. Elementary principles of agriculture; a text book for the common schools. 48 Elementary Principles of Agriculture They also take in some of the substances that are dis-solved in the soil moisture. Root-hairs give off carbonicacid gas and possibly other acids, which help to dissolvesome substances in the soil. This may be easily demon-strated by allowing roots to grow on a poUshed marbleslab. 77. The Amount of Root Growth is large. A plantmust have a large root surface to absorb enough waterto make up for the loss from a large leaf surface. A largeleaf surface is, of course, beneficial, becau
. Elementary principles of agriculture; a text book for the common schools. 48 Elementary Principles of Agriculture They also take in some of the substances that are dis-solved in the soil moisture. Root-hairs give off carbonicacid gas and possibly other acids, which help to dissolvesome substances in the soil. This may be easily demon-strated by allowing roots to grow on a poUshed marbleslab. 77. The Amount of Root Growth is large. A plantmust have a large root surface to absorb enough waterto make up for the loss from a large leaf surface. A largeleaf surface is, of course, beneficial, because it means somuch more surface for absorbing the carbon dioxid andenergy from the suns rays. There must, however, be abalance between the activities of the root surface andthe leaf surface. 78. The Distribution of Roots in the soil varies withthe kind and condition of the soil, but, roughly, the. Fig. 31. When trees are dug up. the large roots are found spreading in thefirst few feet of soil. These roots had a spread of forty teet. The Plant as Related to the Soil 49 roots are said to spread through an area equal to thatshaded by the branches. Only in exceptional conditionsdo the roots extend very deeply into the soil. Even inforest trees, the most vigorous roots are found in thefirst foot or two of soil. In young trees, the tap-rootis often noticed to grow directly down for some distance,but, when the trees are old, the side roots will be foundto be many times larger. (See Fig. 31.) 79. The Total Length of the Roots is very great. Hell-riegel* noted that a vigorous barley plant in a rich porousgarden soil had one hundred and twenty-eight feet ofroots, while another growing in coarse-grained, compactsoil had only eighty feet of roots. One-fortieth of a cubicfoot sufficed for these roots. It may be readily under-stood that all the soil was occupied. Professor Clark,after making
Size: 1634px × 1530px
Photo credit: © The Reading Room / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookdecade1910, booksubjectagriculture, bookyear
