Control of Stem Elongation and Flowering in Scrophularia marilandica

The influence of temperature, photoperiod. and certain metabolities was determined for stem elongation and flowering in Scrophularia marilandica. Induction for flowering did not occur until several weeks after the beginning of rapid stem elongation. From the experiments reported it is concluded that S. marilandica is a high-temperature quantitative long-day plant. Temperatures above 20°C negate the absolute requirement for long days for flowering. Plants exposed to photoperiods as brief as 4 hours flowered, given high temperatures. Stem elongation was found to be a necessary prerequisite for flowering. The process of stem elongation was somewhat more sensitive to inhibition by low temperatures than flowering and to a great extent more sensitive than leaf formation and leaf growth. Vernalization was found to be unnecessary for stem elongation and flowering. Gibberellic acid promoted stem elongation and branching without flowering under conditions resembling cool short days. Other metabolities were tested but had no observable effects.