Seeding Density Research Articles

The Effect of Seeding Density in Direct Sowing Cultivation on Physico-chemical Properties of Rice

The Effect of Seeding Density in Direct Sowing Cultivation on Physico-chemical Properties of Rice

Response of Mungbean Cultivars to Different Seeding Densities at Dry Land Conditions

Response of Mungbean Cultivars to Different Seeding Densities at Dry Land Conditions

Influence of Seeding Density on Contents and Uptake of N, P and K in Linseed (Linum usitatissimum L.)

Field experiments were conducted at the University of Wales, Aberystwyth, UK to evaluate the effects of seeding density and row spacing on the contents and uptake of N, P and K in linseed during 1993 and 1994. The contents of all three nutrients decreased with age of the plants up to the start of flowering, but N and P slightly increased at maturity in both the experiments. The increase of N and P at maturity could be the result of greater accumulation of these elements in the seeds. The uptake of all three elements (N, P and K) increased progressively with age of the plants, with a peak at maturity, but the level of K decreased by almost half in both experiments between flowering and maturity. The progressive increase of uptake with age of the plants may be related to total dry matter production. The decrease of K at maturity indicated that lower plant parts (stem and leaves) accumulated a higher percentage of K than seeds. The senescence of leaves at maturity might also have contributed to the decrease of K at maturity. The characteristics of the crop were in general quite similar in 1993 and 1994. The small variations found in the contents and uptake of N, P and K could be due to variation in weather conditions and the total length of the growth period. In 1993, the weather was moist and relatively cool, while in 1994 it was dry and relatively hot.

Response of Fourth Ratooning of Sugarcane to Different Patterns of Plantation and Seeding Densities

Response of Fourth Ratooning of Sugarcane to Different Patterns of Plantation and Seeding Densities

Growth of tissue-engineered human nasoseptal cartilage in simulated microgravity.

To evaluate the feasibility of in vitro fabrication of tissue-engineered cartilage from human nasoseptal chondrocytes for autologous reconstruction. Hyaline cartilage was reconstituted from chondrocyte-polyglycolic acid scaffolding constructs in a 3-dimensional mammalian cell culture cascade. This included monolayer cellular amplification, cell seeding in the spinner flask, and tissue growth in simulated microgravity. The quality of the fabricated cartilage analogue was found to depend on the initial cell density, duration of incubation, and bioreactor type. Dynamic seeding was nearly completed within the first 10 hours of inoculation regardless of the cell source (cryogenically preserved vs fresh chondrocytes) or presence of serum. A duration of incubation in excess of 4 weeks was required for complete matrix biosynthesis at low seeding densities in the spinner flasks. Seeding densities greater than 2.3x10(6) chondrocytes per scaffold were required for early hyaline cartilage formation as well as longer-time mature matrix regeneration. In addition, maintaining the structural integrity of the unreinforced scaffold, which is necessary for continued mature matrix regeneration, was achievable through postseeding tissue growth in simulated microgravity. Once combined with polyglycolic acid scaffolds in the bioreactor cascades that allow efficient seeding and quiescent tissue growth, human septal chondrocytes become a valuable source of reproducible ex vivo cartilage regeneration in the laboratory.

Response of Late Sown Wheat to Seeding Density and Nitrogen Management

Response of Late Sown Wheat to Seeding Density and Nitrogen Management

Effects of Salinity on Grain Yield and Yield Components of Rice at Different Seeding Densities

One possible management option for growers in dealing with decreases in rice (Oryza sativa L.) production caused by salinity is to compensate yield reduction by increasing seeding density. Our objectives were to investigate the effects of salinity and seeding density on grain yield and yield components, and analyze the relationships of the yield components to final grain yields at different seeding densities under salinity. Plants were grown in the greenhouse in sand irrigated with nutrient solutions. The treatments included seeding densities of 400, 600, and 720 seeds m−2 and salt levels of 1.0, 3.9, and 6.5 dS m−1. Salinity effects were highly significant on grain yield, plant stand, seed weight per plant, seed weight per panicle, and spikelets per panicle, but not significant on panicle density, kernel weight, and shoot weight per plant at seeding densities tested. Grain yield was not significantly increased with an increase of seeding density. Plant stand and panicle density were significantly increased, while seed weight per plant, fertility, and harvest index were significantly decreased with increases of seeding densities. The density‐dependent seed weight per plant under salinity was explained by the competition within and among plants at high‐density populations affected by salinity. Seed weight per panicle accounted for 62% of total variation and contributed more than panicle density to the grain yield under salinity. It was concluded that yield loss under moderate salinities may not be compensated for by increasing seeding density above normal density levels.

Effect of Seeding Density on the Fodder Yield and Quality of Two Maize Varieties

Effect of Seeding Density on the Fodder Yield and Quality of Two Maize Varieties

Nano-particles seeding and its characterization by X-ray photoelectron spectroscopy (XPS)

Abstract We present a new procedure for pretreatment seeding by ultrasonic agitation of silicon substrates in diamond nano-powder suspensions to which HF and KOH were added X-ray photoelectron spectroscopy (XPS) was used to measure the surface coverage by diamond nuclei immediately after the pretreatment. Coverage percentages of 70, 40 and 55% were obtained for the HF, KOH and the original diamond slurry, respectively. The seeding density (SD) was calculated from the known nano-particles size, determined independently from X-ray diffraction of the powder. For nano-particle size of ∼6 nm, we obtain nominal seeding densities of the order ∼1012 cm−2. The advantage of the high coverage was most evident for films deposited at low substrate temperature (570 °C). The potential of the new seeding procedure and the XPS characterization method are discussed.

Wheat Leaf Rust Severity as Affected by Plant Density and Species Proportion in Simple Communities of Wheat and Wild Oats

ABSTRACT While it is generally accepted that dense stands of plants exacerbate epidemics caused by foliar pathogens, there is little experimental evidence to support this view. We grew model plant communities consisting of wheat and wild oats at different densities and proportions and exposed these communities to Puccinia recondita to induce wheat leaf rust. Wild oats was included because it is a common competitor of wheat and may act as a barrier to the dispersal of P. recondita spores among wheat plants. Disease severity was estimated as percentage of wheat flag leaves covered by rust lesions. Seeding density rarely had a significant influence on rust severity, probably because of compensation due to increased tillering at low seeding densities. In contrast, increasing the proportion of wheat in mixtures with wild oats consistently increased wheat leaf rust severity. Regression parameters describing wheat leaf rust severity as a function of wheat seeding density did not differ significantly between pure wheat stands and wheat-wild oat mixtures and, thus, failed to support an effect of wild oats on wheat leaf rust other than through its competitive impact on wheat tiller density.

Bone formation by three-dimensional stromal osteoblast culture in biodegradable polymer scaffolds.

Bone formation was investigated in vitro by culturing stromal osteoblasts in three-dimensional (3-D), biodegradable poly(DL-lactic-co-glycolic acid) foams. Three polymer foam pore sizes, ranging from 150-300, 300-500, and 500-710 microns, and two different cell seeding densities, 6.83 x 10(5) cells/cm2 and 22.1 x 10(5) cells/cm2, were examined over a 56-day culture period. The polymer foams supported the proliferation of seeded osteoblasts as well as their differentiated function, as demonstrated by high alkaline phosphatase activity and deposition of a mineralized matrix by the cells. Cell number, alkaline phosphatase activity, and mineral deposition increased significantly over time for all the polymer foams. Osteoblast foam constructs created by seeding 6.83 x 10(5) cells/cm2 on foams with 300-500 microns pores resulted in a cell density of 4.63 x 10(5) cells/cm2 after 1 day in culture; they had alkaline phosphatase activities of 4.28 x 10(-7) and 2.91 x 10(-6) mumol/cell/min on Days 7 and 28, respectively; and they had a cell density that increased to 18.7 x 10(5) cells/cm2 by Day 56. For the same constructs, the mineralized matrix reached a maximum penetration depth of 240 microns from the top surface of the foam and a value of 0.083 mm for mineralized tissue volume per unit of cross sectional area. Seeding density was an important parameter for the constructs, but pore size over the range tested did not affect cell proliferation or function. This study suggests the feasibility of using poly(alpha-hydroxy ester) foams as scaffolding materials for the transplantation of autogenous osteoblasts to regenerate bone tissue.

Effect of omega-6 lipid-rich borage oil feeding on immune function in healthy volunteers.

Several studies have shown that dietary omega-3 lipid-rich fish oil can decrease the production of TNFa and L-l by human peripheral blood mononuclear cells (PBMC), as well as reducing lymphoproliferative responses[ 1-31, However, the effects of omega-6 lipids upon cytokine production have been less well studied. In this study we have examined the effects of omega-6 lipid-rich borage oil feeding on cytokine production, lymphoproliferation and modulation of T cell subsets. Eight healthy volunteers orally ingested 1Sml of refined borage seed oil daily for twelve weeks. The fatty acid composition of the oil was 37% linoleic acid (18 :2d) , 22% y-linolenic acid (18:3w6), and 18% oleic acid (l8:l) . Peripheral blood was collected in heparin prior to feeding and at four, eight, and twelve weeks during oil feeding. After centrifugation, to remove the plasma, PBMC were separated on a Lymphoprep density gradient. Proliferation was measured as uptake of '[Hlthymidine over the final seven hours of a 96 well plate three day culture. Seeding density was at IxlOf'cells/nil in 10% autologous plasma and with anti-CD3 (Spg/ml) or PHA (5pg/ml) as mitogens. Bulk culture supernatants were collected after 24 hours of culture with antiCD3, PHA or LPS (Ing/ml) at 2x IOhcellslml, and cytokine content was quantified using commercially available ELISAs (R&D Systems). The proportions of lymphocytes i n whole blood that were CD4', CD8'. CD4SRA' or CD4SRO'. were assessed using directly con.jugated antibodies and flow cytometric analysis. No statistically significant change in proliferation was noted during the course of oil feeding (Table I ) . This questions the in i ,iiv) relevance of studies where polyunsaturated lipids added in i,ifro suppress proliferative responses. Borage oil did not alter LPS-induced TNFa production. This contrasts with fish oil and so suggests differing mechanisms of action. Production of IFNy in response to PHA was also tinaiiectcd. However. PHA-induced TGFPI production significuntly increased during the cotirsc of oil feeding (Table 2).

Transplantation of human endothelial cell monolayer on artificial vascular prosthesis: the effect of growth-support surface chemistry, cell seeding density, ECM protein coating, and growth factors.

The failure rates of synthetic vascular grafts, when placed in low blood flow environments in humans, are not acceptable. Thus, endothelial cell (EC) seeding technology of vascular grafts was developed to prepare prostheses lined with a human monolayer expressing optimal thromboresistant properties. In a clinical setting, endothelialization of a graft can be achieved using higher cell seeding densities, or by creating a surface on which EC can adhere and grow to confluence. But, human endothelial cells show little or no proliferation on the currently available graft materials. In this study, surface modification of PTFE and ePTFE by ammonia plasma treatment was carried out to enhance its interactions with ECM protein, EC growth factors, and with EC harvested from human umbilical vein (HUVEC), and from human saphenous veins (HSVEC). Our data shows that various vascular graft materials generated from ammonia plasma treated PTFE and ePTFE exhibited statistically significant improvements in HUVEC and HSVEC growth when compared to their respective controls (p values < 0.001). Growth of HSVEC on ammonia plasma treated ePTFE without ECM protein coating was also found to be statistically significant in comparison to that on fibronectin coated ePTFE (p < 0.001). The final HSVEC cell densities found on various ePTFE surfaces prepared from ammonia plasma treated ePTFE, suggests that transplantation of HSVEC monolayers on vascular prostheses can be established within clinically relevant times. Ammonia plasma treatment process provides an unique opportunity to surface modify prosthetic materials of various construct to transplant mammalian cells including those that have undergone ex vivo gene transfer, and to deliver angiogenic molecules to a target area for tissue development.

The Impact of Rye Cover Crops on Weed Populations in a Tomato Cropping System

A reduced-till (RT) experiment determined the effect of rye seeding density and method of kill on rye biomass persistence, weed suppression, and tomato yield. ‘Wheeler’ rye was seeded at 56, 110, and 170 kg ha−1in the fall of 1988 and 1989 in Champaign, IL; Lexington, KY; and Lafayette, IN. One wk before transplanting tomatoes, rye was desiccated either by applying glyphosate at 1.1 kg ha−1and mowing (RT-glyphosate) or by mowing alone (RT-mowed). Both methods left rye residues on the soil surface as a mulch. Seeding density did not affect rye biomass, weed control, or tomato yield. Rye biomass differed depending on location and year, ranging from 320 to 1150 gm−2. Rye was completely killed by glyphosate, but regrew following mowing. RT-glyphosate suppressed weeds for 4 to 8 wk, which was similar to the suppression from conventional tillage (fall plowing with spring disking and harrowing) with trifluralin and metribuzin (CT-herbicide). Weed communities varied, but redroot pigweed and giant foxtail were present at all three locations. All treatments required supplemental weed management for commercially acceptable control. Except for IL in 1990, processing tomato yields (kg ha−1) in RT-glyphosate with hand-weeding were equal or better than yields in the CT treatments.

Hepatocyte Culture between Woven Capillary Networks: A Microscopy Study

A multi-compartment capillary membrane culture model with independently perfused three-dimensionally woven capillaries was developed for immobilization of hepatocytes in bioreactors. This enables spatial restructuring of cells and enhanced mass transfer performance with more efficient oxygenation and metabolite exchange. Seeding density defines cell behaviour in this model. With low densities cells attach to the membranes and flatten. Increasing density leads to spontaneous formation of aggregates which are immobilized between the capillaries.

Effects of Seeding Density on the Frost Damage of Wheat Tillers.

Degrees of frost damage were observed for three varieties of winter wheat at the different seeding densities. Shoot nitrogen, phosphorus, potassium, sugars and starch contents were measured at the internode elongation stage. Grain yield was high in the low seeding density plots (150 seeds/m2) and low in the high seeding density plots (300 seeds/m2). Although the early tillers died from frost damage, the late tillers escaped frost damage in the low seeding density plots. These tillers showed high nitrogen and potassium contents of shoots, so that they bore spikes and contributed much to yield. In the high seeding density plots, shoot nitrogen and potassium contents were small and the later tillers were weakened. Consequently, these tillers did not bear spikes, even after early tillers died from frost damage, so that grain yield showed a marked decrease in the high seeding density plots.

Synthesis and Expression of Smooth Muscle Phenotype Markers in Primary Culture of Rabbit Aortic Smooth Muscle Cells: Influence of Seeding Density and Media and Relation to Cell Contractility

Rabbit aortic smooth muscle cells (SMC) were seeded at moderate or high densities and grown either in the presence of serum or in the serum-substitution formula Monomed. Expression and synthesis of marker proteins caldesmon, calponin, smooth muscle myosin, and vinculin were monitored during SMC cultivation. Contractility was tested by the ability of cultured SMC to deform silicone membranes following ionomycin treatment. The results show that cells of moderate density grown in Monomed, as opposed to those grown in 5% serum, have the smooth muscle isoform of caldesmon 1.6-fold higher, calponin 1.4-fold and smooth muscle myosin 1.4-fold higher on Day 14 of cultivation. Synthesis of these proteins corresponded to their expression in SMC. The metavinculin:vinculin ratio slightly decreased over the first days with a following reestablishment on Day 8. Contraction was observed until Day 13, compared with Day 7 for cells grown in the presence of serum. High seeding density also prevented a decrease in the expression of smooth muscle markers with the exception of smooth muscle caldesmon whose content in the high density SMC culture was not significantly different from that in the moderate density culture. The period of contractility of SMC in the high density culture was also similar to that in the moderate density culture in the presence of serum. We conclude that cultivation of primary SMC in Monomed allows the maintenance of cells in the contractile phenotype more effectively than high initial seeding density.

Implantation of in vitro endothelialized polytetrafluoroethylene grafts in human beings

To assess the impact of in vitro endothelialization on prosthetic graft patency, we performed femorotibial reconstruction in four patients. Polytetrafluoroethylene grafts (6 mm), lined with cultivated autologous endothelial cells, harvested from the veins of the forearm, were used. Autologous endothelial cells were harvested enzymatically and characterized by morphology and factor VII staining. After a cultivation period of 17 to 23 days, the cell count increased from 27 +/- 3 x 10(4) endothelial cells to 5.4 +/- 1.1 x 10(6). Endothelial cell seeding on polytetrafluoroethylene prostheses was then performed. To improve endothelial cell attachment to the graft surface, polytetrafluoroethylene grafts (60 to 70 cm; 6 mm diameter) were precoated with fibrin glue containing fibrin and fibronectin and the fibrinolysis inhibitor aprotinin. Seeding density of 49 +/- 10 x 10(3) endothelial cells per square centimeter yielded a preconfluent monolayer immediately after seeding, as demonstrated by scanning electron microscopy. A second cultivation period of 6 days, after seeding and before implantation, was necessary for establishment of a confluent monolayer and to allow for maturation of the endothelial cell cytoskeleton as well as production and excretion of extracellular matrix. Grafts endothelialized in vitro were implanted in four patients requiring femorotibial reconstruction. Scintigraphic studies with indium 111-labeled platelets demonstrated little or no platelet deposition, indicating persistent endothelialization. All grafts remained patent at 3 months after implantation.

Effect of Nursery Seeding Density and Seedlings Hill on Late Transplanted Rice

Effect of Nursery Seeding Density and Seedlings Hill on Late Transplanted Rice

Effects of Seeding Density on Growth and Yield of Barley

Effects of Seeding Density on Growth and Yield of Barley