Relative growth and nutrient accumulation rates for tobacco

Summary Tobacco plants (Nicotiana tabacum L.) were grown from transplanting until floral expression in the phytotron units of Southeastern Plant Environment Laboratories to evaluate the relationship between relative growth rate (RGR) and relative accumulation rates (RAR) of N, P, K, Ca, and Mg. RAR is calculated to be analogous to RGR. Plants were grown in both controlled-environment rooms with artificial light and air-conditioned greenhouses with natural light at three temperature conditions and three application rates of N-P-K. RGR and RAR were calculated only for the period of grand growth which occurred within the interval from 7 to 32 days after transplanting. In general, neither RGR nor RAR were affected by temperature or nutrient level. However, both temperature and nutrient level affected dry matter accumulation of the plants apparently by an influence on the rapidity with which plants adjusted to their new environment during the initial 7-day interval after transplanting. RAR for P and K were coequal with RGR of the whole plant; thus, the concentrations of P and K within the plant tended to remain constant during growth. RAR for N, Ca, and Mg were less than RGR for the whole plant; thus, internal concentrations of these nutrients declined during growth. RAR of N, Ca, and Mg for the whole plant were equivalent to RGR of the roots. As a rationale for the association of RGR of roots and RAR of N, it is proposed that the soluble carbohydrate pool in the roots concurrently influences both N absorption, as NO₃ ^-, and growth of new roots of immature plants. Research reported in this paper was supported in part by National Science Foundation (RANN) Grants GI-39229 and GI-39230. Operation of the Phytotron Units of Southeastern Plant Environmental Laboratories at Duke and North Carolina State Universities was supported by National Science Foundation Grants GB-28950-1A and GI-28951. Approved as Paper Number 4773 of the Journal Series of the North Carolina Agricultural Experiment Station, Raleigh, NC. Research reported in this paper was supported in part by National Science Foundation (RANN) Grants GI-39229 and GI-39230. Operation of the Phytotron Units of Southeastern Plant Environmental Laboratories at Duke and North Carolina State Universities was supported by National Science Foundation Grants GB-28950-1A and GI-28951. Approved as Paper Number 4773 of the Journal Series of the North Carolina Agricultural Experiment Station, Raleigh, NC.     

Relative growth rates of maxillary mesenchyme in the chick embryo

Chick embryos were injected with [3H]-thymidine at days 3-7 of incubation and were fixed and embedded in plastic. The embryos were divided into three stage groupings of development [Hamburger and Hamilton: J Morphol 88:49-92, 1951], and labeling indices were determined for each of the following delineated regions within the maxillary process at each stage: region 1, subepithelial mesenchyme located at the medial side of the maxillary process adjacent to the roof of the stomodeum; region 2, subepithelial mesenchyme at the ventral tip of the maxillary process (as seen on cross section); region 3, subepithelial mesenchyme at the lateral portion of the maxillary process below the eye; and region 4, interior mesenchyme defined as the central portion of the maxillary process and separated from the epithelium by the three other regions. Results indicated that differences exist among the regions examined and that these differences were stage specific. At stages 19-21 and stages 24-25 1/2, growth rates were higher in subepithelial regions than interiorly. At stages 28-29, however, a statistically significant difference among the regions was not found. These results suggested that there is an association between growth rates in the maxillary process mesenchyme and its proximity to the overlying epithelium and that these effects are related to the stage of development.     

Pigment-specific rates of phytoplankton growth and microzooplankton grazing in a subtropical lagoon

Phytoplankton growth and microzooplankton grazing rates wereevaluated in one station in Bahía Concepción,located in the middle region of the Gulf of California, México.We used high-performance liquid chromatography (HPLC) estimationsof phytoplankton pigment signatures to evaluate the annual variationof taxon-specific grazing and growth rates obtained with thedilution technique. Chlorophyll-a (Chl-a) concentrations variedwidely (0.34–3.32 µg L^–1) and showed two maxima,during late spring and autumn, associated with the transitionbetween mixed and stratified conditions. Phytoplankton growthrates varied seasonally with the lowest rates during summer(range: 0.01–2.55 day^–1 for Chl-a; 0.00–3.84day^–1 for Chl-b; 0.26–3.29 day^–1 for fucoxanthin;0.00–6.27 day^–1 for peridinin; 0.00–4.35 day^–1for zeaxanthin). Microzooplankton grazing was an important lossprocess (range: 0.0–1.89 day^–1 for Chl-a; 0.00–3.12day^–1 for Chl-b; 0.26–3.29 day^–1 for fucoxanthin;0.00–2.03 day^–1 for peridinin; 0.00–3.51 day^–1for zeaxanthin). Average grazing rates accounted 68–89%of estimated average phytoplankton pigment-specific growth rates.The analysis of pigment signatures indicates that diatoms anddinoflagellates were the dominant groups, and contrary to expectationfor typical subtropical lagoons, the specific growth rates inBahía Concepción showed a pronounced seasonalvariability, linked to transitional hydrographic conditions.Our results indicate a close coupling between the communitymicrozooplankton grazing and phytoplankton growth rates, withoutselective feeding behavior. These results suggest that microzooplanktonplay a critical role and may significantly modify the availabilityand efficiency of transfer of energy to higher trophic levels.     

Relative growth rates of predator and prey dinosaurs reflect effects of predation

Hadrosaurs grew rapidly, and quantifying their growth is key to understanding life-history interactions between predators and prey during the Late Cretaceous. In this study, we longitudinally sampled a sequence of lines of arrested growth (LAGs) from an essentially full-grown hadrosaur Hypacrosaurus stebingeri (MOR 549). Spatial locations of LAGs in the femoral and tibial transverse sections of MOR 549 were measured and circumferences were calculated. For each bone, a time series of circumference data was fitted to several stochastic, discrete growth models. Our results suggest that the femur and the tibia of this specimen of Hypacrosaurus probably followed a Gompertz curve and that LAGs reportedly missing from early ontogeny were obscured by perimedullary resorption. In this specimen, death occurred at 13 years and took approximately 10-12 years to reach 95 per cent asymptotic size. The age at growth inflection, which is a proxy for reproductive maturity, occurred at approximately 2-3 years. Comparisons with several small and large predatory theropods reveal that MOR 549 grew faster and matured sooner than they did. These results suggest that Hypacrosaurus was able to partly avoid predators by outgrowing them.     

Relative growth rates of limb muscles in the diprotodont marsupial, Setonix brachyurus

The fore- and hindlimb muscles of 12 Setonix brachyurus joeys, aged 5 to 175 days postpartum, and four adults were dissected out and weighed. Individual muscles and muscle groups were analysed for absolute and relative growth changes. From comprising almost 59% of the total limb musculature at birth the forelimb muscles finally constitute just over 9% in the adult; the hindlimb muscles start at just over 41% and end at almost 91%. In both limbs, the extensor actions predominate in the proximal limb segment because of their propulsive functions, whereas in the distal segment the flexor muscles tend to be the larger because of their shock-absorbing and spring functions. During growth of the fore-limb there is a relative increase in the size of latissimus dorsi and triceps brachii and a decrease in the distal segment muscles; in the hindlimb the gluteal and hamstring muscles increase at the expense of the distal segment muscles. Specializations for speed include long distal hindlimb segments and proximally located muscle bellies. The above findings reflect the adaptations and changing locomotor patterns from birth to adult in the Quokka.     

Abundance,growth and grazing loss rates of picophytoplankton in Barguzin Bay,Lake Baikal

The abundance, growth, and grazing loss rates of picophytoplankton were investigated in August 2002 in Barguzin Bay, Lake Baikal. Water samples for incubation were taken once at a near-shore station and twice at an offshore station. Contributions of picophytoplankton to total phytoplankton were high (56.9–83.9%) at the offshore station and low (5.8–6.8%) at the near-shore station. The picophytoplankton community in the offshore station comprised mainly phycoerythrin (PE)-rich cyanobacteria, with eukaryotic picophytoplankton being less abundant. In contrast, as well as PE-rich cyanobacteria and eukaryotic picophytoplankton, phycocyanin (PC)-rich cyanobacteria were found in the near-shore station. At the offshore station, growth and grazing loss rates on 25 August were 0.56 and 0.43 day⁻¹, respectively, and on 29 August, 0.69 and 0.83 day⁻¹, respectively. At the near-shore station, growth and grazing loss rates were 1.61 and 0.70 day⁻¹, respectively. These results show that there is a difference in the abundance, composition, and ecological role in the microbial food web of picophytoplankton between the near-shore and the offshore areas in Barguzin Bay.     

Use of radiolabeled tracers in dilution grazing experiments to estimate bacterial growth and loss rates

Dilution grazing experiments were conducted to determine growth and loss rates of glucose-metabolizing and total bacteria. Bacterial growth rates were low and losses to grazers negligible in samples collected from the Celtic Sea in June 1986. Growth and loss rates of glucose-metabolizing bacteria were higher than growth and loss rates of total bacteria in a sample collected from the North Sea in October 1986.     

Relative growth of tissues at different somatic growth rates in rainbow trout Salmo gairdneri Richardson

Growth of tissues (heart, spleen, liver, gonad, gut, skin, visceral fat and carcase) in immature rainbow trout relative to growth of whole fish, was examined by means of allometric analysis (y=ax^b; Huxley, 1932) of wet and dry weights. Relative growth rates of tissues are compared in an initial sample of fingerlings (< 11·29 g), and in fish (> 11·29 g) growing rapidly (at 12°C ad libitum rations) and slowly (at 12°C, 4–5% rations, and 7°C ad libitum rations). In the fingerlings of the initial sample, the major tissues by weight (liver, gut, skin, visceral fat) increased relatively more rapidly than whole body weight (i.e. with positive allometry; b> 1·00), and carcase increased more slowly than body weight (b< 1·00). Above fingerling size, the reverse holds: tissues other than carcase (with exception of visceral fat) increased less rapidly than body weight (b < 1·00), and carcase more rapidly (b > 1·00). These principles hold for post-fingerling, immature rainbow trout, regardless of growth rate differences of whole fish, and even in fish that also received bGH (bovine growth hormone). The characteristic b (slope) values in the allometry equations for the wet and dry weights of the various tissues tend to remain constant, despite whole fish growth rate differences and the effects of this constancy are to maintain approximate constancy of body proportional (%) wet and dry weights. It is emphasized however that the effect of b values only slightly > or < 1·00 can cause important changes in the proportional (%) weights of major tissues as fish continue to increase in size. In low (4–5%) rations fish (without bGH) the slope (b) value for gut is less than for fish on ad libitum rations with the result that gut proportional weight is significantly less among these fish. In fish on ad libitum rations at 7°C, the slope (b) value for skin is greater than for all other (12°C) groups; skin proportional weight for the 7°C group is therefore, significantly greater. The overall impression of relative growth in immature rainbow trout is of remarkable conservativeness of body proportional weights regardless of overall somatic growth rate.     

Relative growth rates of leaves from soybean grown under drought-stressed and irrigated field conditions

Abstract. The relative growth rates and leaf area were graphed against leaf area, normalized with respect to final leaf area, to assess the applicability of the Lockhart cell wall expansion equation to soybean, Glycine max (L.) Merr., leaf development under field conditions. For leaves that had completed more than 20% of their growth, relative growth rates decreased linearly with an increase in the normalized leaf area, indicating that these leaves were undergoing strictly expansive growth. Drought stress significantly decreased the relative growth rate of these larger leaves. Small leaves which had completed less than 20% of their growth, were found to have highly variable relative growth rates. The large variability in relative growth rates indicated that the Lockhart cell wall expansion equation was inadequate to evaluate the growth of these young leaves. Drought stress had virtually no influence on the relative growth rates observed in the small leaves.     

Time-series measurement of grazing rates of zooplankton and bivalves

The current state of the art in automated measurement of grazingrates of zooplankton and bivalves is evaluated. Limitationsto the development of automated methods are discussed with referenceto theoretical considerations. Different approaches to time-seriesmeasurements are examined, and some inadequately investigatedtime scales for measurement of grazing rates are outlined. Levelsof automation of existing experimental systems are described,and a recently developed grazing system based on in vivo fluorescenceadvanced. The new system is suited to use with zooplankton orbivalves, but depends on precise calibration of in vivo fluorescence.It facilitates rapid measurement of functional response to foodconcentration, estimation of time-series rates at constant foodconcentrations, and measurement of rates while simulating patchyfood distribution. Results derived from experiments with krill(Nyctiphanes australis) and cockles (Chione stutchburyi) usingthis grazing system are presented, and some future directionsfor instrument development suggested.     

Seasonal grazing rates and food processing by tropical herbivorous fishes

Seasonal variability in grazing rates and food-processing characters were assessed for three abundant fishes in a tropical rocky shore: the damselfish Stegastes fuscus , the parrotfish Sparisoma atomarium , and the surgeonfish Acanthurus bahianus . Significant differences were found in grazing rates among hour of day and seasons, and in food-processing characters among seasons for the three fishes. Grazing rates for S. atomarium and A. bahianus peaked at 1300 and 1400 hours for S. fuscus . Three main periods of different intensity in bite rates, low, intermediate and intense, were identified for all fishes. As expected, total bite rates, ingestion rates and gut fullness were highest in A. bahianus , the largest species studied, followed by S. atomarium and S. fuscus. S. atomarium with fused jaw teeth, holds the highest bite size and S. fuscus the lowest one. Gut turnover was high for S. fuscus and similar for S. atomarium and A. bahianus . Grazing rates and food-processing characters seem to vary between seasons not only due to changes in temperature, but also affected by other factors. Fishes employ different food-processing mechanisms and bear some differences in food-processing characters to achieve optimal energetic supplies from a poor nutrient food resource.     

Phytoplankton growth and the microscale nutrient patch hypothesis

It has been hypothesized that phytoplankton in situ grows fasterthan measured nutrient concentrations should allow, and thatmicroscale heterogeneity in nutrient concentration permits phytoplanktonto maintain the elevated growth rates. An examination of literaturedata failed to reveal any significant difference between observedgrowth rates and those predicted from steady-state N-growthkinetics. On the other hand, P kinetics may underestimate growthrates. However, it is demonstrated that a non-homogeneous nutrientsupply regime should actually decrease phytoplankton growthrates, regardless of the physical characteristics of the patches.Patchiness cannot account for elevated phytoplankton growthrates in situ.     

Variability of important vital rates challenges the demographic buffering hypothesis

Selection is assumed to eliminate life-histories showing high variability in vital rates that have the greatest influence on population performance. Therefore, an inverse variability-importance relationship of vital rates is believed to be a universal pattern for diverse life-histories. We tested for such a relationship using multi-year demographic data on a large number of populations of two perennial plant species. Applying different approaches, we first examined the overall variability-importance relationship for the average main vital rates (survival, growth, retrogression, fecundity) per species, and then separately for each population. We found an overall inverse relationship between temporal variation and importance of the average main vital rates for both study species, but these negative species-level correlations were mainly caused by different scales of the examined vital rates. When variability-importance relationships were examined across individual demographic transitions within populations, the abundance of positive and negative correlations depended largely on the method used, and positive correlations were more common after correcting vital rates for sampling variation than when using uncorrected vital rates. Our results cast doubt on the generality of the demographic buffering hypothesis, suggesting that the inverse variability-importance relationship may not be a universal pattern when vital rates are examined for multiple populations of the same plant species.     

Relative enantiomer binding and reaction rates with propanediol dehydrase

In the dioldehydrase reaction, L(+) propanediol reacts at a faster rate than the D(?)-isomer in competitive reactions, but when the diols are run independently the rate of the D(?)-isomer is 2.3 times greater than that of the L(+)-isomer. It is assumed that this reversal is due to a difference in the Michaelis-Menten constants. A ratio of K_mD(?)/K_mL(+) = 3.2 ± 0.3 at 25° is calculated from a series of competitive reactions. It is concluded that the binding site is such that while both isomers are accomodated readily, the D(?)-isomer is hindered to some degree in its approach to the binding site. However, once the enzyme-substrate complex is formed, the D(?)-isomer is in a more favorable configuration for further reaction.     

Effect of collection and acclimation period on grazing rates of limnetic zooplankton

Grazing rates of Daphnia sp. and Diaptomus oregonensis measured using an in situ method (Haney 1971) were compared with rates measured by collecting animals in vertical townets and placing them in experimental chambers either immediately or after a 24-h acclimation period. Experiments with acclimation yielded grazing rates of Daphnia that were statistically higher than in situ rates, whereas experiments conducted without acclimation yielded significantly lower rates. In situ grazing rates of Diaptomus were statistically higher than those for both townet techniques; experiments without an acclimation yielded higher rates than those for experiments with a 24-h acclimation period.     

Aphid growth and reproductive rates

Aphid size, although generally a good indicator of fecundity is not a good indicator of aphid performance over a wide range of conditions. In general, the greater the mean relative growth rate (MRGR) of apterous morphs of Rhopalosiphum padi (L.), the greater their fecundity. Intrinsic rate of increase (r_m) is even more closely correlated with mean relative growth rate than fecundity.Once these criteria are quantified for a morph of a particular species of aphid over a range of conditions the morphs intrinsic rate of increase on a particular host can be estimated by a quick measure of its mean relative growth rate.

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Résumé La taille des pucerons, bien que considérée généralement comme un bon indice de la fécondité, n'est pas un bon indice pour leurs performances dans une grande gamme de conditions. En général, plus le taux moyen de croissance relative est élevé chez les types aptères de Rhopalosiphum padi, plus leur fécondité est importante. Le taux intrinsèque de croissance (r_m) est encore plus étroitement lié au taux moyen de croissance relative que la fécondité.Une fois que ces critères ont été quantifiés pour un type d'une espèce donnée de puceron dans une gamme de conditions, les taux intrinsèques de croissance des différents types sur un hôte particulier peuvent être estimés par une mesure rapide de leur taux moyen de croissance relative.

     

Measurement of rates of grazing of the ostracod Cyprinotus carolinensis on blue-green algae

Measurements were made of the rates of grazing of the ostracod Cyprinotus carolinensis fed ¹⁴C-labelled filamentous blue-green algae (cyanobacteria). The grazing rate was a linear function of food concentration at densities below 1.1 µg dry weight of algae · ml^-1 and independent of concentration at densities above 11.5 µg algae · ml^-1. Starvation affected grazing rates significantly, but light vs. dark feeding, animal density, and the volume of feeding container did not. Grazing on Nostoc sp. was a linear function of ostracod size. Respiration of C. carolinensis and the blue-green algae was not a significant factor in the tests of grazing.     

Theory of grazing optimization in which herbivory improves photosynthetic ability

Herbivory had been generally considered to have a negative effect on plants, but a lot of studies have recently indicated that continuous herbivory pressure has a positive effect on plant performance, known as "grazing optimization." Based on field observations, we analytically examined a hypothesis of grazing optimization in which herbivory improves the photosynthetic ability of individual plants. We examined plant performance under various herbivory pressures and considered the evolution of plant phenology in response to a given herbivory pressure. First, we compared plant performances measured under their native conditions with specific herbivory levels. This was called the long-term response. Second, we examined the performances of plants adapting to a certain level of herbivory pressure under a non-native herbivory intensity. This was called the short-term response. According to numerical analysis, in realistic situations, grazing optimization is unlikely to be observed as a long-term response. However, grazing optimization can occur as short-term response if a plant is adapted to a certain level of herbivory pressure and the photosynthetic ability decreases significantly with the increasing size of vegetative parts. Our results suggest that improved photosynthetic ability by herbivory can result in grazing optimization, although it is constrained by the functional form of photosynthetic ability, native conditions, and experimental design.