Page:Life Movements in Plants.djvu/267

Rh 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 con- traction. The contractile reaction of light is seen to counternct the normal expansion, with diminution of diasto- lic limit of 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-7'ecoT'd : Experi- ment 9o. — In studying the effect of rise of temperature on the pulsation of leaflets of Desmodium, v/e discover similar

Fig. 87. — Eft'ect of rise of tempera* ure on pulsation of leaflet of Desmodium ff^runs. Horizontal line represents the duration of gr^f^u^' 'is" of temperature from 3U'C. to 35^0. Note the expansive effect of rise of temperature in' reduc- tion of systolic limit of pulsation.

antagonistic reactions of light and warmth. The leaflet was placed in a plant-chamber with an electric arrange- ment for gradual rise of temperature. The first two