There is no line of demarcation between tropic and nastic movements.
In a differentially excitable organ the effect of strong unilateral stimulus becomes internally diffused, and causes greater contraction of the more excitable side of the organ.
In the absence of transverse conduction, the positive curvature reaches a maximum without neutralisation or reversal. The leaflets of Erythrina indica and of Clitoria ternatea thus fold upwards, the apices of the leaflets pointing towards the sun.
Internally diffused excitation under strong light induces greater contraction of the more excitable half of the pulvinule, causing upward folding of Mimosa leaflet, and downward folding of the leaflets of Biophytum and Averrhoa.
XXXV.—EFFECT OF TEMPERATURE ON PHOTOTROPIC
CURVATURE
By
Sir J. C. Bose,
Assisted by
Guruprasanna Das.
I shall in this chapter deal with certain anomalies in phototropic curvature, brought about by variation of temperature and by seasonal change; certain organs again are apparently erratic in their phototropic response.