Effects of lead arsenate sprays on the fruit growth and sugar and acid contents in Natsudaidai (Citrus natsudaidai HAYATA)

Abstract

In Ehime Prefecture, Natsudaidai (Citrus Natsudaidai HAYATA) is one of the most important citrus fruits. Its production, however, has not yet developed so rapidly as that of Unshu, because of the high acidity of its juice. This experiment was conducted to observe the reducing effect of the lead arsenate spray on the acid content of the fruit juice.
1. The acids in the juice was most effectively reduced by the treatment at an early fruit growth stage when they were most actively formed. However, the water soluble organic acid content of leaves was not affected. The sugar content of the juice was increased by the treatment.
2. The activity of phosphoenolpyruvate carboxylase was lowered in the vesicles of the fruit which was sprayed with lead arsenate. It was also much depressed in the exrtacts from the normal fruit when arsenic trioxide (As₂O₃) was added.
3. Arsenic was detected in the vesicles of the treated fruit.