Page:Life Movements in Plants.djvu/256

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LIFE MOVEMENTS IN PLANTS

stimulus on tissues in which growth, on account of extreme sub-tonicity, has been brought to a state of standstill.

SUMMARY.

The modifying influence of tonic condition on response is similar in pulvinated and growing organs.

The motile organ of Mimosa in a condition of sub-tonicity, exhibits a positive response, by expansion, increase of turgor, and erection of the leaf. Continuous stimulation converts the abnormal positive to normal negative.

In sub-tonic growing organs stimulus likewise induces a positive response, by expansion, increase of turgor and acceleration of the rate of growth. Continuous stimulation converts the abnormal acceleration to normal retardation.

Sub-minimal stimulus tends to induce even in normal tissues, an acceleration of rate of growth. Stimulus of moderate intensity induces in the same tissue the normal retardation of growth.

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