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被子植物的柱头承受花粉并为花粉萌发提供必须基质和识别,柱头下为花柱结构,是花粉管生长的通道。柱头与花柱形成一个整体,使花粉管到达胚珠。花柱是花粉-雌蕊相互作用的部位,也是自交不亲和性反应的场所,因此,花柱的结构必然对花粉管的生长产生影响,并在雌蕊对花粉管的识别过程中发挥主导作用[1-2]。同时,柱头与花柱也分别是孢子体与配子体自交不亲和性反应发生的场所,花粉管生长分别在柱头和花柱中受到抑制[3]。我国学者过去曾在少数植物中开展过关于花柱结构的专门研究:胡适宜等[4]对王百合(Lilium regale Wilson)花柱通道细胞的超微结构研究发现,其通道细胞分泌面的细胞壁的内侧具有许多伸向细胞质的内突,证实通道细胞是一种典型的分泌型传递细胞。狭叶锦鸡儿(Caragana stenophylla Pojark.)花柱道中含有丰富的营养物质,有的是通道细胞分泌,有的是分泌面的壁破裂后原生质流入花柱道中[5]。荞麦(Fagopyrum esculentum Moench)成熟的柱头表面无乳突细胞,柱头细胞的细胞壁存在发达的壁内突,花柱为实心型无引导组织[6]。而在大多数植物中,对发生在柱头和花柱中的自交不亲和性研究多是观察花粉管发生的抑制反应,对花柱本身的结构特征或变化则很少提及[3, 7-10]。
油茶(Camellia oleifera Abel.)为山茶科(Theaceae)山茶属(Camellia)常绿灌木或小乔木,是我国南方重要且特有的木本食用油料树种[11]。油茶在我国种植历史悠久,但生产中产量一直很低,存在花多果少、坐果率低的症结。本研究组历时8年,通过大量研究已探明油茶为自交不亲和性植物,自交不亲和反应发生在花柱基部[7, 12-14]。这一发现主要基于对自交花粉管生长情况的观察而得出,并未涉及花柱的结构特征和变化趋势。但随着研究的深入,在进一步解析自交花粉管在花柱中的抑制机制和花粉管在花柱中的定向生长等一系列问题时受到阻碍,在之前的研究中尚未开展花柱结构的研究,因而不能将自交不亲和反应发生前、后花柱结构变化进行关联分析以阐明自交不亲和性发生的细胞学机制。为解决上述问题,应首先探明油茶未授粉前成熟花柱的结构特征,因此,本研究基于前期研究的基础,利用切片技术观测柱头和花柱的显微和超微结构特征。同时在山茶属植物中,也还未见关于花柱结构的详细、系统的报道,特别是未见油茶花柱超微结构方面的报道。本研究可为进一步解析油茶自交不亲和反应的花粉管-花柱互作机制提供理论依据,同时也为油茶远缘杂交育种工作奠定理论基础,丰富油茶生殖生物学资料。
油茶柱头和花柱的显微与超微结构特征
Microstructure and Ultrastructure Characteristics of Stigma and Style of Camellia oleifera
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摘要:
目的 从显微和超微层面探究油茶柱头和花柱的结构特征,可为探讨油茶自交不亲和性的细胞学机制提供理论依据,同时也为油茶杂交育种工作奠定基础。 方法 以开花当天的雌蕊为试验材料,利用细胞学方法研究油茶柱头和花柱的显微及超微结构特征。 结果 油茶雌蕊具完整的柱头、花柱和子房结构,湿性柱头其表面密布乳突细胞,排列紧密,细胞质浓厚,细胞器丰富,细胞间具有丰富的分泌物。基本组织细胞内含物和细胞器较少,细胞壁薄且壁外无分泌物。整个花柱由35根独立花柱组成,上端约2/3部分相互分离形成离生区,从2/3处开始到花柱基部相互连接形成合生区。每根花柱中空,由外表皮、基本组织和花柱道内表皮构成。花柱通道细胞外充满大量分泌物,该细胞比基本组织细胞大而规则、细胞质浓厚,具有腺质细胞的特点。花柱道从上到下贴合逐渐紧密,花柱基部的各花柱道之间相互连通,形成狭小的缝隙。 结论 本研究分析了油茶柱头和花柱的显微及超微结构特征,探明柱头乳突和花柱通道细胞为分泌型细胞,基本组织细胞结构单一,从柱头到子房花柱道逐渐变窄,在基部相互连通形成狭小的缝隙,花柱通道细胞从上至下壁外分泌物和细胞内细胞质浓度、细胞器数量与种类具有逐渐增加的趋势和特点。 Abstract:Objective To investigate the structural characteristics of the stigma and style of Camellia oleifera at the microscopic and ultramicroscopic levels and provide a theoretical basis for elucidating the cytological mechanism of breeding self-incompatibility reactions in C. oleifera style, while at the same time to establish a theoretical foundation for hybrid breeding of C. oleifera. Method Using the pistil of C. oleifera on the day of blooming as the experimental material, the microscopic and ultramicroscopic structural characteristics of C. oleifera stigma and styles were observed to study them from a cytological perspective using cytological method. Result The pistil of C. oleifera is composed of an intact stigma, style, and ovary. C. oleifera has a wet stigma. The papillary cells are densely distributed on the receptive surface. They are densely arranged with concentrated cytoplasm and abundant organelles. Abundant secretions are presented among papillary cells. Generally, there is less content and fewer organelles in tissue cells, the cell wall is thinner, and there are no secretions outside the cell wall. The style of C. oleifera is composed of 3-5 independent styles. The upper 2/3 of the style are separated from each other, whereas between the lower 2/3 and the base of style they begin to fuse. Each style of C. oleifera is hollow and composed of an epidermis, parenchymal tissue, and the inner surface of the style duct. The area outside the style duct cells is filled with large amounts of secreted mucous substances. The cells are more organized and larger than those in the parenchymal tissue, have dense cytoplasm, and have characteristics of glandular cells. The style duct becomes gradually denser from top to bottom with continuously decreasing gap size. At the base of the style, the style ducts fuse with each other, forming a small cavity. Conclusion The microscopic and ultramicroscopic structural characteristics of the stigma and style of C. oleifera is analyzed. The cells of the stigma papilla and style duct are secretory cells. The parenchymal tissue cells in the style have a uniform structure. The style duct gradually narrows from the stigma to the ovary. In the base of the style, each style duct fuses with each other to form a small cavity. It is characterized by the substances secreted by the style duct cell wall, cytoplasmic density, and a gradually increasing tendency in the number of types of organelles. -
Key words:
- Camellia oleifera
- / stigma
- / style
- / microstructure
- / ultrastructure
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