. Plants and their ways in South Africa. Botany; Botany. Plants and their IVavs in Soiitli Africa Of the great root system of trees, only the tips are absorbing food material. As they push forward, the tips are protected by a short-lived cap of tissue, which is constantly being renewed as it is worn off. Water and solutes (mineral substances dissolved in water) enter the root by osmosis ^ and diffusion, and pass into the bundles of long slender tubes (vascular bundles), that continue from the root through the stem to the very tips of the leaves. The tubes are not continuous throughout the leng
. Plants and their ways in South Africa. Botany; Botany. Plants and their IVavs in Soiitli Africa Of the great root system of trees, only the tips are absorbing food material. As they push forward, the tips are protected by a short-lived cap of tissue, which is constantly being renewed as it is worn off. Water and solutes (mineral substances dissolved in water) enter the root by osmosis ^ and diffusion, and pass into the bundles of long slender tubes (vascular bundles), that continue from the root through the stem to the very tips of the leaves. The tubes are not continuous throughout the length of the plant but the con- tents pass from one tube to another adjacent one. Water is required for food material, some is retained within the cells, the cell walls are per- meated with it and part of the water taken in passes out through the leaves and stem into the air: The escape of water is called tran- spiration. Cell sap contains sugar and acidsj These cause the inflow of water by osmosis. The water constantly passes from cells with less dense to those with more dense osmotic substances. If transpiration hastens the upward ascent of water the solutes are not necessarily hastened since they obey different condi- tions.'- Solutes pass from cells having a greater to those having a less concentration of solutes. The water, in its long journey, must not be dried up, and to guard against this, under the thin outer dress of stems and ' See p. 57. 2 In a tobacco field Hasselbring (" Bot. ; Jan. 1914) found that plants which absorbed and transpired the most water contained a smaller percentage and quantity of Fig. 36. — C, central cylinder, consisting of pith, vascular bundles, and pericycle ; R, corte.\: : E, piliferous layer; II-', root-cap. (From Edmonds and Marloth's " lilemen- tary Botany for .South Africa ".). Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloratio
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectbotany, bookyear1915
