Environmental control of growth and development of Scrophularia marilandica.

Seedlings of Scrophularia marilandica were grown at different combinations of day/night temperature and photoperiod under controlled conditions. The species flowered in long days. The stems of plants grown at low temperature and short photoperiod failed to elongate. Treatment with gibberellic acid (GA3) simulated the effect of increasing temperature and photoperiod and caused stem elongation in plants which would otherwise not have elongated. Application of GA3 to plants grown at high temperature and long photoperiod resulted in increased stem elongation and flowering. The growth retardant (2-chloroethyl)trimethylammonium chloride (CCC) had little effect on rosette plants grown at low temperature and short photoperiod. Application of CCC to +GA3 plants grown at a higher temperature and long photoperiod gave a significant increase in stem height. The interaction between temperature and applied GA is described in an experiment using plants grown at high and low temperatures for varying periods of time.