Translocation of Uranin within the Living Ovules of Vanilla

In the ovules of Vanilla (Vanilla planifolia Andr.) before fertilization, outer integument surrounded the lower part of ovule. Uranin got into ovule through funiculus, forming, the first center of fluorescence at the chalaza zone of ovule. Then uranin was transported to micropyle end along inner integument, forming the second center of fluorescence at micropyle end of inner integument. Soon, fluorescence appeared in the egg apparatua. After fertilization, the outer integument ovule extended upward, forming micropyle ogerber with inner integument. After getting into ovule through funiculus, uranin spreads to- ward several directions: l. transported to outer integument at the entrance of micropyle; 2. transported downward to chalaza zone along outer integument at the side of funiculus; 3. extended from chalaza zone to the inside and to the outer integument at the side far from funiculus The ovules of Vanilla had no vascular bundles. On transporting in inner integument, however, the cells in inner layer next to the embryo sac appeared to be the major passage. In mature embryo sac, there was cuticle between inner integument and embryo sac at the half of micropyle end. But between embryo sac at the half of chalaza end and nucellus, cuticle was absent. Nutrient could get into embryo sac from chalaza end undoubtedly. As egg apparatus showed the fluorescence after formation of fluorescence center of inner integument at micropylar end, the possibility that nutrient got into embryo sac from micropyle could not be excluded.     

Development of ovule,fruit and seed of Xyris (Xyridaceae,Poales) and taxonomic considerations

The development of the ovule, fruit and seed of Xyris spp. was studied to assess the embryological characteristics of potential taxonomic usefulness. All of the studied species have (1) orthotropous, bitegmic and tenuinucellate ovules, with a micropyle formed by both the endostoma and exostoma; (2) a cuticle in the ovules and seeds between the nucellus/endosperm and the inner integument and between the inner and outer integuments; (3) helobial, starchy endosperm; (4) a reduced, campanulate and undifferentiated embryo; (5) a seed coat formed by a tanniferous endotegmen, endotesta with thick‐walled cells and exotesta with thin‐walled cells; and (6) a micropylar operculum formed from inner and outer integuments. The pericarp is composed of a mesocarp with cells containing starch grains and an endocarp and exocarp formed by cells with U‐shaped thickened walls. The studied species differ in the embryo sac development, which can be of the Polygonum or Allium type, and in the pericarp, which can have larger cells in either endocarp or exocarp. The Allium‐type embryo sac development was observed only in Xyris spp. within Xyridaceae. Xyris also differs from the other genera of Xyridaceae by the presence of orthotropous ovules and a seed coat formed by endotegmen, endotesta and exotesta, in agreement with the division of the family into Xyridoideae and Abolbodoideae. © 2015 The Linnean Society of London, Botanical Journal of the Linnean Society, 2015, 177 , 619–628.     

Embryology and fruit development in four species of Pistacia L. (Anacardiaceae)

Pistacia atlantica, P. palaestina, P. lentiscus and P. saportae , were found to have great similarity in their embryology and fruit development. The anatropous, pendulous and crassinucellate ovule was initially unitegmic; later, the integument split close to the micropyle, forming a partial second integument. After anthesis there was a development of a hypostase and an obturator. The development of the Polygonum-type embryo sac followed division of a megaspore mother cell, giving a tetrad or triad of megaspores. The functional megaspore was the chalazal one. The ovary developed into a mature pericarp after anthesis, even when pollination was prevented, and before the zygote divided. Therefore, the fruit can be parthenocarpic. The ovule started to grow after initiation of embryo development until it filled the cavity within the pericarp. The zygotes were dormant for 4–18 weeks after pollination. In P. saportae reproduction became arrested during the development of the embryo sac; only very few abnormal embryos were found. No fixed pattern of embryo development could be discerned. The endosperm was initially nuclear, becoming cellular when the embryo started to develop. The seed coat was derived from the integument and the remnants of the nucellus.     

An anatomical study of ovary-to-cuke development in consistently low-producing trees of the ‘Fuerte’ avocado (Persea americana Mill.) with special reference to seed abortion

Summary Cukes develop from female-sterile, cryptically male flowers on consistently low-producing Fuerte trees. A hypostase that has, as yet, not been reported for the avocado, is present in the chalazal tissue of the mature ovule and aborting seed. This layer seems to play a role in the degeneration of the peripheral nucellar tissue and the non-development of the intercalary meristem of the pachychalaza. The ultimate cause of cuke formation, however, seemingly lies in the disturbance of the polarity of the primordial nucellar tissue. Additional megagametophytes and non-functional megaspores that develop in the nucellus effect the collapse of the chalazal region of the embryo sac. Degeneration of these gametophytes and megaspores causes the formation of nucellar cavities that isolate the embryo sac from the nutritive tissues and chalazal flow of nutrients. The micropylar region of the embryo sac contains a well-developed egg cell, synergids and central cell nucleus. An embryo and a limited amount of endosperm tissue are formed. Because the endosperm is starved of nutrients, the formation of this tissue is curtailed at an early stage, and embryo development ceases. A meristematic zone that initiates from the inner layers of the outer integument, directly opposite the place where the vascular supply to the chalaza terminates, causes abnormal growth in the outer integument. It is suggested that, due to the absence of meristematic activity in the chalazal region of the embryo sac and the non-developing pachychalaza, resources are redistributed towards the stronger sink, i.e. the outer integument. Consequently, this part of the seed coat proliferates, while the embryo sac and pachychalaza degenerate. In spite of the abortion of the seed, the pericarp of the cuke continues to develop, possibly because the pericarp of the avocado contains phytohormones.     

The phenotype of Arabidopsis ovule mutants mimics the morphology of primitive seed plants

In seed plants, the ovule is the female reproductive structure, which surrounds and nourishes the gametophyte and embryo. This investigation describes the PRETTY FEW SEEDS2 (PFS2) locus, which regulates ovule patterning. The pfs2 mutant exhibited developmental defects in the maternal integuments and gametophyte. This mutation was inherited as a maternal trait, indicating that gametophyte defects resulted from ovule patterning aberrations. Specifically, the boundary between the chalaza and the nucellus, two regions of the ovule primordia, shifted towards the distal end of pfs2 ovule primordia. Results indicated that the PFS2 locus could: (i) be involved in the development of either the nucellus or the chalaza; or (ii) establish a boundary between these two regions. Examination of genetic interactions of the pfs2 mutation with other well-characterized ovule loci indicates that this locus affects integument morphogenesis. Interestingly, the pfs2 inner no outer and pfs2 strubbelig double mutants had inner integuments that appeared similar to their ancestral precursor. The fossil record indicates that the inner integument evolved by fusion of sterilized sporangia or branches around a central megasporangium. The question of whether the structures observed in these double mutants are homologous or merely analogous to the ancestral precursors of the inner integument is discussed.     

The embryology ofStegnospermataceae,with a discussion on its status,affinities and systematic position

The embryology ofStegnosperma halimifolium andS. watsonii has been studied in detail. The tapetum is of the secretory type and its cells become multinucleate. Simultaneous cytokinesis in the pollen mother cells follows meiosis. The ripe pollen grains are 3-celled. The ovule is crassinucellate, bitegmic and amphitropous, with the micropyle formed by the inner integument alone. The female archesporium is one celled, and the parietal tissue 3–5 layered. The embryo sac development conforms to thePolygonum type. A central strand, 6 or 7 cells thick, differentiates inside the nucellus and extends from the base of the embryo sac to the chalazal region. The endosperm is nuclear. The embryogeny conforms to the Caryophyllad type. The seed coat is formed by the outer epidermis of the outer integument and the inner epidermis of the inner integument. Based on this evidence and other data, the status of the genus as an independent family,Stegnospermataceae (Stegnospermaceae) is confirmed. Apparently, it forms a connecting link betweenPhytolaccaceae andCaryophyllaceae.     

Cytological Observation on Megasporogenesis and Embryo Sac Development of Regenerated Ovule in Hyacinth

The morphogenesis of regenerated ovule and cytological changes of its megasporogenesis and embryo sac development were studied. Results showed as follows: 1. the differentiation of the regenerated ovule had followed a normal process in the order of inner integument , outer integument and then funiculus. But the form of the regenerated ovules in vitro was quite different from that of ovule in vivo. Most of the regenerated ovules were orthotropous and hemianatropous , only a few were anatropous which are the same with that in vivo. 2. the megasporogenesis and the embryo sac development also had normal cytological process ,and the Polygonum type-embryo sac consisted of one egg, two synergids , one central cell and three antipodals could be seen in mature regenerated ovule. These ex-perimental results make clear that the regenerated ovule differentiated directly from explant could accomplish the complex processes of megasporogenesis and embryo sac development. By this fact ,authors infer that once the differentiation of ovule primordium, the complex biochemical programs for the megasorogenesis and embryo sac development can be controlled by the ovule itself and need no more information from flower bud and /or plant.     

SOME HISTOCHEMICAL,ULTRASTRUCTURAL, AND NUTRITIONAL ASPECTS OF THE OVULE OF QUERCUS GAMBELII

Histochemical analyses of the ovule of Quercus gambelii show that the major food reserves (starch grains and lipids) are located almost exclusively within the outer integument. Vascular traces are present only within this integument which contains numerous, well-developed plasmodesmata. The inner integument is virtually devoid of any food reserves and has very few plasmodesmata. The ovule has a persistent chalazal extension of residual nucellar cells (called the postament) which projects into the embryo sac. Due to the above information and the fact that the synergids rarely contain starch and no plasmodesmata are present in the walls of any of the cells of the egg apparatus (Mogensen, 1972), it is concluded that the synergids play little or no role in embryo sac nutrition. Rather, it is proposed that the pathway of available food materials in the young ovule is from the outer integument to the chalaza and through the postament into the embryo sac.     

ANATOMY OF THE SEED OF CONVOLVULUS ARVENSIS

Sripleng , Aksorn , (Kasetsart U., Bangkok, Thailand), and Frank H. Smith . Anatomy of the seed of Convolvulus arvensis. Amer. Jour. Bot. 47(5) : 386—392. Illus. 1960.–The anatropous ovule has a small, ephemeral nucellus covered by a massive integument. Shortly after fertilization, a lateral pouch develops from the upper portion of the embryo sac toward the dorsal side of the ovule and then downward. This leaves a partial integumentary septum in the base of the seed. The cellular endosperm is mostly absorbed by the embryo. Two—6 cell layers persist on all sides of the seed except below the cotyledons on the dorsal side where larger amounts persist. Over most of the seed the dermatogen develops into an epidermis that consists in part of groups of thick-walled elongate cells that produce the papillose appearance of the mature seed. The cells beneath the dermatogen divide periclinally and form 2 layers. The outer layer undergoes anticlinal divisions and differentiates a subepidermal layer of small, rectangular, thick-walled cells that become lightly lignified and suberized. The cells of the inner layer undergo some anticinal and periclinal divisions, elongate and differentiate as palisade sclerenchyma. The inner layers of the integument consist of parenchyma cells that are crushed and partially absorbed at maturity. The pad on the basal end of the seed, between the hilum and micropyle, is derived from a multiple epidermis that is differentiated into several layers of rectangular cells and a layer of palisade sclerenchyma. The subepidermal and palisade layers found over other parts of the seed dip beneath the pad.     

Embryological studies inGlaucidium palmatum Sieb. et Zucc. with a discussion on the taxonomy of the genus

Embryological features ofGlaucidium palmatum are as follows: the ovule is anatropous and bitegmic; the archesporium is hypodermal and multicelled, consisting of about 10 to 15 cells; all the archesporial, cells develop directly into megaspore mother cells, only three or four of which, however, generally complete meiotic divisions; before and during meiosis, dermal cells of the nucellar apical part undergo successive periclinal divisions forming a thick nucellar cap of as many as 20 cell-layers; embryo sac formation is of the Polygonum type; multiple embryo sacs occur frequently; antipodal cells are small in size and ephemeral or persistent; the inner integument is 3 to 5 cell-layers thick, and the outer integument 7 to 13 cell-layers thick; the outer integument is vascularized; a micropyle is formed by the inner integument alone; the endosperm is of the Nuclear type; embryogeny is of a type similar to the Onagrad type. In light of evidence from embryology and other sources it seems that there is ample reason for recognizing the family Glaucidiaceae which is distinct from the Ranunculaceae and its related families. Several common embryological features suggest an affinity between the Glaucidiaceae and the Paeoniaceae.     

大叶杨配囊及胚珠的形成和发育

本文应用细胞化学方法研究了大叶杨胚珠、胚囊的形成和发育过程中核酸、蛋白质及不溶性多糖的分布和消长。大孢子母细胞、大孢子四分体及功能大孢子中含较少不溶性多糖,但却含丰富的RNA和蛋白质。功能大孢子经分裂发育成八核的蓼型胚囊。四核胚囊开始积累细胞质多糖,成熟胚囊中除反足细胞外充满淀粉粒。反足细胞形成后不久即退化。助细胞具多糖性质的丝状器,受精前两个助细胞退化。卵细胞核对Feulgen反应呈负反应。二极核受精前由胚囊中部移向卵器,与卵器接触后融合形成次生核。发育早期的胚珠为厚珠心,双珠被。晚期,内珠被退化,故成熟胚珠为单珠被。四核胚囊时期,珠孔端珠心组织退化,胚囊伸向珠孔形成胚囊喙。合点端珠心组织含丰富的蛋白质和核酸,这一性质与绒毡层性质相似,可能涉及胚囊的营养运输。胚囊的营养来源于子房和胎座细胞内贮存的淀粉粒。     

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。     

Comparative ovule and megagametophyte development in Hydatellaceae and water lilies reveal a mosaic of features among the earliest angiosperms

Background and Aims: The embryo sac, nucellus and integuments of the early-divergentangiosperms Hydatellaceae and other Nymphaeales are comparedwith those of other seed plants, in order to evaluate the evolutionaryorigin of these characters in the angiosperms. Methods: Using light microscopy, ovule and embryo sac development aredescribed in five (of 12) species of Trithuria, the sole genusof Hydatellaceae, and compared with those of Cabombaceae andNymphaeaceae. Key Results: The ovule of Trithuria is bitegmic and tenuinucellate, ratherthan bitegmic and crassinucellate as in most other Nymphaeales.The seed is operculate and possesses a perisperm that developsprecociously, which are both key features of Nymphaeales. However,in the Indian species T. konkanensis, perisperm is relativelypoorly developed by the time of fertilization. Perisperm cellsin Trithuria become multinucleate during development, a featureobserved also in other Nymphaeales. The outer integument issemi-annular (‘hood-shaped’), as in Cabombaceaeand some Nymphaeaceae, in contrast to the annular (‘cap-shaped’)outer integument of some other Nymphaeaceae (e.g. Barclaya)and Amborella. The megagametophyte in Trithuria is monosporicand four-nucleate; at the two-nucleate stage both nuclei occurin the micropylar domain. Double megagametophytes were frequentlyobserved, probably developed from different megaspores of thesame tetrad. Indirect, but strong evidence is presented forapomictic embryo development in T. filamentosa. Conclusions: Most features of the ovule and embryo sac of Trithuria are consistentwith a close relationship with other Nymphaeales, especiallyCabombaceae. The frequent occurrence of double megagametophytesin the same ovule indicates a high degree of developmental flexibility,and could provide a clue to the evolutionary origin of the Polygonum-typeof angiosperm embryo sac.     

Interactions among Genes Regulating Ovule Development in Arabidopsis Thaliana

The INNER NO OUTER (INO) and AINTEGUMENTA (ANT) genes are essential for ovule integument development in Arabidopsis thaliana. Ovules of ino mutants initiate two integument primordia, but the outer integument primordium forms on the opposite side of the ovule from the normal location and undergoes no further development. The inner integument appears to develop normally, resulting in erect, unitegmic ovules that resemble those of gymnosperms. ino plants are partially fertile and produce seeds with altered surface topography, demonstrating a lineage dependence in development of the testa. ant mutations affect initiation of both integuments. The strongest of five new ant alleles we have isolated produces ovules that lack integuments and fail to complete megasporogenesis. ant mutations also affect flower development, resulting in narrow petals and the absence of one or both lateral stamens. Characterization of double mutants between ant, ino and other mutations affecting ovule development has enabled the construction of a model for genetic control of ovule development. This model proposes parallel independent regulatory pathways for a number of aspects of this process, a dependence on the presence of an inner integument for development of the embryo sac, and the existence of additional genes regulating ovule development.     

Ephemeral and non-ephemeral structures during seed development in two Cytisus species (Papilionoideae,Leguminosae)

Abstract

Seed formation involves not only the embryo and endosperm development, but also the formation of a series of either ephemeral or non-ephemeral structures. In this article, we study several of those structures in Cytisus multiflorus and Cytisus striatus. The endosperm development is first nuclear and later cellular, except for the chalazal area, whose development is always nuclear. It generates, in the early developmental stages, a sac-like haustorium. As the seed develops, two structures seem to be closely related to nutrient mobilization to the embryo sac: on the one hand, a group of cells and a channel, located in the chalazal area and closely related between them and to the endosperm haustorium, which could be interpreted as a hypostase and on the other hand, an endothelium, derived from the inner integument, which later degenerates leaving no trace in the mature seed. All of these structures would be associated with the directionality of assimilates from ovule tissues to embryo sac. In mature seed and surrounding the embryo appears a unicellular layer of cells rich in proteins (aleurone layer), which is the origin of the outermost layer of the cellular endosperm. The seed coat is made up only of the outer integument.     

小叶兜兰的果实生长和雌配子体发育

为了解濒危兰科植物小叶兜兰(Paphiopedilum barbigerum Tang et Wang)胚珠和雌配子体的发育过程,采用常规石蜡切片技术对其果实的生长动态进行了研究。结果表明,授粉后60~75 d的蒴果内种子数量迅速增加,到授粉后120 d时种子充满整个蒴果。授粉后40 d的胎座上分化形成多数由1层表皮细胞包被1列细胞的胚珠原基;授粉后60 d时位于胎座指状结构末端处紧靠表皮细胞下方的孢原细胞分化为大孢子母细胞。之后,大孢子母细胞经过减数分裂和有丝分裂最终形成成熟胚囊;授粉后135 d胚囊发育成熟,附着在胎座上的种子个体分化明显。小叶兜兰胚囊的发育类型为双孢子葱型,胚珠为倒生胚珠,薄珠心,单珠被,成熟胚囊为8核。这为小叶兜兰的生殖生物学及繁殖体系的建立提供理论依据。     

Embryo sac, endosperm, and seed of Nemophila (Boraginaceae) relative to taxonomy, with a remark on embryogeny in Pholistoma

Studies on embryology and seed morphology are complementary to molecular phylogenetics and of special value at the genus level. This paper discusses the delimitation and evolutionary relationships of genera within the tribe Hydrophylleae of the Boraginaceae. The seven Nemophila species characterized by a conspicuous seed appendage are similar in embryology and seed structure. The ovule is tenuinucellate and unitegmic with a meristematic tapetum. The embryo sac penetrating the nucellar apex is of the Polygonum type, has short-lived antipodal cells, and an embryo sac haustorium. The endosperm is cellular, producing two terminal endosperm haustoria, of which the chalazal has a lateral branch. Embryogeny is of the Chenopodiad type (as in Pholistoma). The seed coat is formed from the small-celled inner epidermis of the integument. The large-celled outer epidermis of the integument disintegrates into scattered cells. Seed pits evolve from irregularly placed inner epidermal cells of the integument. The chalazal part of the ovule produces a cucullus, that functions as an ant-attracting elaiosome. Those species of Nemophila with a conspicuous cucullus form a natural genus. Nemophila is most closely related to Pholistoma. The integumentary seed pits of Nemophila might have evolved from ovular seed pits similar to those in Pholistoma.     

Seed coat development in Leucospermum cordifolium (Knight) Fourcade (Proteaceae) and a clarification of the seed covering structures in Proteaceae

MANNING, J. C. & BRITS, G. J., 1993. Seed coat development in Leucospermum cordifolium (Knight) Fourcade (Proteaceae) and a clarification of the seed covering structures in Proteaceae . The development of the seed coat and pericarp is studied in Leucospermum cordifolium from ovule to mature seed. The ovule and seed are characterized by a tegmic pachychalaza. The pericarp is adnate to the integuments from anthesis and remains unthickened to maturity. The outer integument forms the seed coat and the seed is endotestal: the outer epidermis becomes tanniniferous and the inner epidermis develops into a crystalliferous palisade. The inner integument degenerates at an early stage. Examination of the literature reveals that the crystal palisade layer of the outer integument has been erroneously assumed to constitute an endocarp. This finding indicates that a re-interpretation of all published information on the seed coat in indehiscent Proteaceae is necessary before any speculations on the phylogenetic significance of the seed coat can be entertained.