Late Embryogeny of Fokienia

The young embryo of Fokienia became massive and columnar in the middle of July in Chekiang, China. The polarity of the embryo has already been evident at this time. The cell in the free apex of the columnar embryo are smaller, while in the opposite end the cells continuous to the suspensor are larger in size and irregular in arrangement. Then a group of root initials appears at the middle part of the arc formed by the arrangement of the cells about 10 cells deep from the free apex. All kinds of tissues and organs of the embryo were differentiated in the first week of August. And the root initials become evident. Finally the root initials give rise to the procambium and the embryonic cortex upward and the root cap downward. There are about 20 layers of cells of the procambium in width and only about 10 layers of cells in cotyledonal procambium strand in the mature embryo. The cells of the embryonic cortex are continuous to those of the pericolumn of the root cap. The embryonic epidermis is absent in root cap. The embryo became fundamentally mature about the end of September. The hypocoty and cotyledons are well developed and each constitutes about 40% of the total length of the mature embryo. The root cap is rather weak, only about 10% of the total length. And the rest is the degenerated suspensors. The pith and secretory cells are absent in the mature embryo. The cotyledonal number of the embryo is 2. In mature ovule, there are 15 layers of nucellar cells in width in micropylar part but only 4—5 layers around the rest of the female gametophyte. The megaspore membrane is about 3.6μin thickness. When the young embryo is in the columnar stage, the nuclei of the female gametophytic cells are dividing and forming polynucleate cells. Thus, each cell usually has 2—4 nuclei. In this case, the cells of female gametophyte are large and isodiametric and about 60—120 μ in diameter. But the cells in the outer layer of the female gametophyte are rather small and they are usually uninuclear, rarely binuclear. The present article also deals with the starch distribution during the late embryogeny.     

The Variations of the Starch in Pinus tabulaeformis during Embryogenesis

The presence or absence and the distribution of the starch during embryogenesis of Pinus tabulaeformis have been investigated by using the usual histochemical methods. The embryogenesis of the pine may be divided into six stages. In the course of embryo development the accumulation of starch has been observed in the nueellus, the megaspore mother cell and the megaspore, in the female gametophyte, in the pollen grain and in the embryo itself. The larger starch region, however, is only seen in the free apex of the ovule, the female gametophyte and the root cap-suspensor region of the embryo. During embryogenesis the starch region in the free apex of the nucellus appears before the pollination and persists until the late stage of the development of the young embryo. In the female gametophytc the starch region appears about the time of fertilization or at the early stage of proembryogenesis. It is always surrounding the developing young embryo, moves progressively toward the chalazal end of the female gametophyte after the development of the young embryo and then disappears when the embryo is approaching maturity. The starch region in the embryo itself appears in the basal region of the young embryo before the differentiation of the root initials and then develops into the root cap suspensor starch region and finally disappears until the complete development of the embryo and the seed maturity. The starch region, therefore, is the main site for supplying the carbonhydrate for the developing pine embryo. Many young embryos are distributed in the narrow and long embryonal cavity of the female gametophyte during the stage of cleavage polyembryony. But usually only one of them which can obtain the sufficient saeeharide material becomes the dorminant embryo. It is, therefore, considered that the carbonhydrates may be one of the important factors involving the embryo selection. In the mature seed, with the exception of a few residual starch grains scattered in the root cap-suspensor region, no starch grains are found in other organs or 9issues of the embryo. Hence, we may conclude that the starch grains participate actively in the carbonhydrate metabolism and finally they are almost entirely consumed off and they are, therefore, not the reserve material of the pine seed.     

The Development and Structure of the Late Embryo in Torreya grandis

The materials used in this investigation were collected during 1980–1983 from Zhuji county of Zhejiang province, China. Seed of Torrcya grandis is an important dry “fruit” and used for edible oil. It is endemic to China. The primordia of male strobili are differentiated before October in the first year, while those of female strobili occur later. The microspore mother cells and megaspore mother cells are found in March and April in the second year respectively. The fertilization takes place in August and the dormant embryo overwinters at the proembryo stage. Eventually the proembryo begins to differentiate and its development starts in July of the third year. Thus the interval from fertilization to latembryogeny of Torreya grandis lasts for about 11 months. When the seeds of Torreya grandis are shed 'in August the embryo within the seed is still immature. It requires a period of after-ripening. The experiments show that the embryo resumes to develop and differentiate during 1–3 months in stratification in moist sands. The development and structure of late embryo are characterized as follows: 1. The cotyledon of the mature embryo in Torreya grandis is of 15000 μm in length and 87% of the embryo. The hypocotyl is vary shert and only 13% of the embryo. This kind of structure of the embryo in Torreya is very rare among conifers and in some degree similar to that of Keteleeria. When seed is shed the meristem of cotyledon is just differentiated and only 100–200 μm in length at the end of July to the middle of August. As the seeds are stratified in moist sands for 1–3 months, the cotyledon increases about 100 times than in room temperature in Zhuji county. 2. There is a large secretory canal in either side between the procambium and the cortex of the mature embryo. The secretory canal consists of epithelial cells of 4–5 layers. It is very peculiar in conifers. 3. The shoot apex does not begin to differentiate, until the seed has been fallen from the tree. 4. The column of the root cap is rather short and consists of the cells of about 10 layers in height and 6 layers in width. 5. Proteins are only found in the focal zone of the free apex of the young embryo but without any starch grains. The starch is abundantly distributed in the opposite end from the root initials down to root cap and the entire transitional zone. It is interesting to note that neither proteins nor starch grains are found in the suspensor system. It is assumed that the protein may be the main form of storing material in the actively growing cells and tissues of embryo in Torreya grandis.     

Embryo and endosperm development is disrupted in the female gametophytic capulet mutants of Arabidopsis

The female gametophyte of higher plants gives rise, by double fertilization, to the diploid embryo and triploid endosperm, which develop in concert to produce the mature seed. What roles gametophytic maternal factors play in this process is not clear. The female-gametophytic effects on embryo and endosperm development in the Arabidopsis mea, fis, and fie mutants appear to be due to gametic imprinting that can be suppressed by METHYL TRANSFERASE1 antisense (MET1 a/s) transgene expression or by mutation of the DECREASE IN DNA METHYLATION1 (DDM1) gene. Here we describe two novel gametophytic maternal-effect mutants, capulet1 (cap1) and capulet2 (cap2). In the cap1 mutant, both embryo and endosperm development are arrested at early stages. In the cap2 mutant, endosperm development is blocked at very early stages, whereas embryos can develop to the early heart stage. The cap mutant phenotypes were not rescued by wild-type pollen nor by pollen from tetraploid plants. Furthermore, removal of silencing barriers from the paternal genome by MET1 a/s transgene expression or by the ddm1 mutation also failed to restore seed development in the cap mutants. Neither cap1 nor cap2 displayed autonomous seed development, in contrast to mea, fis, and fie mutants. In addition, cap2 was epistatic to fis1 in both autonomous endosperm and sexual development. Finally, both cap1 and cap2 mutant endosperms, like wild-type endosperms, expressed the paternally inactive endosperm-specific FIS2 promoter GUS fusion transgene only when the transgene was introduced via the embryo sac, indicating that imprinting was not affected. Our results suggest that the CAP genes represent novel maternal functions supplied by the female gametophyte that are required for embryo and endosperm development.     

The Ultrastructural Feature and Distribution of Microbodies in Mature Embryo Cells of Pinus bungeana

The material of pine seeds used in this investigation was collected in 1982 from Peking. The microbodies of mature embryo ceils are very well developed and their diameter averages about 2–3 μm, even up to 4.3 μm. The appearance is usually ovoid or elliptic. The microbodies are essentially glyoxysomes. The microbody matrix is composed of two types of substances, one type is of a finely granular material in a densely arrangement (Plate Ⅲ Fig. 6); the other is of coarsely granular or flocculant in appearance and the elements of the matrix are loosely distributed. These matrices usually contain an amorphous inclusion or crystalline arrays in regular arrangement. The inclusion sometimes occupies a small portion of the microbody matrix (Plate Ⅲ, Figs, 5, 6) and sometimes the inclusion occupies nearly the entire glyoxysome (Plate Ⅱ, Fig. 3). It is interesting that the “pockets” frequently appear in the microbodies of mature embryo cells, and those are actually as a result of invagination in microbodies (Plate Ⅱ, Fig. 4). In addition, an electron-transparent “oil body-like space” occurs occasionally in microbody (Plate Ⅰ, Fig. 1). The periphery of “space” is a constitutive part of matrix or continuing with the matrix. This “space” may be due to the degradation in a part of the matrix. While the periphery of the pocket is membranaceous and an electron-opaque cytoplasmic groundplasm was found within the pocket. The microbodies of mature embryo cells in Pinus are mainly distributed in pericolumn cells of the root cap and cortical cells of the hypocotyl. Besides the dominant organelles of lipid bodies in the cells of above mentioned tissues, there are also microbodies, amyloplasts, mitochondria, plastids, endoplasm reticulum and Golgi apparatus, of which the microbodies are the most aboundant organelles. In contrast, the microbodies and other organelle are rare in the parenchyma of the cotyledons in Pinus. Their common and outstanding characteristics in various tissues of mature embryo is that the entire cytoplasm of the cells is almost full of the lipid bodies, and each organelle is directly surrounded by a number of lipid bodies (Plate Ⅰ—Ⅲ, Figs. 1–6). Because of the other organelles are rare in parenchyma of the cotyledons, the lipid bodies are so appressed with each other that the inlaid periphery of lipid bodies frequently occurs in some degree. To sum up, based upon 'the state of distribution of microbodies in mature embryo tissues, cotyledons of Pinus could be considered as the main storage organ of nutrient substances, while the root cap and hypocotyl are the important sites of glyoxysome metabolism. The function of glyoxysomes is to convert lipid into the carbohydrates and to transfer the latter to embryos for growth.     

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.     

The Embryogeny of Cryptomeria fortunei

The embryogeny of Cryptomeria fortunei was observed. By the middle of March the nucleus of functioning megaspore divides twelve times to form about 3000–4000 free nuclear female gametophyte. Wall formation is centripetal. By the end of May the archegonial complex containing 12–16 archegonia surrounded by jacket layer is present at the micropylar end of the gametophyte. The pollen grains are shed at the uninucleate stage. After pollination the pollen grains swell. The microspore nucleus moves to one side and divides to form a large generative nucleus and a small tube nucleus, The generative cell then divides to form a body cell and a stalk cell. When the pollen tube passed through the nucellus and reached the archegonial complex the nucleus of the body cell divides to form two male cells, generally only one of which enters the arehegonium and the fertilization takes place in the upper part of an egg cell. A number of eggs in an archegonial complex may be fertilized. After the fusion of the male nucleus with the egg nucleus, the zygote divides three times to form eight nuclei, which become organized into primary embryo cells and the open tier. The former are only two or three cells, while the latter has five or six cells open towards the top and divides to form the prosuspensor tier and the upper tier. Thus, the pro-embryo of Cryptomeria belongs to the standard type, according to Doyle (1963). Excepting the simple polyembryony, the cleavage polyembryony is a common character in the embryogeny of Cryptomeria. The mature embryo consists of the radicle, the hypocotyl, the plumule and three cotyledons. When the embryogeny of Cryptomeria fortunei is compared with that of C. japonica, there are many differences obtained. The number of archegonia in the archegonial complex of C. fortunei is less than that of C. japonica. The former does not form the archegonial chamber and the chalazal and lateral archegonia, while the latter does.     

Storage reserves and cellular water in mature seeds of Araucaria angustifolia

Seed tissues of Araucaria angustifolia (Bertol.) Kuntze were investigated using histochemistry, transmission electron microscopy (TEM) and energy dispersive X-ray (EDX) analysis. Moisture content and water status in tissues were also evaluated. In the embryo, TEM studies revealed the presence of one to several central vacuoles and a peripheral layer of cytoplasm in cells from different tissues of the cotyledons and axis. In the cytoplasm, lipid bodies, starch grains, mitochondria and a nucleus are evident. In most tissues, vacuoles contain proteins, indicating that the storage proteins are highly hydrated. In cells of the root cap, proteins are stored in discrete protein bodies. Both protein storage vacuoles and discrete protein bodies have inclusions of crystal globoids. EDX analysis of globoids revealed the presence of P, K and Mg as the main constituents and traces of S, Ca and Fe. In the root and shoot meristems, deposits of phytoferritin are present in the stroma of proplastids. The gametophyte consists of cells characterized by relatively thin cell walls and one to several nuclei per cell. Protein and lipid bodies are present, although starch is the most conspicuous reserve. Immediately after shedding, moisture content is approximately 145% (dry weight) for the embryo and 95% (dry weight) for the gametophyte. Calorimetric studies reveal that axes and cotyledons have a very high content of freezable water, corresponding to types 5 and 4, i.e. dilute and concentrated (or capillary) solution, respectively. The results are discussed in relation to the behaviour of the species, which has been categorized as recalcitrant.  © 2002 The Linnean Society of London . Botanical Journal of the Linnean Society , 2002, 140 , 273−281.     

芡个体发育早期的研究

本文研究了芡个体发育的早期, 即心形胚至种苗。心形胚至成熟胚表现为:苗端先发育, 根端弱育;胚芽叶节上的节生根原基先发育, 根端无明显分化。种子胚至种苗表现为:种子萌发时, 下胚轴末端产生多细胞分枝下胚轴毛;种苗形成中, 节生根先发育, 胚根后发育, 且长达1mm左右即停止生长。这些器官发育顺序上的特点在被子植物中是很特殊的, 应该是系统发生上的原始性状。下胚轴毛是水生或湿生被子植物比较普遍的性状, 是区分下胚轴与胚根的指示性状。     

Comparative developmental anatomy of seedlings in nine species of podostemaceae (subfamily Podostemoideae)

The developmental anatomy is described for seedlings of nine Asian and Australian species of Podostemaceae, subfamily Podostemoideae. The hypocotyl is rudimentary (except in Zeylanidium olivaceum) and does not form a primary root in any of the species examined. An adventitious root forms endogenously in the hypocotyl of six species with ribbon-like or flattened subcylindrical roots, and in Z olivaceum with foliose roots. In contrast, it forms exogenously in Hydrobryum griffithii and Synstylis micranthera with foliose roots. The juvenile root becomes flattened and dorsiventral, branches exogenously (in Polypleurum stylosum, P. wallichii and Z. lichenoides) and produces shoots endogenously (in P. stylosum, P. wallichii, S. micranthera and Z. lichenoides). The root meristem is simple, composed of surface and uniform inner cells, and is devoid of root cap initials in all species. The reduced meristem morphology of seedling roots may be primitive in the Asian-Australian Podostemoideae. A root cap or protective tissue did not form during the culture period, even in the seven species with capped adult roots, probably due to its delayed development. It was absent throughout ontogeny in the other two species. No obvious shoot apical meristem forms between the cotyledons. One to several leaves occupy the shoot apical area in species with endogenous adventitious roots, while no leaves are formed in species with exogenous roots. These differences suggest recurrent origins of foliose roots in the Asian clade. Similarities between the unique seedling morphology and mutant Arabidopsis phenotypes are discussed.     

MORPHOLOGY AND ANATOMY OF NEW SPECIES OF SCHIZAEA AND ACTINOSTACHYS

The gametophyte, old embryo, and sporophyte of Schizaea pseudodichotoma sp. nov., sporophyte and female parental gametophyte of S. diversispora hybr. nov. (S. pseudodicholoma X probably S. dichotoma), sporophyte of S. rhacoindusiata sp. nov., and gametophyte, old embryo, and sporophyte of Actinostachys macrofunda sp. nov. are described. The taxonomy of Schizaea is discussed and the system of Diels is strongly supported. The two sectional names used by Diels, Euschizaea Hook, and Lophidium Rich, are replaced by Pectinatae Prantl and Schizaea respectively. The prime morphological significance of Schizaea pseudodicholoma lies in its leafless embryo and its simple leaf differing from other species in its section, and that of Actinostachys macrofunda lies in its reduction to nearly complete heterotrophic existence and its frequent multiple annulus. Fungal hyphae have been traced from Schizaea and Actinostachys through the substratum and into root nodules of Casuarina and into roots of two other angiosperms.     

Kin selection and conflict in seed maturation

There are four genetically distinct components in the developing seeds of flowering plants: maternal sporophyte, gametophyte, endosperm, and embryo. Each component can potentially influence the quantity or quality of nutrients provided to the embryo of its seed, thereby reducing the amount available to embryos in other seeds of that plant. The theory of kin selection predicts that each component will be selected to favor its own embryo over the other embryos to the extent that it is more closely related to its own. Under this criterion, an embryo should be selected to try to acquire more nutrients than the endosperm should be selected to provide, the endosperm should try to supply more than the gametophyte should, and the gametophyte more than the parent sporophyte. Evidence for this conflict of interests is found in the higher frequency of endopolyploidy, nutrient-absorbing haustoria, and food storage tissues in the embryo and endosperm than in the gametophyte of maternal tissues.This theory also suggests how the gametophyte, which is the nurse tissue of gymnosperm seeds, was displaced from this role in the flowering plants by an endosperm initiated by a secondary fertilization. “Neoteny” in the pro-angiosperms created conditions in which (1) an endosperm initiated by double fertilization would be more closely related to the embryo than is the gametophyte and (2) the endosperm would be formed early enough to be of significant aid to the embryo.If this theory is correct it (1) requires a different approach to the study of seed morphology and physiology, (2) increases the plausibility of arguments that flowering plants are a polyphyletic group, (3) provides evidence that parents cannot always control the outcome of conflict with their offspring, and (4) forges a conceptual link in our understanding of the evolution of social interactions in plants and animals.     

Characterization of Soybean Plasma Membrane during Development: FREE STEROL COMPOSITION AND CONCANAVALIN A BINDING STUDIES

Plasma membrane preparations from soybean root and hypocotyl contained the following free sterols: cholesterol, campesterol, stigmasterol, and sitosterol. The cholesterol level was relatively low in root plasma membrane (less than 0.5%) but was 1.4 to 2.4% in hypocotyl membrane. The relative levels of the three other sterols fluctuated with cellular development and tissue source. Campesterol level decreased with the development of both root and hypocotyl membrane. With development, stigmasterol increased greatly in root membrane but remained constant in hypocotyl membrane, and sitosterol, the major free sterol component of all membrane preparations, decreased in root membrane but increased slightly in hypocotyl membrane.     

The auxin-insensitive bodenlos mutation affects primary root formation and apical-basal patterning in the Arabidopsis embryo

In Arabidopsis embryogenesis, the primary root meristem originates from descendants of both the apical and the basal daughter cell of the zygote. We have isolated a mutant of a new gene named BODENLOS (BDL) in which the primary root meristem is not formed whereas post-embryonic roots develop and bdl seedlings give rise to fertile adult plants. Some bdl seedlings lacked not only the root but also the hypocotyl, thus resembling monopteros (mp) seedlings. In addition, bdl seedlings were insensitive to the auxin analogue 2,4-D, as determined by comparison with auxin resistant1 (axr1) seedlings. bdl embryos deviated from normal development as early as the two-cell stage at which the apical daughter cell of the zygote had divided horizontally instead of vertically. Subsequently, the uppermost derivative of the basal daughter cell, which is normally destined to become the hypophysis, divided abnormally and failed to generate the quiescent centre of the root meristem and the central root cap. We also analysed double mutants. bdl mp embryos closely resembled the two single mutants, bdl and mp, at early stages, while bdl mp seedlings essentially consisted of hypocotyl but did form primary leaves. bdl axr1 embryos approached the mp phenotype at later stages, and bdl axr1 seedlings resembled mp seedlings. Our results suggest that BDL is involved in auxin-mediated processes of apical-basal patterning in the Arabidopsis embryo.     

Development of Embryo and Fruit in Ipomoea batatas Lam

This paper deals with the development of the embryo and the formation of the fruit for lpomoea batatas Lam. based on the observation of its flower bud differentiation, megasporogenesis and the development of the female gametophyte, microsporogenesis and the development of the male gametophyte. The pollen grain germinated on the stigma about 10–30 min. after pollination. The pollen tube penetrated the transmitting tissue in the middle of the style between 30–60 min. after pollination. After 2 hours the tip of the pollen tube reached the micropyle. Double fertilization completed after 5 or 12 hours then the zygote and the endosperm nucleus formed. The first mitotic division of the endosperm nucleus takes place about 12 hours after pollination, earlier about 3 hours than the first division of the zygote, the latter gives rise to a terminal cell and a basal cell by a transverse division. The second division is transverse in the terminal cell, forming two cells. The basal cell divides longitudinally into two adjoining cells. The terminal cell becomes the proembryo with four cells, and at the same time, the basal cell becomes the suspensor with four cells after 41–52 hours. The proembryo gradually becomes globular, cordate and torpedo-shaped, respectively about 96–120, 144–156, 168-192 hours after pollination. The cotyledons of the embryo gradually prolongate 10 days after pollination. The embryo almost completes its development within 21–30 days after pollination. he fruit is a capsule. The ovary gradually swells 3–4 days after pollination, then forms fruit, which ripens about 21–30 days after pollination, 2R.=4–8 mm. A fruit contains 1–4 seeds. 7,000 fruits were analysed in 1983, the results are as follows: 64.6% of then with only one seed in a capsule, 31.8% two seeds, 5.48% three seeds and 0.1% four seeds. The seeds are small, 2R. from 3.84 mm to 2.84 mm. The shape and the weight of the seeds are different from each other because of difference in number of seeds within a capsule.     

Anatomy of Jojoba (Simmondsia chinensis) seed and the utilization of liquid wax during germination

Much work has been done on the agricultural potential of Jojoba, but little on the anatomy of the mature plant or seed. Our investigations concern the structure of the embryo of mature seeds and their external morphology during early germination. The embryo is straight and investing. A hypocotyl sheath surrounds the radicle like a hollow cone. The apical meristem is a low mound of cells in a shallow depression between the broad short petioles of the cotyledons. During germination these petioles lengthen and force the embryo away from the coytledons and seed coat. The hypocotyl elongates and the primary root rapidly extends and is well developed before the apical meristem becomes active. A mature imbibed seed contains approximately fifty percent liquid wax. After germination there is a linear decrease in the amount of wax to approximately ten percent at thirty days.     

Rapid propagation of Eleutherococcus senticosus via direct somatic embryogenesis from explants of seedlings

Explants from three different parts (cotyledon, hypocotyl or root) of one week-old seedlings of Eleutherococcus senticosus were cultured on Murashige and Skoog (MS) medium with 1.0 mg l^-1 2,4-D. Somatic embryos were formed directly from the surfaces of explants. The frequency of direct somatic embryo formation was the highest in the hypocotyl segments (75%) as compared to cotyledon (56%) or root segments (12%). When hypocotyl explants from 3 different stages of seedlings (zero, one or three week-old) were cultured on MS medium with 1.0 mg l^-1 2,4-D, the frequency of somatic embryo formation rapidly declined as the zygotic embryos germinated. However most somatic embryos (93%) from explants of zygotic embryos developed as fused state (multiple embryo), whereas somatic embryos (over 89%) from more developed seedlings developed into single state (single embryo). Single embryos germinated and regenerated into plantlets with both shoots and roots, while multiple embryos only regenerated into only multiple shoots. Plantlets that regenerated from single embryos of E. senticosus were acclimatized in a greenhouse. This revised version was published online in June 2006 with corrections to the Cover Date.     

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.     

蒙古黄芪的胚胎学

蒙古黄芪(Astragaius monghocus Bge.)雄性原为花药表皮下单列细胞,小孢子四分体为四面体型,胞质分裂为同时型。单子叶型花药壁。分泌型绒毡层,其细胞核始终一个,细胞里含有一至多个草酸钙晶体。二细胞型花粉:单室子房,多胚珠,弯生,双珠被,厚珠心。蓼型胚囊。雌性孢原为珠心亚表皮下多细胞。直线形大孢子四分体,合点端第一、或第二、或第三个大孢子有功能。成熟胚囊具有盲囊结构;花粉管通过退化助细胞进入胚囊。双受精属于有丝分裂前配子融合类型;胚的发育为柳叶菜型。核型胚乳。胚乳细胞在球形胚时期开始形成。在胚乳发育过程中,合点端胚乳游离核存在着聚集、合并、无丝分裂和胚乳细胞内多核合并等现象。