‘早籽银桂’大小孢子发育与花器形态变化

Development of Micro- and Mega-spores and Morphology of Floral Organ in Osmanthus fragrans ‘Zao Zi Yin’

摘要:

为了解桂花两性株孢子发育和花器形态的关系，对早籽银桂（Osmanthus fragrans ‘Zao Zi Yin’）大小孢子发育过程和花器外部形态进行了观察。。结果表明，圆珠期花芽突然膨大时，小孢子母细胞减数分裂启动，至花芽顶壳期进入四分体时期，四分体多数呈四面体型，少数呈十字交叉型，也有介于二者之间的排列方式；柃梗期时小孢子发育至单核靠边期；香眼期至盛花期形成二细胞型花粉并发育成熟；花药长度由0.3 mm增加至1 mm，颜色由无色透明变为鲜黄色。雌蕊柱头二裂，子房2室，每室2胚珠，胚珠横生，单珠被，薄珠心，珠柄不明显。二细胞花粉时期，大孢子母细胞减数分裂形成大孢子，至盛花期胚囊发育为成熟的8核蓼型胚囊。雄蕊发育早于雌蕊，花开后雌、雄蕊趋于同熟。大小孢子细胞学发育时期与花器形态建成密切相关，根据花器形态特征可判断大小孢子发育时期。

Abstract:

In order to understand the relationship of spore development with morphology of floral organ in Osmanthus fragrans, the changes in morphology of floret organ during micro- and megaspores development of ‘Zao Zi Yin’ bisexual plant were observed. The results show that the meiosis of microspore mother cell started when flower bud at ball-shaped stage suddenly expanded, and it came into tetrad stage at top bract stage. Majority of microspore tetrads were tetrahedral, minority were decussate, and others between the two ways. Flower bud was at the bud-pedicel stage, microspore develop to the late uninucleate stage, and flower bud from bud-eye stage to full blooming stage, microspore form 2-celled pollen and mature, the anther length increased from 0.3 mm to 1 mm, color changed from colorless transparent to bright yellow. Pistil stigma two lobed, ovary 2 rooms, each room 2 ovules, amphitropous ovule, unitegmic, tenuinucellate, and funicle was not obvious. During two-cell pollen period, the megaspore mother cell goes on meiosis to form megaspore. To flowering stage, the 8-nuclear sac was mature with polygonum type. The development of stamen was earlier than that of pistils, they tend to mature at the same time after flowering. So, the micro- and mega-sporogenesis had high relation with morphology of floret organs. It was suggested that the micro- and mega-spore development period could be judged according to morphological characters of floral organs.