Letteratura scientifica selezionata sul tema "Seed coat outer integument"

In order to understand how and what structures of the tomato ovule with a single integument form the seed coat of a mature seed, a detailed study of the main development stages of the tomato ovule integument was carried out using the methods of light and electron microscopy. The integument itself it was shown to transform in the course of development into the coat (skin) of a mature seed, but the outer and inner epidermises of the integument and some layers of the integument parenchyma are mainly involved in this process. The outer epidermis cells are highly modified in later stages; their walls are thickened and lignified, creating a unique relatively hard outer coat. The fate of the inner epidermis of integument is completely different. It is separated from the other parenchyma cells of integument and is transformed into an independent new secretory tissue, an endothelium, which fences off the forming embryo and endosperm from the death zone. Due to the secretory activity of the endothelium, the dying inner parenchyma cells of the integument are lysed. Soon after the cuticle covers the endosperm, the lysis of dead integument cells stops and their flattened remnants form dense layers, which then enter the final composition of the coat of mature tomato seed. The endothelium itself returns to the location of the integument inner epidermis.

Seeds of soybean (Glycine max (L.) Merr.) were harvested from greenhouse-grown plants and fractures of the seed coat were examined with a scanning electron microscope. The seed coat was well differentiated from the outer integument when the seed had reached approximately 30% maximum seed size. At this time, the osteosclereids began to separate, becoming fully detached along their radial walls by 50% maximum seed size. Macrosclereid secondary wall development occurred during growth of the seed from 50 to 100% maximum seed size. Near R6 (100% maximum seed size) the endothelium began differentiation from the integumentary tapetum (inner integument) and was fully differentiated by physiological maturity (R7). From R7 to harvest maturity (R8) the seed lost moisture content and decreased in size. The parenchyma of the seed coat collapsed in response to this dehydration.

<p>The semi-permeable layer is a layer in the seeds of certain plants that restricts or impedes the exchange of the solute while allowing the permeability of internal and external water and gas, which is valuable protection to sustain the health and secure the growth, development and germination. In this study, the formation time and location of the semi-permeable layer in seed coats of <em>Elymus nutants</em> (Griseb.) and <em>Elymus sibiricus</em> (L.) were investigated. The experimental seed materials were gathered in the field from the flowering to seed maturation. The light microscopy and transmission electron microscopy for lanthanum nitrate identification were used to examine the characteristics of pericarp, seed coat and nucellus. The results showed that the semi-permeable layer was identified as the position, which can inhibit the penetration of the lanthanum, and it was checked as an amorphous membrane located at the outermost layer of the seed coat that is firmly attached to the seed coat. With seed development, the cells had differentiated and some parts of the ovary and the outer integument had disappeared. The semi-permeable layer originated from the outer layer of the inner integument, which was the original form of the seed coat. It can be stained by the Sudan III and clearly distinguished from other parts of the seed. The formation time of the semi-permeable layer in both species was nearly at 10 to 12 days post-anthesis (dpa), whereas seed physiological maturity was 24 to 26 dpa.</p>

Combinational traits of seed size and seed-coat hardness in Citrus garrawayi (F.M.Bailey) (syn. of Microcitrus garrowayi) were investigated as markers for estimation of seed morphological and physiological maturity. Seed size (length) and coat hardness correlated well with changes in seed coat and embryo morphological development, dry-weight accumulation, decreases in moisture content and a significant increase in germinability. Seed moisture content decreased from 82 ± 1% in immature seeds to 40 ± 1% at seed maturation. The outer integument of immature seeds consisted of thin-walled epidermal fibres from which outgrowths of emerging protrusions were observed. In comparison, mature seed coats were characterised by the thickening of the cell walls of the epidermal fibres from which arose numerous protrusions covered by an extensive mucilage layer. Immature seeds, with incomplete embryo and seed-coat histodiffereniation, had a low mean germination percentage of 4 ± 4%. Premature seeds, with a differentiated embryonic axis, were capable of much higher levels of germination (51 ± 10%) before the attainment of mass maturity. Mature seeds, with the most well differentiated embryonic axis and maximum mean dry weight, had the significantly highest level of germination (88 ± 3%).

Abstract Phylogenetic relationships in Styracaceae are well understood, but embryological characters and the ontogeny of integument(s) are still uncertain in many species. The goals of this study are to evaluate the systematic implications of embryological characters in Styracaceae, clarify the character evolution of the number of integuments and suggest a mechanism for the transition between unitegmic and bitegmic ovules. We examined the embryological characters of four genera and five species of Styracaceae, most of which were shared across taxa. However, Styrax has specific embryological features including bitegmic ovules, a multiplicative and sclerotic outer mesotesta and vascular bundles in the testa, all possible autapomorphies. The other three genera of Styracaceae share a unitegmic ovule, a parenchymatous mesotesta and a seed coat without vascular bundles, possible plesiomorphies with Diapensiaceae and Symplocaceae. The transition from a unitegmic to a bitegmic condition can be interpreted to be caused by a downwards shift of the boundary between the inner and outer integument, due to reduced activity in the subdermal initials and increased activity in the dermal initials of the outer integument at its base.

Abstract Background and Aims Seeds are dispersed by explosive coiling of the fruit valves in Cardamine hirsuta. This rapid coiling launches the small seeds on ballistic trajectories to spread over a 2 m radius around the parent plant. The seed surface interacts with both the coiling fruit valve during launch and subsequently with the air during flight. We aim to identify features of the seed surface that may contribute to these interactions by characterizing seed coat differentiation. Methods Differentiation of the outermost seed coat layers from the outer integuments of the ovule involves dramatic cellular changes that we characterize in detail at the light and electron microscopical level including immunofluorescence and immunogold labelling. Key Results We found that the two outer integument (oi) layers of the seed coat contributed differently to the topography of the seed surface in the explosively dispersed seeds of C. hirsuta vs. the related species Arabidopsis thaliana where seed dispersal is non-explosive. The surface of A. thaliana seeds is shaped by the columella and the anticlinal cell walls of the epidermal oi2 layer. In contrast, the surface of C. hirsuta seeds is shaped by a network of prominent ridges formed by the anticlinal walls of asymmetrically thickened cells of the sub-epidermal oi1 layer, especially at the seed margin. Both the oi2 and oi1 cell layers in C. hirsuta seeds are characterized by specialized, pectin-rich cell walls that are deposited asymmetrically in the cell. Conclusions The two outermost seed coat layers in C. hirsuta have distinct properties: the sub-epidermal oi1 layer determines the topography of the seed surface, while the epidermal oi2 layer accumulates mucilage. These properties are influenced by polar deposition of distinct pectin polysaccharides in the cell wall. Although the ridged seed surface formed by oi1 cell walls is associated with ballistic dispersal in C. hirsuta, it is not restricted to explosively dispersed seeds in the Brassicaceae.

For some horticultural plants, auxins can not only induce normal fruit setting but also form fake seeds in the induced fruits. This phenomenon is relatively rare, and, so far, the underlying mechanism remains unclear. In this study, “Fenghou” (Vitis vinifera × V. labrusca) grapes were artificially emasculated before flowering and then sprayed with 4-CPA (4-chlorophenoxyacetic acid) to analyze its effect on seed formation. The results show that 4-CPA can induce normal fruit setting in “Fenghou” grapes. Although more seeds were detected in the fruits of the 4-CPA-treated grapevine, most seeds were immature. There was no significant difference in the seed shape; namely, both fruit seeds of the grapevines with and without 4-CPA treatment contained a hard seed coat. However, the immature seeds lacked embryo and endosperm tissue and could not germinate successfully; these were considered defective seeds. Tissue structure observation of defective seeds revealed that a lot of tissue redifferentiation occurred at the top of the ovule, which increased the number of cell layers of the outer integument; some even differentiated into new ovule primordia. The qRT-PCR results demonstrated that 4-CPA application regulated the expression of the genes VvARF2 and VvAP2, which are associated with integument development in “Fenghou” grape ovules. Together, this study evokes the regulatory role of 4-CPA in the division and continuous redifferentiation of integument cells, which eventually develop into defective seeds with thick seed coats in grapes.

The seed of huauzontle (Chenopodium berlandieri ssp. nuttalliae) was studied by light microscopy and scanning electron microscopy. When the outer integument arises around the young ovule, instead of covering the inner integument and the nucellus, it grows backwards and partially surrounds the funiculus . When the pericarp is removed from the mature fruit, the seed is straw colored, because only the tegmen covers the seed. The chalaza of this seed has the form of a truncate cone, with the elliptical base towards the nucellus. In this zone of contact between the chalaza and the nucellus. a cuticle is deposited that surrounds some cells and makes a three dimensional network. This chalazal network is in contact with a smooth nucellar cuticle that fom1s part of the seed coat. The inversion of the inner integument could represent a selected mutation during the process of domestication.

La taille des graines est un trait agronomique majeur : de grosses graines stockent plus de réserves nutritives et produisent des plantules plus vigoureuses. Comme d’autres organes végétaux, la croissance de la graine, chez Arabidopsis, repose sur des interactions biochimiques et mécaniques entre deux compartiments génétiquement et physiquement distincts : l’albumen et les téguments. En particulier, les deux couches du tégument externe jouent un rôle fondamental dans la morphogénèse de la graine puisque des réponses mécaniques spécifiques se produisant dans chacune de ces couches détermineraient à la fois la taille et la forme de la graine. Le but de ma thèse a donc été de tester la contribution mécanique du tégument externe à la morphogénèse de la graine en étudiant les défauts mécaniques et de croissance des graines d’apetala2 (ap2), un mutant d’identité du tégument externe. Le travail de ma thèse suggère que l’activité d’AP2 promeut initialement la croissance de la graine, mais l’inhibe ensuite, en modifiant la composition en pectine et en hémicellulose des deux couches du tégument externe et donc leurs propriétés mécaniques. En parallèle, mon travail prouve que l’activité d’AP2 contrôle aussi la forme de la graine, alors qu’elle n’affecte pas la réponse des microtubules aux contraintes mécaniques dans les téguments. Enfin, je montre qu’altérer les propriétés du tégument externe peut, en retour, affecter le développement de l’albumen et ses propriétés mécaniques. En somme, le travail de ma thèse permet de mieux comprendre comment les interactions mécaniques et les réponses cellulaires aux contraintes mécaniques contrôlent la morphogénèse des plantes
Seed size is a major agronomic trait: large seeds store more nutritious compounds and generate more vigorous seedlings. Like in many plant organs, seed growth in Arabidopsis relies on biochemical and mechanical interactions between two genetically and physically distinct seed compartments: the endosperm and the surrounding seed coat. Accordingly, the two layers of the seed coat outer integument play a key role in seed morphogenesis as distinct mechanical responses occurring in each of these layers are thought to determine both the size and the shape of the seed. The goal of my thesis was thus to test the mechanical contribution of these two outer integument layers to seed morphogenesis by studying the mechanical and growth defects of the mutant of outer integument identity apetala2 (ap2). The work of my thesis allowed me to show that AP2 activity initially promotes seed growth but then inhibits it by tuning the composition in pectin and hemicellulose, and thus the mechanical properties, of the walls of both layers of the outer integument. In parallel, my results also suggest that AP2 activity affects seed shape without influencing microtubule response to forces in the seed coat. Finally, I also proved that altering the properties of the seed coat can, in turn, affect endosperm development and mechanical properties. Taken together, the work of my thesis provides a better understanding on how mechanical interactions and responses control morphogenetic processes in plants

Abstract Orchid seeds have been called ‘dust seeds’ due to their minute size (0.15-6.0 mm) and light weight, sometimes no more than a microgram (Ziegler 1981). They generally lack endosperm, and at maturity the uniseriate epidermis of the outer integument forms a loose sheath or tunic around the embryo. Their shapes vary from small ovoid or ellipsoid seeds with a proportionately large embryo that may have relatively poor aerodynamic qualities (more commonly found in terrestrial orchids) to balloonshaped, winged or filiform seeds designed to be carried over great distances on air currents. The presence of orchids on most remote oceanic islands attests to the long-distance dispersal of these seeds, although published studies on orchid seed dispersal are rarely performed. Although easily dispersed by wind, orchid seeds have little desiccation tolerance, and it is doubtful whether they can sustain long periods of suspension in the atmosphere without damage to the embryo.

Biologically seed is a small embryonic plant along with either endosperm or cotyledons, enclosed with in an outer protecting covering called seed coat. During the time of seed development large metabolic conversions take place, including proper partitioning of photo-assimilates and the formation of complex polymeric forms of carbohydrate, protein and fats for storing as seed reserves. In developing phase of seeds, every detail information stored in the embryonic plant are genetically and sometimes epigenetically also predetermined and influenced by various environmental/external factors already faced by the mother plant. In the growth cycle of plants, seed germination and seedling establishment are the two critical phases where survivability of the seedlings in natural habitats is a matter of question until the onset of photosynthesis by the established seedling. The various sequence of complex processes known to occur in both the phases i.e., an array of metabolic activities are initiating which eventually leads to the renewal of embryo growth of the dormant seeds and ultimately seedlings are established. Efficient seed germination is an important factor for agricultural sciences and successful establishment of germinated seedling requires a rapid and uniform emergence and root growth. With these aspects of seed physiology kept in mind the present chapter will be designed in such a way where, a gap filling, inter linking, eco- and farmers\' friendly technology i.e., ‘seed priming’ (a pre-sowing partial hydration of seeds) will be considered to improve the rate and uniformity of germination and seedling establishment. Under optimal and adverse environmental conditions, the primed seeds of diversified species lead to an enhanced germination performance with increased vigor index has been reported by various scientists which indicates a good establishment of seedlings in the field and thereafter enhance the performance of crops as a whole.

Black gram(Vigna mungo L)CV T-9plants were grown till maturity i. e. 74days at 0.0065, 0.013(deficient) and0.065(adequate)mg cu l-1 of cu in refined sand. Cu deficiency i. e. 0.0065,0.013 cu l-1 caused phenotypes are that Compared to control 0.065mg cul-1 cu supply the plants were stunted ,leaves were discoloured and old leaves became.Necrotic and withered and the number of flowers, pods and seeds are highly reduced. The size and number of pods were significantly reduced in cu deficiency. The seed weight marginally decreased at both the cu deficient levels. All the stages of determinations(day 24,60,74)the decrease in total dry weight was 29-30% at 0.0065mg cu l-1and14-17% at 0.013 mg cu l-1as compared to that of control. The concentration of cu in both leaves and seeds increased with an increase in cu supply, the cu concentration in deficient cu was higher in younger leaves than that of older leaves. Cu deficiency reduces growth , male and female fertility and this effectsthe seed quality of a plant.The cu deficiency also effect the economy of the crops .The delayed flowering,senescence and entirely abolished gynoecium fertility were also seen in cu deficient (o.o65ml cu l-1 blackgram plants).The cu deficiency affects the pollen producing capacity when the pollen grains were germinated in an artificial medium the observation showed that 30-35%pollen grains were viable in deficiency as compared to 61% at normal cu and the tube length was also decreased at deficient cu .The pollen grains sticked to stigma surface also showed esterase activity and the esterase activity was studied in stigma under control condition was much higher than that of deficient cu supply.After clearing with NAOH and staining with aniline blue the whole mount of ovule showed that phenolic compounds were localized more in micropylar region of the outer integument on the placental side in cu deficient material ,whereas in control this type of deposition was not observed ,cell division in this region of integument is more frequent in the control(0.065mgl-1)cu supply.As compared to deficient(0.0065mg cul-1),on the protein basis the activities of peroxidase ,acid phosphatase and alkaline phosphatase decreased in both male and female parts i. e. stamen, ovaries, stigma and style.While on the fresh weight basis the activity of peroxidase increased in cu deficient supply. The activity of acid phosphatase and alkaline phosphatase increased in ovary stigma style and stamen. In the stamen the acid phosphatase activity decreased in cu deficient level.Compared to control the concentration of sugars both reducing and non-reducing in leaves (source)as well as developing pods(sink)decreased at deficient cu at 0.0065mgl-1 this indicates of lower synthesis and lesser incorporation of sugars in biosynthesis of starch at deficient cu. The decrease in starch content was 43-49% from that of the control cu supply both leaves (source) and pods (sink). The concentration of soluble nitrogen compounds (non-protein nitrogen) lowered as compared to control cu supply while the decrease in total and protein nitrogen in seeds ranged from 30-32% in both deficient levels of cu .The decreased pod : leaf ratio of non-protein nitrogen and increased that of protein nitrogen at deficient cu indicates hampered translocation of soluble nitrogenous compounds from source to sink.The ovaries of mature buds showed accumulation of sugars and phenols was more pronounced at the lower cu level i.e (0.065 mg cu l-1)In mature seeds the decrease in protein content in cu deficient blackgram seeds ws maximum in albumins and vicilins and minimum in legumins . The sulphur containing amino acid i.e lysine , methionine and cysteine : increased with an increase in cu supply from 0.0065 to 0.065 mg cu l-1

The presence of iron (iron oxide from carbon steel piping) buildup in Boiling Water Reactor (BWR) circuits and wastewaters is decades old. In, perhaps the last decade, the advent of precoatless filters for condensate blow down has compounded this problem due to the lack of a solid substrate (e.g., powdex resin pre-coat) to help drop the iron out of solution. The presence and buildup of this iron in condensate phase separators (CPS) further confounds the problem when the tank is decanted back to the plant. Iron carryover here is unavoidable without further treatment steps. The form of iron in these tanks, which partially settles and is pumped to a de-waterable high integrity container (HIC), is particularly difficult and time consuming to dewater (low shear strength, high water content). The addition upstream from the condensate phase separator (CPS) of chemicals, such as polymers, to carry out the iron, only produces an iron form even more difficult to filter and dewater (even less shear strength, higher water content, and a gel/slime consistency). Typical, untreated colloidal material contains both sub-micron particles up to, let’s say 100 micron. It is believed that the sub-micron particles penetrate filters, or sheet filters, thus plugging the pores for what should have been the successful filtration of the larger micron particles. Like BWR iron wastewaters, fuel pools/storage basins (especially in the decon. phase) often contain colloids which make clarity and the resulting visibility nearly impossible. Likewise, miscellaneous, often high conductivity, wastesteams at various plants contain such colloids, iron, salts (sometimes seawater intrusion and referred to as Salt Water Collection Tanks), dirt/clay, surfactants, waxes, chelants, etc. Such wastestreams are not ideally suited for standard dead-end (cartridges) or cross-flow filtration (UF/RO) followed even by demineralizers. Filter and bed plugging are almost assured. The key to solving these dilemmas is 1) to break the colloid (i.e., break the outer radius repulsive charges of the similar charged colloidal particles), 2) allow these particles to now flocculate (floc), and 3) form a type of floc that is more readily filterable, and, thus, dewaterable. This task has been carried out with the innovative application of electronically seeding the feed stream with the metal of choice, and without the addition of chemicals common to ferri-floccing, or polymer addition. This patent-pending new system and technique is called Seeding And Filtration Electronically, or the SAFE™ System. Once the colloid has been broken and flocking has begun, removal of the resultant floc can be carried out by standard, backwashable (or, in simple cases, dead-end) filters; or simply in dewaterable HICs or liners. Such applications include low level radwaste (LLW) from both PWRs and BWRs, fuel pools, storage basins, salt water collection tanks, etc. For the removal of magnetic materials, such as some BWR irons, an ElectroMagnetic Filter (EMF) was developed to couple with the ElectroCoagulation (EC), (or metal-Floccing) Unit. In the advent that the wastestream primarily contains magnetic materials (e.g., boiler condensates and magnetite, and hemagnetite from BWRs), the material was simply filtered using the EMF. Bench-, pilot- and full-scale systems have been assembled and applied on actual plant waste samples quite successfully. The effects of initial feed pH and conductivity, as well as flocculation retention times was examined prior to applying the production equipment into the field. Since the initial studies (Denton, et al, EPRI, 2006), the ultimate success of field applications is now being demonstrated as the next development phase. For such portable field demonstrations and demand systems, a fully self enclosed (secondary containment) EC system was first developed and assembled in a modified B 25 Box (Floc-In-A-Box) and is being deployed to a number of NPP sites. Finally, a full-scale SAFE™ System has been deployed to Exelon’s Dresden NPP as a vault cleanup demand system. This is a 30 gpm EC system to convert vault solids/sludges to a form capable of being collected and dewatered in a High Integrity Container (HIC). This initial vault work will be on-going for approximately three months, before being moved to additional vaults. During the past year, additional refinements to the patent pending SAFE™ System have included the SAFER™ System (Scalant and Foulant Electronic Removal) for the removal by EC of silica, calcium and magnesium. This has proven to be an effective enabler for RO, NF and UF as a pretreatment system. Advantages here include smaller, more efficiently designed systems and allowed lower removal efficiencies with the removal of the limiting factor of scalants. Similarly, the SAFE™ System has been applied in the form of a BAC-UP™ System (Boric Acid Clean-Up) as an alternative to more complex RO or boric acid recycle systems. Lastly, samples were received from two different DOE sites for the removal of totally soluable, TDS, species (e.g., cesium, Cs, Sr, Tc, etc.). For these applications, an ion-specific seed (an element of the SMART™ System) was coupled with the Cs prior to EC and subsequent filtration and dewatering, for the effective removal of the cesium complex and the segregation of low level and high waste (LLW & HLW) streams.