suitable human culture medium, and these organs or tissues will undergo cell division and form new tissues. However, there is no cell differentiation in this tissue. Under the conditions of proper illumination, temperature and certain nutrients and hormones, these cells begin to differentiate, produce tissues and organs, and then develop into complete plants.

Plant tissue culture not only has less materials, short culture period and high reproduction rate, but also is convenient for automatic management. This technology has been widely used in the rapid propagation of fruit trees and flowers and the cultivation of virus-free plants. For example, the shoot tips of orchids and chrysanthemums can produce 400,000 orchid seedlings a year. For another example, plants that reproduce asexually for a long time often accumulate a large number of viruses in their bodies, thus affecting the yield and ornamental value of plants. It has been found that only the shoot tip and root tip are virus-free. Therefore, many virus-free strains of plants, such as potato, Gramineae and chrysanthemum, have been obtained by tissue culture from shoot tips, and considerable economic benefits have been achieved.

6. Cloning

explain

1, single-celled organisms can only divide and reproduce.

2. The "bud" in "bud grafting propagation" refers to the bud growing on the mother, not the structure of the real bud on higher plants. For example, potatoes are propagated by buds or tubers, which are vegetative rather than budding. In essence, the "bud" is the same as the mother, but the bud is smaller.

3. Spores in asexual reproduction "spores" in asexual reproduction are asexual spores with the same number of chromosomes or DNA as somatic cells. Therefore, asexual spores can only be produced by mitosis or amitosis, but not by meiosis.

4. Vegetative reproduction is reproduction by using vegetative organs of plants. Only higher plants can differentiate roots and leaves. Therefore, it is an asexual reproduction mode of higher plants, and it is impossible for lower plant cells to carry out vegetative reproduction.