四种裸子植物叶精油化学成分的研究

采用气相色谱—质谱—计算机联用仪对穗花杉、南方红豆杉、三尖杉和罗汉松叶精油化学成分的研究发现,三尖杉和穗花杉叶精油的组成特点极为相似,相同成分１３个,占各自精油组成的４８．０７％和３３．３２％．三尖杉和南方红豆杉叶精油的相同成分４个,占各自精油组成的１６．１４％和４０．５９％．在一定程度上支持三尖杉科和红豆杉科的亲缘关系接近,红豆杉科可能是通过穗花杉属和三尖杉科相联系的观点．罗汉松和穗花杉叶精油的相同成分４个,占各自叶精油组成的比例为２４．０９％和２０．８２％,比罗汉松和南方红豆杉、三尖杉之间组分的相似性要高．反映出罗汉松科和红豆杉科之间有一定联系,穗花杉属是认识红豆杉科、三尖杉科和罗汉松科之间系统关系的关键属     

部分裸子植物叶片总蛋白分析

采用ＳＤＳ－ ＰＡＧＥ 技术, 分析了红豆杉科（Ｔａｘａｃｅａｅ） 植物南方红豆杉（ Ｔａｘｕｓ ｃｈｉｎｅｎｓｉｓｖａｒ－ ｍａｉｒｅｉ （Ｌｅｍｅｅ ｅｔ Ｌｅｖｌ－） Ｃｈｅｎｇ ｅｔ Ｌ－Ｋ－Ｆｕ） 、穗花杉（ Ａｍｅｎｔｏｔａｘｕｓ ａｒｇｏｔａｅｎｉａ （Ｈａｎｃｅ） Ｐｉｌ ｇｅｒ） 、云南穗花杉（ Ａ－ ｙｕｎｎａｎｅｎｓｉｓ Ｌｉ） 、白豆杉（ Ｐｓｅｕｄｏｔａｘｕｓｃｈｉｅｎｉｉ（Ｃｈｅｎｇ） Ｃｈｅｎｇ） 以及三尖杉科（Ｃｅｐｈａｌｏｔａｘａｃｅａｅ） 、植物三尖杉（ Ｃｅｐｈａｌｏｔａｘｕｓ ｆｏｒｔｕｎｅｉ Ｈｏｏｋ－ｆ－） 、粗榧（ Ｃ－ｓｉｎｅｎｓｉｓ （Ｒｅｈｄ－ｅｔＷｉｌｓ－） Ｌｉ） 、海南粗榧（ Ｃ－ｈａｉｎａｎｅｎｓｉｓ Ｌｉ） 、篦子三尖杉（ Ｃ－ｏｌｉｖｅｒｉ Ｍａｓｔ－） 和罗汉松科（Ｐｏｄｏｃａｒｐａｃｅａｅ） 、植 物罗汉松 （ Ｐｏｄｏｃａｒｐｕｓ ｍａｃｒｏｐｈｙｌｌｕｓ （ Ｔｈｕｎｂ－ ） Ｄ－Ｄｏｎ） 、鸡毛 松（ Ｐ－ｉｍｂｒｉｃａｔｕｓ Ｂｌ－） 、竹柏（ Ｐ－ ｎａｇｉ（Ｔｈｕｎｂ－） Ｚｏｌｌ） 、陆均松（ Ｄａｃｒｙｄｉｕｍ ｐｉｅｒｒｅｉ Ｈｉｃｋｅｌ） 共１２ 种植物的叶片蛋白, 在蛋白质水平上采用     

Biochemical Systematics of Gymnosperms (3)—On the Systematic Position of Tax aceae from Their Seed Protein Peptides and Needle Peroxidases

The major peptides in the seed of Taxus and Pseudotaxus have molecular weight about 31, 22 and 20 kilodaltons (Kd) shown by SDS polyacrylamide gel electrophoresis. The seed protein peptides of Cephalotaxus is very similar to those of Taxus and Pseudotaxus except a few bands of high molecular weight. Some considerable differences in peptide pattern exist between Amentotaxus and the three genera cited above. The former has a new major peptide, 33K, but lacks 22 K. The seed of Torreya does not contain peptide 44 K, although Torreya and Amentotaxus have many bands in common. To a certain extent, the seed protein peptides of Podocarpus nagi are similar to those of the above taxa. A great range of divergency in needle peroxidases among different genera of Taxaceae has been observed by using electrophoresis, while the zymogram of Cephalotaxus is somewhat similar to that of Taxus. Two series of protein data demonstrate, that there is an evolutionary tendency from Taxus to Torreya through Pseudotaxus and Amentotaxus within Taxaceae. And the Taxaceae is closely related to Cephalotaxus by way of Taxus. The systematic positionof the Taxaceae, therefore, should be placed under the Coniferales.     

红豆杉科及相关类群rbcL基因PCR—RFLP分析

运用RFLP方法对红豆杉科及相关类群14种植物叶绿体rbcL基因PCR产物进行限制酶酶切分析,共获29个酶切变异位点。采用PHYLIP软件包对限制位点变异数据进行极大简约法分析得到18个步长为6的最简约树并求得一致树,结果显示：⑴红豆杉科和三尖杉科属单系群;⑵穗花杉属Amentotaxus以置于红豆杉科内为宜,不支持将穗花杉属独立成科的处理方式;⑶白豆杉应为红豆杉科内一个属Pseudotaxus;⑷三尖杉属内篦子三尖杉地位特殊,可设篦子三尖杉组;⑸不赞同将竹柏类从罗汉松属中分离出去成立新科;⑹红豆杉科、三尖杉科和罗汉松科三者间,前两者的关系更为接近。     

红豆杉科及相关类群rbc L基因PCR-RFLP分析

运用RFLP方法对红豆杉科及相关类群14种植物叶绿体rbcL基因PCR产物进行限制酶酶切分析,共获29个酶切变异位点。采用PHYLIP 软件包对限制位点变异数据进行极大简约法分析得到18个步长为6的最简约树并求得一致树,结果显示：（1）红豆杉科和三尖杉科属单系群;(2) 穗花杉属Amentotaxus以置于红豆杉科内为宜,不支持将穗花杉属独立成科的处理方式;(3)白豆杉应为红豆杉科内一个属Pseudotaxus;(4) 三尖杉属内篦子三尖杉地位特殊,可设篦子三尖杉组;(5) 不赞同将竹柏类从罗汉松属中分离出去成立新科;(6) 红豆杉科、三尖杉科和罗汉松科三者间,前两者的关系更为接近。     

The phylogenetic position of taxaceae based on 18S rRNA sequences

The evolutionary position of the yew family, Taxaceae, has been very controversial. Some plant taxonomists strongly advocate excluding Taxaceae from the conifer order and raising its taxonomic status to a new order or even class because of its absence of seed cones, contrary to the case in the majority of conifers. However, other authors believe that the Taxaceae are not fundamentally different from the rest of the conifers except in that they possess the most reduced solitary-ovule cones. To resolve the controversy, we have sequenced the 18S rRNA genes from representative gymnosperms: Taxus mairei (Taxaceae), Podocarpus nakaii (Podocarpaceae), Pinus luchuensis (Pinaceae), and Ginkgo biloba (Ginkgoales). Our phylogenetic analysis of the new sequence data with the published 18S rRNA sequence of Zamia pumila (a cycad) as an outgroup strongly indicates that Taxus, Pinus, and Podocarpus form a monophyletic group with the exclusion of Ginkgo and that Taxus is more closely related to Pinus than to Podocarpus. Therefore, Taxaceae should be classified as a family of Coniferales. Our finding that Taxaceae, Pinaceae, and Podocarpaceae form a clade contradicts both the view that the uniovulate seed of Taxaceae is a primitive character and the view that the Taxaceae are descendants of the Podocarpaceae. Rather, the uniovulate seed of Taxaceae and that of some species of Podocarpus appear to have different origins, probably all reduced from multiovulate cones. Correspondence to: W.-H. Li     

红豆杉科、三尖杉科和罗汉松科植物叶片结构的比较观察

扫描电镜和光镜下的叶表皮特征以及叶片解剖结构的研究结果,支持在红豆杉科内建立白豆杉属的处理方式;赞同在三尖杉属内建立篦子三尖杉组,叶片解剖结构方面,三尖杉科和红豆杉科的穗花杉属的相似之处颇多。而叶表皮形态特征方面又表现为三尖杉科和罗汉松科更加接近。反映了出了红豆杉科、三尖杉科和罗汉松科之间的密切而又复杂的系统关系。     

A Contribution to Pollination and Fertilization of Amentotaxus argotaenta

The present investigation was conducted during 1980–1982, and mater- ials collected from Jin-Fo shan (Golden Buddha Mountain), at a height of 1400-1600 m, Sichuan province, China. Pollination of Amentotaxus argotaenia began to proceed last week of May, and came into bloom the first week of June. The male strobiles were almost entirely wilting at June 12–15. Thus, florescence of Amentotaxus spread over a period of 3 weeks. While the pollen grains approaching to maturity, most of the microspores divide to form a larger tube cell and a smaller antheridial initial. In this case the mature pollen grains of Amentotaxus consist of two cells. Then pollen grains are attracted down into the pollen chamber in the apex of the nucellus after pollination. The pollen chamber of Amentotaxus in longitudinal section looks like a flask in shape and is very much similar to that of Ginkgo biloba. As pollen grains at pollen chamber begin to germinate, the antheridial initials divide again to give rise to a spermatogenous cell and a sterile cell. At first, the spermatogenous cell is of a size only 11–13 μ in diameter. When the pollen tube reaches the middle part of the nucellus, the spermatogeneous cell is of a size about 30 μ. In the middle of July, pollen tube approaches the top of the female gametophyte. In this time, the spermatogenous cell has already been mature enough and is of 58–85 μ in diameter. The nuclei of spermatogenous ceils, 30–36 μ in size, are usually lying in the lateral side of the cytoplasm at its micropylar end. From the middle to the end of July, spermatogenous cells divide to form two unequal sperms, one of which is larger than the other and is the functional one. The large sperm is almost round in shape and about 56 μ in diameter. The small sperm is elliptic in shape, non-functional, and about 33 μ in diameter. The nuclei of the large and small sperms are about 40 μ and 26 μ, respectively. In some cases there are lateral pollen tube and sperms in the ovules of Amentotaxus, or the pollen tube even grows toward the lower part of female gametophyte in the chalazal end and there are well developed sperms in such a case. In the middle of July, nucleus of the central cell divides to form a ventral canal nucleus and an egg nucleus. The former then breaks down quickly and the latter continues to develope and moves toward the central part of the egg cell gradually. It is interesting to note that there are a number of nucleolus-like grains in the cytoplasm of the egg cell in Amentotaxus. The large nueleolus-like grains contain a larger central vacuole with several smaller vacuoles surrounding it. These grains show a positive reaction and blue colour by PAS and aniline blue black or coomassie brilliant blue, respectively. The above facts show that the nucleolus-like grains contain not only po- lysaccharides, but also protein. Similar grains may also found in the developing pollen tube. This is a unique feature in Amentotaxus and even in Gymnosperms. Otherwise, there are often two groups of the dense cytoplasm under the egg nucleus in Amentotaxus. Fertilization of Amentotaxus took place around July 20–29 (1980–1982). Interval between pollination and fertilization was about two months. After male nucleus fuses entirely with the female nucleus, the zygote begins to divide by mitosis. During fertilization, in addition that the large sperm enters the egg cell and fuses with the egg nucleus, the small sperm, tube nucleus, and sterile cell are often delivered into the egg cell. But they are disintegrated gradual]y and eventually. It is worthy to note that the nucleolus-like grains and the starches in pollen tube are also released into the egg cell. Then enlargement, fusion, and budding in the nucleolus-like grains may be found within the cytoplasm of the egg cell after fertilization. The history of investigating Amentotaxus found in 1883 has been lasting a long period of 100 years. But researches in sex production has never been studied before. The present work has shown that fertilization in Araentotaxus is very much similar to that in Taxus, Pseudotaxus, and Torreya. In other words, they all belong to the same type, that is, mitosis of zygote taking place after fusion of the two sexual nuclei. This condition constitutes one of the features of Taxaceae. But fertilization in Cephalotaxaceae is different from that of Taxaceae in having mitosis taking place before fusion of the two sexual nuclei. Pollination of Amentotaxus is similar to that of Cephalotaxus with dual-cell pollen grains at shedding stage. On the other hand, interval between pollination and fertilization in Austrotaxus lasts for 13.5 months, and this is the longest one in Taxaceae, and it is similar to that of Cephalotaxus proceeding for 14 months. To sum up, from the point of view of pollination, fertilization, and embryogenesis, Amentotaxus could be considered a primitive type in Taxaceae. Perhaps an order of systematic position of the genera belonging to Taxaceae can be arranged thus: Amentotaxus, Austrotaxus, Taxus, Pseudotaxus, and Torreya. And Cephalotaxaceae may be related to Taxaceae by way of Amentotaxus.     

Investigation on Sexual Reproductive Cycle in Torreya grandis

Before May the first, the ovular primordium of Torreya grandis has differentiated. From this early moment the primordium look like the parabolic form and it is surrounded by many pairs of scales, of which a pair of the inner scales are lying at the same level as the primordium of ovule. About May the first of the second year, the differentiation of the various tissues in the ovule has essentially completed. And the fertilization takes place from the end of August to the beginning of September. After overwintering, the proembryo developes into a young embryo in April of the third year, and at the last stage both the seed and the embryo become mature from September to November. In the Taxaceae, the embryogenesis is similar in Amentotaxus,Austrotaxus, Taxus, and Pseudotaxus; their proembryos form cell wall all at the stage of 16-free nuclei and simple polyembryony is common among them. In Torreya, however, the cell wall of proembryo appear at the stage of 4 or 8-free nuclei, and cleavage polyembryony is its feature. On the basis of our observation, the sexual reproductive cycle of Torreya grandis seems to have two important features, one of which is rather long (31 moths from ovular primordium to seed maturity; about 4 months from pollination to fertilization and 7-8 months for development of proembryo). The state of the long sexual cycle in Amentotaxus and Austrotaxus is different from each other; in the former development of young embryo lasts 10-11 months, and in the latter the interval between pollination and fertilization is 13.5 months. The second feature of the sexual cycle in Torreya grandis is over two winters: development of the sporogenous cells in the first, and the proembryo development in the second. From the point of view of phylogenesis, some primitive characters are present in the sexual cycle of Torreya grandis although a specialized feature of the embryogenesis occurs in some degree.     

太白红杉雌配子体的形成、受精、胚胎发育及其系统学意义

太白红杉(Iarix chinensis Beissn)雌球花于7月中下旬开始分化,9月上旬至9月中旬形成大孢子母细咆,10月中旬,大孢子母细胞进入休眠期。翌年4月底至5月初解除休眠,大孢子母细胞进行减数分裂,于5月10日左右形成直列四分体,随后珠孔端的3个大孢子退化,合点端的1个大孢子进一步发育,成熟卵细胞于7月初受精;花粉管将内含物释放入卵细胞后在尾部形成浓密物质沉淀;受精后,合子被染色较深的新细胞质所包围,并发现存在多精入卵的现象。合子经过两次连续有丝分裂,产生4个游离核后伴随新细胞质一起移至合点端,接着同时进行一次有丝分裂产生8个核,并分成上下两层后形成细胞壁,但上层细胞顶部不形成细胞壁。原胚发育属于松型。在幼胚阶段,我们发现部分胚珠发育异常,其雌配子体有的变为半透明状,有的则干瘪萎缩。太白红杉具简单多胚和莲座胚。9月中旬,成熟胚形成,成熟胚具5～6枚子叶。太白红杉从雌球花花芽分化到胚胎成熟历时14个月。     

穗花杉染色体的研究

穗花杉为国家三级重点保护的珍稀濒危植物,雌雄异株。根尖细胞染色体分析表明：雌株和雄株的染色体数目为２ｎ＝４０,其中第１对和第２对为中部着丝粒染色体,第３－２０对为端部着丝粒染色体。核型为２ｎ＝４０＝４ｍ＋３６Ｔ。雌雄株除第２对的长度稍有差异外,其余各对的相对长度和臂比都较近似,可能尚无性染色体分化。Ｇｉｅｍｓａ Ｃ带显示,间期核有３个较大的染色中心,最长的３条染色体的中央缢痕有深染色带纹,可能是着     

Chloroplast matK gene phylogeny of Taxaceae and Cephalotaxaceae,with additional reference to the systematic position of Nageia

Reported in the present paper is a robust chloroplast matK gene phylogeny of Taxaceae, Cephalotaxaceae and Podocarpaceae represented by 10 species of seven genera, with three species of the Pinaceae as outgroups. The matk length of the 13 species ranges from 1488 bp to 1548 bp, which results from indels, in particular, 1-bp(base pair) insertion near the 3’ end of the gene in some groups. A 27 bp deletion was found at the nucleotide position 213 from the 5’ end of the matk gene of Pseudotaxus chienii. The aligned sequences used in PAUP and MEGA analyses were 1568 bp and 1494 bp respectively. In the matK gene, the rates of variation at the first, second and third codon positions are similar although the mean frequency of synonymous substitution is approximately twice as high as that of nonsynonymous substitution. Branch-and-Bound search found only one most parsimonious tree (tree length = 895, CI = 0.850, RI = 0. 876), in which all clades were strongly supported by bootstrap test. According to the tree, Taxaceae and Cephalotaxaceae are monophyletic groups, and the sister group relationship between the two families was confirmed. Taxus is closely related to Pseudotaxus while Torreya is the sister group of Amentotaxus. In addition, the close relationship between Nageia and Podocarpus was resolved. The present study supports the generic status of Pseudotaxus and Amentotaxus in point of cladistic analysis and genetic distance, but contra-dicts the establishment of the family Nageiaceae.     

Early Embryogeny and Its Starch Distribution in Amentotaxus

The present paper deals with the early embryogeny of Amentotaxus argotacnia (Hance) Pitger and its variation in starch distribution. Amentotaxus is endemie to China. The proembryos of Amentotaxus occurred at the end of July to early August, 1980–1981, When the zygote has sueeessive]y divided for four times, the daughter nuelei are becoming smaller and smaller after each division. At first, the zygote is 80–100 μ in diameter. Then, tbe free nuclei of the proembryo are 50–70 μ in diameter in two-nucleate stage, 36–50 μ in four-nucleate stage, and 29–32 μ in eight- to sixteen-nueleate stage, respectively. The wall formation of proembryos in Amentotaxas as in most other members of Taxaeeae also takes place at 16-nucleate stage. After wall formation the cells u each proembryo are arranged in two groups, upper one constitutes the cells of open tier (O) and the lower one, the primary embryonic eells (PE). The ratio of 0 to PE is 9:7 or 8:8 in some eases. The cells of open tier elongate and divide to form the ceils of upper tier (U) and the prosuspensor eens (S). In such ease, The ratio is U:S:PE= 8:8:8. When the eells of open tier and primary embryonie tier sometimes divide simultaneously, the primary embryo cells result in the embryo cells (E), and the ratio is U:S:E=9:9:14 or U:S:E=8:8:16. The young embryos of Amentotaxus begin to differentiate in the first week of August in Jin-Foshan (Golden Buddha Mountain), 1400 to 1600m. Sichuan Province, China The developmental features of the young embryo in Amentotaxus are as follows: (1) The development of the young embryos lasts for 10 to 12 months. This is very unique in Gymnosperms. The development of tile embryo in Amentotaxus is in some deg ree similar to that of Ginkgo, beeause their young embryos develop in maternal plants, whereas the late embryogeny takes place after shedding of the seed. (2) The young embryos pass through the winter at multieellular stage and the late embryos are still undifferentiated when the arils are getting red and the seeds begin to shed. It is interesting to note that the development of embryos are still staying at embryo seleetion stage of simple polyembryony when seeds were stored for six months in 15-20℃. As far as our information goes, the embryos in seeds should get over another winter until embryo matures. The embryos in Amentotaxus is un;quo in this respect and it is considered to be primitive. Though the seeds of pteridosperms have large female gametophytcs, none of embryos have been found in their fossil seeds. Probably their embryos are not well developed when the seeds mature and shed. Thus the embryos of fossil seeds are not easily preserved (Cronquist, 1968). The condition of embryonic developaleut in Amentotaxus resembles strongly with that in pteridosperms. From above, Amentataxus eould be the most primitive genus in Taxaceae. (3) Simple polyembryony in Amentotaxus is pronfinent. The prosuspensors sometimes divide to give rise to “suspensor embryos”. The general tendency of the starch distribution in male and female gametophytes is that the main regions of stareh are gradually transferred frmn mieropylar to chalazal end wiht the development of the ovule. After pollen germination the stareh proceeds together with the sterile cell, tube nueleus and spermatogenous cell down the arehegonium. In early developmental stage of female gametophyte, the starch region always appears round the upper part of the archegonia; after fertilization they mainly appear in tissue of female gamctophyte near the proembryo or young embryo to form the pyramidal region. It is worthy to note that the starch grains of male gametophyte are larger in size than those of female gametophyte and the former is much less in nmnber than the latter. So far as the embryo proper is concerned the starch grains densely appear armmd the nuclei of the embryos, espeeially those of the prosuspensors. Besides, near the basal part of aril and integument there is a stable region of polysaeeharide which shows the positive reaetion for PAS. This region is always present from the origin of aril to its mature and is an important feature of the ovule and seed in Amentotaxus,     

Studies on Pollen Morphology of Taxaceae of China

The present study deals with pollen morphology of 4 genera and l0 species of Taxaceae in gymnosperms. Pollen grains of the family are spheroidal or subspheroidal, 20.8μm in diameter and with laptoma or papilla in the distal face. Exine is two-layered, with sexine equal to nexine in thickness, but sometimes the stratification is indistinct. The surface is scabrous or slightly granular under LM. Coarse verrucae and fine tuberculae on pollen surface are observed under SEM. From thin section, endexine is shown to have lamellate structure, and ectexine is made of verrucate elements. In Amentotaxus argotaenia, some pollen grains show remnant saccate. According to pollen morphology, this family may be divided into two tribes: 1, Pseudotaxeae (including Pseudotaxus only), and 2, Taxeae (including Taxus and Torreya). Owirg to the special feature of pollen grains in Amentotaxus the present author suggests that the genus be separated from Taxaceae and raised to the level of family, Amentotaxaceae.     

The Ovule Structure and Development of Male and Female Gametophytes in Araentotaxus

The ovules of Amentotaxus are 2–2.5 cm in length and about 1.3 cm in width. Aril, which contains about 14—17 secretory canals in transection, is com- posed of parenchyma. The vascular bundles are absent in aril. The integument is com- posed of ceils of outer, middle, and inner regions. The middle region of the integument is about 10 cells in thickness. The Integuments are basally parenchymatous before pollination and then the cells become elongating and thickenning in middle region after pollination. Finally the micropylar canal is forced to be closed. In addition, there are 8–14 vascular bundles with centripetal xylem arranged in a ring in integument. One of the most remarkable feature of the ovule is that there is a pollen chamber formed at the top of nucellus before pollination. At this time because epidermis of nucellus does not disintegrate, the pollen chamber looks like conical in longitudinal section. After pollination the pollen chamber was becoming closed due to elongation and thickenning of cells in the middle region of integument. At the base of ovule there are 4–5 pairs of bracts which contain a larger secretory cavity and a centripetal xylem in a vascular bundle. It is interesting that wax layer of 30–40 μm thick is covered on the surface of integument, aril and bract. Usually 3–4 microsporangia which are hypodermal in origin, occur in abaxial side of a microsporophyll. In some cases the tapetum is partly enlarging and extruding into the developing tetrahedral tetrads. The mature pollen comprises an antheridial initial and a tube cell. About 20 pollen grains may germinate in the same ovule. The megaspore divide successively 8 times to produce 256 nuclei and then cell wall formation takes place. The female gametophyte is about 830–908 μm in length and 500 μm in width. The archegonia are single, terminal, and 6–7 in number. The mature archgonium, with ventral canal nucleus, is about 430 μm in length and 80–108 μm in width. The female gametophyte is often growing against the upper part of the nuceilus and makes the cells of the latter gradually to be disintegrated. The ovule construction of Amentotaxus is in some degree similar to that of Ginkgo in having a comparatively well developed pollen chamber. The mature pollen of Amentotaxus, which is similar to that of Cephalotaxus is composed of 2-cells. In sum, Amentotaxus perhaps is the most primitive genus in Taxaceae and it is closely related to Cephalotaxus.     

A Study on the Genus Cephalotaxus Sieb. et Zucc.

The genus Cephalotaxus contains a small number of species. It is adequately appreciated as a newly discovered cancerresistant medicament for the alkaloids obtained from its branches leaves and barks are of curative effect. This paper deals with the classificatory revision based on the morphological features, with the reference to the anatomical characters of leaves, types of alkaloids and pollen morphology observed. Two new combinations are proposed, and 4 species and varieties are reduced in the paper. The genus Cephalotaxus is thus suggested to consist of 2 sections and 9 species. The trees occur in East Asia and the north of Indo-China, with 88% found in China where is the distribution centre and refuge of the genus. The genus in discussion is of unique morphological features which are distinctly different from these of Amentotaxus, Cephalotaxaceae, containing a single genus of Cephalotaxus, is closely related to Taxaceae, and therefore the Cephalotaxaceae is best placed in the Taxinieae of Coniferales.     

部分裸子植物假种皮微形态特征及其分类学意义

应用扫描电镜对红豆杉科、三尖杉科和罗汉松科植物假种皮的微形态特征进行了研究,结果表明：可以把红豆杉科植物分为两类,即具规则型网状纹饰的红豆杉属和具无规则型网状纹饰的白豆杉属、穗花杉属和榧树属。在后三属中,穗花杉属的穗花杉和白豆杉属的纹饰特征更为相近,同属厚网脊亚型。而云南穗花杉和榧树属的特征相近,属薄网脊亚型。假种皮表面纹饰特征显示不宜将红豆杉（T．chinensis）再分为两个独立的种,认为设立红豆杉和变种南方红豆杉（T．chinensisvar.mairei）的处理方式更加合理。三尖杉科（属）蓖子三尖杉（C．oliveri）假种皮纹饰的网脊、网底分化程度、细胞大小、单位面积细胞数和本届的其它植物差异很大,为建立蓖子三尖杉组提供了进一步的佐证。假种皮的微形态特征还支持把宽叶粗榧（C.sinensisvar.latifolia）上升为种C．latifolia的观点。罗汉松科假种皮纹饰类型的观察结果表明罗汉松属和陆均松属是自然分类群。尽管罗汉松属竹相组假种皮纹饰的网脊变异范围相对较大,但是变异范围仍在属内,不支持将其独立为新科的观点。假种皮的表面纹饰特征还表明三尖杉科和红豆杉科之间的联系密切。     

Contrasted pollen capture mechanisms in Phyllocladaceae and certain Podocarpaceae (Coniferales)

Comparative study shows that Phyllocladus and representative Podocarpaceae differ in the mechanism by which pollen is introduced into the pollen chamber and onto the apex of the nucellus ("pollen capture"). Both types involve a pollination drop, but only in Podocarpaceae is it consistently inverted and in contact with adjacent surfaces. Phyllocladus has functionally nonsaccate pollen (although a vestigial saccus has been claimed); its pollen is wettable and sinks in water. Podocarpaceae (except Saxegorhaea) have saccate pollen, which is nonwettable and floats on water. In Phyllocladus the pollination drop receives the pollen directly and presence of pollen stimulates complete drop withdrawal, which may be a metabolic process. Once pollinated, an ovule does not resecrete a pollination drop. In Podocarpaceae the drop usually receives the pollen indirectly via pollen scavenging and saccate pollen is preferentially captured. The retraction of the drop appears to be the result of evaporation and is presumably nonmetabolic. Drop secretion can be repeated in the presence of pollen. A major consequence of these contrasted mechanisms is that in Phyllocladus the entire contents of the pollination drop are ingested, whereas in Podocarpaceae only that part of the drop that includes saccate pollen is ingested. Because of differences in repeatability of the secretion process, Podocarpaceae are likely to capture more pollen. In neither mechanism does the process favor 'own" pollen. but in Podocarpaceae all but saccate pollen is excluded. We thus have further evidence for differences in pollen capture mechanisms in conifers with a pollination drop, and differences in the behavior of the pollination drop itself.     

极小种群野生植物崖柏的生殖物候、传粉及胚胎发育研究

以濒危植物崖柏（Thuja sutchuenensis Franch.）为对象,对其生殖物候、传粉机制进行观察,并采用石蜡切片法对其胚胎发育过程进行研究。结果显示：崖柏于8月分化出大、小孢子叶球,次年3月传粉,为花粉无气囊、具传粉滴、胚珠直立型传粉机制,球果于10月开裂;显微观察发现,传粉期花粉进入珠孔后,贮藏在珠心上方的贮粉室内,同时珠心组织中分化出孢原细胞,进入雌配子体发育阶段,5月中旬,花粉管开始萌发,6月初完成受精,进入胚胎发育阶段,10月初,胚胎发育成熟。研究表明崖柏从大、小孢子叶球形成至种子成熟的整个发育过程中均存在败育,而胚珠败育及雌配子体游离核时期至幼胚发育期间的败育是其生殖障碍的主要原因。本研究获得了崖柏生殖生物学的基础资料,为其人工繁育和制定保护策略提供了重要依据。     

The Reproductive Biology of Totara (Podocarpus totara) (Podocarpaceae)

A reproductive cycle of totara (Podocarpus totara) in New Zealandis complete within 2 years. After strobilus initiation in September,there is a 9 month period of winter dormancy until emergenceduring the growth flush in July–August of the followingyear. Female strobili bear only one or two ovules which arepollinated mid-October to mid-November at the megaspore tetradstage. Pollen germination and fertilization occur rapidly duringDecember. The pollen tube carries the body cell, sterile andtube nuclei with at least three prothallial nuclei, and branchesout after reaching the archegonia. The four–six archegoniacontain egg nuclei with no distinct perinuclear zone and a largechalazal vacuole. Fertilization by the larger of the two unequalmale gametes is accompanied by a degradation of egg cell cytoplasm.The three-tier proembryo contains a binucleate embryonal tierof only one cell. Soon after embryo penetration into the megagametophyte,the binucleate embryonal-tier cell undergoes mitosis and cellwall formation resulting in four uninucleate cells. Some ovulescontained secondary embryos thought to be the product of suspensorcleavage. Embryo maturation occurs by February.Copyright 1999Annals of Botany Company Podocarpus totara, totara, conifer, podocarp, reproductive biology, embryology.