For every gardener, at least a professional, even an amateur, it is important to know how to plant your plantings. There are many ways, and one of the most interesting and effective is the method of microclonal propagation. What it is, how all its basic wisdom works, and in our material.
What is this?
Let's start right away with the most important thing. In the phrase "microclonal reproduction" the second word is clear to everyone, but the first - only to the elite. To clarify the situation. What is "microclonal"?
Speaking of “clever” scientific language, this is a special subspecies of vegetative propagation using a technique called “in vitro”, which makes it possible to obtain plants in a shorter time. We will understand further and more clearly, and for this we first recall what vegetative reproduction is, and explain what the term "in vitro" means.
In the scientific wilds
From the course of school biology, we know that plants can be propagated in two ways: by the seed (when we spread the seeds into the soil) and vegetative. Vegetative propagation is asexual, it occurs by separating a certain part from the parent plant. Budding, rooting of young shoots, bulb transplanting - all this is vegetative propagation.
It would seem that using seeds to increase the number of plants is much easier - there is no such trouble. However, this method has many disadvantages; in some cases, it is impossible to use seeds at all - and the vegetative method, whose undeniable advantage over the first one is to preserve the set of genes of the parent plant, remains the only available and convenient. But unfortunately, he has enough shortcomings. For example, the lack of the necessary efficiency (in, for example, plants such as oak, pine and so on), "old" tree species (which are more than 15 years old) are not able to propagate by cuttings, such procedures are rather laborious and energy-consuming, not always obtained plants correspond norm and sample (may be infected) - and so on.
And precisely for these cases, there is a technology of microclonal propagation of plants, which, like Chip and Dale, is in a hurry to help. As mentioned above, it is carried out using the "in vitro" technique, which is translated from the Latin language as "in vitro". Thus, this technique allows you to "clone" in a "test tube" a plant with genes exactly the same as in the parental individual. This is due to the fact that the cell is able to give life to a new organism under the influence of external factors.
The technology of microclonal propagation has, undoubtedly, a number of advantages and advantages. We’ll talk about them later.
Why is microclonal propagation better?
To many! And first of all, the absence of viruses and infections in the excreted plants (because special cells are used for this - they are called meristemic, their peculiarity lies in the continuous division and the presence of physiological activity throughout life). Also, plants "harvested" in this way have a fairly high reproduction volume, and the entire breeding process is much faster. Using the technology of microclonal propagation, it is possible to carry out this procedure for those plants for which it is extremely difficult to do this using conventional, "traditional" methods. Finally, in the "in vitro" technique, plants can be grown all year round, not limited to any one interval. So there are really many advantages to this technique. And before delving into the essence of microclonal propagation of plants, we will touch on a little history of the emergence of this method. To whom and how did such an idea come to mind?
Method History
The first successful experiment on orchids was made by a French scientist in the fifties of the last century. Moreover, he did not initially engage in the “in-vitro” technique - it was developed before him, and quite successfully. However, it was Jean Morel - such is the name of the French experimenter - who decided on such an experience and implemented it quite successfully. The works telling about this technique appeared several decades before it - in the twenties of the last century.
A “test tube clone” of a woody plant - specifically aspen - was obtained in the sixties. It turned out to be more difficult to work with a tree than with flowers and other types of plants, however, these difficulties were overcome after a certain period of time. Currently, more than 200 species of trees from more than forty families can be obtained by the "test tube" method. The technology of microclonal propagation of plants is justifying itself and is bearing fruit.
Method Details
As you might have guessed, in the development and application of microclonal propagation of plants, there are many of their subtleties. So, for example, there are special stages in this technology, which is absolutely necessary to observe to obtain the desired result. You need to understand that neglect of the sequence of actions or some stage may bring absolutely not the result that the breeder is counting on. So, we will talk about the stages of this technique further.
Stages of microclonal propagation of plants
This technology involves four "steps" on the path to obtaining the coveted "clones". We will try to talk about them as unscientific as possible, since the terms of biotechnology are still not the most understandable thing for a wide audience. And, by the way, one of these terms is immediately explainable: explant - this is how scientists in this field refer to a new organism separated from the parent organism. That is the same "experimental", which will be grown further.
So, we will pass to our "steps". The first step is the choice of the actual parent - or donor. This issue should be approached with the utmost seriousness and responsibility, because in order to get a good, strong, healthy plant, we and the “original” must choose the same one. An apple is not far from an apple tree, as you know.
At the same stage, it is necessary to isolate and sterilize the explants, and then arrange such conditions so that the growth of these explants in the "in vitro" technique occurs as comfortably as possible.
The second "step" is nowhere easier - this is reproduction itself. It is possible in a month and a half, when the mini-cuttings have already reached the size of peas and have the rudiments of all vegetative organs. It, in turn, is followed by the rooting of the shoots that were obtained in the previous stage. It is carried out when the plant has already formed a good root system.
The last step is to help the plants adapt to the “life” in the soil, grow them in a greenhouse, then transplant them into the ground, or realize - so to say, “departure to the big world”. Strange as it may seem, this stage is the most labor-consuming and costly, because very often, unfortunately, it happens that, once in the soil, the plant begins to lose leaves, stop growing, and then it can die at all. All this happens because test plants lose a lot of water when transplanted into the ground. Therefore, it is necessary to prevent this possibility during transplantation - for which it is recommended to spray the leaves with a 50% aqueous solution of glycerol or with a mixture of paraffin. This must be done throughout the acclimatization period. In addition, in some cases, intentional mycorrhization is advisable - that is, the artificial introduction of fungi into the plant tissue that infects it. This is done so that the plant receives as many useful nutrients and organic substances as possible, and also is protected from various pathogens.
That's all the stages of microclonal reproduction, in which, as we see, there is nothing globally complex or supernatural, however, we repeat again, this whole event requires a lot of responsibility and attention.
Influencing factors
The process of micropropagation, like any other, is influenced by certain factors. We list them, because "you need to know the enemy in person."
- Varietal, species and physiological characteristics of the parent plant - it must be healthy, grow intensively, if necessary, processed by temperature exposure.
- Age, structure and origin of the explant.
- Duration of cultivation.
- The effectiveness of sterilization.
- Successful culture medium.
- Hormones, mineral salts, carbohydrates, vitamins.
- Temperature and lighting.
What you need for micropropagation
Plants that will propagate in the above manner have one very important requirement - in addition to being healthy. This is an indispensable preservation of genetic stability throughout all of the above stages. Apical meristems, as well as axillary buds of stem origin, are best suited for this requirement, which is why they are preferred to be used for the procedure of interest to us.
The above terms should not be understood by ordinary people. Below we will try to explain what kind of animals they are and with what to bring them to the table.
Apical meristems
We have already mentioned the existence of special meristem cells - in other words, educational ones. These are cells that constantly divide, are always in a state of physical activity - due to which the mass of the plant grows and a special tissue of this plant forms. It is called the meristem. There are many different types of meristems. In general, they can be divided into general and special. The concept of common meristems includes three groups that seem to follow one from the other. The very first meristem of the plant is the embryo meristem, from which the apical meristem that interests us arises.
The word "apical" comes from the Latin "apix" and it translates as "top". Thus, this is the apical system of tissues located at the very tip of the embryo - and it is from it that the shoot is subsequently formed and its growth and development begins. So, speaking of the apical meristem as an object for microcloning, we must understand that we take the tip of the embryo for our needs.
With axillary kidneys a little easier. What are kidneys, everyone knows. A sinus kidney is one that is born from a leaf sinus. The leaf sinus, in turn, is the angle between the leaf and its stem; from there the kidney or shoot will just grow. This very part, that is, the future lateral shoot, is also taken for subsequent micropropagation.
Now that the light has shed a little over the veil of secrecy, we can finally go on to the methods of microclonal propagation of plants.
Micro-propagation methods
Microclonal reproduction is all the more good because it assumes basically the possibility of using several different techniques at once. We will try to cover each of them as simply as possible. In total, there are four methods of microclonal propagation of plants.
First. Activation of existing meristems in a plant
What does it mean? In a plant, even such a tiny micro-piece, certain meristems are already laid. This is the top of the stem and axillary buds. In order to microclone a plant, one can "wake up" these sleeping meristems "in vitro". This is achieved either by removal of the apical meristem of the micro sprout, or rather, its stem, and then by grafting the shoot in the “in vitro” technique, or by introducing special substances into the nutrient medium of the plant that activate the growth and development of axillary shoots. The method of activation of "sleeping" meristems is the main, most popular and effective, and it was developed back in the seventies of the last century. The first "experimental rabbit" in the application of microclonal propagation of plants of this type was strawberries. It is important to note, however, that endlessly propagating crops in this way is prohibited, since this is fraught with a loss of the ability to root, and in some cases, the death of the plant.
Second. The advent of adventitious buds by the forces of the plant itself
Any isolated part of a plant has a truly magical ability, its own superpower. If during microclonal propagation the nutrient medium of the plant and all other living conditions are favorable and comfortable, then it can restore the missing parts. A kind of regeneration takes place - plant tissues form adventitious, or accessory buds - that is, those that arise as if from "old stocks", and not from new tissues. Such buds are unusual in that they appear, as a rule, in those places where you can’t wait for their appearance - on the roots, for example. It is in a similar way that many flowers are often propagated, again - strawberries. This is the second most popular and effective method of microclonal propagation of plants.
Third. Somatic embryogenesis
With the second word, everything should be more or less clear. We touch on the first - what does somatic mean? This word in this vein is directly connected with the same cells. Such cells are called those that make up the body of multicellular organisms and do not participate in sexual reproduction. In short, these are all cells except gametes. Somatic embryogenesis is carried out in a rather simple way: embryoids are formed from the above cells (that is, somatic) using the “in vitro” technique, which subsequently, when they arrange suitable conditions for development with an optimal nutrient medium, turn into an independent whole plant. In this case, we can talk about such a thing as totipotency (the ability of any cell to initiate any cellular type of organism due to division). It is believed that eventually such embryos develop into a seedling. Somatic embryogenesis is also good because it is thus possible to obtain artificial seeds. This method was first discovered in the middle of the last century in carrot cells.
Actively a similar method of microclonal propagation of plants is used when propagating oil palm. The thing is that, since it has neither shoots nor side shoots, its vegetative propagation is impossible (or, in any case, very, very difficult), as is the propagation of cuttings. Thus, the above methodology is the only one of all the most accessible and optimal when working with this plant.
Fourth. Work with callus tissue
The next term smoothly “swam” into the network of our narration, and first of all it is required to clarify its meaning. What is callus tissue? Everyone knows that on the wound, when it is a little alive, a drying crust appears. And if you remove it, the wound starts to bleed again. The very same crust, in other words, “healing tissue, is callus tissue. The cells of this tissue, not only contribute to the healing of wounds, are also totipotent - that is, as already explained above, a new plant can arise. And that is precisely why the appearance of adnexal kidneys (adventitious - we have already introduced this term before) on such tissue.
This method of all four of the above is, perhaps, the least popular. First of all, this is due to the fact that too frequent separation of callus tissue cells can lead to gene disorders and mutations of different levels. Since the preservation of the genotype is very important for microclonal propagation, and tissue culture must be maintained at the highest level. In addition, with the above violations, other disadvantages also appear: short stature, susceptibility to diseases, and so on. However, in some cases, propagation is possible exclusively in a similar way - for example, for sugar beets, there is simply no other method to choose.
Further, for example, we will say a few words about the cloning of specific plants, but first, you need to share information about the healing of plants used as planting material. How can this be achieved?
Wellness
It is possible to turn a plant from a patient into a healthy one in several ways, and the first of them is placing the sprout in a special chamber, or box, where sterile conditions are maintained, and “stuffing” it with antibiotics. This method is good for everyone, except that it does not cope with all the bacteria and viruses that plants can be affected by. , , – , , . .
Potato, by the way, is one of those few cultures that can be propagated by the fourth of the above methods. But, of course, this is far from the only way - and often they also resort to activating the "sleeping" apical and axillary meristems. The tubers that are obtained after cloning are exactly the same as the "original" ones - they differ only in their smaller size, these are the so-called micro-tubers. Well, in addition, they will certainly be healthy and not have viruses.
During microclonal propagation of the potato, it is grown in test tubes with two cuttings, the tubes are placed under the light of fluorescent lamps with a power of six to eight thousand lux, the temperature remains at night at around eighteen degrees, during the day - about twenty-five. In Russia, it is potatoes that are grown most actively through cloning.
About apple cloning: what you need to know
In microclonal propagation of the apple tree, the first method is widely used - reproduction using axillary buds. The high ability of this culture to root and the survival rate of a large number of explants is noted.
They were placed in a liquid nutrient medium, which was constantly - daily - updated. The temperature for test plants was also maintained at twenty-five degrees in the afternoon, the experiment was conducted for three to four weeks.
Interesting Facts
- As you can easily guess, this technique acquired its name from the concept of “clone”, which appeared in 1903. From the Greek language this word is translated as “offspring” or “stalk”.
- The first place in our country, where the first experimental attempts at microclonal propagation of plants were carried out, was the Timiryazev Moscow Institute.
- Clonal micropropagation is an excellent method of combating viruses and the ability to produce healthy, non-infectious plants.
- The period that the plant goes through before flowering and the appearance of the fruit is called juvenile - and in those organisms obtained by cloning, it is minimized.
- Leading countries for the production of plants in the above manner are considered the United States of America, the Netherlands, Italy, Poland, Israel and India.
- Almost two and a half thousand species and varieties of plants can now be propagated in the technique of "in vitro".
- At the initial stages, the plants grown by “in vitro” may differ in appearance, however, as they grow, all differences disappear, and in the end the plants become similar, like twins.
- Explants from young plants are better at rooting than from mature ones.
- One of the important conditions in microclonal propagation is the selection of the most favorable nutrient medium for the plant, and it can be either liquid or solid.
- Cells of meristematic tissues usually do not contain viruses.
- The size of the explant is directly related to the possible presence of viruses in it. The smaller it is, the less is the risk of the presence of infections.
- Another name for micropropagation is meristemic reproduction.
This is information about the microclonal propagation of plants - the topic is how complex, so interesting.