GRAIN HEADS AS CHEMICAL RESERVOIRS.

Globe, Volume XXIV, Issue 2692, 23 November 1882, Page 4

GRAIN HEADS AS CHEMICAL RESERVOIRS.

Mon. Isidore Pierre has established some ■valuable facts regarding the growth and maturing of grain and the manner of distribution of various chemical constituents through the grain plant during its progressive development. In the younger period of plant life thoi'e is a general con■dition of succulence, during which the various chemical foods taken up by the roots nitrogen compounds, phosphoric acid compounds, starch, gum, vegetable acids, &e. —are hold in solution by the water of the cells, and are pretty evenly distributed through the plant. That is, a chemical analysis of any two parts, as stem and ears of grain, would show about the same elements in each and similarly proportioned. But as ripening of the grain begins this order of things suffers change As water holding the compounds in solution is diffused through the plant some of it necessarily permeates the tissues of the young grain, and it is in these tissues that, owing to some cause of which we are yet in ignorance, the chemical substances are rendered insoluble, and are deposited as solid matter, chiefly as -starch and gluten, in the young but rapidly growing grain. The water in the grain, being thus deprived of its dissolved matter, becomes a much weaker solution than is constituted by the other water in the plant, water farther removed from the grain, but nevertheless in contact, directly or indirectly, with that in the grain ; and the tendency will he for tills weaker solution to draw material continually from the stronger solutions of the other parts, which material is in turn deposited in the grain. Thus a continual movement of plant food towards the grain takes place. It will he noticed that this process does not involve any absolute movement of the water in the plant, but only of the substances which are soluble in the water. We have in fact a solution which is continually getting weak at certain points, mid as the nature of a solution is to pre serve its uniformity, there is necessarily a continuous movement of the dissolved matter in the direction of those places where the soluble compounds as such disappear. This process of ripening of the grain, then, is of an essentially different character from that involved in the usual transfer of material from one part of the plant to another, as from root to leaf, or from one leaf to another; the former is. in fact, a movement of soluble materials through the water to a place where they get precipitated, the latter is a bodily movement of the entire solution. It follows, therefore, that the process of ripening of grain may take place even when the plant is severed from its roots, and this inference is justified by the practice, sometimes adopted, of harvesting grain crops before they are ripe and allowing maturation to complete itself after cutting. The longer and better the straw of such prematurely cut grain the better will the Reads ripen, but in all such kernels may be expected to be more or less crinkled, not so plump, and not so heavy per bushel as those normally ripened in fine weather.

Many proofs of the upward migration of the proximate principles during the process of ripening have been afforded by the results of analysis. An examination of the stems and leaves of wheat, barley, oats, and rye, after the ripening of the fruit, reveals the fact that the proximate principles have practically disappeared. Analyses of the straw prove that the soluble nitrogenous matters are present in only •very small quantities, that the starchy and sugary substances have disappeared, and that the phosphatic salts, particularly 4hose containing potash, have likewise gone. In one experiment the ash of the waving stalk and ear gave forty-nine per cent, of potash, while the fifth leaf below the ear gave in its ash only twelve per cent., and yet all the potash of the ear comes from the soil and must pass through the entire plant. The relative weights of straw and grain at different dates likewise afford confirmatory facts; in one instance a certain quantity of com cut on July 6th weighed when fresh 15371 b, and of this the grain was found to weigh 7551 b, or nearly one-half; whereas, on July 25th, a weight of 27351 b of freshly cut corn yielded 20701 b ■of grain, which is nearly three-quarters of ■the entire weight. M. Isidore Pierre has established the fact that during the last month preceding maturation the stems and leaves of the wheat plant lose to the ears at least two-thirds of their nitrogen. As is well known, in harvesting cereals it is by no means necessary to wait till the grain is completely ripe—indeed, all the changes which grain undergoes in its passage from the ripe to tho dead ripe stage are for the worse. The cutting should always be commenced in good time, provided the weather is favorable ; the sheafs in stack will finish the ripening of the ■grain just as well as though they were still attached to the soil. It has been thought that somewhat premature cutting, even •though it might not in the slightest degree affect the maturation of the grain, might nevertheless enfeeble the germinating ■power of seed grain, but this fear is quite baseless, inasmuch as the perfection of the germinative faculty of the grain invariably precedes its maturation as a fruit and seed.