Page:Life Movements in Plants.djvu/272
response of pulvinated and growing organs will be seen in the following tabular statement:
TABLE XXI.—TIME RELATIONS OF MECHANICAL RESPONSE OF PULVINATED AND GROWING ORGANS.
| Specimen. | Latent period. | Apex-time. | Period of recovery. |
Motile pulvinus of Mimosa pudica. … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … |
0.1 sec. | 1803 secs. | 16 minutes. |
Motile pulvinus of Neptunia oleracea. … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … |
0.6 sec.„ | 180 secs.„ | 60 minutes.„ |
Growing bud of Crinum … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … … |
1.0 sec.„ | 240 secs.„ | 607 minutes.„ |
The contraction in growing organs under stimulus is sometimes considerable. Thus in the filamentous corona of Passiflora quadrangularis the contraction may be as much as 15 per cent. of the original length. This is not very different from the excitatory reaction of the typically sensitive stamens of the Cynereæ, which exhibits a contraction from 8 to 22 per cent.
MODIFICATION OF RESPONSE BY CONDITION OF SUB-TONICITY.
In Mimosa the normal response to direct stimulus is negative, the leaf undergoing a fall. But sub-tonic specimens exhibit a positive response with erection of the leaf. The action of the stimulus itself improves the tonic condition, and the abnormal positive is thus converted into normal negative, through diphasic response (p. 147). Similarly in growing organs, while the normal effect of stimulus is incipient contraction and retardation of growth under condition of sub-tonicity the response is by acceleration of growth. Continuous stimulation converts this