Life movements in plants / by Sir Jagadis Chunder Bose.
- Jagadish Chandra Bose
- Date:
- 1923
Licence: In copyright
Credit: Life movements in plants / by Sir Jagadis Chunder Bose. Source: Wellcome Collection.
47/332 page 621
Licence: In copyright
Credit: Life movements in plants / by Sir Jagadis Chunder Bose. Source: Wellcome Collection.
![ANGLE OF INCLINATION AND GEO-ELBCTR] C EXCITATION G21 A and B and the resulting electric response disappear on the return ol the specimen to the vertical or zero position. The specimen is next inclined to -90°; A now becomes the under, and B the upper and the excited side (left hand figure), The electro-motive change now undergoes a reversal, Id becoming galvanometrically negative. The induced electromotive variation thus obtained is of consider- able intensity, often exceeding 15 millivolts. We shall now describe the experimental results on the relation between the angle of inclination and the resulting geo-electric excitation. Excitatory Reaction at 45° and 90°.—In this investigation the first difficulty encountered is the accurate determination of the angle of inclination. An index is attached to the plant, and a stationary circular scale enables us to find the angle through which the plant is in- clined to the vertical. But the vertical or zero reading itself is subject to an error of a few degrees; this is accen- tuated by the fact that we have no means of knowing whether the perceptive layer inside the plant is exactly parrallel to the surface of the stem or the petiole. The only means of eliminating the error is by obtaining two responses, say at + 45° and - 45°, by the Method of Reversal; in the first the index reading is + 45° subject to the correc- tion E, which is the error of the setting of the index. Now this error will make the actual angle 45°+ E and 45° - E in the two readings for inclinations to the right and the left, i.e., the angle will be greater in one case and correspondingly smaller in the other. Hence the mean of the two responses obtained through successive positive and negative inclina- tions of the specimen will reduce or eliminate not only this error, but also that due to the physiological asymmetry. I give below a series of galvanometric responses of the petiole of Tropaeolum, when carried through Experiment 235 ,v * the entire cycle ol inclination from the vertical to + 45° (as read by the movement of the index), back to zero,](https://iiif.wellcomecollection.org/image/b29818709_0047.jp2/full/800%2C/0/default.jpg)
