Abstract
A correlation between early drop of fruit and indole derivatives was investigated using histochemical techniques. In vitro and in vivo, the indole derivatives formed a blue pigment with a peak of absorbency at 618nm by p-dimethylaminobenzaldehyde-nitrite reaction and a correlation between the concentration of the pigment and absorbancy at 620nm was observed. At all stages of seed development the embryo was found to give a strong reaction while the endosperm gave a weak or no reaction, and the nucellus gave a moderate reaction. The relative content of indole derivatives in the embryo, endosperm and nucellus tissue was calculated. The relative content of these derivatives in embryos was very low until the 50th day after full bloom, but showed a marked increase between the 50th and the 90th day, and remained at a very high level until harvest. The relative content in the endosperm and nucellus tissue was very low in all stages.
Early drop of fruit was enhanced by a high night temperature (25°C) for 30 days beginning on the 10th day after full bloom. A reduced rate of fruit enlargement for two days was utilized to distinguish potential drop fruits. Potential drop fruits abscised within 6 to 10 days after that distinction. Fruit drop process was divided into four stages (potential drop fruit stage A, stage B, stage C and abscission). Since no difference in the concentration of indole derivatives was recognized between fruits of stage A and the persistent one, the indole derivatives are considered to have no correlation with early drop of fruit.
