Studies on the forcing of Aster savatieri MAKINO

XIII. Histochemical changes in the shoot apex in cold and non-cold treated plants

Abstract

The histochemical studies were carried out to clarify the effect of low temperature treatment (4-5°C, 5 weeks) on changes in substances in the shoot apex of Aster savatieri MAKINO.
Shoot tips were fixed in FAA (formalin-alcoholacetic acid) solution for detection of deoxyribonucleic acid (DNA), ribonucleic acid (RNA), polysaccharides and reducing sugars, and in 10% neutral formalin solution for histone. The preparation was made by the use of paraffin method.
Frozen and free hand sections were applied to detect indole compounds and peroxidase activity. Results of the observation were summarized as follows;
1. The shoot apex in cold treated plants showed an increase of RNA, indole compounds and peroxidase activity, and histone in the nuclear sap.
2. No changes of DNA in shoot apices of the plants were observed.
3. The shoot apex in the cold treated plants showed an increase in reducing sugars and a significant decrease in polysaccharides.
In contrast to this, the shoot apex in the non-cold treated plants showed the inverse relation between reducing sugars and polysaccharides.
4. From these data it may be suggested that the endogenous GA-like substances, which were increased by low temperature treatment, caused an increase of indole compounds and RNA, and also promoted the hydrolysis, translocation and redistribution of carbohydrates in the shoot apex. Such the sequential changes in substances during low temperature treatment may be important for the stem elongation of Aster savatieri MAKINO.