Effect of the number of pollinated styles on the pollen tube growth and fertilization in 'Niitaka' pear (Pyrus pyrifolia Nakai)

摘要

This study was carried out to investigate the cause of asymmetric fruit formation by observing the pollen tube growth and the fertilization in 'Niitaka' pear (P. pyrifolia) after style excision and artificial pollination. In case of pollination on one style, pollen tube grew less rapidly than the pollination on three or five styles. The fertilization of the ovule with a pollen tube in the micropyle was observed from 4 days after pollination, and the fertilization was terminated within 8 days afterpollination. The number of seeds of fruits by pollination on only one style was 7.1 per fruit, indicating that pollen in one style contribute to the fertilization of ovules in the other carpels. Many pollen tubes grew through a stylar canal of pollen transmitting tissue to the stylar base, but they grew into irregular direction on the margins of carpel and some pollen tubes entered through open carpels and penetrated the micropyle of each ovule in the locule.