. A compendium of general botany. Plants. 262 GOMPENDIVM OF GENERAL BOTANY. Tissue-tension may be mentioned as the first result of unequal growth. («) Tissue-tension. To illustrate this phenomenon a longitudinal section may be cut from the middle portion of a growing stem or petiole (Z in Fig. 170, a). A vertical surface view of this section is shown in h and c. The medulla m and cortex r do not cease to grow at tlie same time as the woody tissue h. In the uninjured organ this difference must produce tensions; the woody elements are passively elongated and continually strive to contract; the c
. A compendium of general botany. Plants. 262 GOMPENDIVM OF GENERAL BOTANY. Tissue-tension may be mentioned as the first result of unequal growth. («) Tissue-tension. To illustrate this phenomenon a longitudinal section may be cut from the middle portion of a growing stem or petiole (Z in Fig. 170, a). A vertical surface view of this section is shown in h and c. The medulla m and cortex r do not cease to grow at tlie same time as the woody tissue h. In the uninjured organ this difference must produce tensions; the woody elements are passively elongated and continually strive to contract; the cortical and med- ullary cells are hindered in their growth, are compressed, and con- tinually strive to r A 771 A T f—^ r h m h r Fig. 170. Isolating the individual parts of the section verifies the above statement by the shortening or elongating of the various elements. For the same reason the bisected organ curves outward. The medulla elongates more than the cortex (c). Increasing the turgor by placing the section in water will further increase the curvature. Corresponding phenomena may be observed in transverse sections. From what has just been stated it follows that tissue-tensions are produced by a decrease and increase in the turgor' as well as by unequal growth. The following remarks will have a bearing upon tissue-tension due to turgor. The form of the cells and their ex- pansibility in different directions influences the phenomenon of ten- sion in a high degree. In those roots which become shortened in the turgescent state and elongated in the wilted state, we must • According to N. J. C. Muller, a hydrostatic pressure of 13i atmospheres can be demonstrated in the medull;iry cells oi Helianthus ; according to Am- BRONN, 9-12 atmospheres in petioles of 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
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectplants, bookyear1896
