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    油松大孢子叶球发生发育的形态与解剖学观察

    Morphologic and anatomical observations in the process of ovulate strobilus generation and development in Pinus tabuliformis

    • 摘要: 为了准确掌握油松大孢子叶球发生发育过程的外部形态特征及内部胚珠生长的解剖学特征,建立其外部形态和内部组织发育的对应关系,本研究采用形态观测和石蜡切片法,在2013—2016年对北京地区油松大孢子叶球,从花芽分化到种子成熟的过程进行了形态学和解剖学观察。结果显示:北京地区油松的花芽在第1年8月初分化,9月底大孢子叶球原基形成。原基在冬季休眠,至第2年春季继续发育。大孢子叶球在4月初从形态学上可辨,到4月10日左右,胚珠进行细胞分化,此时,大孢子叶球纵径约为5.0 mm。大孢子母细胞在4月20日左右形成,随后进行减数分裂形成功能大孢子。至5月10日左右,大孢子叶球接受小孢子叶球的传粉,随后,珠鳞的颜色由红转绿再逐渐变为棕色。同时,球果缓慢长大,其胚珠内的功能大孢子进行几次分裂,在6月初形成16~32个核的雌配子体,胚珠发育进入游离核分裂期。球果在冬季转入休眠,此时,大孢子叶球纵径约为11.0 mm。至第3年春季,胚珠内部的雌配子体继续发育,4月20日左右含有几千个游离核,此时,大孢子叶球纵径约为21.0 mm。雌配子体在4月30日左右进入细胞化时期,5月初颈卵器开始发育,形成卵细胞,此时,大孢子叶球生长至37.0 mm。待卵细胞在5月10日左右发育成熟时,雌配子体细胞化过程也全部结束。在雌配子体发育、球果长大的同时,珠鳞的颜色逐渐复绿。受精于5月20日左右进行,此时,大孢子叶球纵径约为45.0 mm。受精后,胚胎不断发育。球果在7月10日长约58.0 mm,之后略有萎缩,珠磷逐渐木质化成为种磷。至10月底,球果开裂,长约53.0 mm,种子成熟并弹出。北京地区油松的大孢子叶球从花芽分化、原基形成、胚珠分化、大孢子母细胞产生与分裂、传粉、雌配子体与颈卵器发育、卵细胞成熟、受精、胚胎发育至大孢子叶球成熟形成种子,历时2年2个月。本研究为裸子植物大孢子叶球发生发育的相关研究提供了形态学和解剖学依据。

       

      Abstract: In order to accurately grasp the characteristics of the external morphology and the internal anatomy of ovule growth in the process of ovulate strobilus generation and development in Pinus tabuliformis and establish the corresponding relationship between external morphology and internal tissue development, morphological measurement and paraffin section detection were adopted to perform morphology and anatomy observation on ovulate strobilus of P. tabuliformis in Beijing throughout its whole development process from flower bud initiation to seed maturation during 2013-2016. The results indicated that the flower bud of P. tabuliformis in Beijing presented differentiation in the early August of the first year, and the ovulate strobilus primordium formed at the end of September, entered dormancy in winter, and continued to develop in the spring of second year. Ovulate strobilus could be distinguished in morphology in the early April. Around April 10, the ovule cell started differentiation, the longitudinal diameter of ovulate strobilus was about 5.0 mm at this time. The megaspore mother cell formed around April 20 and subsequently made the meiosis to form the functional megaspore. Around May 10, ovulate strobilus caught the pollens from the staminate strobilus, subsequently, the color of cone scales changed from red to green, and then to brown. Simultaneously, the cones grew up slowly, in which the functional megaspore presented several mitosis to form the megagametophyte with 16-32 free nuclei. The ovule entered megagametophyte free nuclei period at the beginning of June, and entered dormancy in winter. At this time, the longitudinal diameter of ovulate strobilus was about 11.0 mm. Until the spring of the third year, the megagametophyte re-developmented, and around April 20, contained thousands of free nuclei. The longitudinal diameter of ovulate strobilus was about 21.0 mm at this time. The ovule entered megagametophyte cellularization period around April 30, and at the beginning of May, the archegonium started development and formed egg cell. At this time, the longitudinal diameter of ovulate strobilus was about 37.0 mm. Until the egg cell matured around May 10, the cellularization process of female gametophyte completed. During the period of the megagametophyte and cone development, the color of cone scales returned to green gradually. Fertilization started around May 20, and the longitudinal diameter of ovulate strobilus was about 45.0 mm at this time. After that, the embryo developed continuously. The longitudinal diameter of ovulate strobilus was about 58.0 mm on July 10. Subsequently, ovulate strobilus atrophied slightly, and the cone scales were gradually subject to lignification and became seed scales. Until the end of October, the cone cracked, its longitudinal diameter was about 53.0 mm, and the seeds matured and were popped up. The ovulate strobilus development of P. tabuliformis in Beijing lasted for 2 years and 2 months from flower bud differentiation, primordium formation, ovule differentiation, megaspore mother cell generation and meiosis, pollination, megagametophyte and archegonium development, egg cell maturation, fertilization, embryonic development to ovulate strobilus and seed maturation.This study provids morphology and anatomy basis for relevant researches on the development of gymnosperms strobilus.

       

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