Page:Life Movements in Plants.djvu/223
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TURGOR AND TENSION ON GROWTH
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the leaf of Mimosa and the movement due to growth, which is summarized as follows:—
(1) An increase or positive variation of turgor induces an erection or positive response of the leaf of Mimosa, and a positive variation or enhancement of the rate of growth.
(2) A diminution or negative variation of turgor induces a fall or negative response of the leaf of Mimosa, and a negative variation or retardation of the rate of growth.
EFFECT OF EXTERNAL TENSION.
Experiment 73.—The recording levers are at first so balanced that very little tension is exerted on the plant. Record of normal growth is taken of a specimen of Crinum. The tension is gradually increased from one gram to ten grams. The table given above shows how growth-rate increases with the tension till a limit is reached, after which there is a retardation.
TABLE XV.—EFFECT OF TENSION ON GROWTH.
| Tension. | Rate of growth. |
100 (Normal) … … … … … … … … … … … … … … … … … … … … … … … … … … … … |
0.41 μ per second. |
104 grams … … … … … … … … … … … … … … … … … … … … … … … … … … … … |
0.44 μ per„ second.„ |
106 grams„ … … … … … … … … … … … … … … … … … … … … … … … … … … … … |
0.48 μ per„ second.„ |
108 grams„ … … … … … … … … … … … … … … … … … … … … … … … … … … … … |
0.52 μ per„ second.„ |
10 grams„ … … … … … … … … … … … … … … … … … … … … … … … … … … … … |
0.40 μ per„ second.„ |
SUMMARY.
Increase of turgor induced by irrigation enhances the rate of growth. Irrigation with warm water induces a further augmentation of the rate of growth.