Competition for light and its effect on leaf and spikelet development of wheat plants

1968 ◽  
Vol 19 (2) ◽  
pp. 191 ◽  
Author(s):  
DW Puckridge
Keyword(s):  
Population Density ◽  
Grain Yield ◽  
High Density ◽  
Main Stem ◽  
Light Environment ◽  
Low Density ◽  
Competition For Light

The effect of changes in the light environment of wheat plants at different stages in their growth was examined by growing single plants in tubes and changing the spacing of the tubes (population density) during development. Individual leaves on the main stem were reduced in both area and weight by transfer of the plants from high density to low density during the period from initiation of growth of the leaf on the apex to its appearance above the sheath. The number of fertile spikelets per ear was increased by transfer to low density in the period between formation of double ridges and ear emergence. It is suggested that the potential for grain yield of a wheat ear is affected by the light environment of the shoot at any stage before ear emergence.

scholarly journals Population Density or Populations Size. Which Factor Determines Urban Traffic Congestion?

2021 ◽  
Vol 13 (8) ◽  
pp. 4280
Author(s):  
Yu Sang Chang ◽  
Sung Jun Jo ◽  
Yoo-Taek Lee ◽  
Yoonji Lee
Keyword(s):  
Population Density ◽  
Population Size ◽  
Traffic Congestion ◽  
Critical Role ◽  
Small Population ◽  
High Density ◽  
Urban Traffic ◽  
Contradictory Result ◽  
Low Density

A large number of articles have documented that as population density of cities increases, car use declines and public transit use rises. These articles had a significant impact of promoting high-density compact urban development to mitigate traffic congestion. Another approach followed by other researchers used the urban scaling model to indicate that traffic congestion increases as population size of cities increases, thus generating a possible contradictory result. Therefore, this study examines the role of both density and population size on traffic congestion in 164 global cities by the use of Stochastic Impacts by Regression on Population, Affluence and Technology model. We divide 164 cities into the two subgroups of 66 low density cities and 98 high density cities for analysis. The findings from the subgroups analysis indicated a clear-cut difference on the critical role of density in low-density cities and the exclusive role of population size in high-density cities. Furthermore, using threshold regression model, 164 cities are divided into the two regions of large and small population cities to determine population scale advantage of traffic congestion. Our findings highlight the importance of including analysis of subgroups based on density and/or population size in future studies of traffic congestion.

Effects of population density on female and male burrow characteristics in the fiddler crab, Uca bengali Crane, 1975

Crustaceana ◽  
2015 ◽  
Vol 88 (12-14) ◽  
pp. 1283-1299 ◽  
Author(s):  
Fahmida Wazed Tina ◽  
Mullica Jaroensutasinee ◽  
Krisanadej Jaroensutasinee
Keyword(s):  
Body Size ◽  
Population Density ◽  
Fiddler Crab ◽  
High Density ◽  
The Other ◽  
Low Density ◽  
Density Effects ◽  
Egg Incubation ◽  
Other Hand ◽  
Males And Females

We examined the effects of population density on body size and burrow characteristics ofUca bengaliCrane, 1975. We predicted that (1) males in high-density areas (HD) should be larger in size and build higher quality burrows than males in low-density areas (LD), and (2) HD females should be larger in size, but build lower quality burrows than LD females, as HD females can find higher numbers of good quality male burrows around them for breeding and egg incubation. Our results showed that males and females in HD were larger in size than those in LD. Since HD males were larger in size, they built higher quality burrows than males in LD. On the other hand, even though LD females were smaller in size than HD ones, they built higher quality burrows than HD females. Our results thus indicate that density effects both body size and burrow characteristics.

scholarly journals Effects of Diaphorina citri Population Density on Daily Timing of Vibrational Communication Calls: Potential Benefits in Finding Forage

Insects ◽  
2020 ◽  
Vol 11 (3) ◽  
pp. 182
Author(s):  
Richard W. Mankin ◽  
Rikin Patel ◽  
Mason Grugnale ◽  
Ethan Jetter
Keyword(s):  
Population Density ◽  
Chemical Cues ◽  
Reproductive Fitness ◽  
High Density ◽  
Vibrational Communication ◽  
Low Density ◽  
Diaphorina Citri ◽  
Conspecific Density ◽  
Potential Benefits ◽  
Communication Calls

Adult Diaphorina citri (ACP) use visual and chemical cues to locate young citrus flush shoots on which they forage and oviposit, and they use vibrational communication duetting calls as cues to help locate mates. For individual pairs, calling and mating usually peaks between 10:00 and 15:00. To explore whether call rates (calls/h) are affected by interactions with nearby conspecifics, rates were compared in small citrus trees on which either 5 or 25 ACP female and male pairs had been released at 17:00 for later recording from sunrise (06:00) to 22:00. Final ACP locations were noted 40 h after release. Call rates were similar in both treatments during normal mating hours. However, rates were significantly higher for low- than high-density treatments between 06:00 and 10:00, which suggests calling during this period may be affected by conspecific density. Both sexes aggregated on flush at both densities. We discuss the potential that ACP producing calls near sunrise, outside of normal mating hours, might benefit from gains in reproductive fitness in low-density contexts if they call not only to locate mates but also to locate preferred flush—in which case, co-opting of vibrations to disrupt both mating and foraging may be feasible.

Palmer Amaranth (Amaranthus palmeri) Demographic and Biological Characteristics in Wide-Row Soybean

Weed Science ◽  
2017 ◽  
Vol 65 (4) ◽  
pp. 491-503 ◽  
Author(s):  
Nicholas E. Korres ◽  
Jason K. Norsworthy
Keyword(s):  
Mortality Rate ◽  
Population Density ◽  
Seed Production ◽  
Biomass Production ◽  
High Density ◽  
Palmer Amaranth ◽  
Low Density ◽  
Seedling Mortality ◽  
Trade Off ◽  
Flowering Initiation

Knowledge of Palmer amaranth demographics and biology is essential for the development and implementation of weed management strategies. A field experiment was conducted to investigate the effects of Palmer amaranth density on seedling mortality, flowering initiation, and flowering progress throughout the growing season and biomass production and fecundity in wide-row soybean. The experimental design was a randomized complete block design with three levels of Palmer amaranth density-clusters: high, medium, and low. Palmer amaranth mortality rate was greater at high Palmer amaranth population density-cluster, reaching a peak within 30 to 40 d after Palmer amaranth emergence (DAE) (0.55 and 0.80 for 2014 and 2015, respectively), in comparison with mortality rate at medium and lower density-clusters. Likewise, as Palmer amaranth density increased, biomass and seed production per unit area of the weed also increased. Biomass production at the high density-cluster in 2014 was 664.7 g m−2compared with 542.9 and 422.1 g m−2at medium and low density-clusters, respectively. Similarly, biomass production at high density-cluster in 2015 was 100.6 g m−2compared with 37.3 and 34.2 at medium and low density-clusters, respectively. In addition, seeds produced at high density-cluster were 1.5 million and 245,400 seeds m−2for 2014 and 2015, respectively. Seed production was reduced by 29% and 54% in 2014 and by 65% and 75% in 2015 at medium and low density-clusters, respectively. Earlier flowering initiation (i.e., between 30 to 40 DAE) occurred in higher Palmer amaranth density-clusters, indicating a trade-off between reproduction and survival at high densities and more stressed environments for species survival. Palmer amaranth male-to-female sex ratio was greater at high densities, 1.3 and 1.9, compared with lower densities of 0.6 to 0.7 and 0.7 to 0.8 in 2014 and 2015, respectively. The plasticity of Palmer amaranth population and population-structure regulation, vegetative growth, and flowering shifts at various levels of intraspecific competition (i.e., high vs. low population density-clusters) and the trade-off between these biological transitions merits further investigation.

scholarly journals Respuesta de fertilización y densidad de siembra en líneas de maíz.

2016 ◽  
Vol 9 (2) ◽  
pp. 113
Author(s):  
Hugo Tosquy ◽  
Guillermo Castañón
Keyword(s):  
Population Density ◽  
Grain Yield ◽  
Plant Density ◽  
High Density ◽  
Soil Mineral ◽  
Mineral Fertilization ◽  
Primary Element ◽  
Negative Effect ◽  
Area Unit ◽  
Treatment Design

An experiment was carried out in the Cotaxtla Experimental Field during the 1995 spring-summer cycle to study effects of soil mineral fertilization and population density in six parentallines of the best hybrids from tropical Mexico. The experimental desigp. used was the randomized block s in divided plots with two repetitions, and a complete factorial treatment design 24. Large plots consisted of lines LE-36, LE-37, LRB-14, D-539, POB 21 and POB 43. Small plots were formed by the treatments resulting from the combination of plant density (PD) at 50, and 62.5 thousand pl/ha, nitrogen (N), phosphorus (P) and potassium (K) at 161-184,46-69 and 0-60 kilograms per hectare, respectively. Out of the 18 variables studied, only 4 were not significant for the lines. The density of 62,500 pVha showed the highest grain yield. However, the same trait did not respond to a more intense fertilization with N-P-K, but the combination of each major primary element at its highest level helped to stop the negative effect of high density in grain traits. There was an additive effect in the interaction lines x density for grain yieId. This variable increased in all lines when there was a greater number of pIants per area unit.

scholarly journals Global Adaptations Resulting from High Population Densities in Escherichia coli Cultures

2000 ◽  
Vol 182 (15) ◽  
pp. 4158-4164 ◽  
Author(s):  
XueQiao Liu ◽  
Christina Ng ◽  
Thomas Ferenci
Keyword(s):  
Escherichia Coli ◽  
Population Density ◽  
Outer Membrane ◽  
High Density ◽  
Low Density ◽  
Membrane Composition ◽  
High Culture ◽  
General Stress Response ◽  
Trehalose Synthesis

ABSTRACT The scope of population density effects was investigated in steady-state continuous cultures of Escherichia coli in the absence of complications caused by transient environmental conditions and growth rates. Four distinct bacterial properties reflecting major regulatory and physiological circuits were analyzed. The metabolome profile of bacteria growing at high density contained major differences from low-density cultures. The 10-fold-elevated level of trehalose at higher densities pointed to the increased role of the RpoS sigma factor, which controls trehalose synthesis genes as well as the general stress response. There was an eightfold difference in RpoS levels between bacteria grown at 108 and at 109cells/ml. In contrast, the cellular content of the DNA binding protein H-NS, controlling many genes in concert with RpoS, was decreased by high density. Since H-NS and RpoS also influence porin gene expression, the influence of population density on the intricate regulation of outer membrane composition was also investigated. High culture densities were found to strongly repress ompF porin transcription, with a sharp threshold at a density of 4.4 × 108 cells/ml, while increasing the proportion of OmpC in the outer membrane. The density-dependent regulation ofompF was maintained in rpoS or hnsmutants and so was independent of these regulators. The consistently dramatic changes indicate that actively growing, high-density cultures are at least as differentiated from low-density cultures as are exponential- from stationary-phase bacteria.

scholarly journals Stereoscopic Planting in Ridge and Furrow Increases Grain Yield of Maize (Zea mays L.) by Reducing the Plant’s Competition for Water and Light Resources

Agriculture ◽  
2021 ◽  
Vol 12 (1) ◽  
pp. 20
Author(s):  
Shoutian Ma ◽  
Fujian Mei ◽  
Tongchao Wang ◽  
Zhandong Liu ◽  
Shouchen Ma
Keyword(s):  
Spatial Distribution ◽  
Soil Moisture ◽  
Grain Yield ◽  
Dry Matter ◽  
High Density ◽  
Light Transmittance ◽  
Dry Matter Accumulation ◽  
Competition Intensity ◽  
Planting Pattern ◽  
Competition For Light

Increasing planting density is an important ways to increase maize yield. A hot topic of conversation in the current research is how to improve crop light efficiency and yield potential by optimizing the cultivation mode under high density planting is a hot topic in current research. Thus, in this study, a field experiment was conducted to explore the effects of stereo-planting patterns on water and the utilization light resource and maize yields. Planting patterns included the conventional flat planting pattern (as the control, CK) and the stereo-planting in ridge and furrow (T). Each planting pattern had three planting densities, i.e., 60,000 plants ha−1 (D1), 75,000 plants ha−1 (D2) and 90,000 plants ha−1 (D3). The results showed that stereo-planting affected the physiological characteristics of plants by changing the spatial distribution of soil moisture. At the silking stage (R1), photosynthetic rate (Pn) of plants on the ridge was similar to CK, and transpiration rate (Tr) was significantly lower than that of CK. Pn of maize in the furrow was significantly higher than that of CK, and Tr was similar to CK. Stereoscopic planting had different effects on intraspecific competition intensity in maize population in different growing stages. In the six-leaf stage (V6), stereo-planting increased competition intensity of maize on the ridge, but lowered that of maize in the furrow by affecting the spatial distribution of soil moisture. During the R1 stage, stereo-planting increased the light transmittance rate within the canopy and eased the plant’s competition for light by reducing plant height and leaf area of maize under three density conditions. Stereo-planting had no effect on grain yield and dry matter accumulation of ridge-planted maize in the later growing stage, but it did increased the dry matter accumulation and grain yield of furrow-planted maize due to the improvement of the light environment and photosynthetic characteristics of the population. In two test years, stereo-planting increased 5.0–11.0% average yield of maize compared to CK under three density conditions. These results indicate that stereo-planting can reduce the plant’s competition for light and water resources and improve its physiological traits of plant by optimizing its spatial distribution of soil moisture and canopy structure, thus further increasing grain yield of maize under high-density planting conditions.

Effects of time and rate of nitrogen application on tillering, ‘sharp eyespot’ (Rhizoctonia solani) and yield in winter wheat

1969 ◽  
Vol 72 (2) ◽  
pp. 273-280 ◽  
Author(s):  
P. M. Bremner
Keyword(s):  
Winter Wheat ◽  
Grain Yield ◽  
Rhizoctonia Solani ◽  
Nitrogen Fertilizer ◽  
High Density ◽  
Low Density ◽  
Nitrogen Application ◽  
Severe Attack ◽  
Early Application ◽  
Sharp Eyespot

SUMMARYVarious rates of nitrogen fertilizer were applied in early and late spring to two densities of winter wheat to examine their effects on grain yield and its components. A severe attack of ‘sharp eyespot’ (Rhizoctonia solani) allowed an assessment of the effects of the treatments on the incidence of this disease.The disease level was much higher where nitrogen was applied early and increased with increase in nitrogen up to 120 units applied; it was slightly higher at the higher density. Grain yield was slightly greater where nitrogen was applied late; early application gave more, but smaller, ears. Main shoots produced at least 70% of the grain in the high-density plots but less than 50% at the low density. Tillers appearing after early March contributed little to grain yield at the higher density but substantially at the lower one. Tillers produced after early April died without heading. In general, the chances of survival of a tiller diminished with delay in the time of its appearance, but some early tillers died while later ones survived and produced ears. The chances of survival of later tillers were greater at low density and high rates of nitrogen.

Photoperiod and population density interact to affect reproductive and immune function in male prairie voles

1996 ◽  
Vol 270 (3) ◽  
pp. R571-R577 ◽  
Author(s):  
R. J. Nelson ◽  
J. B. Fine ◽  
G. E. Demas ◽  
C. A. Moffatt
Keyword(s):  
Population Density ◽  
Immune Function ◽  
High Density ◽  
Adrenal Function ◽  
Day Length ◽  
Low Density ◽  
Prairie Voles ◽  
Extrinsic Factors ◽  
Short Day ◽  
Long Day

Seasonal breeding of rodents is often associated with changes in adrenal function; altered adrenal function could account, in part, for seasonal changes in immune function and, ultimately, influence seasonal fluctuations in survival. Animals commonly monitor the annual change in photoperiod to ascertain the time of year and to make appropriate seasonal adjustments in physiology and behavior. Several extrinsic factors affect reproductive responsiveness to photoperiod. The interaction between population density and reproductive and adrenal responsiveness to photoperiod was assessed in the present experiment. Adult male prairie voles (Microtus ochrogaster) were maintained individually for 10 wk in long [light:dark (LD) 16:8] or short (LD 8:16) photoperiods in rooms with either high (10.96 animals/m3) or low (0.18 animals/m3) population densities. Regardless of population density, short-day voles regressed the size of their reproductive organs; reproductive organ masses were higher in long-day voles housed in high-density compared with low-density rooms. Paired adrenal masses were reduced in short-day voles, but were unaffected by population density; serum corticosterone concentrations were significantly elevated in short-day compared with long-day animals. In both photoperiods, basal blood corticosterone levels were higher in voles from low-density compared with high-density rooms. Splenic masses were unaffected by day length, but were elevated among high-density animals. Similarly, serum immunoglobulin (IgG) levels were elevated among high-density animals. These results suggest that population density per se, in the absence of behavioral interactions, can affect reproductive size, and possibly function, in long-day conditions, and that prairie voles, which are highly social, exhibit higher corticosterone and lower IgG levels in low compared with high densities. These results may be important in understanding arvicoline population fluctuations, as well as improving animal husbandry practices in the lab.

Quantitative defect studies in semiconductor TEM samples prepared by low angle ion milling

1995 ◽  
Vol 53 ◽  
pp. 512-513
Author(s):  
L. Mulestagno ◽  
J.C. Holzer ◽  
P. Fraundorf
Keyword(s):  
Sample Preparation ◽  
Milling Time ◽  
High Density ◽  
Low Density ◽  
Ion Milling ◽  
High Quality ◽  
Variable Angle ◽  
Major Disadvantage ◽  
Induced Defects

Due to the wealth of information, both analytical and structural that can be obtained from it TEM always has been a favorite tool for the analysis of process-induced defects in semiconductor wafers. The only major disadvantage has always been, that the volume under study in the TEM is relatively small, making it difficult to locate low density defects, and sample preparation is a somewhat lengthy procedure. This problem has been somewhat alleviated by the availability of efficient low angle milling.Using a PIPS® variable angle ion -mill, manufactured by Gatan, we have been consistently obtaining planar specimens with a high quality thin area in excess of 5 × 104 μm2 in about half an hour (milling time), which has made it possible to locate defects at lower densities, or, for defects of relatively high density, obtain information which is statistically more significant (table 1).

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