Potential Relative Growth Research Articles

Early Development Drives Variation in Amphibian Vulnerability to Global Change

Understanding how natural selection determines species’ life histories can reveal their resilience or sensitivity to anthropogenic changes. For example, the safe harbor hypothesis posits that natural selection will favor life histories that maximize the time spent in the safest life stages; a second theoretical prediction suggests that species with complex life histories will maximize the growth potential of a life stage relative to its safety. Amphibians exhibit complex life histories, with a diversity of developmental strategies occurring across taxa. Many strategies involve the complete elimination of a particular life stage, and thus provide an excellent opportunity to evaluate the main tenets of the safe harbor hypothesis and understand the consequences of this developmental variation for conservation of threatened amphibians. We develop a general framework for understanding developmental life histories of amphibians – including the special cases of paedomorphism, direct development, and viviparity – based on the relative growth potential and safety offered by aquatic and terrestrial habitat, which we tested using a global trait database. We then compare the IUCN Red List status of species differing in developmental mode, revealing that most fully aquatic species and species with an aquatic larval stage are currently of Least Concern, despite the fact that freshwater habitats are being lost at a much faster rate compared with terrestrial ecosystems. The higher proportion of direct developing and viviparous species that are threatened can be attributed to their smaller ranges, the fact that they are more likely to be found in rainforest habitats, and their relatively slow life histories. We conclude that an amphibian’s developmental mode reflects the relative costs and benefits of different habitats, and that this could contribute to the resilience or vulnerability of amphibians to future anthropogenic change.

잠재적 후보기술 경로 탐색방법 : 바이오 연료 사례

Existing main path analysis is useful to clarify the backbone of technology developments over the past, but has difficulty in identifying future technology candidates, and also in anticipating changes in the mainstream technology. Our method develops a growth velocity indicator, and combines it with key-route analysis and traversal counts measure in the main path analysis. It enables us to identify rapidly growing paths of future technology candidates, and further to evaluate the relative growth potential of such paths by which can replace the mainstream technology in the main path. Our method can contribute to identifying future technology candidates in a quantitative way by using patents, and broaden the scope of main path analysis research toward foresight. It can be useful for technology strategy in practice. Biofuel technology is exemplified.

Growth and fitness of triazine‐susceptible and triazine‐resistant common waterhemp (Amaranthus tuberculatus var. rudis)

Two greenhouse trials were conducted over a 2 year period (2004 and 2005) to compare the relative growth potential and fitness of triazine‐susceptible (TS) and triazine‐resistant (TR) waterhemp biotypes. Waterhemp plants from each biotype were grown in 6 L pots in the greenhouse in a completely randomized design. There was no difference in leaf number, plant height, plant biomass, time to bud or time to flower between the two biotypes. The TR female waterhemp plants produced 30% less reproductive biomass and 39% less seed than the TS biotype. The fitness penalty associated with triazine resistance was related to reproductive capability, not to vegetative growth.

Maturational and functional related differences in rat craniofacial growth

Background Whilst decreases in masticatory muscle function have been linked with increased prevalences of craniofacial dysmorphology and malocclusion in humans, the relative susceptibility of the different craniofacial components remains poorly understood. Methods Thirty-two wild-type male Sprague-Dawley rats were randomly assigned to two groups ( n = 16 each), one raised on a soft diet (SD) and the other on a hard diet (HD). Body weights and three radiographs (lateral, dorso-ventral, and tibial X-rays) were taken at baseline (T1 = 23 days old) and every 2 weeks thereafter for 8 weeks (T5 = 79 days old). The X-ray images were scanned, standardised points were digitised, and linear measurements were calculated. Multilevel statistical models were used to describe longitudinal absolute growth changes and statistically evaluate group differences. Relative maturity curves were generated for each measurement based on the animals’ T5 status. The experimental effect was calculated as the absolute and relative growth differences between the HD and SD groups. Results The HD group was significantly heavier than the SD group at T5, but no differences in tibial length were observed. Eight of the 20 craniofacial measurements (40%) showed significant size differences at the end of the experiment, with the SD group showing deficiencies in each instance. All of the vertical measurements, as well as most of the mandibular (67%) and transverse (67%) measures, showed absolute growth deficits in the SD group. Relative maturity curves demonstrated considerable variation among craniofacial structures (ranging from 42 to 98%). The neurocranial measures were the most mature; the mandibular measures were the least mature; the viscerocranial measures, which were most variable, tended to be intermediate. Whilst unrelated to the absolute experimental effect, the structures’ relative maturity explained almost 70% ( r = −0.82) of the relative experimental effect. Conclusion The results of this study support the notion that masticatory function is a key determinant of the craniofacial growth pattern and that its effects are modulated by the relative growth potential of the different craniofacial components.

Potato microtuber production and performance: A review

Almost half a century has passed sincein vitro tubers (microtubers) were first described in potato, but their adoption as a seed propagule has been uneven globally. Consensus is lacking regarding optimal production practices for microtubers and their relative productivity in relation to other propagules for minituber production. There is significant uncertainty regarding the utility of microtubers for evaluation of agronomic characters. However, the application of microtubers in germplasm conservation is widely accepted. Microtubers are producedin vitro in a plethora of different growing systems with varying environment, media constituents, and storage intervals. Many of the interactions between growth parametersin vitro and subsequent productivity appear to be genotype-specific. Accordingly, microtubers come in different sizes, have different dormancy requirements, and differ widely in relative growth potential and productivity. Despite these differences, there is evidence for strong analogies in growth responses between fieldgrown tubers and microtubers. The use of microtuber technology in seed tuber production, breeding programs, germplasm conservation, and research appears to have enormous potential. This review discusses microtuber production, yield and performance,in vitro screening, and germplasm storage and exchange.

Growth responses to elevated CO2 in NADP-ME, NAD-ME and PCK C4 grasses and a C3 grass from South Africa

The potential use of C4 biochemical subtypes [nicotinamide adenine dinucleotide phosphate-malic enzyme (NADP-ME), nicotinamide adenine dinucleotide-malic enzyme (NAD-ME) and phosphoenolpyruvate carboxykinase (PCK)] as delimiters of plant functional types (PFTs) with distinct responses to rising atmospheric CO2 concentrations was investigated in South African grass species. Gas exchange and above-ground growth in ambient and elevated CO2 (360 and 660 µmol mol–1 , respectively) were determined in three NADP-ME species, two NAD-ME species, two PCK species and one C3 species, all excavated from the same field site. Plants were grown in open-top chambers in a greenhouse for 178 d. Net CO2 assimilation rates were only significantly increased in one NAD-ME species, but stomatal conductances decreased (in six out of eight species, by a mean of 46%) and instantaneous leaf water-use efficiency increased (in all species, by a mean of 89%) in elevated CO2. These responses did not differ between photosynthetic pathways. Parameters derived from photosynthetic CO2 and light response curves were also not differentially influenced by CO2 treatment between pathways. Gas exchange responses were generally poorly related to CO2 responsiveness. Significant increases in leaf growth and canopy leaf area in elevated CO2 were found in two NADP-ME species, whereas increases in non-leaf above-ground growth were measured in three species representing all three C4 subtypes. Growth responses in elevated CO2 were apparently not simply correlated with biochemical subtype characteristics, although the most significant responses (particularly at the leaf level) were found for the NADP-ME pathway. This result was more likely attributable to the significant positive correlation found between CO2 responsiveness of leaf growth and relative leaf regrowth potential of individual species, the latter being higher in the two responsive NADP-ME species. Therefore, categorisation of PFTs according to relative growth potential may be more appropriate for predictions of CO2 responsiveness in C4 grasses.

Modelling and measurement of the nitrogen cycle in a vegetable field in Switzerland. I. A soil‐plant model for the nitrogen cycle

AbstractCorrect nitrogen fertilization is particularly important in vegetable growing, because not only the nitrate content of the product but also leaching of nitrate into the groundwater is affected. To apply the appropriate amount of fertilizer at the right time, the supply of plant‐available nitrate throughout the whole vegetation period has to be known. This may be achieved by repeated soil nitrate measurements (KNS‐System), however, the work involved in carrying out soil analyses is considerable. A reliable nitrogen‐prediction‐model would facilitate the task.A dynamic system model for the nitrogen cycle in a soil‐plant system is presented to predict yield, nitrate uptake and nitrogen leaching. To account for particularities of the site, specific information collected from the soil profile is required as input. Expected growth and nitrate uptake of the plant, the amount of fertilizer and plant residues applied, time of cultivation and climatic information are also required (list of inputs in table 1). Simulated crop growth is driven by potential relative growth which is dependent on the air temperature. Exponential growth is restricted by either a factor for maximal weight of a single plant, by maximal yield of the crop or by shortage of nitrogen in the plant. The nitrate uptake into the plant is governed by passive uptake through transpiration. It may be enhanced by a sink factor for active uptake when the simulated nitrogen content in the plant is lower than the expected value. Nitrate uptake thus depends on transpiration, water and nitrate availability in the rooted soil layers. Water (and hence nitrate) transport through the soil profile is divided into rapid transport in the macropores of the soil for a water content above field capacity and slow transport in the soil matrix for a water content below field capacity; the corresponding transfer factors have to be estimated in the field.As revealed by a sensitivity analysis (table 2) the input parameters having the greatest influence on final yield and nitrate uptake of lettuce are air and soil temperature, precipitation and the water content at field capacity. Parameters which increase nitrate availability have a favourable effect on nitrate uptake. Nitrate leaching over winter from a fallow plot is approximately proportional to water loss below the rooted soil layers; thus precipitation and water content at field capacity are the main factors affecting nitrate leaching.Calibration and validation of the model against data collected from a commercial vegetable field with different crops is presented in part II of the paper.

Catch-up growth in pigs: a relationship with muscle cellularity

ABSTRACTAn investigation was made into a possible relationship between the relative growth potential and skeletal muscle fibre number in low birth weight Large White pigs and their heaviest birth-weight littermates. Estimates of the total fibre number of m. semitendinosus were made from 23 pairs of ‘small’ and ‘large’ littermates. Littermates were slaughtered at the same age and were of a mean live weight 86 (s.d. 15) kg. Small littermates (mean birth weight 939 (s.d. 164) g) had, on average, lower live weights at slaughter (P < 0·001) and lower muscle fibre numbers (P < 0·05) than their large littermates (mean birth weight 2085 (s.d. 343) g). However, pigs within the low birth-weight category exhibited various degrees of catch-up growth with their heaviest littermates and some individuals actually exceeded their large littermates in live weight at slaughter. The relative live weights at slaughter and relative muscle fibre numbers of small and large littermates were determined by expressing the value for the small littermate as a proportion of the corresponding value for its large littermate. No correlation existed between relative live weight at slaughter and relative muscle fibre number of small and large littermates. The small littermates were then divided into two groups by their mean value of relative small to large slaughter weight (0·84). The littermates of low relative slaughter weight (≤0·84) exhibited a large range of muscle fibre numbers although their mean fibre numbers were lower than their large littermates (P < 0·05). This large range was probably responsible for the lack of correlation mentioned above. Those small littermates which exhibited a good degree of catch-up growth (relative slaughter weight >0·84) possessed fibre numbers which were not significantly different from those of their large littermates. These results suggest that pigs which exhibit an appreciable degree of catch-up growth always contain high relative numbers of fibres in their muscles. Those which show a poor degree of catch-up growth (≤O·84) exhibit a range of fibre numbers because there may be environmental and other factors which prevent some pigs from realizing their full growth potential. The results of the present study advocate muscle fibre number as an indicator at birth of potential for post-natal growth performance.

Exposed Crown Surface Area: A Mathematical Index of Individual Tree Growth Potential

A mathematical index representing relative growth potential of an individual tree is developed as a function of crown-surface area exposed to sunlight and distance from the crown to d.b.h. The index measures the relative competitiveness of an individual tree rather than the relative competitive pressure being exerted on an individual tree by surrounding trees. It effectively accounted for variation in 5-year d.b.h. growth of an even-aged pine stand.

Multimarket Demand Functions in the Presence of Supply Constraints: International Demand Functions for Cotton and Wool

studied in isolation without loss in explanatory power, although economists on occasion have ignored such interdependence, emphasizing the special conditions which diminish or eliminate the importance of feedback effects in their particular case. We proceed in the spirit of general equilibrium analysis to study the demand side of the world markets for cotton, wool and synthetic fiber, specifying and estimating interrelated fiber-demand curves for subgroups of thirtyone countries (excluding the United States) in the postwar (1949-1964).1 Since traditional multimarket demand models are inappropriate here because of the existence of severe synthetic-fiber supply limitations, we derive the demand functions by further constraining the consumer utility-maximization problem. This study is not so comprehensive, for example, as Witherell's [17] for wool or Desai's [3] for tin in the sense that we do not investigate both demand and supply and the determination of the world price and inventory levels, but it is more comprehensive in the sense that we do account for interaction between related markets. The estimated models suggest insights into the historical instability of world textile-fiber prices and the dangers inherent in price-support schemes with minimal working capital, into the nonexistence of textile cycles in countries outside the United States, and into the relative growth potential of cotton and wool textile in-