STEM ELONGATION OF DENDRANTHEMA AND TOMATO PLANTS IN RELATION TO DAY AND NIGHT TEMPERATURES
Temperature drop for two hours before sunrise did not affect the stem elongation in either of the species. Far red light inhibited stem elongation in tomato, possibly through a high irradiance response (HIR) of phytochrome which altered the competence of the plants to respond to the morning drop. Red light did not affect the elongation in tomato. In Dendranthema, red light inhibited elongation and far red light increased elongation through an induction response of phytochrome.
An endogenous elongation rhythm was found in tomato. The largest growth rate occurred during the night. The rhythm was controlled by irradiance level, temperature changes and light quality.