Life movements in plants / by Sir Jagadis Chunder Bose.

  • Jagadish Chandra Bose
Date:
1923
Catalogue details

Licence: In copyright

Credit: Life movements in plants / by Sir Jagadis Chunder Bose. Source: Wellcome Collection.

    299/332 page 873
    GENERAL RFVTEW S ? | > temperature and of increasing light, the effect of tem- perature being predominant. The leaf thus continues to fall till thermal noon, which is about *2 p.m. The diurnal curves of the petioles of Cassia alata and of Helianthus annuus are similar to that of Mimosa (p. 597). GEOTROPISM. Mechanical response.—The stimulus of gravity is shown to induce an excitatory reaction similar to that under other forms of stimulation. The upper side of the horizon- tally laid shoot is directly stimulated and undergoes contrac- tion (p. 440). Electric response.—The excitatory reaction of the upper side is exhibited by an induced change of galvano- metric negativity. The lower side shows a change of galvanometric positivity indicative of increase of turgor and enhancement of the rate of growth (p. 447). The method of geo-electric response is more sensitive in the detection and quantitative determination of the effect of stimulus of gravity than the method of mechanical response. Explanations of opposite reactions at different sides of the organ.—The geotropic up-curvature is only possible by differential reaction at opposite sides of the organ ; this is demonstrated by the results of electric investigations which show that the upper side exhibits contraction, while the lower undergoes expansion. It is further shown that this difference in the reaction is due to the fact that the stimulus is direct at the upper and indirect at the lower side (p. 610). Geotropic excitations at various angles.-—The excita- tion is found to increase as the sine of the angle of inclina- tion. This relation is only approximate, for the excitation is relatively greater at larger angles than the value deduced from the law of sines (p. 625) The critical angle for immediate geotropic excitation.- The excitation at lower angles is disproportionately less; the
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