Selection as a scientific discipline is characterized by the high degree of complexity: it borrows from general disciplines their methods and laws about plants and animals making them detailed up to the cultivar according to it’s needs. In managing heredity it is based entirely on the data of genetics, cytology and embryology.
A lot has been written about the significance of cereals in human life. Excavations permit to establish that the cereals had been introduced in cultivation at the dawn of agriculture. From the primary centres of agriculture the cereals had spread to new regions in the wake of the settling mankind. Together with the experience of ploughers the knowledge of the cereal structure was accumulated. With the aid of selection it became possible to fundamentally change the plant habitus, significantly raising the part of corn in the whole yield of the biomass, to create the sorts reactive to the increase of fertilizer doses, to increase the quality of grain and even set to the forming of new sorts by hybridization.
However, the attempts of further interference into plant life for the sake of increasing its productivity revealed the necessity of getting data from scientific area which has recently been considered strictly theoretical. By this area is meant plant embryology.
The necessity of obtaining embryological information when working out selection programs or constructing industrial techniques is corroborated, in particular, by the fact that in plants organogenesis is continued throughout its ontogenesis. And if, for instance, we take spring wheat, the processes being in the centre of attention of embryologists-botanists, by their duration take two thirds of the vegetative period: from the building up of the inflorescence up to the formation of the kernel.
For scientists of the whole world more and more urgent becomes the question of new, untraditional approaches and methods permitting to bring to light all potentialities of the plant organism, as well as to get new forms and sorts in shorter time.
The individual development of plant organism and cognition of the essence and reasons of the formconstructing processes is one of the principal problems of our time.
Plant embryology — the science on regularities of the origin and development of the first stages of ontogenesis is going through its flourishing period determined by the general progress of natural sciences. The further development of biology is impossible without the knowledge of the tirst stages of ontogenesis — embryology. That is why it appeared in the centre of attention not only of embryologists, but also of geneticists, biochemists, physiologists, cytologists, biophysicists and selectionists and is a necessary basis for experimental and theoretical investigations dealing with the problems of reproduction. Besides that, embryology disposes of a number of fundamental discoveries which can be widely introduced into practice (cytoplasmic male sterility — CMS, phenomenon of apomixis, distant hybridization and some others).
Up to recent time selectionists were unable to predict with certainty the results of some or other crossing, its possibility to be put into practice and reproductive ability of the progeny. As a matter of fact, the processes occurring in the flower — the fertilization, the development of the endosperm and the embryo, the formation of reproductive organs were practically out of control. It is quite evident that the possibility of regulation of separate stages of the development of embryonic structures is directly and closely dependent on the completeness of our knowledge of the normal morphogenetic processes occurring in them. Thus, the description of embryological development at the cell, tissue and organismic levels is a necessary theoretical basis for further broadening and extending of investigations in the areas of genetics and selection.
Any work connected with the influence of biotic and abiotic factors at the critical periods in early ontogenesis also needs a knowledge of the entire picture of events developing at the early stages of ontogenesis which determine the whole further process of development.
Such discoveries of the XXth century as haploidy, parasexual hybridization and growing plants from somatic cells which are of all-biological significance, especially for the practice of agriculture, cannot be effectively used without the knowledge of embryology. Without deep knowledge of embryonic processes it is also impossible to make effective use of different methods of investigation, such as distant hybridization, growing of hybrid embryos on the artificial nutritive medium, polyploidy, experimental mutagenesis, influence of ionizing irradiation and the conditions of growing and so on.
Sometimes it is impossible to forecast the prospects of using embryology as applied to cereals — it is easier to decide to those who have met with some difficulties. The fact is that all processes appear to be dependent on the environmental conditions, that is, for example, on the time of watering or applying herbicides and so on.
In connection with the fact that all processes occurring in the flower and resulting in the formation of grains are complicated and many-sided, it became necessary to illustrate them by a great amount of drawings and photoes which make up the «Atlas» where the embryology of some cereals is reflected.
A drawing, by the expression of a famous embryologist S. G. Navashin, is «the language of a morphologist», it not only illustrates the occurring processes, but also reveals their depth, dynamics and integrity.
A short description of all embryonic processes in the chapters of the given work was necessary for presentation of data not reflected in the drawings. This will enable the reader to understand more deeply the different aspects of formation of embryonic structures taking part in the building up of the corn.
Many researchers repeatedly turned to the study of embryology of cereals. The monographs dy Ya. S. Modilevsky with his collaborators, by A. A. Chebotar — on maize, by Т. B. Batygina on wheat have been published. Separate questions of embryology of cereals are covered in the works of both Soviet (V. G. Aleksandrov, M. S. Yakovlev and others) and foreign (K. Norstog, A. Diboll, S. Russell, H. L. Mogensen and others) scientists. The complexity of methods and the great range of problems, as well as the appearance of new discoveries and requirements of practice called for the creation of the «Atlas», where the embryological processes of the main cereals would be considered. The idea of publishing an Atlas «The Grain of Cereals» belongs to the well-known botanist P. A. Baranov.
The analysis of literature on embryology has shown that the majority of processes taking place during the development of embryonic structures is submitted to general regularities according to the law of homologous rows by N. I. Vavilov. That is why the author in some cases specially shows the similarity of some embryonic processes in different species, and in others is restricted only by a description of them in one cereal.
The author met with great difficulties during the process of writing this book, in particular, with different degrees of knowledge of embryology of cereals. Therefore the author does not claim to have fully presented the embryology of all cereals: the relative significance of the chapters has proved unequal. Most fully are described the embryonic processes in wheat. The main attention is paid to the description of embryonic development at the light level; the successes in the area of electron and luminescent microscopy, however, have also found their reflection in this work. Besides, the author has attempted to show some applied aspects of embryology where the experimental method of investigation (the culture of isolated embryos, haploidy etc.) has become established. Moreover, on the basis of theoretical principles of cultivation in artificial conditions (in vitro) of different generative structures worked out by the author and her colleagues (of the anther, the embryo etc.) some methodical advice has been recommended which could be applied in selection. For instance, various methods of obtaining haploids have been brought out, and there has been worked out a scheme of the effect of the removal of sporophytic and gametophytic determination. A new regularity has been established — the autonomy of the embryo — the stage from which the embryo is able to complete its development and produce a normal plant in isolated condition.
From the viewpoint of systemic approach which the author has been working out for many years as applied to embryonic structures, all embryonic processes are determined. The majority of them develop in conjunction and certain correlations in morphogenetic processes determining the specific character of normal embryonic development are revealed. The disturbance of such conformity leads to the disturbance of homeostasis, which is manifested in various anomalies both of separate organs and the whole plant system, where everything is subjected to common, but quite certain laws of development.
The «Atlas» intended for the readers’ attention is devoted not only to the description of the main embryonic processes occurring in the flower and the fruit (kernel) of the main cereals (wheat, rye, maize, barley, oats and triticale), but also to the embryonic processes being conjugated with the process of formation and functioning of separate shoots and the plant as a whole. The knowledge of the laws of morphogenesis is especially important for the selectionists, agriculturists who judge on the development of the plant by phenophases.
The author found it reasonable for the sake of easiness of perception, not to quote the original works, but to confine herself by the list of literature due to which it is possible to get a more detailed information on questions the reader is interested in.
In the «Atlas» are used original drawings, as well as photographs taken from native and foreign literature.
The author is heartily thankful to A. A. Chebotar, A. M. Moshkovich who have given microphotoes illustrating the meiotic cycle in diploid and tetraploid rye and also to V. E. Ogorodnikova and A. A. Chebotar who have kindly presented the materials on electron microscopy characterizing the separate processes in the development of wheat, barley and oats anther. The author is very much obliged to A. P. Frumkina and N. D. Tichenko for the illustrative material dealing with the germination of pollen tubes obtained by the method of luminiscent microscopy. The author is very much obliged to I. N. Orlova for microphotoes demonstrating some processes of endosperm development and some aspects of embryo and endosperm development of triticale. By I. N. Orlova was also written the chapter «The method of preparation of the embryo sac of wheat, rye and triticale». The author brings her sincere thanks to G. Ya. Petrov for the materials on triticale embryology. The author is very thanklul to L. I. Orel who has presented some microphotoes by the late I. D. Romanov and her own original microphotoes characterizing the vital state of wheat pollen and some aspects of pollen development in the case of CMS. The author is grateful to V. K. Simonenko who has presented some materials and photoes for the chapter on CMS in cereals. The author is heartily thankful to S. A. Ignatova, S. V. Lukjanyuk and N. I. Prichodko for the materials on obtaining haploids.
There is no doubt, the illustrations of the cone of growth of wheat made by N. N. Rytova are very interesting and the author is very grateful to her. The original grawings of O. A. Khvedinich have revealed complicated and intimate processes of barley and triticale fertilization and the author is deeply thankful to her. The work has gained from electron microscopic photoes kindly presented by I. G. Shmaraev, which are included in the chapter «The development of endosperm» written together. The author is sincerely thankful to all collaborators of the Institute of Plantgrowing who kindly presented specimens of various species of cereals for our work. The author is very grateful for the remarks and helpful advice of the executive editor of the book M. S. Yakovlev, to the reviewers A. A. Yatcenko-Khmelevsky and N. N. Cvelev and also to S. A. Reznickoval, Y. V. Gamalei and A. E. Vasiljev for their recommendations and important advice on electron microscopy.
The author is heartily grateful to H. L. Mogensen, M. L. Rusche, I. H. N. Schel, H. Kieft, Van Lammeren for the light and electron photoes on separate stages of Hordeum vulgare and Zea mays development sent by them and also to K. Norstog, S. Russel, A. G. Diboll, D. A. Larsen and others for the materials from their works without which the data on some aspects of cereal embryology would have been incomplete.
Some techniques of studying separate embryonic processes as applied to cereals are included into the «Atlas». They are taken from «The methodical recommendations. . .» (ed. by L. I. Orel) developed and modified by the researchers of the Department of Cytology and Anatomy of N. I. Vavilov All-Union Institute, and from the work of Z. V. Abramova and E. M. Esimbaeva (Selection and Seedbreeding, 1973, N 3) .
The preparation of the book like this is connected with much technical work in which actively participated the workers of the laboratory of Embryology of Komarov Botanical Institute of the Academy of Sciences of the USSR. The author is deeply thankful for advice and aid to G. E. Kolesova especially and also to E. V. Andronova, G. M. Anisimova, V. E. Vasiljeva, A. E. Vinter, E. V. Dragunova, L. M. Rotenfeld, I. I. Shamrov. The author is sincerely grateful for micro — and coloured photoes to В. T. Shapkov, and tor water-colours to E. N. Batygina.
In spite of the possible drawbacks which can be met with in the book, the author hopes that it will be useful not only for specialists of different profiles, but also to the wide range of readers. Besides, it can be used as a manual for teachers, post-graduate students and students.