Propagation by seeds and spores
Propagation by seeds is sexual reproduction, in which "shuffling" of a gene material takes place, which is of great importance for breeding and allows breeding plants with the desired characteristics. Despite the opportunities concealed in such reproduction, it is rarely resorted to in indoor decorative floriculture( only in cases where vegetative reproduction fails), since it is quite troublesome: the seeds of many ornamental plants have very low germination capacity, which can be only 2 -3%.But plants of open ground, first of all, annuals reproduce more often just like this.
Plants can have a wide variety of seeds and sizes, which causes many features of working with them. The timing of their sowing is also not the same: for some species the seeds are sown immediately after reaching maturation, others in spring or autumn. Some require special pretreatment - preseeding preparation. Strangely enough, it is necessary to carry out, strange as it may seem, not for complete exotics: plant seeds from latitudes close to moderate( the same dry subtropics), remain in a state of rest in winter and are often protected by a shell, which must be removed for better germination. This action is called scarification.
Scarification can be performed by friction( for this, sandpaper is used), "surgically" with a scalpel, seeds of many legumes( eg sophores) are poured over with boiling water.
Another method of presowing seed treatment is stratification, in which artificially changing the quiescent conditions: the seeds are mixed with wet sand or other substrate and held for about a month( depending on the features of the species) at a constant temperature slightly above zero( about 5 ° C).
Seeds of such plants are sown in the spring.
Seeds of most species with large seeds are sown in autumn, pre-etched or disinfected in any available way.
Seeds of tropical plants, as a rule, quickly lose their germination, they should be sown immediately after ripening. In all cases, disinfection is desirable, since pathogens and pests can easily kill a newly germinated plant.
There are different methods of disinfection of seeds. The simplest and fastest is thermal disinfection, in which the seeds are soaked in very warm water( about 50 ° C) for an hour. Chemical disinfection is called etching. For him, various chemicals are used from all the known potassium permanganate( potassium permanganate), suricum, sulfur to many special disinfectants, the assortment of which is very rich and diverse today( the methods of their use are indicated on the packages).For plants sown in open ground, chemical decontamination is a more reliable method, since it helps protect plants from insects, and it is simply impossible to create conditions that fully meet sanitary requirements.
It is best to sow seeds in boxes or cuvettes, and for species with small seeds - in pots, which, firstly, can be disinfected with detergents, and secondly, it is easy to move, thus regulating the dosage of illumination. The soil in them should be quite fertile. Most often used zemlesmes from humus and turf land with the addition of sand;but the requirements of different species to the soil are not the same: for tropical it is better to take a mixture of peat land with sand, for some woody and shrubby species a substrate from sawdust and so on will be suitable. In all cases, it is advisable to lay a drainage layer of gravel or other inert coarse material on the bottom of the container, since soil silt for germinating seeds is fatal.
Large seeds are embedded in the ground to a depth of not more than three times the thickness of the seeds themselves, small seeds are sown over the surface without embedding. Not bad, if you cover them with mulch from fine sand or sawdust. Mulching reduces the drying of the soil and prevents the formation of a crust on it. Small seeds can be simply covered with a sheet of paper.
After placing the seeds in the soil, the container is covered with polyethylene and placed in a dark place. On the open ground for the same purposes are exposed to shields or pour a thicker layer of mulch. Shading should be maintained before emergence, but young plants should not be exposed to open sunlight. The exception is the seeds of cacti, they can germinate in the light.
Young seedlings are very tender, so it is especially important to observe for them the correct watering regime( humidity should be kept uniform and constant) and water them carefully so that water jets do not wash off small seeds and do not change the depth of medium filling. Useful is a device for permanent moistening, you can use a sprayer. If the seeds are germinated in a pot, a convenient method is to moisturize through the pan.
It is equally important to observe the correct temperature regime. For subtropical species, room temperature is sufficient, for tropical species it should be higher: 25-28 ° C.It is wrong that for the seeds of all plants the higher the temperature, the better. It is more important to maintain its permanence.
If the shoots have risen densely or are too close together, they must be dived.
Spore propagation of is characteristic of ferns, horsetails and plaunts.
Their spores are sown in a pre-calcined light, loose, wet peat with the sand of the soil mixture on a flat surface and covered with polyethylene or glass from above until sprouts appear. Drainage at the bottom is mandatory. The optimum temperature is 22-25 ° С.