The 6th International Sympsium on Plant Responses to Air Pollution and Global Changes (APGC2004)

‘Kousui’, ‘Housui’ and ‘Nijisseiki’ Japanese pears (Pyrus pyrifolia Nakai) are major cultivars in Japan. The flowering time is a matter of great importance to the fruit growers and the experts concerned. The flowering date of Japanese pear trees (cvs. Kousui) was monitored at 21 experiment stations in various pear-grown regions throughout Japan. The flowering patterns of Japanese pear trees in recent years were classified into 4 types. In the first type, as typically seen in Saitama, flowering date has been advanced gradually. In the second type, flowering has been advanced only slightly. In the third type, as typically seen in Ooita, flowering date has been clearly delayed. No apparent shifts in flowering date were evident in the forth type. Yearly variation of harvest date was examined by regression analysis and evaluated for the flowering pattern by the similar method. Harvest date was delayed in Fukuoka and Fukushima. Conversely, in Akita, Toyama, Chiba, Ibaraki and Tottori, harvest time was advanced.

     Yearly variation of flowering and harvest time in ‘Housui’ and ‘Nijisseiki’ Japanese pears was evaluated by the similar method to compare with that in ‘Kousui’. At the present, it is assumed that the effect of global warming, especially in cold period, on the flowering dates may be seen as the acceleration of flowering time caused by the advanced ecodormancy break that negated part of the delays in endodormancy completion due to insufficient chilling temperature.

Key words: Ecodormancy, Endodormancy, Flowering, Global warming, Pyrus pyrifolia,