Abstract
Two types of ascospore liberation from perithecia of Valsa ceratosperma were demonstrated by field and laboratory experiments.
When the dry barks of cankered apple tree bearing perithecial stromata were kept in a moist chamber, no ascospore was discharged. During the prolonged incubation, asci were pushed up through the perithecial neck, and they continued to crowd out of the ostiole, accumulated in a ball without ejecting the ascospores. The ascus balls were also found on the perithecial stromata of cankered apple trees in orchard indicating their dispersal by rainfall. Gutter-trap experiments on the selected, cankered trees showed that the rainwater flowing down stromatal areas contained many ascospores and asci. In early spring when this experiment was started, this type of dispersal had attained its measurable level, and it was maintained for about four months.It was found that water saturation of the barks was needed to initiate ascospore discharge. After initiation, the discharge continued for several hours. In the course of this, the free-water supply to the bark surfaces at given times temporarily enhanced the rate of discharge. This type of dispersal in orchard was studied by a slide-trap method. It was found that the duration of the air-borne dispersal was quite identical with that of the water-borne dispersal.
Temperature, between 10 and 25°C, did not affect discharge. At 3°C, however, the initiation was delayed, and low but fairly constant rate of discharge was maintained.
The maximum distance of discharge from the stromata held at 4mm in height on the slide glass was 6.3mm and the average was 2.8mm. Lifting the specimen to 10mm in height resulted in only a few extention of the maximum and the average distance.
