The motor mechanism of plants / by Sir Jagadis Chunder Bose.

  • Bose, Jagadis Chandra, 1858-1937.
Date:
1928
Catalogue details

Licence: In copyright

Credit: The motor mechanism of plants / by Sir Jagadis Chunder Bose. Source: Wellcome Collection.

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    sensitiveness: some respond with a prompt and active movement to but a slight stimulus, whereas others respond but sluggishly to even a fairly strong stimulus. What, now, is the ultimate mechanism of the individual contractile cell ? What is its condition preliminary to con- traction ? The first essential is that it should be in good tonic condition, and this is true of all active living cells. What, exactly, are the factors in the state of ‘ tonus ’ is not clear, but they must include the excitability that enables the protoplasm to respond to stimulation ; and, further, a store of latent energy necessary for the work, whatever it may be— in this case it is contraction—which the cell has to perform. Its mechanical condition is that it is in a state of internal tension, generally termed ‘ turgor,’ like an inflated football; the vacuole contains as much sap as it can hold. The elastic cell-wall is stretched to its utmost ; but, as it is readily permeable, there must be some structure which prevents the escape of liquid under pressure from the cell. The structure in question is the lining layer of proto- plasm, which is a semi-permeable membrane allowing the entrance of water but resisting the escape of the cell-sap. The accumulation of water in the vacuole is the effect of the osmotic action of substances dissolved in the cell- sap. When a stimulus acts upon the turgid contractile cell, the result is that the cell as a whole shrinks, cell-sap escapes through the protoplasmic lining, and the cell loses its turgidity. On the cessation of stimulation, recovery of the previous condition of the cell begins with reabsorption of water, and ends in the restoration of turgor. How are these events to be interpreted ? They have been interpreted in various ways which need not be dis- cussed here. It must suffice to say that, as the protoplasm has inherent motility, and is known to be sensitive to the action of stimuli, it is the chief factor in maintaining or producing variation of the turgidity of the cell. In response to a stimulus it ‘ contracts/ a process which must be associated with a sudden increase of its permeability so as