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At least 127 records · Page 7Linked to original sources
PubMed2001

The consequences of dioecy for seed dispersal: modeling the seed-shadow handicap.

Recent evidence has suggested that clades of dioecious angiosperms have fewer extant species on average than those of cosexual (hermaphroditic and monoecious) relatives. Reasons for the decrease in speciation rates and/or increase in extinction rates are only beginning to be investigated. One possibility is that dioecious species suffer a competitive disadvantage with cosexuals because only half of the individuals in a dioecious population are seed bearing. When only females produce seed, offspring will be more spatially clumped and will experience more local resource competition than when every individual produces seed. We examine two spatially explicit models to determine the effect of a reduction in seed dispersers on the invasibility and persistence of dioecious populations. Even though dioecious females were allowed to produce twice as many seeds as cosexuals, our results show that a reduction in the number of seed dispersers causes a decrease in the ability of dioecious progeny to find uninhabited sites, thus reducing persistence times. These results suggest that the maintenance of dioecy in the presence of hermaphroditic competitors requires a substantial increase in relative fitness and/or a large dispersal advantage of dioecious seeds.

Biological Evolution↗
PubMed1990

Nutritive value of rubber seed (Hevea brasiliensis) meal: utilization by growing pigs of semipurified diets in which rubber seed meal partially replaced soybean meal.

Thirty-six four-way cross (Chester White X Landrace X Large White X Yorkshire) growing barrows and gilts were used to investigate the effects of replacing graded levels of protein from soybean meal with equivalent levels of protein from rubber seed meal in 16% CP semipurified diets on the performance characteristics, hematocrit, plasma metabolites and N utilization of pigs. The first diet (control) was largely cornstarch-soybean meal in which the soybean meal supplied all of the CP. In other diets, rubber seed meal replaced 10%, 20% and 30%, respectively, of the protein of soybean meal in the control diet. Twenty gilts were used in a 28-d growth trial and 16 barrows were used in an 8-d digestion trial (4-d collection). There were no differences (P greater than .05) in ADG, ADF intake and in the feed:gain ratios, even though there was a trend for lower ADG and gain:feed ratio as the level of rubber seed meal increased in the diet. There were no differences in hematocrit, but plasma protein and albumin tended to be depressed when rubber seed meal provided more than 10% of the dietary protein. Apparent digestibilities of GE, DM and N were lower with rubber seed meal at 20% of the protein than with any other diet, but apparent N retained and the percent of digested N retained were not depressed significantly (P greater than .05). Although rubber seed meal protein is of poorer quality than soybean meal protein for growing pigs, at least 10% of dietary protein can be provided by rubber seed meal without adversely affecting growth and N utilization.

Animal Feed↗
PubMed2001

[Seeds latency of Stylosanthes hamata (Leguminosae) and its relation with morphology of the seed-coat].

The seed of Stylosanthes hamata is characterized by it's a high level of dormancy, which is imposed by seed-coat impermeability to water entry (harseededness or hard-seed condition). The level of hardseededness between upper and lower articulations of seven diploid and five tetraploid accessions was studied under tropical conditions. Germination tests on naked seeds (relative humidity: 55-65%, constant temperature: 27-30 degrees C, photoperiod: 12/12 hr) showed that hard-seed percentage was, in most cases, over 85% independent of ploidy level and seed position within the fruit. Histochemical analysis indicated that hardseededness in this species was associated with a completely sealed microphile and hilum. This feature was also associated to: a) an epidermis consisting of a palisade-like layer of macrosclereids, b) a like-line at the outermost region of these cells and c) a high concentration of hydrophobic compounds located all across the seed-coat.

Climate↗
PubMed2005

Seeding of human endothelial cells on valve containing aortic mini-roots: development of a seeding device and procedure.

PURPOSE: Complete covering of an artificial valvular scaffold with endothelial cells may prevent thromboembolic complications and lead to an excellent biocompatibility. For this purpose, we developed a seeding device for reproducible cell seeding on valve containing aortic roots. DESCRIPTION: Human endothelial cells and fibroblasts were obtained from saphenous vein pieces. Cryopreserved aortic roots (n = 25) were put into an especially developed tube, set on a rotator, and incubated with the cell suspension. The device rotated in two axes (sagittal and axial), ensuring slight movements of the leaflets. The rotation alternated with resting periods, allowing cell attachment to the surface. Different resting periods were tested (groups 1, 2, and 3 were 30, 45, and 60 min, respectively; n = 5 each). Total incubation time was 24 hours followed by further culturing for 6 days. In two further groups (groups 4 and 5; n = 5 each), a modified inlay was used to allow the cell suspension to flow around the entire graft. In group 4 the grafts were again incubated with human endothelial cells; however, in group 5 pre-seeding with autologous fibroblasts was done in addition. Immunohistochemical staining with antibodies against factor VIII, CD31, laminin, collagen IV, and CD90 were done, and scanning electron microscopy was done after initial seeding and after 6 days in culture. EVALUATION: Seeding resulted in homogenous cell layers on the luminal surface of the free walls in all groups. With resting periods of 45 minutes, these results were also obtained on the leaflets, whereas the other resting times resulted in defects of the endothelial cell layer on the cusps. After 6 days under culture conditions, the endothelial cell layers were confluent and viable, with the exception of the leaflets in group 1. With the modified inlay (groups 4 and 5), confluent cell layers were also achieved on the outer surface. In group 5 pre-seeding with autologous fibroblasts resulted in enhanced synthesis of extracellular matrix proteins, as was demonstrated with immunohistochemical staining for collagen IV and laminin. CONCLUSIONS: With this newly developed seeding device, confluent cell layers on valve containing aortic roots were reproducibly achieved. The technique enables further experimental research and even clinical application.

Aortic Valve↗
PubMed2000

Susceptibility of unprotected seeds and seeds of local bambara groundnut cultivars protected with insecticidal essential oils to infestation by Callosobruchus maculatus (F.) (Coleoptera: Bruchidae).

Ten local cultivars of bambara groundnut, Vigna subterranea (L.) Verdcourt obtained directly from farmers in Potiskum, Nigeria and from the Institute for Agricultural Research, Samaru, Nigeria were compared with three improved varieties developed at the International Institute of Tropical Agriculture, Ibadan, Nigeria for their susceptibility to infestation by Callosobruchus maculatus (F.). Three cultivars (Maifarinhaneh, Angale and Bunmonu) with a susceptibility index (SI) of 3.06-3.71 were identified as slightly susceptible to C. maculatus; four cultivars (Bagantere, Bakingangala, Ole and Bakiyawa 1) and one improved variety (TVSU 1061) with an SI of 4.39-4.93 as moderately susceptible; and three cultivars (Bidi, Uzu and Dadinkowa 1) and two improved varieties (TVSU 702 and TVSU 751) with an SI of 5.00-5.34 as susceptible. Five of the cultivars were used to examine the ability of beetle populations to overcome varietal resistance over six successive generations. Development time was significantly longer but percentage of adults that emerged and susceptibility of bambara groundnuts were significantly lower in F(4), F(5) or F(6) generations than in the F(1) or F(2) generation. The efficacy of combining insecticidal essential oils obtained from clove, Syzgium aromaticum, West African black pepper (WABP), Piper guineense, and ginger, Zingiber officinale applied at the rate of 2 mg/20 g seed and six of the local bambara groundnut cultivars (Angale, Maifarinhaneh, Bakingangala, Bagantere, Bunmonu and Bidi) with differing susceptibilities to C. maculatus (F.) was also assessed during a 3-month storage period. The three essential oils significantly reduced the percentage of C. maculatus adults that emerged from the bambara groundnut cultivars in the F(1) generation and the number of adult offspring that developed in the cultivars during the 3-month storage period. The mean number of progeny that developed in untreated seeds and seeds treated with clove, WABP and ginger oils during the study period were 73.0, 0.0, 0.1 and 0.2, respectively. No adult C. maculatus, however, developed in slightly and moderately susceptible cultivars treated with essential oils. Treatment of seeds of Bidi (a susceptible cultivar) with the essential oils reduced the percentage of adults that emerged in the F(1) generation from 26.8% in untreated seeds to 0.0, 0.1 and 0.4% in seeds treated with clove, WABP and ginger oils, respectively; and reduced loss in seed weight after three months' storage from 34% to 0.0, 0.01 and 0.1%, respectively.

Journal Article↗
PubMed1997

Automated matching of corresponding seed images of three simulator radiographs to allow 3D triangulation of implanted seeds.

To match corresponding seed images in different radiographs so that the 3D seed locations can be triangulated automatically and without ambiguity requires (at least) three radiographs taken from different perspectives, and an algorithm that finds the proper permutations of the seed-image indices. Matching corresponding images in only two radiographs introduces inherent ambiguities which can be resolved only with the use of non-positional information obtained with intensive human effort. Matching images in three or more radiographs is an 'NP (Non-determinant in Polynomial time)-complete' problem. Although the matching problem is fundamental, current methods for three-radiograph seed-image matching use 'local' (seed-by-seed) methods that may lead to incorrect matchings. We describe a permutation-sampling method which not only gives good 'global' (full permutation) matches for the NP-complete three-radiograph seed-matching problem, but also determines the reliability of the radiographic data themselves, namely, whether the patient moved in the interval between radiographic perspectives.

Algorithms↗
PubMed2007

A greedy heuristic using adjoint functions for the optimization of seed and needle configurations in prostate seed implant.

We continue our work on the development of an efficient treatment-planning algorithm for prostate seed implants by incorporation of an automated seed and needle configuration routine. The treatment-planning algorithm is based on region of interest (ROI) adjoint functions and a greedy heuristic. As defined in this work, the adjoint function of an ROI is the sensitivity of the average dose in the ROI to a unit-strength brachytherapy source at any seed position. The greedy heuristic uses a ratio of target and critical structure adjoint functions to rank seed positions according to their ability to irradiate the target ROI while sparing critical structure ROIs. Because seed positions are ranked in advance and because the greedy heuristic does not modify previously selected seed positions, the greedy heuristic constructs a complete seed configuration quickly. Isodose surface constraints determine the search space and the needle constraint limits the number of needles. This study additionally includes a methodology that scans possible combinations of these constraint values automatically. This automated selection scheme saves the user the effort of manually searching constraint values. With this method, clinically acceptable treatment plans are obtained in less than 2 min. For comparison, the branch-and-bound method used to solve a mixed integer-programming model took close to 2.5 h to arrive at a feasible solution. Both methods achieved good treatment plans, but the speedup provided by the greedy heuristic was a factor of approximately 100. This attribute makes this algorithm suitable for intra-operative real-time treatment planning.

Algorithms↗
PubMedDate not supplied

Short-term culture of human neonatal myofibroblasts seeded using a novel three-dimensional rotary seeding device.

A crucial factor in the tissue engineering of heart valves is an effective cell seeding with uniform cell distribution on biodegradable scaffolds to eventually form functional tissue constructs in vitro. In our laboratory, we developed a new cell-seeding device for optimal cell distribution for tissue-engineered heart valve constructs. In the present study, we developed a new cell-seeding device made of acrylic glass that is completely transparent (University Hospital Benjamin Franklin, Berlin, Germany). The polymeric heart valve scaffold is fixed in a small-volume, cylindrical cell-seeding chamber, and is surrounded by optimal cell suspension. The cell-seeding chamber is placed in a clear acrylic bowl so that it can be rotated in all directions to provide optimal cell distribution to all areas of the heart valve construct. We thus developed a highly isolated cell-seeding device that is driven by an independently developed rotating machine consisting of two independent motors (University Hospital Benjamin Franklin, Berlin, Germany). The whole system provides a high level of sterility and fits into a humidified incubator. Our newly developed cell-seeding device enables sterile conditions and optimal cell distribution for the controlled fabrication of autologous tissue-engineered heart valve constructs.

Biocompatible Materials↗
PubMed1969

Ethylene as a Component of the Emanations From Germinating Peanut Seeds and Its Effect on Dormant Virginia-type Seeds.

The embryonic axes of Spanish-type peanut seeds that do not exhibit dormancy to any extent were found to produce ethylene during germination. Virginia-type peanut seeds of the extremely dormant variety NC-13 produced low levels of ethylene when imbibed but not germinating. Treatments that released dormancy of NC-13 peanut seeds resulted in increased ethylene production by the embryonic axis. The estimated internal concentration of ethylene in Virginia-type peanut seeds was 0.4 ppm at 24 hr of germination. Fumigation with an external concentration of 3.0 to 3.5 ppm for 6 hr was sufficient to break dormancy of Virginia-type peanut seeds. These results suggest that ethylene is associated with the germination processes of non-dormant seeds and participates in the breaking of seed dormancy of dormant peanut varieties.

Journal Article↗
PubMed1974

Seed aging: chromosome stability and extended viability of seeds stored fully imbided.

Increase in moisture content of seeds of Lactuca sativa L. and Fraxinus americana L. in air-dry storage caused a rapid decline in longevity and an increase in the rate of accumulation of chromosome aberrations. Storage of seeds fully imbibed but unable to germinate allowed a high germination capacity to be maintained for long periods, together with a very low incidence of chromosome aberrations. Seedlings grown from dry-stored seeds showed an increase in morphological abnormalities with length of storage, whereas seedlings from imbibed-stored seeds appeared normal. It is suggested that in dry tissues, enzyme-controlled turnover and repair may be temporarily suspended, and that this may be an important factor in the loss of seed viability in storage. The effect of increasing seed longevity by lowering the moisture content of dry-stored seeds is discussed in relation to this hypothesis. The relevance of the proposal is also discussed in relation to ecological studies.

Journal Article↗
PubMed1981

Studies in Wild Oat Seed Dormancy: I. THE ROLE OF ETHYLENE IN DORMANCY BREAKAGE AND GERMINATION OF WILD OAT SEEDS (AVENA FATUA L.).

Seed of Avena fatua were shown to exhibit a characteristic loss of dormancy during dry storage at 25 C, whereas similar seed stored at 5 C maintained dormancy. 2-Chloroethylphosphonic acid was shown to increase germination of partly dormant seed imbibed under certain temperature regimes; a similar effect could not be established for fully dormant or fully nondormant seed. Using gas-liquid chromatography, natural ethylene levels were followed during imbibition of fully dormant and nondormant seed. A large peak in production was observed in the period prior to radicle emergence in the case of the nondormant seed. Measurements of ethylene production taken at 15 C, following periods of after-ripening in moist soil at either 5 or 25 C, indicated that endogenous production was unlikely to be a main cause of dormancy breakage in this species. The possibility that endogenous ethylene could play a role in natural dormancy breakage in aged seeds is discussed. The practical possibilities of 2-chloroethylphosphonic acid as a dormancy breaking agent in a field situation are outlined.

Journal Article↗
PubMed2006

A unifying framework for seed sensitivity and its application to subset seeds.

We propose a general approach to compute the seed sensitivity, that can be applied to different definitions of seeds. It treats separately three components of the seed sensitivity problem--a set of target alignments, an associated probability distribution, and a seed model--that are specified by distinct finite automata. The approach is then applied to a new concept of subset seeds for which we propose an efficient automaton construction. Experimental results confirm that sensitive subset seeds can be efficiently designed using our approach, and can then be used in similarity search producing better results than ordinary spaced seeds.

Algorithms↗
PubMed2025

ODR1, the key seed dormancy and germination regulator, promotes seed Proanthocyanidin biosynthesis via interaction with TTG1 and modulation of MBW complex activity.

Seed dormancy and germination are crucial for both plant survival and reproduction and for crop sowing and harvesting. Proanthocyanidins (PAs), one of the most abundant seed metabolites, play a role in enhancing dormancy and inhibiting germination. Multiple regulatory factors involved in PAs biosynthesis can alter seed dormancy or germination capacity. However, whether the dormancy or germination factors reciprocally influence the PAs biosynthesis is unclear. Here, we report that ODR1, a seed dormancy and germination key factor and a transcriptional (co-) repressor, can regulate seed PAs biosynthesis and act as a transcriptional co-activator. The odr1 mutant shows lighter seed coat color, decreased PAs contents, and reduced expression of PAs biosynthesis genes, which are restored in the ODR1 complementary lines. ODR1 interacts with TTG1 and forms a complex with TTG1/TT2/TT8 (three MBW complex components), enhancing their activation on promoters of PAs biosynthesis genes like DFR and ANS. Overexpressing TTG1 in the odr1-2 mutant rescues or even reverses PA-related phenotypes of odr1-2, confirming that ODR1-mediated regulation of PAs biosynthesis is dependent on TTG1. Moreover, three homologous copies of ODR1 in rapeseed were identified, and simultaneous knockout of them reduces the PAs contents. These results revealed the previously uncharacterized functions of ODR1 in PAs biosynthesis, suggested its conservation between Arabidopsis and rapeseed, and provided important gene resources for rapeseed variety improvement.

Proanthocyanidins↗
PubMed1975

[Isothiocyanate and vinyl thio-oxazolidone contents of rape seeds and rape seed oil].

Comparative studies on the isothiocyanate content of rape-seeds and rape-seed oil show that, apart from nearly 300 mg/100 g of vinyl thio-oxazolidone, rape-seeds contain almost 200--300 mg/100 g of isothiocyanates of which 3-butenyl isothiocyanate and 4-pentenyl isothiocyanate (ratio of 4:1) are the main components as evidenced thin-layer and gaschromatographically. Only about 1 mg/100 g of isothiocyanates are found in pressed rape-seed oil; and but circa 10 mg/100 g, in extracted rape-seed oil. 3-Butenyl isothiocyanate and 4-pentenyl isothiocyanate (ratio of 4:1) are once more the main components. Thioglycerides are not detected in the oil. Vinyl thio-oxazolidone is found only in extracted rape-seed oil (about 2 mg/100 g).

Chromatography, Gas↗
PubMed2000

Gravity independence of seed-to-seed cycling in Brassica rapa.

Growth of higher plants in the microgravity environment of orbital platforms has been problematic. Plants typically developed more slowly in space and often failed at the reproductive phase. Short-duration experiments on the Space Shuttle showed that early stages in the reproductive process could occur normally in microgravity, so we sought a long-duration opportunity to test gravity's role throughout the complete life cycle. During a 122-d opportunity on the Mir space station, full life cycles were completed in microgravity with Brassica rapa L. in a series of three experiments in the Svet greenhouse. Plant material was preserved in space by chemical fixation, freezing, and drying, and then compared to material preserved in the same way during a high-fidelity ground control. At sampling times 13 d after planting, plants on Mir were the same size and had the same number of flower buds as ground control plants. Following hand-pollination of the flowers by the astronaut, siliques formed. In microgravity, siliques ripened basipetally and contained smaller seeds with less than 20% of the cotyledon cells found in the seeds harvested from the ground control. Cytochemical localization of storage reserves in the mature embryos showed that starch was retained in the spaceflight material, whereas protein and lipid were the primary storage reserves in the ground control seeds. While these successful seed-to-seed cycles show that gravity is not absolutely required for any step in the plant life cycle, seed quality in Brassica is compromised by development in microgravity.

Brassica↗
PubMed2002

Proteomics of Arabidopsis seed germination. A comparative study of wild-type and gibberellin-deficient seeds.

We examined the role of gibberellins (GAs) in germination of Arabidopsis seeds by a proteomic approach. For that purpose, we used two systems. The first system consisted of seeds of the GA-deficient ga1 mutant, and the second corresponded to wild-type seeds incubated in paclobutrazol, a specific GA biosynthesis inhibitor. With both systems, radicle protrusion was strictly dependent on exogenous GAs. The proteomic analysis indicated that GAs do not participate in many processes involved in germination sensu stricto (prior to radicle protrusion), as, for example, the initial mobilization of seed protein and lipid reserves. Out of 46 protein changes detected during germination sensu stricto (1 d of incubation on water), only one, corresponding to the cytoskeleton component alpha-2,4 tubulin, appeared to depend on the action of GAs. An increase in this protein spot was noted for the wild-type seeds but not for the ga1 seeds incubated for 1 d on water. In contrast, GAs appeared to be involved, directly or indirectly, in controlling the abundance of several proteins associated with radicle protrusion. This is the case for two isoforms of S-adenosyl-methionine (Ado-Met) synthetase, which catalyzes the formation of Ado-Met from Met and ATP. Owing to the housekeeping functions of Ado-Met, this event is presumably required for germination and seedling establishment, and might represent a major metabolic control of seedling establishment. GAs can also play a role in controlling the abundance of a beta-glucosidase, which might be involved in the embryo cell wall loosening needed for cell elongation and radicle extension.

Arabidopsis↗
PubMed1998

wrinkled1: A novel, low-seed-oil mutant of Arabidopsis with a deficiency in the seed-specific regulation of carbohydrate metabolism.

During oil deposition in developing seeds of Arabidopsis, photosynthate is imported in the form of carbohydrates into the embryo and converted to triacylglycerols. To identify genes essential for this process and to investigate the molecular basis for the developmental regulation of oil accumulation, mutants producing wrinkled, incompletely filled seeds were isolated. A novel mutant locus, wrinkled1 (wri1), which maps to the bottom of chromosome 3 and causes an 80% reduction in seed oil content, was identified. Wild-type and homozygous wri1 mutant plantlets or mature plants were indistinguishable. However, developing homozygous wri1 seeds were impaired in the incorporation of sucrose and glucose into triacylglycerols, but incorporated pyruvate and acetate at an increased rate. Because the activities of several glycolytic enzymes, in particular hexokinase and pyrophosphate-dependent phosphofructokinase, are reduced in developing homozygous wri1 seeds, it is suggested that WRI1 is involved in the developmental regulation of carbohydrate metabolism during seed filling.

Arabidopsis↗
PubMed2000

A new set of Arabidopsis expressed sequence tags from developing seeds. The metabolic pathway from carbohydrates to seed oil.

Large-scale single-pass sequencing of cDNAs from different plants has provided an extensive reservoir for the cloning of genes, the evaluation of tissue-specific gene expression, markers for map-based cloning, and the annotation of genomic sequences. Although as of January 2000 GenBank contained over 220,000 entries of expressed sequence tags (ESTs) from plants, most publicly available plant ESTs are derived from vegetative tissues and relatively few ESTs are specifically derived from developing seeds. However, important morphogenetic processes are exclusively associated with seed and embryo development and the metabolism of seeds is tailored toward the accumulation of economically valuable storage compounds such as oil. Here we describe a new set of ESTs from Arabidopsis, which has been derived from 5- to 13-d-old immature seeds. Close to 28,000 cDNAs have been screened by DNA/DNA hybridization and approximately 10,500 new Arabidopsis ESTs have been generated and analyzed using different bioinformatics tools. Approximately 40% of the ESTs currently have no match in dbEST, suggesting many represent mRNAs derived from genes that are specifically expressed in seeds. Although these data can be mined with many different biological questions in mind, this study emphasizes the import of photosynthate into developing embryos, its conversion into seed oil, and the regulation of this pathway.

Arabidopsis↗