白刺胚乳早期发育的超微结构研究

白刺(Nitraria sibirica)胚乳发育经历游离核阶段、细胞化阶段和被吸收解体阶段。游离核胚乳沿胚囊壁均匀排列为一层,胞质浓厚,其中有丰富的质体、线粒体、高尔基体、内质网和各种小泡等细胞器。珠孔区域的胚囊壁具发达的分枝状壁内突,而周缘区域的胚囊壁具间隔的钉状内突,内突周围的细胞质中具多数线粒体和小泡。胚乳细胞化时,初始垂周壁源于核有丝分裂产生的细胞板。在细胞板两端开始壁的游离生长,一端与胚囊壁相连接,另一端向心自由延伸。壁的游离生长依赖于小泡的融合。早期胚乳细胞具大液泡,具核或无核,细胞质中有大量的线粒体,质体缺乏,其壁仍由多层膜结构组成。     

薏苡胚乳细胞化的超微结构观察

采用透射电镜对薏苡早期的胚乳细胞化进行了研究,在胚乳游离核时期,胚乳游离核及细胞质绕中央细胞分布,游离核间没有发现胚囊壁内突、成膜体等结构。胚乳细胞化过程中初始垂周壁形成过程如下：（１）胚乳细胞质中出现液泡,使细胞质和核向中央液泡推进：（２）一对相邻细胞核间液泡成对存在,且呈垂周分布,而且两液泡间的细胞质很狭窄;（３）在这狭窄的细胞质中出现成行排列的小泡;（４）小泡融合形成细胞板,细胞板悬于两液泡     

矮生菜豆胚乳细胞形成时的超微结构研究

应用透射电镜对矮生菜豆的游离核胚乳、胚乳细胞及珠被绒毡层的超微结构进行了观察,揭示了胚乳细胞化过程中自由生长壁的形成方式。实验表明,在游离核胚乳中存在大量有被小泡,胚乳游离核的外层核膜发生明显外突并以出芽的方式产生有被小泡。初始胚乳细胞壁为自由生长壁,大量有被小泡融合于自由生长壁末端使之不断延伸并产生分枝。与珠被绒毡层相邻的胚乳细胞产生发达的壁内突,具有传递细胞特征;在这些细胞中出现大量的核糖体及粗糙内质网,表现现高度的合成活性。     

毛竹茎纤维次生壁形成过程的超微结构观察

利用透射电镜观察了毛竹（Ｐｈｙｌｌｏｓｔａｃｈｙｓ ｐｕｂｅｓｃｅｎｓ Ｍａｚｅｌ）茎纤维发育过程中次生壁的形成过程。纤维发育早期,细胞具有较大的细胞核和核仁;细胞质浓稠,具有核糖体、线粒体和高尔基体等细胞器。随着纤维次生壁的形成,细胞壁加厚,细胞质变得稀薄,内质网和高尔基体的数量明显增加,并且两者共同参与了运输小泡的形成;在质膜内侧可观察到大量周质微管分布。随着次生壁的进一步加厚及木质化,细胞壁     

大葱卵器及受精后助细胞的超微结构

章丘大葱（Ａllium fistulosum L.cv.Zhangqiu)的卵器由１个卵细胞及２个助细胞组成,观察到不少卵器没有卵细胞,只有２个助细胞。卵细胞的核及大部分细胞质位于细胞的合点端,１个大液泡占据了细胞其他部位。卵细胞含有很多的核糖体及多聚核糖体、嵴明显的线粒体、粗面内质网、高尔基体具小泡,卵细胞似是一个活跃的细胞。细胞外被细胞壁,其合点端及侧方与助细胞共同壁不连续,助细胞有一较大的核,位于细胞膨大的部位,众多的小液泡遍布细胞中。核糖体及聚合核糖体、线粒体,粗面内质网及风心圆环状粗面内质丰富,高尔基体及小泡常见,反映了其活跃的代谢作用。助细胞合点端及侧方与卵细胞、中央细胞的共同壁不连续,与卵细胞共同壁含胞间连丝,壁不连续处,有不状多层膜结构伸入卵细胞质,显示助细胞可能对卵细胞提供营养,伟粉后,一个助细胞退化,宿存助细胞至随胚胚期尚存在,它经历了一个缓慢的退化过程,出现质壁分离,细胞质变稀,液泡扩大,细胞器逐渐减少,在椭形胚期,宿存助细胞核内的染色质及核仁消失,有细胞质侵入核内,因宿存助细胞壁变厚,细胞质出现现脂滴,宿存助细胞可能仍有合成功能,宿存助细胞壁出现若干无壁部位,细胞内的营养物质可能通过无壁部位向胚乳转运,供游离核胚乳及胚乳细胞化初期的发育。     

毛竹茎秆纤维发育过程的超微结构观察

利用透射和扫描电镜观察了毛竹（Phyllostachys edulis (Carr.) H. De Lehaie）茎秆纤维发育过程中的超微结构变化。在纤维细胞初生壁形成期,细胞质中线粒体、内质网、高尔基体等细胞器数量有明显的增加,出现大量的由内质网与高尔基体分泌形成的运输小泡,周质微管平行分布于质膜内侧,出现环状片层结构,并在细胞壁与质膜之间出现壁旁体结构。随着次生壁的逐渐形成,细胞质中细胞器逐渐地解体并出现多泡小体;纤维细胞核出现染色质凝聚并边缘化,但在8 年生的纤维中可以持续存在;在纤维次生壁形成的整个阶段都存在与周围细胞相联系的胞间连丝和运输小泡;次生壁 在前4 年加厚明显,以后加厚程度减缓,但可以持续很长一段时间,并随着加厚出现宽窄交替的多层结构。结果表明,线粒体、内质网、高尔基体和壁旁体等细胞器与周质微管一起参与了初生壁和次生壁早期的形成;纤维细胞次生壁的形成过程就是一个漫长的程序性细胞死亡（PCD）,而PCD 的产物与胞间连丝一起参与了次生壁的形成与加厚;染色质凝聚并边缘化的细胞核与胞间连丝的持续存在,证明毛竹茎秆纤维细胞是一种典型的长寿细胞。     

花生成熟花粉的超微结构

花生（Arachis hypogaea L．）成熟花粉为二细胞型,具3个萌发沟,少数有4个。外壁呈蜂窝状。花粉壁由覆盖层、基粒棒、外壁内层及内壁构成。线粒体嵴密集、相互平行,脂体被粗面内质网包围。粗面内质网与外核膜相连,亦与线粒体相连。高尔基体甚少。营养核无核仁及染色质,与生殖细胞相连形成雄性生殖单位（male germ unit）。生殖细胞锤形、有壁,见一末端延伸成长尾状（长8μm）。细胞质含核糖体、线粒体、微管,未见体。在有些生殖细胞核内观察到具双层膜、少量嵴及深色内含物的球形结构,其米来源及本质尚不知,有待进一步研究确定。     

薏苡胚乳传递细胞的超微结构

传粉后１０ ｄ,薏苡（Ｃｏｉｘ ｌａｃｒｙｍ ａ－ｊｏｂｉＬ．）颖果基部胚乳最外层传递细胞具长而多的壁内突,第二层细胞的壁内突较第一层的短而少,均具瓣裂的细胞核、丰富的线粒体、粗糙内质网、核糖体、产生小泡的高尔基体及与壁内突质膜相连的、含深色物质的囊泡。线粒体分布于壁内突附近或其间。授粉后２５ ｄ,第一、二层细胞壁内突发达,几乎充满了细胞,但细胞器可见。第四层传递细胞具树枝状及网状的壁内突,大量线粒体、具质体膜的淀粉粒、脂体存在壁内突附近或壁内突的间隙内。高尔基体常见,仅见很少的片段内质网。第五层传递细胞具短的壁内突、较大的淀粉粒及许多小蛋白质体。两个时期的第一、二层细胞内均未观察到胞间连丝。授粉后２５ ｄ,第四层及以上的传递细胞的细胞壁和呈网状的壁内突均含有胞间连丝。还讨论了各种细胞器的作用及各层传递细胞的功能     

毛竹茎秆纤维发育过程的超微结构观察

利用透射和扫描电镜观察了毛竹(Phyllostachys edulis(Carr.)H.De Lehaie)茎秆纤维发育过程中的超微结构变化.在纤维细胞初生壁形成期,细胞质中线粒体、内质网、高尔基体等细胞器数量有明显的增加,出现大量的由内质网与高尔基体分泌形成的运输小泡,周质微管平行分布于质膜内侧,出现环状片层结构,并在细胞壁与质膜之间出现壁旁体结构.随着次生壁的逐渐形成,细胞质中细胞器逐渐地解体并出现多泡小体;纤维细胞核出现染色质凝聚并边缘化,但在8年生的纤维中可以持续存在;在纤维次生壁形成的整个阶段都存在与周围细胞相联系的胞间连丝和运输小泡;次生壁在前4年加厚明显,以后加厚程度减缓,但可以持续很长一段时间,并随着加厚出现宽窄交替的多层结构.结果表明,线粒体、内质网、高尔基体和壁旁体等细胞器与周质微管一起参与了初生壁和次生壁早期的形成;纤维细胞次生壁的形成过程就是一个漫长的程序性细胞死亡(PCD),而PCD的产物与胞间连丝一起参与了次生壁的形成与加厚;染色质凝聚并边缘化的细胞核与胞间连丝的持续存在,证明毛竹茎秆纤维细胞是一种典型的长寿细胞.     

柽柳胚和胚乳发育的观察

利用常规石蜡制片技术,对柽柳（Tamarix chinensis Lour.）胚和胚乳的发育过程进行了观察。结果表明,胚发育属茄型,其基细胞先行纵裂。胚柄基部发育迅速,具吸器作用,球形胚期胚柄最为发达,其细胞质丰富,贮藏淀粉类物质,至晚心形胚期胚柄依然存在。助细胞被受精产生多胚现象。胚乳发育属核型,初生胚乳核常常晚于合子分裂,胚乳核的分裂速度慢于胚体细胞的分裂速度。当胚乳游离核为 32个时,以自由生长细胞壁的方式进行胚乳细胞化。胚乳细胞进一步增殖极少。珠心细胞只有两层,细胞核大,胞质丰富,内含贮藏物质,至心形胚期逐渐解体。     

Development of basal endosperm transfer cells in Sorghum bicolor (L.) Moench and its relationship with caryopsis growth

During sorghum caryopsis development, endosperm epidermal cells near the basal main vascular bundle are specialized by depositing wall ingrowths, differentiating into basal endosperm transfer cells (BETCs). All the BETCs together compose the basal endosperm transfer layer (BETL). BETCs are the first cell type to become histologically differentiated during endosperm development. The initiation and subsequent development of BETCs shows the pattern of temporal and spatial gradient. The developmental process of BETL can be divided into four stages: initiation, differentiation, functional, and apoptosis stage. A placental sac full of nutrient solutions would emerge, enlarge, and eventually disappear between the outmost layer of BETL and nucellar cells during caryopsis development. BETCs have dense cytoplasm rich in mitochondria, lamellar rough endoplasmic reticulum, Golgi bodies, and their secretory vesicles. They show a series of typical characteristics of senescence such as nuclei distortion and subcellular organelle deterioration during their specialization. BETCs probably play an active role in nutrient transfer into the starchy endosperm and embryo. The occurrence, development, and apoptosis of BETCs are in close relation to the caryopsis growth and maturation especially the enrichment of endosperm and the growth of embryo. The timing when BETL is fully developed, composed of three to four layers in radial direction and 70 to 80 rows in tangential direction, consists with the timing when average daily gain of caryopsis dry weight reaches its maximum. It is conceivable that measures that delay the senescence and death of BETCs would help to increase the crop yield.     

Embryo and Endosperm Development in Isatis Tinctoria L. and the Histochemical Study of Its Storage Reserve

The ovule is anatropous and bitegmic. The nuceIlar cells have disorganized except the chalazal proliferating tissue. The curved embryo sac comprises an egg apparatus and a central cell with two palar nuclei and wall ingrowths on its micropylar lateral wall. The antipodal cells disappear. Embryo development is of the Onagrad type. The filament suspensor grows to a length of 785 μm and degenerats at tarpedo embryo stage. The basal cell produces wall ingrowths on the micropylar end wall and lateral wall. The cells of mature embryo contain many globular protein bodies, 2.5–7.5 μm in diameter, composed of high concentration of protein and phytin, insoluble polysaccharide and lipid. The cells, except procambium, also contain many small starch grains. Some secretory cavities scattered in the ground tissue have liquidlike granules composed of protein, ploysacchaide and lipid. Endosperm development follows the nuclear pattern. At the late heart embryo stage, the endosperm around the embryo and the upper suspensor and the peripheral endosperm of the basal region of the U-shaped embryo sac becomes cellular. The endosperm at micropylar and chalazal ends remains free nuclear phase until the late bended cotyledon stage. Wall ingrowths at both micropylar and chalazal end wall and lateral wall of the embryo sac become more massive during endosperm development. Wall ingrowths also occur on the outer walls of the outer layer endosperm cells at both ends and lateral region of the embryo sac. When the embryo matures, many layers of chalazal endosperm ceils including 2–4 layers of transfer cells, a few of micropylar endosperm cells and 1–5 layers of peripheral endosperm cells are present. The nutrients of the embryo and endosperm at different stages of development are also discussed.     

Transfer Cells in Suspensur and Endosperm during Early Embryogeny of Vigna sinensis

During early embryogeny, structural differentiation of the suspensor and endosperm can be observed with the formation of cells with wall ingrowths. In the early proembryo stage, wall ingrowths are seen only on the boundary walls of the embryo sac around the proembryo and at the chalazal end. Later, ingrowths appear in the outer walls of the basal suspensor cells and some wall ingrowths also begin to develop in the outer walls of cellular endospermic cells adjacent to the nucellar cap and the inner integumentary tissues. The suspensor appears to remain active throughout the differentiation stages. Two regions can be clearly distinguished in the suspensor: a basal region and a neck region. Wall ingrowths appear to form only in the cells of the basal region. During the development of the cellular endospermic sheath, its cell number and size both increase slightly. Later, these cells rapidly become separated from each other. Those endospermic cells that abut directly onto the integumentary tissues also develop wall ingrowths. In the region of the fluid endosperm, wall ingrowths are especially abundant in the boundary walls on the ventral side of the embryo sac. The possible pathway of nutrient flow to the developing embryo is discussed.     

Early Endosperm Development in Ovules of Soybean, Glycine max (L) Merr. (Fabaceae)

Endosperm development was studied in normally setting flowersand pods of soybean from anthesis to a pod length of 10–20mm. The free-nuclear stage following double fertilization istypified by loss of starch and increasing vacuolation. The cytoplasmprovides evidence of extensive metabolic activity. Wall ingrowths,already present at the micropylar end of the embryo sac wallprior to fertilization, develop along the lateral wall of thecentral cell as well as at the chalazal endosperm haustorium.Endosperm cellularization begins when the embryo has developeda distinct globular embryo proper and suspensor. Cellularizationstarts at the micropylar end of the embryo sac as a series ofantidinal walls projecting into the endosperm cytoplasm fromthe wall of the central cell. The free, growing ends of thesewalls are associated with vesicles, microtubules, and endoplasrnicreticulum. Pendinal walls that complete the compartmentalizalionof portions of the endosperm cytoplasm are initiated as cellplates formed during continued mitosis of the endosperm nuclei.Endosperm cell walls are traversed by plasmodesmata. This studywill provide a basis for comparison with endosperin from soybeanflowers programmed to abscise. Glycine max, soybean, endosperm, ovules     

Ultrastructure of endopolyploid antipodals inAconitum vulparia Rchb.

Summary The ultrastructure of antipodals ofAconitum vulparia Rchb. was studied at two stages of development: at the earlier stage the endosperm has several nuclei, at the later one the endosperm is multinucleate. Over the investigated period the antipodal size enlarges distinctly. The wall ingrowths increase in size and number. Finally, they occur throughout the antipodal walls except for a small area in the extreme chalazal part, sunk deep into the nucellar podium. There are no plasmodesmata in the antipodal cell walls. The cytoplasm is dense and rich in ribosomes; it shows weak vacuolation. The rough endoplasmic reticulum is well developed. At the later stage dilated cisternae of endoplasmic reticulum are formed. Mitochondria, plastids and active dictyosomes are abundant. At the later stage some giant mitochondria are present; their matrix contains a large clear area with fine fibrils and an aggregation of fibrillar material. At this stage of development plastids have two types of inclusions: electron-transparent vacuoles and aggregations of electron-dense granules. The giant endopolyploid nuclei are considerably larger than those at the mature embryo sac stage; they are lobed on all sides.During the studied periodA. vulparia antipodals seem to be at their most active state.     

Development of Embryo and Endosperm and Nutrient Accumulation in Vigna sesquipedalis (L.) Fruwirth

The structure of embryo sac, fertilization and development of embryo and endosperm in Vigina sesquipedalis (L.) Fruwirth were investigated. Pollization occures 7–10h before anthesis, and fertilization is completed 10 h after anthesis. After fertilization, wall ingrowths are formed at the micropylar and chalazal ends of the embryo sac. Embryo development conforms to the Onagrad type, and passes through 2 or more celled proembryo, long stick-shaped, globular, heart shaped, torpedo, young embryo, growing and enlarging embryo and mature embryo. Wall ingrowths are formed on the walls of basal cells and outer walls of the cells at basal region of suspenser. The suspensor remains as the seed reaches maturity. The starch grains accumulate in the cells of cotyledons by 9–16 days after anthesis, and proteins accumulate by 12–18 days after. The endosperm development follows the nuclear type. The endosperm ceils form at the micropylar end, and remain free nuclear phase at chalazal end. The outer cells are transfer cells. Those cells at the micropylar end form folded cells with wall ingrowths. At heartembryo stage, the endosperm begins to degenerate and disintegrates before the embryo matures.     

Studies of Ultrastructure and ATPase Localization of Mature Embryo Sac in Vicia faba L.

Studies of ultrastructure and ATPase localization of the mature embryo sac in Vicia faba L. show that the egg cell has no cell wall at thechalazal end, it has a chalazally located nucleus and a large micropylar vacuole. There are many nuclear pores in the nuclear membrane. The cytoplasm is restricted around the nucleus. Dictyosome and mitochondria are few. There are some starch grains and lipid grains in the egg cytoplasm. There are no obvious differences between two synergids. No cell wall is seen at the chalazal end either, but there are some vesicles which project to vacuole of the central cell and fuse with its vacuolar membrane. Plasmodesmata connections occur within the synergid wall where it is adjacent to the central cell. The synergid has a micropylarly located nucleus and a chalazal vacuole, the nucleus is irregularly shaped. The synergid cytoplasm is rich in organelles. The filiform aparatus is of relatively heterogeneous structure. The central cell is occupied by a large vacuole and its cytoplasm is confined to a thin layer along the empryo sac wall, but is rich in various organelles, starch grains and lipid bodies. Nucleolar vacuoles are often present two polar nuclei. The nuclear membranes of two polar nuclei have partly fused. ATPase reactive product was located obviously at the endoplasmic reticulum in cytoplasm of the egg cell and central cell. The embryo sac wall consists of different density of osmiophilic layer. There are some wall ingrowths in chalazal region of the embryo sac. The long-shaped and cuneate cells of chalazal region are peculiar. Special tracks of ATPase reactive products are visible at their intercellular space which may be related to transportation of nutrients.     

SECRETIONS FROM THE PISTIL OF LILIUM LONGIFLORUM

The pistil of Lilium longiflorum secretes two forms of exudate, one from the stigma surface and the other from the canal cavity. Electrophoretic studies of these exudates have revealed quantitative and qualitative differences in protein profiles. The exudatic components which are transferred to the cell wall by endoplasmic reticulum and Golgi vesicles, are stored within the cell wall of the secretive tissues and secreted from the cell walls directly. The cell wall structure of these secretive tissues differs. The canal cell wall has thick characteristic ingrowths that are supplied mainly from Golgi vesicles, while the papilla cell wall of the stigma is thinner, lacks ingrowths, and is supplied from ER vesicles.