. Science of plant life, a high school botany treating of the plant and its relation to the environment. Botany. The Structures and Processes of Roots 177 Root pressure. If a number of well-watered plants are cut off just above the soil, some of them will exude water for a day or two. Experiments have shown that the sap may in some cases be forced out with pres- sure sufficient to raise water 30 or 40 feet. This , pressure is called root pressure. When such pressures exist in plants, they probably aid in the Hfting of water in stems. Under these cir- cumstances transpiration pulls on the colum
. Science of plant life, a high school botany treating of the plant and its relation to the environment. Botany. The Structures and Processes of Roots 177 Root pressure. If a number of well-watered plants are cut off just above the soil, some of them will exude water for a day or two. Experiments have shown that the sap may in some cases be forced out with pres- sure sufficient to raise water 30 or 40 feet. This , pressure is called root pressure. When such pressures exist in plants, they probably aid in the Hfting of water in stems. Under these cir- cumstances transpiration pulls on the columns of water in the water-conducting vessels from the top, and root pressure pushes on them from below. Extensive experiments have shown, how- ever, that root pressure is inter- -->---r - - " mittent. It may exist at one f"' '°?- A plant with its stem cut m â¢' two and connected again with a tube time and not at another, and similar to that shown in Figure 102. when transpiration is most active ^ "^^ <= p'^°'- ^^ =^'- ting the plant in bright sunsliine, the pressure is Wantmg entirely, transpiration may be increased. The Because of all these facts, it is mercury is then almost immediately â â -IT jiii i drawn toward the plant. generally believed that root pressure is not a necessary factor in the raising of water in stems. Imbibition and osmosis lead to the development of root pressure, and they are partly responsible for the flow of maple sap (page 135). Grapevines pruned in the spring exude. 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 Transeau, Edgar Nelson, 1875-1960. Yonkers-on-Hudson, N. Y. , World Book Co.
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Keywords: ., bookcentury1900, bookdecade1920, booksubjectbotany, bookyear1921
