. A text-book of plant physiology. Plant physiology. 210 PLANT PHYSIOLOGY cell into soluble, portable, and useable compounds (see pp. 29-30). If the work of the enzyms is interfered with by light, the functions of the cell must be altered or become deranged. The substances composing the living protoplasm may also be as sensitive to light as its products. The sensi- tiveness to light of the com- pounds in and perhaps compos- ing their cells is the reason for the sensitiveness of living organ- isms to light. The influence of light, like the influence of gravity, may show itself in the kind, rate
. A text-book of plant physiology. Plant physiology. 210 PLANT PHYSIOLOGY cell into soluble, portable, and useable compounds (see pp. 29-30). If the work of the enzyms is interfered with by light, the functions of the cell must be altered or become deranged. The substances composing the living protoplasm may also be as sensitive to light as its products. The sensi- tiveness to light of the com- pounds in and perhaps compos- ing their cells is the reason for the sensitiveness of living organ- isms to light. The influence of light, like the influence of gravity, may show itself in the kind, rate, and direc- tion of growth, and in the posi- tion of the organ and organism. Plants kept in darkness will be longer than plants under nor- mal illumination. Seeds sprouted in darkness, and seedlings grow- ing where no light falls upon them, grow under the influences of all other forces than light. When the influence of light is wholly eliminated, root, stems, and branches grow longer but are proportionally more slender than in ordinary sunlight, the leaves are smaller and weaker, flowers do not form (see pp. 271-4). That stems are more slender and mechanically weak- er in darkness than in light may be due to the less than nor- mal weight of the small weak leaves—to the absence of me- chanical strain (see p. 188). The leaves require a certain amount of light in order properly to develop the food- manufacturing tissues. Tet, comparing the total growth of plants of the same species in light and in darkness, it will be clear that the growth is greater in darkness so long as. Figure 15. Branch of Cactus, the young parts of which grew in darkness. (From Goebel.). 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 Peirce, George James, 1868-1954. New York, H. Holt
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