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.     

An embryological study and systematic significance of the primitive gymnosperm Ginkgo biloba

Ginkgo biloba L.is considered one of the most ancient seed plants,with several primitive features of plant reproductive process.However,the phylogenetic position of Ginkgo and its relationship with other extant seed plants remain unclear.To gain a better understanding of these issues,we observed the embryological development of G.biloba using semi-thin sections and scanning electron microscopy.In late August,the zygote moved from the end of the micropylar to the middle of the archegonium,and mitosis resulted in many free nuclei distributed randomly in the archegonium.Afterwards,the cell wall was formed and the proembryo began to differentiate into the embryonal region and the underdeveloped presuspensor region.In early October,the embryo differentiated into two cotyledons,plumule,hypocotyl,radicle,and suspensor tissues.Subsequently,the two cotyledons grew rapidly,but the undeveloped suspensor began to degenerate and gradually disappear,indicating that the embryo had begun to mature.During early embryo development,the main supply of nutrients was carbohydrate in the cells of the jacket,tentpole,and surrounding endosperm,whereas endosperm provided nutrients during embryo maturation.Our results indicate that Ginkgo is extremely similar to cycads in terms of embryology but more similar to conifers in macromorphology and vegetative anatomy,suggesting that the Ginkgo lineage may have an intermediate phylogenetic position between cycads and conifers.     

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,     

黑节草未成熟种子的形态发育及其在离体培养时的表现

黑节草(Dendrobium candidum Wall ex Lind.)2—6个月种龄的胚均处于球形胚阶段,不同种龄的胚在体积大小、胚细胞数目、胚细胞内的淀粉粒含量和超微结构上有差异。在离体培养条件下黑节草种子萌发率可达95％,种子萌发后形成原球茎,原球茎可以直接发育形成幼苗,又可以由原球茎产生大量愈伤组织,由愈伤组织再分化发育成幼苗。种子萌发过程中,胚顶端分生组织细胞的淀粉逐渐消耗,淀粉的变化与分生组织和子叶的形成有明显的相关性。     

蚕豆胚珠发育过程中淀粉动态的观察

蚕豆胚珠发育过程中淀粉动态变化如下:1.发育早期,整个胚珠中未见淀粉粒。其后首先在合点区出现淀粉,而后从合点向珠孔逐渐扩大分布范围。2.珠心和内、外珠被中均含有淀粉粒,尤以内珠被的淀粉增长迅速,数量多、个体大。受精后,内珠被解体,淀粉出现在外珠被细胞中,推测营养物质可通过整个胚囊表面进入其中。3.合点与胚囊之间的珠心细胞特化或长形。可能有助于营养物质进入胚囊。4.功能大孢子中贮存丰富的淀粉粒,它和珠心细胞一起是胚囊发育时的营养来源。5.卵细胞受精后,所含淀粉粒的数量和大小明显增长,随着合子和胚细胞的分裂,其中贮存的淀粉逐渐被消耗,到多细胞球形胚时完全消失。6.胚乳核周围始终未出现淀粉粒。7.胚器官分化之后,子叶和胚轴等处逐渐出现淀粉粒,其中生长活跃的结构如生长点、维管束等不贮存淀粉。8.子叶中的淀粉粒含量迅速增加,颗粒特大,是种子内营养物质的最终贮存场所。     

The Cytological and Histochemical Studies of Developing Soybean,Cotyledons

In the late globular proembryos, three regions could be identified, i. e. the cotyledon primordium, the epiphysis and the hypocotyl-hypophysis. In the cotyledon primordia, the mitotic frequency of the cells was comparitively high, the directions of the mitotic planes were mostly perpendicular to the long axis of the embryo, the size of the nucleolus was comparitively large, and the cytoplasm density was high. In the epiphysis region, however, the mitotic frequency of the cells was low, the size of the nucleolus was small, and as the first pair of leaf primordia appeared the mitotic frequency of the cells in that region began to increase. In the hypocotyls hypophysis region the mitotic frequency of the cells as well as the size of the nucleolus lied in between the corresponding values of those of the above two regions, the cytoplasm density was low and the size of the vacuoles was large. As the proembryo continued to develop the direction of the mitotic plane changed gradually, from mostly perpendicular to the long axis of the embryo to mainly inclined, or even parallel to that axis. As a result, the proembryo developed from a heart-shaped embryo into a torpedo-shaped embryo. After the first pair of leaf primordia appeared from the young embryo, the vacuoles in the cells of the cotyledons grew in size rapidly. About twenty to twenty five days after flowering, the starch grains, the protein bodies and the lipid granules began to accumulate in the cells of the cotyledons and gradually increased both in size as well as in quantity. About fifty days after flowering the diameter of the starch grains reached its maximum value of 6.2–7.0 μm, and decreased in value thereafter till the time of harvesting when most of the starch grains disappeared except those in the palisades. On the other hand, fifty to sixty days after flowering, the diameters of the lipid granules and of the protein bodies reached their maximum values of 5.4–7.0 μm and 6.2–7.0 μm, respectively. The observation revealed that the formation of the protein bodies was related to the vacules.     

黄精种子萌发过程发育解剖学研究

采用石蜡切片技术对成熟黄精种子形态及萌发过程中的形态学变化及解剖结构特征进行了研究,以阐明黄精种子繁殖的生物学机制。结果显示:(1)成熟的黄精种子由外而内依次为种皮、胚乳和胚等3部分组成。其中种皮由一层木质化的细胞组成;胚乳占据种子的大部分结构,胚乳细胞含有大量淀粉,细胞壁增厚;胚处于棒型胚阶段。(2)黄精种子在萌发过程中棒型胚靠近种脐端分化为吸器、子叶联结和子叶鞘,靠近种孔的部位分化出胚根、胚轴和胚芽。(3)黄精种子萌发首先由子叶联结伸长将胚芽和胚根原基推出种孔,紧接着下胚轴膨大形成初生小根茎,吸器留在种子中分解吸收胚乳中的营养物质。(4)通过子叶联结连通吸器和初生小根茎,将胚乳中的营养物质由吸器-子叶联结这个通路转移到初生小根茎中,为初生根茎上胚芽和胚根的进一步分化提供物质保障。(5)黄精种子自然条件下萌发率较低,而且当年不出土。研究表明,黄精种子的繁殖生物学特性是其生态适应的一种重要机制。     

Embryogenesis in Najas marina L.: Structural and histochemical approach

In Najas marina L. few polysaccharide grains are observed in zygote, basal cell and embryonal cells until the initiation of embryonic shoot-apex. With the formation of the shoot-apex, numerous polysaccharide grains engorge in the embryonal cells. The basal cell wall, subjacent to the nucellus, stains intensely with PAS (Peiodic Schiff's)-reaction. The concentration of proteins and RNA increases in the basal cell.Interestingly, the embryo shows intraseminal germination. The cells of embryonic shoot-apex, embryonic leaves, root primordium and procambial cells show a few polysaccharide grains while the cells of hypocotyledonary and cotyledonary regions are engorged with polysaccharide (starch) grains. Uniform distribution of proteins and RNA is observed in the embryonic shoot-apex, embryonic-leaves, root primordium and procambium, but the cells of hypocotyledonary and cotyledonary zones exhibit a low profile for these metabolites. The initial root-primordium remains quiescent. Three or 4 epidermal cells, subjacent to this quiescent primordium, differentiate; show densely stained, polarised, protein bands; and act as the future root primordium.The nucleus of the basal cell becomes polyploid and densely stains for proteins, RNA and DNA. At the globular proembryo stage, numerous nucleolar bodies migrate towards the periphery of the nucleus and at the 3-leaf embryo stage, these nucleolar bodies, rich in proteins and RNA, are located in the cytoplasm revealing nucleo-cytoplasmic interaction. The basal cell that never divides, but only enlarges, is persistent in the mature seed.     

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.     

Male Cones in Taxaceae s. l. - an Example of Wettstein's Pseudanthium Concept

Abstract: Male cones of Taxus baccata L. and Torreya californica Torr. are mostly regarded as simple strobili ("flowers"). In the past some authors assumed that every single "sporangiophore" of Taxus baccata represents a whole "flower". The male cone of Taxus would then represent a compound strobilus ("inflorescence"). A cone of Cephalotaxus harringtonia (Knight ex J. Forbes) K. Koch and Cephalotaxus fortunei Hook. can easily be recognized as a compound strobilus composed of several simple strobili.
Our developmental studies by SEM give clues to the assumption that a simple male strobilus in Cephalotaxus is not homologous to the male strobili in Taxus and Torreya. Developmental, morphological and anatomical studies suggest that the simple strobili of Taxus and Torreya are derived from the compound strobili in Cephalotaxus by a transformation of the simple strobili into single sporangiophores. With respect to morphology, the male cones in Taxus and Torreya are simple strobili, but comparative developmental studies show that they are derived from compound strobili in a process similar to Wettstein's pseudanthium hypothesis. In the light of our studies, it is not unlikely that the male cones in Pinaceae also represent transformed compound strobili.     

The Tridimensional Morphology of Rice Embryo Development with Special Reference to the Scutellum and the Coleoptile

Using scanning electron microscopy and semi-thin plastic sections, the pattern of development of the rice ( Oryza sativa L. ) embryo from 2 days after pollination (DAP) to maturity was followed. ( 1 ) At 2 DAP, the young embryo was observed to consist of an embryo proper, a hypoblast and a suspensor. The trum-pet-shaped hypoblast was a transitional region situated between the suspensor and the embryo proper. To label the hypoblast as suspensor is incorrect. During this time, dorsiventrality was established, but a radicle was not yet differentiated. Therefore it is still referred to as a proembryo. (2) 3 ~ 5 DAP, the embryo underwent definite morphological and anatomical changes. In the young embryo at 3 DAP the scutellum and colcoptile appeared simultaneously directly from the proembryo. The coleoptile did not originate from the scutellmn. During these foremost 3 days, the coleoptile primordium underwent a special kind of morphological change and formed a young coleeptile having the shape of an inverted hollow cone. This process revealed the true mechanism of c61eeptile formation. Anatomical observation indicated that the embryo at 3 DAP began to differentiate procambium, ground meristem and root cap. At 4 DAP a dome-like growth cone and protoderm of radicle appeared. Then the shoot-root axis became established. At 5 DAP the plumule, hypocotyl and radicle were formed. (3) It was shown that the embryo of rice actually has two cotyledons: the scutellum (a part of the embryonic envelope) and the coleeptile (The scutellum being the lateral cotyledon, a part of outside cotyledon, and the coleoptile the apical cotyledon--the coleoptile may be considered to be a modified form of a cotyledon). This kind of structural arrangemem can be referred to as dimorphic cotyledon.     

香榧主产区林地土壤养分空间异质性及其肥力评价

选取浙江省香榧(Torreya grandis cv.Merrillii)主产区为研究对象,系统采集表层土壤(0—20 cm)样品121个,基于地统计学及Moran′s I等空间分析方法揭示土壤养分的空间异质性,估算了香榧林地土壤综合肥力并分析其影响因素。结果表明:研究区土壤pH较低,有机质、碱解氮、有效磷和速效钾含量较高,平均含量分别为4.91、30.60 g/kg、136.77 mg/kg、15.02 mg/kg、153.42 mg/kg;基于半方差函数分析得出,土壤pH和养分要素属于中等空间相关性,其中pH的变程最小为3.29 km,有机质、碱解氮、有效磷和速效钾的变程分别为8.52、5.84、8.82、6.49 km;克里格空间插值和局部Moran′s I指数结果揭示土壤pH、有机质、碱解氮、有效磷和速效钾均存在明显的空间分布格局和局部空间聚集现象,土壤有机质、碱解氮、有效磷和速效钾低值区主要分布在诸暨市和东阳市,高值区主要分布在柯桥区和嵊州市,而pH的空间分布格局与之相反;诸暨市和东阳市部分地区土壤综合肥力指数较低,而其他区域的土壤肥力水平较高。总体上,浙江省香榧主产区土壤酸化以及养分失衡现象较为严重,尤其是速效钾含量过高。从相关性分析结果来看,环境变量对香榧林地土壤养分的影响较小,而林龄对土壤pH和养分的影响较大。可见,研究区土壤养分受人为活动影响明显。因此,需根据实际情况,改善林农的施肥管理方式,调整施肥数量和结构并开展土壤酸性改良,因地制宜制定区域施肥规划。     

稻属植物胚的形态结构与二（异）型子叶

长久以来植物学界认定稻 (OryzasativaL .)是单子叶植物。作者从稻胚发育的研究中确认稻胚具二型子叶 ,并非单子叶。稻属其他种的胚胎形态与O .sativa是否相同 ?是否具二型子叶 ?根据扫描电子显微镜的观察结果 ,稻属 (Oryza) 2 2个种和亚种的胚的形态结构可以分为两种类型。O .sativa等 16个种胚具腹鳞和侧鳞 ,属第一类型 ;O .meyeriana (Zoll.etMor.exSteud .)Baill.ssp .tuberculataW .C .WuetY .G .Lu ,G .C .Wang等 6个种 (亚种 )胚缺腹鳞和侧鳞 ,属第二类型。O .sativa和O .meyerianassp .tuberculata的胚胎发育过程所出现的盾片原基、胚根鞘原基、胚芽鞘原基和生长锥均来自原胚 ,前二者发育成胚套 ,是外围子叶 ;胚芽鞘原基发育成围在生长锥外并盖住生长锥的空心的倒锥状胚芽鞘 ,是顶生子叶。第一类型与第二类型稻胚都具有二型子叶。第二类型稻胚在盾片原基发育过程中并不分化出腹鳞和侧鳞 ,因而造成第二类型稻胚缺腹鳞与侧鳞。稻的二型子叶源于原胚的背腹极性分化     

In Vitro Seed Germination and Developmental Morphology of Seedling in Cymbidium ensifolium

The process of in vitro seed germination of Cymbidium ensifoliumcultivar Si-ji-lan could be divided into the following five stages: (1) Proembryos wereswollen, outer layer cells became irregular in shape. The tangential wall of outer layer cells of proembryos was thickened. The terminal cells were much smaller than basiccells. (2) Seeds germinated and differentiated into protocorms with terminal or lateralmeristem. (3) On one flank of the terminal meristem a single cotyledon was differen-tiated. (4) After the first foliage leaf was formed in the opposite side of the cotyledon,the protocorms developed into rhizomes. (5) As the third or forth leaf was formed, young roots were initiated. The results stained by Suden IV shot that the possiblecause for quite slow seed germination rate of Cymbidium ensifolium in vitro is due tothe thickened layers of seed coat, reducing its penetrability on the surface of proem-bryo. During seed germination the lipid and starch in the embryo cells were reduced.The reduction of starches may be closely correlated to the meristem formation.     

Dynamics of storage reserve deposition during Brassica rapa L. pollen and seed development in microgravity

Pollen and seeds share a developmental sequence characterized by intense metabolic activity during reserve deposition before drying to a cryptobiotic form. Neither pollen nor seed development has been well studied in the absence of gravity, despite the importance of these structures in supporting future long-duration manned habitation away from Earth. Using immature seeds (3-15 d postpollination) of Brassica rapa L. cv. Astroplants produced on the STS-87 flight of the space shuttle Columbia, we compared the progress of storage reserve deposition in cotyledon cells during early stages of seed development. Brassica pollen development was studied in flowers produced on plants grown entirely in microgravity on the Mir space station and fixed while on orbit. Cytochemical localization of storage reserves showed differences in starch accumulation between spaceflight and ground control plants in interior layers of the developing seed coat as early as 9 d after pollination. At this age, the embryo is in the cotyledon elongation stage, and there are numerous starch grains in the cotyledon cells in both flight and ground control seeds. In the spaceflight seeds, starch was retained after this stage, while starch grains decreased in size in the ground control seeds. Large and well-developed protein bodies were observed in cotyledon cells of ground control seeds at 15 d postpollination, but their development was delayed in the seeds produced during spaceflight. Like the developing cotyledonary tissues, cells of the anther wall and filaments from the spaceflight plants contained numerous large starch grains, while these were rarely seen in the ground controls. The tapetum remained swollen and persisted to a later developmental stage in the spaceflight plants than in the ground controls, even though most pollen grains appeared normal. These developmental markers indicate that Brassica seeds and pollen produced in microgravity were physiologically younger than those produced in 1 g. We hypothesize that microgravity limits mixing of the gaseous microenvironments inside the closed tissues and that the resulting gas composition surrounding the seeds and pollen retards their development.     

THE DEVELOPMENT OF THE SEED OF ABUTILON THEOPHRASTI I. OVULE AND EMBRYO

Winter , Dorothy M. (Iowa State U., Ames.) The development of the seed of Abutilon theophrasti. I. Ovule and embryo. Amer. Jour. Bot. 47(1): 8–14. Illus. 1960.—Abutilon theophrasti Medic, is a widespread annual weed which produces an abundance of seed in capsules which mature within 20 days after pollination. Ovule differentiation may be observed at least 8 days before anthesis when a sporogenous cell becomes evident and 2 integuments are initiated. An 8-nucleate embryo sac is produced from the chalazal megaspore approximately 2 days before anthesis. The outer integument of the mature campylotropous ovule consists of 2 cell layers, the inner integument has 6 to 15 cell layers. The initially free-nucleate endosperm becomes cellular betwen 3 and 7 days after pollination. At maturity a thin layer of gelatinous endosperm encases the embryo. The Asterad-type proembryo of Abutilon has a stout suspensor and develops rapidly. Four days after pollination cotyledons are initiated; 4 days later a leaf primordium is evident. Fifteen days after pollination the embryo, which has essentially completed its growth, consists of a large hypocotyl with root promeristem and root cap at its basal end, and 2 flat, folded, leaflike cotyledons enclosing a small epicotyl at its upper end. The epicotyl consists of an embryonic leaf and a stem apex.     

STUDIES ON THE SEED OF BANANA. I. ANATOMY OF THE SEED AND EMBRYO OF MUSA BALBISIANA

Mc Gahan , Merritt W. (United Fruit Co., Norwood, Mass.) Studies on the seed of banana. I. Anatomy of the seed and embryo of Musa balbisiana. Amer. Jour. Bot. 48(3): 230–238. Illus. 1961.—The seed coat of Musa balbisiana Colla consists of a relatively thick outer integument and a 2–cell-layered inner integument. The entire seed coat is sclerified, but routine tests for lignin are negative. Within the outer integument there is a zone of unusual sclereids tentatively termed “multiluminate.” Between the inner integument and the remnants of the nucellus is a cuticle 10–12 μ thick. The micropylar plug and collar are typical of the genus. The chalazal mass is an annular region of gelatinous cells. The mature embryo is comprised of a massive cotyledon, an epicotyl with 1 leaf primordium, a primary root primordium, and several adventitious root primordia. Procambium is well developed, but no mature vascular elements are present in the embryo.     

小麦受精过程的细胞化学研究

小麦成熟胚囊卵细胞中存在较多围核分布的淀粉粒和少量散布的脂类颗粒;两个助细胞中积累很多脂类,未见有淀粉粒存在;中央细胞中存在中等量均匀分布的淀粉粒和脂类颗粒。受精时期,胚囊内各细胞中淀粉粒变化不大。精卵核融合时,卵细胞和中央细胞中的脂类分别存在一个积累高峰。合子与相应时期游离核胚乳中的脂类颗粒均较少。原胚初期,每个原胚细胞及胚乳原生质中均积累较多脂类。珠孔附近的内珠被细胞中脂类颗粒较多,并存在一个有规律的变化。在观察的所有发育时期的胚珠中,均未发现贮存蛋白质。胚珠中脂类的一系列变化可能与雌性细胞的营养、胚胎发育初期的养料及花粉管的定向生长等有关     

长喙毛茛泽泻胚中营养物质的积累与消耗

长喙毛茛泽泻是一种水生濒危植物。它的种子中没有胚乳,营养物质以淀粉和帽白体的形式贮藏在胚中。胚不同部位物质积累情况差异较大,下胚轴和子地细胞中的淀粉,蛋白体数目多,体积大,胚芽和胚根分生细胞中只贮藏有少量的淀粉粒和蛋白体。     

枣合子胚和体细胞胚发育过程的观察与比较

本实验对临猗梨枣、壶瓶枣、晋矮1号等13个品种的枣胚的发育过程进行了观察,并诱导晋矮1号成熟胚的愈伤组织通过体细胞胚发生途径形成再生植株。结果表明:体细胞胚产生于愈伤组织的表层细胞或内部细胞。在鱼雷胚期已有导管的分化,子叶期的维管组织呈“Y”形。枣合子胚及体细胞胚的发育均经历了原胚、球形胚、心形胚、鱼雷胚和子叶胚五个时期。大多数品种的枣胚从球形胚期或心形胚期即开始败育,只有极少数品种可发育到成熟胚,而且合子胚形成的能力、胚败育时发育的程度等均存在着大的品种间差异,同一品种甚至同一子房内胚的发育进程也不同步。