Page:Life Movements in Plants.djvu/267

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LIGHT AND WARMTH ON AUTONOMOUS ACTIVITY
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of application of light is represented by the horizontal line. In Fig. 86 the up-curve represents up-movement of diastolic expansion, and the down-curve of systolic contraction. The contractile reaction of light is seen to counteract the normal expansion, with diminution of diastolic limit of pulsation.

EFFECT OF RISE OF TEMPERATURE ON PULSATION.

It has been shown that while rise of temperature up to an optimum enhanced the rate of growth, the effect of light was to retard it. Hence the effects of light and warmth are antagonistic.

Effect of rise of temperature on pulse-record: Experiment 93.—In studying the effect of rise of temperature on the pulsation of leaflets of Desmodium, we discover similar
Fig. 87.—Effect of rise of temperature on pulsation of leaflet of Desmodium gyrans. Horizontal line represents the duration of gradual rise of temperature from 30°C. to 35°C. Note the expansive effect of rise of temperature in reduction of systolic limit of pulsation. antagonistic reactions of light and warmth. The leaflet was placed in a plant-chamber with an electric arrangement for gradual rise of temperature. The first two

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