The Growth and Development of Caltha introloba F. Muell. II. The Regulation of Germination, Growth and Photosynthesis by Temperature

Abstract

The germination of seeds of Caltha introloba F. Muell. on water was very slow with a lag time of 40-60 days. The optimum temperature for germination varied from 22-27°C and germination was very poor in the range from 0-15°C. Stratification of seeds at low temperature (1-2°C) for a period of 4 months, or treatment of the seeds with 3 × 10^-4M GA₃, more than halved the lag time for germination and considerably enhanced both the rate of germination and the extent of germination under low tempera- ture (0-15°C) conditions. It was concluded that C. introloba seed shed in the summer is unlikely to germinate in the short alpine herb field areas until after snow melt in the following spring.

The optimum temperature for both growth and photosynthesis was approximately 15°C, which is close to the mean maximum temperatures for the summer months. Active photosynthesis however was observed at 0°C and therefore could occur throughout the year, except when the plants are covered by snow.

Two important features in the establishment and growth of C. introloba appear to be the develop- ment of a deeply penetrating tap root system and the accumulation of carbohydrate reserves in the leaves and crown tissue.