银杏繁殖器官形态发育和种子萌发特征
毕业论文关键词：银杏；繁殖器官；解剖；胚珠；种子；萌发
Characteristics of Morphological Development ofReproductive Organs and Germination of Seeds of Ginkgo biloba L. Supervisor:g(City and Environment College, Jiangsu Normal University, Xuzhou,Jiangsu,221116,China)Abstract: The aim is to learn more about the structure and morphologicaldevelopment of reproductive organs of Ginkgo bilaba L., and also about thecharacteristics of reproductive function. At the same time, this study can addsome new materials for the biological research of Ginkgo biloba L.. In the field, and through the outdoor experiment on the germination of the seeds, andunder stereomicroscope and the paraffin section microscope, the authorobserved the characteristics of the morphological structures and developmentof the ovule-seeds of Ginkgo biloba L., and analysed the effect of fleshy outerseed coat on the germination of the embryo. The results showed that, there is adirect continuity between the cavity in the top half of the ovule and the cavityin the top half of the seed. In another words, the cavity in the seed comes fromthe cavity in the ovule. The swellen endotesta, which has an aqueous tissue, inthe upper part of the immature seed, looks like two flaps in the cross section.There is called a slot-shape seed-cavity between the two flaps of the swellenendotesta. The fleshy seed coat of mature seeds can inhibit the germination ofthe embryo obviously, but the after-ripening of the embryo may not be so clear.According to the fact that the cavity in the seed comes from the cavity in theovule, the thin layer between the cavity and endosperm in the seed is from theresidual nucellus instand of the integument.
Keywords: Ginkgo bilaba L.; reproductive organs; anatomy; ovules; seeds;germination
目录
引言.1
1 材料和方法2
1.1 实验材料..2
1.2 实验方法..3
2 结果和分析5
3 讨论..10
3.1 胚珠-种子形态结构和发育特征10
3.2 种子萌发特性.11
致谢..11
参考文献11
引言银杏(Ginkgo biloba L.)也称公孙树、白果树，是银杏科（ Ginkgoaceae）银杏属（Ginkgo）的落叶大乔木，是有名的孑遗植物种类及世界著名的活化石。同时,银杏也是我国特有的珍贵树种，因此,我国也被称为“银杏的故乡” 。银杏高可达40m；树冠广卵形；树皮深纵裂，深褐色。扇形叶，顶端常 2 裂，叶柄长。多为雌雄异株；花期4 至5 月，自然传粉。种子成熟期为 9 至 10 月。成熟种子椭圆形核果状，径长 2cm，淡黄色或橙黄色，外有白粉；外种皮肉质，有浓烈臭；胚乳肉质，甘微苦。[1]银杏在雌、雄配子体的发育、传粉受精作用上表现出了很多特殊的特征。银杏通常为雌雄异株。雄配子体由小孢子发育而来，发育周期长[2]。小孢子经历3 次小孢子经过连续的极性有丝分裂成花粉[3]。雌配子体由大孢子发育而来。银杏的功能大孢子经游离核分裂形成细胞壁。在此过程中，雌配子体在近珠孔端表面分化形成颈卵器母细胞；再经过平周分裂、垂周分裂和斜向分裂形成成熟的颈卵器[2]。通常情况下，一个雌配子体的颈卵器有两个。两个颈卵器之间的雌配子体不断分裂向上突起，最终形成柱状结构，即为帐篷柱，是分泌受精时所需液体的腺体组织[4]。受精作用在颈卵器中完成。受精作用开始时颈卵器腔内充满液体, 这对游动精子进入颈卵器起推动作用[5]。精子利用卵细胞的伸出物进入颈卵器[6]。在卵细胞上部分区域，精子的细胞核与鞭毛带发生分离，精核及其外部分精细胞质向下运动，最终进入卵细胞中，接触卵核。近精核处的卵核产生凹陷，使精核包入其中，最终整个精核都进入卵核。核内随后出现精核和卵核两者的核仁， 两个核仁的融合标志着整个受精过程宣告结束[7]。成熟的银杏种子由肉质外种皮、膜质中种皮、膜质内种皮及种仁构成。FavreDuchartre 在银杏种实发育研究中发现：银杏种子按照种皮、种仁、胚的顺序依次发育[8]。程水源等人又发现在银杏种实的旺盛生长末期和充分成熟期，银杏种实的外种皮、中种皮和种仁间都变现为极明显的正相关；干重、鲜重、体积和纵、横径累积增长变化都呈单“S”形曲线[9]。王建等人经研究分析，也证实了该结论的正确性。同时，他们还总结出：各种生理物质含量随种子生长过程呈规律性变化，且各有其特点[10]。银杏种子还具有生理后熟的特征。
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