Abstract: The microspore mother cell meiosis of different ploidy Phalaenopsis and chromosome number in root tip cell of their hybridswere observed. The results showed that the p loidy segregation appeared in all combinations excep t that of triploid ×triploid, in which no hybrid plants were obtained. Diploid, triploid and tetraploid plants were identified in the combinations of diploid ×diploid, dipoid ×tetraploid and tetraploid ×diploid Phalaenopsis. Diploids, triploids, pentap loids and aneuploids were found in the combinations of diploid ×trip loid and tripoid ×diploid. Triploids, tetraploids, octoploids and aneuploids were identified in the plants of triploid ×tetraploid combinations, while triploids, tetraploids, pentap loids and aneup loids existed in the plants of tetraploid trip loid ones. This indicated that ploidy segregation was related to reciprocal cros
ses. Tetraploid crossed with tetraploid produced diploids, triploids, tetraploids, pentaploids, hexaploids and aneuploids. The ploidy diversity of microspore in Phalaenopsis caused by the abnormal meiosis of microspore mother cells such as chromosome lagging, micronucleus and triad, was one of the main reasons resulting in ploidy diversity of the hybrids.

Key words: Phalaenopsis, polyp loid, meiosis, microspore