. Botany; principles and problems. Botany. Fig. 80.—Geotropism. Four kernels of corn which have germinated in different positions. The young root in every case has grown downward and the young shoot upward. Most leaves tend to take up their position at right angles to the force of gravity and many lateral roots also grow in an approxi- mately horizontal direction. Such organs are said to be diageo- tropic. The advantage of these specific tropisms to the plant is obvious. Plants differ considerably in their inherited adaptations to the influence of gravity. Stems of prostrate plants have lost t
. Botany; principles and problems. Botany. Fig. 80.—Geotropism. Four kernels of corn which have germinated in different positions. The young root in every case has grown downward and the young shoot upward. Most leaves tend to take up their position at right angles to the force of gravity and many lateral roots also grow in an approxi- mately horizontal direction. Such organs are said to be diageo- tropic. The advantage of these specific tropisms to the plant is obvious. Plants differ considerably in their inherited adaptations to the influence of gravity. Stems of prostrate plants have lost their negative geotropism and may even develop into rootstocks or tubers which react toward gravity like roots. The responses of flowers and fruits to this stimulus are also very diverse and for the most part seem to be advantageous to the plant. The mechanism of stimulus and response has been more care- fully studied in the case of geotropism than with other environ- mental factors. If very young seedlings in which the'root and stem are just appearing are fixed in any position whatever, the young root will invariably grow downward and the young stem upward (Fig. 80). By attaching such seedlings to a disc and revolving it rapidly, centrifugal force may be developed which is greater than gravity, and in such a case the young plants orient. 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 Sinnott, Edmund Ware, 1888-. New York, McGraw-Hill
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Keywords: ., bookcentury1900, bookdecade1920, booksubjectbotany, bookyear1923
