EFFECTS OF TEMPERATURE ON FLOWERING AND P OLLEN GERMINATION IN JAPANESE APRICOT CV NANKO

The effects of temperature on flowering and pollen germination in Japa nese apricot (Prunus mume Sieb. et Zucc.) cv. Nanko were investigated in a growth chamber where day and night temperatures were kept constan t at 5-degrees, 10-degrees, 15-degrees and 20-degrees-C and under fiel d conditions from mid-January to mid-April. 1. At higher temperatures, anthesis was earlier and flowering period was shorter than they were at lower temperatures. Trees kept at 5-degrees-C required more days to flower than did those in the field. All floral organs, including the ovary, were bigger at full bloom at lower than at higher temperatures. 2. Pollen, collected from trees in all temperature treatments, germin ated and grew within 4 hours at temperatures ranging from 0-degrees to 30-degrees-C when cultured on 1 % ager and 20 % sucrose. The germinat ion rates at higher temperatures were more rapid than they were at 10- degrees-C and below. Although some pollen germinated at 0-degrees-C, t he optimum range was between 20-degrees to 25-degrees-C in all treatme nts. Pollen tubes grew longer under higher germination temperatures up to 25-degrees-C. Flowers kept at 15-degrees-C had the longest tubes; those kept at 5-degrees-C had the shortest.