. How crops grow. A treatise on the chemical composition, structure, and life of the plant, for all students of agriculture ... Agricultural chemistry; Growth (Plants). 248 HOW CEOPS GEOW. latter, in forcing their way against considerable pressure, often expand around, and partially envelope, the particles of earth. Imbibition of Water by the Root.—The degree of force with which active roots imbibe the water of the soil is very great, is, in fact, sufficient to force the liquid upward into the stem and to exert a con- tinual pressure on all parts of the j)lant. When the stem of a plant in vigo
. How crops grow. A treatise on the chemical composition, structure, and life of the plant, for all students of agriculture ... Agricultural chemistry; Growth (Plants). 248 HOW CEOPS GEOW. latter, in forcing their way against considerable pressure, often expand around, and partially envelope, the particles of earth. Imbibition of Water by the Root.—The degree of force with which active roots imbibe the water of the soil is very great, is, in fact, sufficient to force the liquid upward into the stem and to exert a con- tinual pressure on all parts of the j)lant. When the stem of a plant in vigorous growth is cut oiF near the root, and a pressure-gauge is attached to it as in fig. 43, we have the means of observing and measuring the force with which the roots absorb water. The pres- sure-gauge contains a quantity of mercury in the middle reservoir, b, and the tube, c. It is attached to the stem of the plant, p, by a stout india-rubber pipe, g-.* For accurate measurements the space, a and 5, should be filled with wa- ter. Thus arranged, it is foimd that water will enter a through the stem, and the mercury will rise in the tube, e, until its pres- sure becomes sufficient to balance the absorptive power of the roots. Hales, who first ex- perimented in this manner 140 years ago, found in one instance, that the pressure exerted on a gauge attached in spring-time to the stump of a grape vine, supported a column of mercury 32^ inches high, which is equal to a column of water of 36^ ft. Hofmeister obtained on other plants, rooted in pots, the following results: ? For experimenting on small plants, a simple tnbe of glass may be adjusted to the stump vertically by help of a rubber Tig. 43. Digitized by Microsoft®. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Johnson, Samuel William, 1830-19
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Keywords: ., bookcentury1800, bookdecade1860, booksubjectagricul, bookyear1868
