CONDITIONS GOVERNING GERMINATION.

Otago Witness, Issue 3084, 23 April 1913, Page 14

CONDITIONS GOVERNING GERMINATION.

Some seeds, like the finer grasses, having very delicate rootlets, require better conditions of growth than others, but the principle is the same with all — the seedbed must be worked fine, and be dry and crumbly when the seed is sown. The object of autumn and winter work is to provide the required conditions—viz., a supply of warmth, moisture, and air to the soil, and the farmers’s work will be followed by gratifying crops in proportion to the completeness with which these necessary conditions have been fulfilled. It need hardly be said that germination can only take place in the case of living seeds placed under proper conditions, and care should be exercised to see that a healthy, plump seed is utilised, endowed with vigorous embryo, and richly stored with well-ripened food material. Of the conditions necessary for germination, soil warmth may be largely by thorough drainage and cultivation. Seeds will only germinate within certain welldefined limits of temperature. In the case of wheat and barley, this ranges from 41deg F. to lOOdeg F. The rapidity of germination increases up to about 80dog, and declines again till lOOdeg is reached, at which point germination is again stopped entirely. The minimum, 41deg, is not a low temperature in the shade 6in below the surface, and this fact is one which deserves serious consideration at the hands of practical men. Farmers arrange their sowings, for instance, with the knowledge that the seeds of turnips and mangolds make very little progress if thev are sown before the land gets warmed up with the spring snn and after thorough cultivation. With regard to moisture, when the seeds are moistsened with water the shell, begins to absorb moisture, and becomes soft, and the moisture eventually reaches the embryo inside the seed coats. In some cases the latter offers considerable resistance to the passage of water through it; in others the shell becomes a soft gelantinous mass in a few hours; but it is only when the embryo has absorbed sufficient water to get some of its food constituents dissolved that growth can begin. The amount of moisture required by the seed is really very small. After the husk is penetrated very little is wanted to complete the process of germination. A uniformly damp and porous seedbed, however, and the prevention of any serious less of moisture during germination must be aimed at. The supply of moisture should be maintained until the plant is established at least. Artificial means, such as steeping in water, or dipping in boiling water, or even in some strong acid—afterwards washed off,—are sometimes utilised to shorten the germination process ; but this is unnecessary with most farm seeds. The next indispensable faetor in the germination of seed is the presence of air. When germination begins the food material within the seed begins to change. - Some of the charcoal or carbon in the food reserve begins to burn, with the assistance of the oxygen which has been absorbed from the air. Warmth and the giving off of carbonic acid are the outward results, while the food of the seedling is made liquid, and ready for immediate use. Without air the process cannot begin or be continued. Plants also take up some of the oxygen they require from the air by means of their roots, and the maintenance of a good supply of fresh air is necessary for the life and work of a root. Good cultivation, and particuarly autumn cultivation, has for one of its chief objects the aeration of the soil. Mr A. H. Hall states the case thus:—“We may conclude that germination is a process of breathing or burning, in which some of the seed material combines with the oxygen of the air to produce carbon dioxide and water; only by this sort of burning does the infant plant get the energy to go on living and working. Indeed, even while the seed is dry, and apparently dormant, it is breathing very slowly, and so consuming parts of its substance; being dry, the embryo cannot draw upon the materials in the endosperm, but is confined to burning up any spare material it possesses within itself. Hence, seeds cannot live for ever; they vary very greatly in their powers of endurance, both with the kind of seed and the way they are stored, but very' few of the ordinary' farm and garden seeds remain alive after 10 years.” But long before death the vigour of seed becomes greatly weakened by age. The produce of old seed is generally less robust than that resulting from seed recently harvested. Generally speaking, if the needful conditions are ensured, and sound, plump seed chosen, the result will be a successful yield of plantlets.