Studies on the forcing of Aster savatieri MAKINO

XII. The changes in free and bound gibberellin-like substances in cold and non-cold treated plants

Abstract

This paper described the changes in the free and bound GA-like substances in flower initiated and vegetative plants of Aster savatieri grown for 5 weeks at a temperature between 4 and 5°C or between 20 and 25°C.
The GA-like substances were extracted by a modified JONES′ method. Extracts were prepared with aqueous solvent after separating a plant into three parts; shoot apex region with younger leaves, rosetted stem and older rosette leaves, using 120 plants. After fractionation, ascending paper chromatography on Toyo No. 51 was carried out using 80% isopropanol as the solvent. Bioassay methods for comparing the activity of GA-like substances in the eluate from different zones of chromatograms were the rice endosperm (Oryza sativa cv. Kotaketamanishiki) test and the rice seedling (cv. Tanginbozu) test. Results were as follows:
The free and bound forms of GA-like substances were present in this plant.
The shoot apex region and rosetted stem in cold treated plants showed an increase of GA-like substances in the free form and a significant decrease in the bound form. While these parts in non-cold treated plants showed a decrease in the free form and an increase in the bound form. Similar tendencies were observed in both flower initiated and vegetative plants. However, the concentrations of GA-like substances in flower initiated plants changed more greatly than those in vegetative ones during the low temperature treatment. Changes in the activity of GA-like substances in older rosette leaves were not great as in shoot apex region and rosetted stem.
Changes in the neutral GA-like substances in plants did not occur during the treatment.
The data indicated that the low temperature caused an increase of the free GA-like substances which played an important role on the rapid stem elongation.