By means of seeds the sexual reproduction of plants is carried out. Reproduction by seeds most often is used for cultivation of annual and biannual plants. The exchange of genetic material happening at the same time plays an important role in selection, it allows to remove new grades of one look.
Instruction
1. At reproduction by seeds at future posterity genetic signs which differ from characteristics of a maternal plant can be shown. It happens because of distribution of prepotent and recessive signs of posterity which happens in compliance to certain ratios.
2. On the short period of time making one or two seasons, in most cases splitting is not shown, and plants with short life cycle keep the external signs. It does not belong to perennial plants therefore for them it is the best of all to use vegetative reproduction.
3. Stability of plants in relation to external factors of the environment and progressive growth in many respects are defined by quality of seeds. Preparation of seeds for crops and their correct selection help to exclude possible problems during cultivation.
4. Bodies of angiospermous plants flowers are generative, fruits with seeds are formed of them. The fruit is formed of a pestle ovary, and from semyazachatok the seed with a germ of a new plant appears. It combines signs of both parents as contains chromosomes of a maternal and fatherly individual.
5. Seeds of flowering plants have the similar building, each of them consists of a seed peel, endosperm and a germ. At many bichromatic plants nutrients are in cotyledons, and at monocotyledonous — in endosperm. Seeds can extend by means of water, wind, self-scattering or by means of animals who eat fruits, acinaceous.
6. Germination of seeds begins at a certain temperature which differs at plants of different groups. For example, at some types growing in a moderate belt and in northern areas, seeds sprout at a low temperature, and at tropical plants — at higher. The structure of the soil, humidity of the environment and presence of oxygen is also of great importance. If seeds are in adverse conditions, they do not sprout.
7. Ontogenesis of plants begins with germination of seeds. Under favorable conditions the sprout of a new organism is formed. If moisture and oxygen arrive in sufficient volume, and temperature condition is optimum, then in endosperm and a germ the speed of exchange processes increases.
8. The seed begins to bulk up, starch, proteins and fats are split on glucose, amino acids and fatty acids. At first the seed leaves a germ back, then its other parts begin to develop gradually.