Growth and tropic movements of plants / by Sir Jagadis Chunder Bose.

  • Jagadish Chandra Bose
Date:
1929
Catalogue details

Licence: In copyright

Credit: Growth and tropic movements of plants / by Sir Jagadis Chunder Bose. Source: Wellcome Collection.

    117/488 (page 81)
    ABNORMAL AND NORMAL RESPONSE gj under stimulation, the rate of growth of that particular specimen of Kysoor was feeble, being as low as o-3 n per second. As the activity of growth is an indication o a healthy tone, the enfeebled rate of growth was a sign 0 the subtonic condition of the plant. It thus appeared that, other things being the same, the abnormal positive is the characteristic response of the subtonic plant. In the parallel phenomenon of response of a pulvinated organ such as the leaf of Mimosa, I have shown (i) that when the tonic level of the pulvinus is below par, the response is abnormal positive, exhibited by the erectile movement of the leaf; and (2) that as a result of continuous stimulation the tonicity is raised to a condition of par. The response is now changed into normal negative as indicated by the fall of the leaf.1 In the responsive variation of growth, likewise, the abnormal positive response of the subtonic specimen was transformed into the normal negative in consequence of improvement of tonic condition attained under continued photic stimulation. The above facts lead to the following generalisation : 1. That while strong light induces retardation of growth in an organ whose tonic condition is normal or above par, it induces acceleration in an organ whose condition is below p'ar ; 2. That by the action of the stimulus of light itself, a subtonic organ is raised to a condition of par with concomitant transformation of its response to that of normal retardation. Continuity between Abnormal and Normal Response The tonic condition of a growing organ may vary widely • of this the following are the two extreme cases : (1) the optimum, and (2) the subtonic. In the optimum condition 1 The Motor Mechanism of Plants (1928), p. 5r. G