槲树雌花和种子生长发育动态研究

Dynamics of female flower and seed growth and development in Quercus dentata

【目的】阐明槲树雌花发育的生殖周期和发育时序特征。【方法】以人工控制授粉后不同发育时期的槲树雌花为试验材料,通过形态学、生理指标测定和石蜡切片等检测方法,对授粉前后不同发育时期雌花及子房的外部形态、种子发育进程和败育动态进行观察。【结果】(1)在雌花整个生长发育过程,刺苞逐渐变硬,苞片由绿转黄,柱头不断萎缩,花柱不断缩短;子房体积不断膨大,外围壳斗逐渐增厚,于授粉后140 d左右形成棕褐色橡子。(2)授粉后17 d,胚珠发育完成;授粉后30 d,胚囊发育成熟;授粉后38 d,初生胚乳核出现,原胚形成;之后经过了大约13 d休眠后,依次经历球型胚、心型胚、鱼雷胚和子叶胚的分化;而胚乳作为滋养组织,一直处于高度分裂状态,在种子成熟期被子叶全部吸收利用,最终收获无胚乳的成熟种子。(3)初步明确了槲树种胚在整个生长周期内共存在2次败育高峰期,分别在授粉后69 d和99 d。(4)种子败育的表观形态主要表现为败育胚子房壁褐化、胚珠皱缩,显微结构上则主要表现为珠被发育异常、胚胎畸形或空腔胚囊。【结论】本研究建立了槲树雌花分化和种子形成过程外部形态变化与内部解剖特点之间的关系,可为今后栎属胚胎学研究、开花结实机理和胚败育机制研究提供理论依据。

[Objective]This paper aims to elucidate the reproductive cycle and developmental timing characteristics of female flowers in Quercus dentata.[Method]This study used artificially pollinated female flowers at different developmental stages as experimental materials.The external morphology,seed development process,and abortion dynamics of female flowers and ovaries at different developmental stages before and after pollination were observed through morphological and histological examination methods,such as paraffin section,as well as physiological indicators.[Result](1)Throughout the entirety of female flower’s growth and development,the spiny bracts underwent a gradual process of hardening,while simultaneously transitioning from a green to yellow hue.Additionally,exhibited a continuous reduction in size,while the style underwent a shortening process.The ovary’s volume,on the other hand,experienced a continuous expansion,with the outer shell gradually thickening,ultimately culminating in the formation of brown seeds at approximately 140 d post-pollination.(2)Observation of paraffin sections showed that at 17 d after pollination,ovule was completed;at 30 d after pollination,the embryo sac matured;at 38 d after pollination,the primary endosperm nucleus appeared,and the pro-embryo formed;after about 13 d of dormancy,it underwent differentiation of globular embryo,heart-shaped embryos,torpedo-shaped embryos,and cotyledon embryos in sequence.As a nourishing tissue,the endosperm had always been in a highly divided state,and was fully absorbed and utilized by the cotyledons during the seed maturation stage,ultimately harvesting mature seeds without endosperm.(3)It was preliminarily confirmed that there were two peak periods of abortion in the entire growth cycle of Q.dentata,which were respectively at 69 d and 99 d after pollination.(4)The appearance of seed abortion was mainly manifested as browning of ovary wall of aborted embryo,shrinking of ovule,and microstructure was mainly manifested as abnormal development of integument,embryo malformation or empty embryo sac.[Conclusion]This study establishes the relationship between external morphological changes and internal anatomical characteristics during the differentiation of female flowers and seed formation in Q.dentata.It provides the theoretical basis for future research on the embryology,the mechanism of flowering and fruiting,and embryo abortion mechanism of Quercus.