Studies on the Stellaria longipes complex: phenotypic plasticity. II. Gibberellins, abscisic acid, and stem elongation

Abstract

Clonal material of one genotype of Stellaria longipes Goldie s.l. was used to investigate whether environmental regulation of the phenotype was mediated through phytohormones. Photoperiod and temperature modified the response of this species to exogenous application of gibberellins (GAs) and abscisic acid (ABA). Application of GAs to ramets in short or long days and low temperature increased stem elongation but did not induce elongation equivalent to that seen in control ramets in long warm days. Application of GAs to ramets in short days (warm or cold) induced elongation equivalent to that of ramets in long days at a similar temperature. Application of (2-chloroethyl)-trimethylammonium chloride resulted in dwarfing at some concentrations, while exposure to other concentrations initially stimulated elongation. Application of ABA reduced elongation in short, cold days but showed no effect under other conditions. Metabolism of radiolabeled ABA and GA3 was similar in both short cold days and long warm days. It was concluded that photoperiodically induced stem elongation could be partially mediated through endogenous levels of GAs. However, a hypothesis based on the idea that temperature-induced changes in elongation are controlled by suboptimal levels of GAs or supraoptimal levels of ABA is inadequate.