Are seedlings, layering and sowing seeds the only way to increase the number of plants offered for sale? As it turns out - not anymore! The more and more commonly used methods were joined byin vitro plant reproductionSee what the in vitro plant propagation looks like, how it is performed and what plants are most often propagated by in vitro method.
In vitro plant reproduction
Gardening has entered a new era, which means that nowadays, in addition to traditional methods of plant reproduction, a whole range of, often quite unusual methods are used.In the first place among these unusual methods is promoted micro-reproduction, i.e.in vitro reproductionIt means the same as glass cultivation and it is not a new technique as it might seem, because its metric indicates several dozen years of attempts, which resulted in the creation of a number of methods of fragment multiplication plants in laboratory conditions.
In vitro plant reproductionis based on the almost unlimited regenerative abilities of all plant cells with an intact nucleus. These predispositions of living plant cells to maintain complete genetic information and complete developmental capacity, regardless of the degree of their differentiation, are referred to as totipotency. This property allows in many cases to recreate a complete plant organism from small sections of leaves, shoots, roots or even in extreme cases - from single cells.
Currentlyin vitro plant reproductionuses almost all ornamental, cultivated and also fruit plants.It is enough to look at the long list of species, which are obtained every year by hundreds of thousands of new specimens using justin vitro reproductionWe will find here min. cloves, gerberas, anthuria, from garden plants there will be narcissus, daylilies and lilies, and from fruit plants - strawberries, blueberries, dogwood and many, many others.
Techniquepropagating plants in vitrois quite simple - it is enough to get a plant growth cone or even a scrap of meristematic tissue with undifferentiated cells with enormous regenerative potential and place it on a properly balanced medium under possibly sterile laboratory conditions. It seems trivial, doesn't it? Well, it is not so.
If the tissues collected forin vitro reproductionare infected with pathogens, the entire culture will turn out to be a great failure at the very beginning. The greatest threat are viruses, which can live in plant cells for a long time without causing any symptoms.If we produce (I think you can call a large-scale plant production using this method) new specimens from a virus-infected mother plant, we will be in for an unpleasant surprise …
"However, to defend against the potential effects of multiplication of sick individuals, each largerin vitro culture laboratorytests the plant material to be multiplied for the presence of viruses, and if any are present, the entire colony of stem cells is subjected to thermotherapy (i.e. the action of high temperature), which effectively inhibits the multiplication of the virus in the plant.
The next stageof in vitro reproduction of plantsis the placement of tissue fragments on a properly selected agar medium. It must contain not only the basic nutrients from which the developing plant will be able to derive, but above all a properly composed set of plant hormones. It is phytohormones that affect the division of plant cells, their growth, differentiation and, consequently, the rebuilding of a complete plant only from a callus nodule, i.e. an undifferentiated colony of stem cells.
To stimulate cell growth, a strictly defined concentration of auxins and cytokinins - two basic groups of phytohormones that condition the proper growth and development of the whole plant are added to the medium. Already at the very beginning of the research onin vitro plant reproductionit was discovered that despite the fact that some plant hormones do not directly stimulate the bud of a new plant, their presence in the wrong concentration causes inhibition of growth and often in as a consequence, the death of the callus. Many years of research have led to the creation of detailed tables of phytohormone concentrations in the media in each of the growth phases and the time for which these compounds should be present in the medium during the multiplication of individual species and even plant varieties. And so in order to stimulate the development of roots, the ratio of auxin and cytokinin concentrations is different than in the case of the development of shoots and leaves.
The norm duringin vitro reproduction of plantsis that in order to stimulate the development of new shoots the proportion of cytokinin hormones in the medium should be increased.However, in order for the seedling to develop a strong root system, it should be transferred to an agar medium with an increased proportion of auxins to cytokinins.
Usually, during transplantation of the growing mass of cells onto a new medium with a strictly defined composition, cell groups can also be collected in order to increase the number of descendants . Doing so results in obtaining a huge number of new plants from one callus pellet in record time. This method of operation is also supported by financial considerations, because a large number of new seedlings, often in millions of pieces, can be obtained on a relatively small area of laboratory tables.
A very important role during the entire cyclein vitro plant reproductionplays the right temperature and photoperiod, i.e. the length of the day and night, which are as important as a properly composed nutrient solution or he althy mother plants.
When the seedlings reach the right size, they are gently moved to the room where their gradual process takes place hardening, i.e. the plant habituation to the conditions in tunnels and greenhouses.
In this way, virtually all garden novelties and curiosities are made available to a wide group of customers and their price drops drastically. For example, this is the case with newly grown varieties of daylilies, which are transferred tomultiplication in in vitro cultures after the first floweringAmericans and the Dutch have achieved such perfection in this method of plant cloning that new from a given year become generally available after one or two seasons. And their price drops from a few hundred dollars in the year of introduction to just a few dozen the next. Varieties with several years of experience are now available for every pocket.
In vitro plant breedingalso provides excellent conditions for the reproduction of orchids and ferns, which under normal conditions were a real test for patience for gardeners. While in the case of ferns, young gametophytes in sterile laboratory conditions, free from unwanted visitors from outside, have excellent conditions for growth, the situation is different with orchid seeds.The Orchideaceae family, to which all cultivated orchids belong, is characterized by a complicated development cycle. These plants live in symbiosis with fungi, also their seeds need the presence of mycelium to germinate properly, which nourishes them, thus compensating for the lack of endosperm that serves as a reserve.
On an agar medium it is much easier to maintain appropriate conditions for the growth of fungal hyphae and protect them against infection with harmful microorganisms that could disturb the seed germination process and the subsequent growth of seedlings related to the symbiosis of their roots with the fungus thallus.
The method of in vitro cultureshas also found application in the field of horticulture, which is the breeding of new varieties. Thanks to it, it became possible to create, sometimes spontaneously in nature, remote hybrids, i.e. crosses between individuals belonging to two different species. This is to obtain valuable plants with a high specific yield and high resistance to diseases and pests, and at the same time not picky in terms of growing conditions.
Obtaining such a hybrid is very difficult and only taking advantage of the benefits offered byin vitro plant reproductionallowed breeding institutions to start research in this direction. Previously, incompatibility mechanisms, mainly based on malnutrition of the developing embryo, or the inability to take nutrients from the endosperm by the germinating plant, prevented the crossing of individuals of two different species. Currently, the embryos are transferred to a properly selected medium from which they can get all the substances necessary for the proper development.
I believe that with this short article I shed some light on this rather difficult topic. The information presented above is only the tip of the iceberg. In turn, the very applications for micro-propagation, also sometimes called
the method of in vitro cultures , could be found even a lot. Thus, this technique should not be equated only with the mass reproduction of ornamental plants, but a broader look at all the ways of its use in the modern world."
Emil Gwizdała
