SEEDS, THEIR LIFE AND PRESERVATION UNTIL PLANTING
First published in 1915 in Sadovod, No. 4
Ivan Michurin

I presume that many fruit and vegetable growers will be extremely interested in clearing up a question of prime importance to their vocation: what causes plant seeds to become damaged, and, sometimes, even to perish, while being preserved for planting, or after planting? It is high time for fruit growers to take the trouble to elucidate as fully as possible and, what is more important, from various points of view, the rather complicated causes of frequent cases of seed spoilage. It is quite difficult to solve this question. Here the experiments and observations of some one person, however outstandingly competent he may be in the domain of fruit growing, will not be enough, will be too one-sided. What is required here is joint work, the conclusions drawn from the results of many years' observations of several persons. I stress the words "many years" because the solution of the serious problems of fruit and vegetable growing in general, and of the given matter in particular, requires the opinions of exclusively such people as have conducted observations over long years of their own work in cultivating various fruit plants, and having had the opportunity to repeat the same experiments several times over, have been able to verify their conclusions. We do not need discourses of various kinds by novices in the field. Not infrequently they only confuse and obscure the solution of a problem, and their premature conclusions in the majority of cases do nothing but harm. And yet on the pages of journals devoted to fruit and vegetable growing one frequently encounters such articles, and sometimes whole brochures by way of supplements, the authors of which left the school bench only five or six years previously. It goes without saying that these first years of every young fruit grower nearly always abound in errors and failures both in the work itself and in the conclusions drawn from their brief and mostly superficial observations, of the erroneous character of which they have not been able to convince themselves because the time has been too short and their work too brief. Such people have still to learn themselves, and yet they take pen in hand and scribble articles in which they set out with aplomb to discourse on the most serious problems of fruit growing.

That is why for the collective elucidation of the problem posed in this article I appeal exclusively to people with extensive experience, to persons who have become grey in the course of many years of labour in practical fruit or vegetable growing. And, of course, various diplomas testifying to special theoretical education can be of little importance in the present instance if only for the fact that in our institutions of learning too little attention is paid to the subject, and, consequently, when students leave school they carry away with them an incomplete knowledge of the factors that exert harmful or useful influence on the qualities or even on the vitality itself of plant seeds in the various stages of their existence from their ripening until their germination.

For my part, I shall attempt here to make known only those interesting facts which I have personally observed repeatedly in the course of my nearly forty years of fruit growing. Incidentally I shall cite some data from the foreign press about tests conducted there on the hardiness of seeds in specially low temperature.

First of all let us consider the nature of the seeds of various plants. Physiology teaches us that each seed is in its way a living organism: the body of the seed consists of numerous cells, part of which comprise the germ, while most of the other cells contain a supply of substances necessary for the vital processes of the germ protoplasm until the plant sprouts from the seed and for the shoot's nutriment until the young roots develop sufficient activity. It can be seen from this that the vital process does not stop in the organism of any seed, even when the seed is still in a state of dormancy, i.e., in a dry state, metabolism though slow is constant, sustaining the life of the germ cell. The proper course of this metabolism depends entirely on the environmental conditions in which the seed finds itself until it germinates. The metabolic process may gather speed or slow down, and, finally, may almost cease completely for a certain period the duration of which differs not only for each species and variety of plant but even for each separate seed.

The seeds of some plant varieties may, under conditions favourable for their preservation, retain their vitality for several decades, while the seeds of other plants barely remain alive a few hours. A great deal has been said of the almost unbelievable vitality of seeds. Many people probably know of the legend about wheat grains that came to life after having been dormant for a thousand years in an Egyptian pyramid. As a result the belief in the stability of the vital source in seeds of plants was greatly strengthened. To what extent this tale is true I shall not undertake to judge, but I well remember that in my early childhood my father and I were planting seeds from a package, and he said that those were seeds from wheat that had been grown from a grain found near an Egyptian mummy; that, of course, particularly intrigued me at the time and served to preserve the legend in my mind to this day. (I believe the seeds in those days were distributed by the Free Economic Society.)

To this day many people are ready to believe such fables, this being possible, in their opinion, because the activity of the protoplasm of the germ cells in some plants, including that of wheat, may pass into a state of complete dormancy, and the metabolism in the seed may cease completely for an indefinitely long period. Consequently, they assert, no losses in the grain will take place during this period, arid in such cases the seed does not, so to say, grow old. But such suppositions and fables about seeds germinating after having lain for thousands of years in the ancient tombs of Gaul or in the catacombs of Egyptian pyramids, should positively not be believed. The absolute cessation of all vital functions of a seed even for a relatively brief period of time must inevitably result in the complete destruction of the seed. Even when it is in a state of dormancy a grain's vital functions do not cease completely, but are merely reduced to an extreme minimum.

In metabolism their store is constantly, though slowly, expended throughout the whole life of the grain, the duration of which, I repeat, differs not only in seeds of different species and varieties of plants but even in each separate seed, because in one and the same fruit the store of vital forces almost always differs from seed to seed. This last can be seen clearly from the fact that their germinating power gradually drops in proportion to the length of time seeds are kept before they germinate. This fact also undoubtedly serves as irrefutable proof that the vital functions of the grain do not cease during its relative dormancy. Expenditure and exhaustion are inevitable, and seeds that have a quantitatively greater store of vital forces are able to live longer than seeds that have a smaller store. Of course, in the fact cited concerning the varying duration of the life of seeds, an important role apart from quantity may also be played by the qualities of the substances contained in each seed which serve as material for the life of the germ cell, but we shall not analyze this now if for no other reason than that it is as yet beyond our power to determine the qualities of the nutritional substances in the seed. In the present case all we can state that will be of benefit to our work is that it is possible for man to take reasonable measures to prevent the materials deposited by Nature in the grain from spoiling, by ascertaining in advance the various causes making for one or another kind of damage to the qualities of seeds while they are being stored.

First of all let us take note of the fact that not all damage to seeds is detrimental to us. It appears that there is such damage that is useful to us in the cultivation of certain plants and we evoke it deliberately. For example, we purposely overdry cucumber and melon seeds and use for planting only the older ones that have been preserved four or five years, because the plants grown from such seeds provide a greater yield.

But this method is advantageous only in the case of cucumbers, melons and certain varieties of squash. In most other cases the seeds of the very latest harvest are preferable because both overdrying and long storage of seeds inevitably have a harmful effect on their qualities, the proportion of germination dropping to a considerable extent, while the plants grown from the surviving seeds do not develop as well as those grown from seeds freshly picked. This is especially evident when rearing fruit-plant hybrids. Here not only is it impermissible to keep the seeds for several years before planting, but often even to dry seeds in the ordinary way for a few extra days vastly lowers the quality of the seedlings grown from them. This is easily noticeable, to an experienced eye, of course, from the habit of even one-year-old seedlings of hybrid fruit trees of cultivated varieties.

The first time I came across and noticed this phenomenon was when planting the seeds of an Aport obtained in 1890 from fertilizing the blossoms of an Aport with pollen of a Kitaika (Pyrus prunifolia). Part of these seeds were planted in one row in a bed of loamy soil in autumn directly after being taken from fruits picked from the trees, while the other seeds were removed from the fruits only in winter, at the end of December, and kept in a heated living room until planted in spring. When the snow melted, these seeds, after moistening, were planted in a second row in the same bed. Both rows of seeds sprouted with very little difference as to time, but with a rather noticeable proportion of losses in the second row, that had been planted in spring. Compared with those planted in autumn there was a 10% loss of seeds which failed to grow.

Then, while cultivating the seedlings from the very first year and throughout the subsequent period until the first transplantation from the bed to their permanent sites the two rows of seedlings sharply differed from one another with respect to the luxuriant development of all parts. After transplantation, which took place at the end of the third year of the seedlings' growth, the difference somehow smoothed out, but with the beginning of fruit bearing the difference between the trees was reflected in the following: although the trees of the second, i.e., spring, planting started their first fruit bearing earlier than did the trees of the first, i.e., autumn, planting, the quality of their fruits as regards size and flavour was far lower. Unfortunately none of these trees showed any outstanding results, and so they were destroyed. But I have at the present time in my nursery six hybrid pear trees obtained from fertilizing the blossoms of a Ussurian pear tree with the pollen of a Beurré Diel. An experiment similar to the one referred to was conducted with the seeds of these hybrids.

In the autumn of 1901 about a dozen seeds—not fully ripe and still rather whitish, it should be noted—were taken from three hybrid fruits of a Ussurian pear tree that had been fertilized by pollen taken from a basket specimen of a Beurré Diel pear tree, and were planted in a box in the open air. The other four fruits were kept until January and the seeds taken from them were planted in the same box only in spring. After sprouting, the seedlings were lined out in beds. No sharp difference was noted either as regards the loss of shoots or the development of seedlings from the two plantings, but later when the trees bore fruit the difference did not fail to manifest itself in a somewhat original manner, namely, the trees of the second, spring, planting in which the dried seeds had been used, started fruit hearing in 1910, and also in 1911 and 1912, whereas the trees of the first, i.e., autumn, planting in which fresh, undried seeds had been used began fruit bearing only in 1913, but the quality of the fruits of the trees that grew from the dry seeds was incomparably worse. In the first place, they all proved to be early-summer ripening fruits, unfit to store for winter, and as regards taste they were very viscous, a characteristic of the Ussurian pear, although in size they were four limes as large as the fruits of the maternal tree. Then altogether inexplicable was the fact that all these trees of the second, spring, planting were less hardy to our climate and especially to the scorching of the stem's bark by the sun. In contrast, three trees of the first, autumn, planting, when fresh seeds were used, yielded, firstly, late-ripening fruit capable of keeping in winter storage until the end of December, a great advantage for new varieties in orchards of our localities in Central Russia, and, secondly, the fruits have an excellent flavour and a flesh that is without granulation and melts in one's mouth. Moreover, the trees themselves are noteworthy for complete hardiness to the climate of our locality, and of all our pear-tree varieties they are the only ones the bark of which does not suffer from sun-scorch.

The greater hardiness of these trees was perhaps due also to the influence of the seeds freezing before germination, but, unfortunately, I was unable to test the correctness of this supposition, or, to be more exact, I could find no method for accurately testing this influence.

Exactly the same experiments were conducted with cherries and the results were also exactly the same. In general, many experiments were conducted along this line but to describe them would be a repetition of practically one and the same thing, and would only uselessly stretch this article. From the experiments cited here we can see clearly, firstly, that excessive drying of seeds of cultivated fruit plants, even if only for a few months, may in the future bring irreparable harm to plants grown from such seeds. Secondly, these experiments also show that in hybridization, when new fruit-plant varieties are bred from seeds, even overdrying, which may at first sight appear to be such an insignificant impairment, has an enormous influence on the hybrid seedling's inclination towards one of the parent plants. Thus, in the first example cited above the hybrid seedlings grown from overdried seeds almost wholly inclined towards the Kitaika, and in; the second example cited, the hybrid seedlings of the pear tree also grown from seeds that had been dried during the winter, inclined towards the wild Ussurian pear tree, whereas the seedlings grown from the seeds that were planted in the autumn, directly after they had been taken out of the fruits, all without exception inclined towards the Beurré Diel, the cultivated parent variety.

The experiments I conducted along these lines, I reiterate once more, were repeated by me several times, and always with the same results.

I presume that the fact that the seeds' dryness alone was enough, as shown by me, to incline the hybrids towards the qualities of one of the parents, along with the many other facts of a negative character as regards the applicability of the Mendelian law to hybridization, will bring Mendel's followers somewhat to reason. Of late, our neophytes in the field of hybridization have tried particularly importunately to foist that pea law—the creation of the Austrian monk—upon us and, what hurts most is that they do not cease their efforts even though this law has been utterly condemned by our Professor M. V. Rytov, who is deserving of respect and whose personal experience certainly makes him highly competent in the realm of hybridization. In Progressivnoye Sadovodstvo i Ogorodnichestvo, issue No. 2 for 1914, he called Mendelism outright "a sorry and miserable creation." Is this not enough for you, gentlemen? Will you nevertheless keep on bothering with this pea law and ignore the word of such a Russian authority as Mr. Rytov? That will be absolutely unreasonable. Of course, such endeavours on the part of our admirers of every foreign nonsense can have no importance whatever for Mr. Rytov, nor will they mislead other people with practical experience of their own, but what colossal harm does such an attitude inflict on young Russian horticulturists who are only beginners, still inexperienced, and are not yet able properly to appraise the works of various authors because they know absolutely nothing about them. These people do not know that Professor Rytov, besides being an instructor in the Goretsky Agricultural School, has worked almost all his life in the field of fruit and vegetable growing and produced a mass of printed works dealing with these spheres of agriculture, whereas Mendel's experiments in hybridization concerned peas exclusively and represent only the notes of a Catholic monk, long since dead, notes that were dug up in the monastery's archives and recently made public by Tschermark, an Austrian professor, and by other foreign scientists. In the spring of 1913 an experimental station called "Mendeleum" was opened in Austria where the Mendelian laws are being studied.

The results of these studies will only be made known in the future, but it is doubtful if the information to be furnished will be truthful.

Judging from my observations I find that Mendel's conclusions are not applicable to the hybridization of fruit trees and berry bushes. As irrefutable proof of this I shall try shortly to describe experiments in crossing cultivated apple varieties with the Niedzwetzkyana apple, which possesses the peculiarity that its leaves, shoots and bark, blossoms and the entire flesh of the fruit have a bright red colour. This property of one of the parent plants has provided an opportunity, unprecedented in the hybridization of fruit trees, for tracing more accurately and in a relatively short time the hereditary transmission to the hybrids of the properties of both parent plants.

I beg pardon for the digression, and I now return to the main theme of the article, i.e., seeds and their preservation.

1Stratification has its negative aspects: an insufficiently free access of air, frequent appearance of mould on the seeds, etc.
*1/4 arshin = 7 inches

From my observations during nearly forty years of work in breeding from seeds new varieties of apple trees and berry bushes, I am fully convinced that seeds of apples, pears, cherries, plums, raspberries, blackberries, currants, strawberries, etc., always lose their good qualities depending upon the length of time they are kept before being planted, even though conditions of storage are the most favourable, not excluding the best stratification1 arrangements. In all cases where seeds cannot be planted shortly after they ripen, the best results are obtained by planting them in autumn with the advent of cold weather. Wherever possible this method should be given preference. Whenever it is impossible to plant in autumn, the best way to preserve the seeds is, of course, by stratification, which consists of the following: the seeds are mixed with or are deposited in layers between slightly moistened river sand previously well washed and tempered in a hot oven. This mixture is placed in a new unenameled earthenware vessel that has been well soaked in boiled water, such as large low pots with narrow necks, or, when the quantity of seeds is small, ordinary flower pots. A hole should be made in the bottom of such a vessel to allow for water that might accidentally get into it to drain. This hole should be covered by a piece of crock, which should be placed inside the pot with the convex side up. Then, after arranging the seeds in the pot in layers with sand in between, or simply mixing the seeds with sand and pouring it into the pot, the latter should be covered with a saucer, of the same kind of material of a somewhat larger diameter than that of the pot's neck, which should without fail be placed upside down. Such a cover fully protects the seeds from injury by mice and, at the same time, effectively prevents water from getting into it. It is best to bury such a vessel with seeds outdoors in the garden to a depth of not more than a quarter of an arshin* above the pot, but it should positively be on a rather high spot where water cannot accumulate during winter thaws or spring floods. The amount of sand to be taken in such a case is no less than three times the quantity of the seeds. For large seeds as, for example, plums and nuts, somewhat more sand should be taken, and for small seeds proportionally less. The moistness of the sand should be uniform and not excessive. A wide and low vessel is preferable to a high and narrow one because seeds have to have free access of air, the oxygen of which is essential for the life of every seed. Seeds that are preserved dry, must not, therefore, be placed in hermetically-sealed vessels such as jars with ground-in stoppers. In such cases it is best to tie a not very compact piece of material around the glass dish containing the seeds. The amount of moisture contained in the air surrounding the seeds that are preserved dry also plays a big part. The very dry air of dwelling rooms, especially those heated by coal or ovens is as harmful to seeds as the air of damp cellars. Seeds keep best in premises that are not heated and not damp. If seeds have to be kept in dwelling rooms they should be kept away from stoves and damp corners. As regards the usual open-air temperature in our locality, whether in slimmer or in winter, dry seeds, i.e., those in a state of dormancy, will not be harmed by them, even at the limits of their fluctuation from +40°R. to -40°R.

The seeds of most fruit plants may be injured by frost only in the following cases: firstly, when they have not yet ripened and contain the excessive moisture of substances that have not completed their process; secondly, when seeds get into an environment where there is just enough moisture and heat for the seeds to germinate, and as a result the process of germination starts, so that frosts which have set in may injure the seeds; and, thirdly, when planted seeds are subjected to excessive and prolonged dampness. In such cases even when there is not enough heat for the process of germination, the seeds may, so to speak, mechanically absorb moisture and swell, and later with the advent of frosts perish in consequence of the rupture of all tissue due to the expansion of the parts that have water frozen in them. That is why many fruit growers willy-nilly prefer stratification for the winter.

In conclusion, I consider it useful to refer to experiments undertaken by foreign scientists involving resistance by dry seeds to the lowest temperatures. These experiments were formerly conducted by such scientists as Romanes, de Candolle, Pictet and others. They subjected seeds to severe cold, to confinement in vacuum tubes and to the action of various gases or steam. Then followed tests with liquid air which produced temperatures of -183° to -192°R.

Brown and Escombe ascertained in Dewar's laboratory that the vitality of the seeds of various plants, as, for example, Umbelliferae and other grasses, is not lost even after being exposed to such a low temperature for as long as 110 hours. After Dewar discovered liquid hydrogen it became possible to obtain a temperature of -250°, which is close to the so-called absolute zero temperature, below which cooling is no longer possible. Next on the program was to test the vitality of the germ of a seed in the extraordinary cold of liquid hydrogen. For this test seeds of the following plants were selected: wheat, barley, mustard, pea, pumpkin and others, and only such as could germinate. The first test consisted in subjecting some of the seeds to freezing for a half hour until the temperature of liquid hydrogen was reached. After first wrapping the seeds in tinfoil Professor Dewar placed them in a glass tube which he cooled first in liquid air and then in. liquid hydrogen, i.e., in a temperature of ‑250°.

When the director of Kew Gardens later planted these seeds in the usual manner, the shoots were normal. A more difficult test was conducted with five other kinds of seeds, which had lain in liquid hydrogen a full six hours without being in any way protected so that they could absorb this incredibly cold liquid.

Dewar, who sent them to Kew Gardens, assumed that these seeds certainly would perish, if cold kills them at all. Yet they sprouted splendidly. It follows from these facts that the state of the protoplasm which is called life cannot be disturbed by cold. Lord Lister considers this discovery to be a fact of extraordinary importance for the comprehension of life in general and its manifold manifestations in particular.

Is this really the case? For my part I am unable to confirm it. But one cannot help regretting a great shortcoming in all of these tests, namely, that we have been left in ignorance of the influence of such temperatures on the quality of the plants grown from seeds that were subjected to these tests. Although we, fruit growers and especially originators of new varieties of fruit plants, cannot in our practical work meet with such low temperatures, nevertheless it would be interesting to know what influence this maximum cold exerts on the qualities of the seeds and the seedlings obtained from them. The fact that the life of the seeds was preserved cannot serve as evidence that the seeds have not suffered the loss of some of their other properties.