STEM ELONGATION OF DENDRANTHEMA AND TOMATO PLANTS IN RELATION TO DAY AND NIGHT TEMPERATURES

Young plants of Lycopersicon esculentum ‘UC 105’ and Dendranthema morifolium ‘Choral Charm’ were grown under three different temperature regimes: constant 20°C night and day, and two different DIF programmes (low day/high night temperature). One DIF programme was a morning drop where the temperature was lowered for 2 hours before sunrise.
The other was a standard DIF programme where the temperature was lowered for the whole of the daily light period.
In combination with the morning drop, plants were treated with red or far red light during the two hours before sunrise.

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.

II European Workshop on Thermo- and Photomorphogenesis in Plants

L. Bertram

DIF, elongation growth rate, far red light, light quality, morning drop, HIR, phytochrome, red light

https://doi.org/10.17660/ActaHortic.1992.327.7