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weight of water. It loses 1.5 per cent of its own weight in 24 hours, 6.7 per cent in 90 hours, and 11.8 per cent in 144 hours. Besides the loss in weight, marked chemical changes take place which greatly decrease its value for bread baking purposes, and probably also as a food for stock. Great loss may thus be occasioned by the sprouting of wheat in field, shock, stack or bin. Experiments indicate that sprouted wheat will regerminate and form healthy sprouts until the stem (plumule) has reached a length of 34-inch in the first germination, and an average of 80 per cent of all sprouted wheat with the length of the stem not exceeding 1/2-inch will again germinate.'
Stooling or Tillering.–Wheat, like other cereals, has the characteristic of throwing out side shoots after the plumule has appeared above the surface. These branches or culms may form at any node covered with soil. The number of such stalks from one seed varies much with conditions. There are usually at least six, but there may be from two to several dozen in extreme cases, 52 spikes having been observed. As a rule, the more favorable the conditions for plant growth, and the thinner the wheat is on the ground, the more it tillers. Cool weather during early development may result in a long period of subsequent growth h MA which encourages tillering. Time of seeding SA SA also has great influence, for late sown wheat may not have time to stool. The habit varies quite materially in different varieties. While thinner sown wheat may tiller more, a greater amount of seed per acre often increases the The
the A stool of wheat. yield, even though there are fewer stools. a single seed origi.
nally at a. Pliny is said to have declared that it was not --uncommon in northern Africa and in Italy to find from 200 to 400 stalks of wheat growing from a single kernel. Humboldt put on record that in Mexico each grain of wheat produced 40 to 70 stalks. It is probable that each of these men was seeing with the eyes of an enthusiast.
The Growth of a Wheat Plant is the aggregate result of the enlargement and multiplication of the cells which comprise it. · · Rept. N. D. Sta., 1901, p. 107.
The culms are from
Generally cells reach their full size in a brief time, and continuous growth depends mainly upon the constant and rapid formation of new cells. The essentials to growth are light, air, moisture, heat and food. In the absence of any one of these, the plant dies, and in their disproportionate combination, growth is sickly. In germination, food is furnished by the seed, and light is not essential. Over light man has no control. He can increase the amount of air that has access to the plant by loosening the soil around its roots. An adaptive control of heat is exercised by sowing during the warm season. By selecting soils, fertilizing and changing existing foods from unavailable to available forms, food can in a great measure be regulated, and water, acting as a solvent and vehicle, can be very largely regulated as to amount by drainage and irrigation. That the growth and multiplication of cells involves a migration of material within the plant has long been recognized. In wheat, as in many other plants, there is a comparatively large development of roots soon after the first leaves appear. Only some low-lying leaves are put forth while the great complex of roots is being formed. In a wheat plant only 23 days old, the roots had penetrated the soil over 1 foot in depth. When the system of roots has been formed, the stalk suddenly shoots up almost to mature stature. Perhaps the roots are completely developed by the time that the formation of grain has begun.
The leaves of the wheat plant, with their chlorophyl cells, have been considered as little laboratories elaborating vegetable matter. Under the influence of light they are able to extract carbonic acid from the atmosphere. This acid is one of the raw materials of these little factories. They decompose it, eliminate the oxygen, and from the residue they manufacture sugar, cellulose, straw-gum, vasculose, and all the ternary matters composed of carbon, oxygen and hydrogen. A perfect system of canals penetrates every part of the plant. These canals are filled with water, which enters at the roots, for leaves do not absorb water to any appreciable extent, and is in constant motion until it is exhaled from the leaves. During one hour of insolation a leaf of wheat exhales an amount of water equal to its own weight. Upon these highways of moving water are borne raw materials destined for the little cell factories, such as nitrates, phosphoric acid, potash and
matter, water sconsumpt. This best th
silica. They, too, are reduced. If there is an abundance of rain, the cells continue work long, elaborate much vegetable matter, and the plant grows.
If the water supply is insufficient and the soil parsimonious, this prodigious consumption cannot be supplied, and dessication of organs takes place. This begins in the oldest leaves, and nearly always the little leaves at the base of the stem become soft, fxabby, and withered. Analyses have been made which show that these leaves let escape some nitrogenized matter, phosphoric acid and potash, which they contained when living, green and turgescent. Thus the closing of one of these groups of little cell. factories by the dessication of a leaf is a very important process to the plant, for less vegetable matter is elaborated than if it had continued its work. In dry years a shortening of the stems and a comparatively small amount of straw results.
The dying of leaves involves not only the closing of these workshops, but the transportation of much of the finished product, stored in them. Metamorphosis of the nitrogenized matter which forms the protoplasm, the living part of the cell, takes place, and it assumes an itinerant property which enables it to pass through membranous walls and migrate over the liquid highways to new leaves. With it are carried phosphoric acid and potash. Some of the elaborated material is thus continually being transported from lower to upper leaves during the entire period of vegetation. Flowering takes place when enough material has been elaborated to nourish the appearing seeds. This migration of substance can take place only when there is plenty of water, and the crop fails when it is too dry. Too much water is also injurious, for it causes a tendency to keep up growth indefinitely." The Minnesota station found that the wheat plant produced nearly one-half its dry and three-fourths its mineral matter by the end of 50 days. This included 75 per cent of the potash, 80 per cent of the phosphoric acid, and 86 per cent of the nitrogen. At 65 days, 65 per cent of dry and 85 per cent of mineral matter had been produced, as well as most of the fiber, which suffered a loss after 81 days. Compared with the processes observed in nitrogenized matter, phosphorus and potash, the
"? Minn: Bul. :29. pp. 152-160.
formation of starch is yet quite a mystery. Its accumulation in the leaves cannot be detected in wheat as it can be in a large number of other species. Neither are reserves of saccharine matters to be found there. It is not until the last stage of vegetation that starch is formed. Consequently climatic influences at the close of the growing period have a marked effect on the amount of starch produced, and cause it to vary greatly from year to year. · The process of transporting elaborated material begins in the planted seed, and does not cease until the wheat is dead ripe. This is the explanation of wheat ripening after it is cut. It also explains the fact that wheat straw, as well as many other straws, is not as well liked by animals, and is not as nutritious, after it is ripe as when green, or when cut before ripe.
Fertilization.—The one-seeded ovulary is a little greenish swelling. It is surmounted by the stigmas, two erect and adjacent aigrettes of plumes. There are three stamens, and the anthers are compactly arranged about the ovulary. At flowering the filaments to which the anthers are attached elongate rapidly. As the anthers are pushed upward, they suddenly overturn, and the pollen falls upon the stigmas, which have
now grow slightly divergent. These delicate operations all take place within the closed flower and generally wheat is thus essentially self-fertilized. The anthers are now pushed outside of the glumes, and the wheat is popularly said to be in flower. As soon as the pollen comes in contact with the stigmas, it germinates by sending out a long tube (called the pollinic branch) into the ovulary. This completes fertilization and the grain is formed. If fertilization in incomplete, the ovularies remain unfertilized, and the spikes bear sterile flowers in which no kernels are formed. It seems that the crop is thus injured when fertilization takes place in rainy weather. The water probably finds its way within the involucre, and the pollen grains are either imperfectly retained, or their germination is irregular. The process of fertilization generally occurs early in the morning, and may require less than an hour of time. After its completion the ovule (seed) grows very rapidly to maturity. The embryo develops first, and then the endosperm.
The Most Favorable Ripening of wheat requires a mild temperature and a slightly clouded sky. A high temperature the month before wheat is ripe diminishes the yield, and in particular prevents the formation of starch. There is a real, though small, loss in wheat from the period when it is “ripe" to the time when it is dead ripe, and it is claimed that this loss does not result from careless handling, or from drying of the grain.'
Deherain offers the explanation that "all the organs of a plant respire by the aid of the oxygen of the air consuming some of their principles. In the seed the combustion chiefly affects the starch, and a crop which remains standing long diminishes in weight both by the loss of seeds that fall and by the slow combustion which continues as long as desiccation is not produced.” What is lost in quantity, however, is perhaps more than gained in quality, for the best flour can be obtained from dead ripe wheat only. Such flour has a better color, and will take more water in bread-making. If the grain is cut before ripe, the most serious feature is increased acidity in the flour. This interferes with fermentation in bread-making, and is liable to make the bread sour or dark.
The Rate of Multiplication of Wheat.-Paley gave 300 grains harvested from one grain sown as a moderate estimate; 400 as a possible one; and 10 to 12 as a practical one. Herodotus said that on the irrigated land of Assyria, wheat yielded from two to three hundred fold, and grew to giant size. Fifty grains of wheat, selected from one spike, were planted, and the 30 grains which grew produced 1434 ounces of wheat. This was sown the next year, and produced 5 pecks of grain, which in turn produced 45 bushels the subsequent year. The 45 bushels produced 537 bushels in another year, enough seed
1 Kedzie, Rept. Mich. Board Agr., 1881-2, p. 337: Mich. Bul. 191, p. 160; Neb. Bul. 32, p. 97.