Effects of begging on growth rates of nestling chicks

We investigated whether an increase in begging levels delaysgrowth of chicks. In experiment 1, we hand-reared nine pairsof ring dove squabs, divided into a control and a begging group.All squabs received similar amounts of food, but those in thebegging group had to beg for a prolonged period in order tobe fed, while squabs in the control group received food withoutbegging. Squabs stopped responding to the treatment after 10days and, at that time, there was no effect of induced beggingon their body mass. In experiment 2, we hand-reared 27 pairsof magpie chicks for 3 days. The design of experiment 2 wassimilar to that of experiment 1. Daily food intake and beggingaffected growth rates. On average, chicks in the begging groupgrew 0.8 g/day less than control chicks, which represents adecrease of 8.15% in growth rate. Because growth is usuallypositively associated with expected fitness, this demonstratesthat begging is a costly behavior, an assumption routinelymade in models of begging behavior.     

Effects of forage availability on growth and maturation rates in water voles

1. In populations of small mammals, food supplementation typically results in higher population densities, body weights, growth rates and reproductive rates. However, few studies have demonstrated a relationship between forage levels and demographic rates in wild populations in the absence of supplementation. 2. We examined the association of levels of available forage with individual growth rates and time to sexual maturity in eight re-introduced and three naturally occurring populations of water voles (Arvicola terrestris). 3. Range sizes were smaller at sites with higher population densities. Mean forage availability and individual growth rates covaried with range size at each site. 4. The weight at which water voles became sexually mature was 112 g for females and 115 g for males and did not vary between study sites. Differences in growth rates therefore translated into differences in the time taken to reach maturity between sites. 5. In the re-introduced populations, mean days to maturity varied inversely with mean range length. Females took 7 days (18%, range 40-47 days) longer and males 5 days (13%, range 40-45 days) longer to reach breeding condition at the sites with the shortest mean range lengths. 6. Evidence from this study suggests a possible mechanism by which increased population densities may reduce maturation rates in water voles through a reduction in mean range size, thereby limiting the availability of forage to each individual.     

Effects of ingesting mercury-containing bacteria on mercury tolerance and growth rates of ciliates

The ciliateUronema nigricans was found to acquire tolerance to mercury after being fed mercury-laden bacteria followed by exposure of washed suspensions of these ciliates to various concentrations of mercury in solution. Significant differences in percent mortality were observed for ciliates fed mercury-laden bacteria compared with control suspensions fed mercury-free bacteria. The phenomenon of acquired mercury tolerance was demonstrated within a single generation time. Ciliates fed mercury-free bacteria and subsequently exposed to increasing levels of mercury in solution showed an elevated tolerance to concentrations which, on initial testing, resulted in mortality of 83% of the ciliate population. The effect of ingesting mercury-laden bacteria on growth rate ofUronema was examined, and results showed no significant differences in growth rates of both 3- and 14-day-old cultures of protozoa that had been fed mercury-laden and mercury-free bacteria under controlled conditions.     

Effects of algal food quality on fecundity and population growth rates of Daphnia

1. Food quality was at least as important as food quantity for both fecundity and population growth responses of the cladoceran Daphnia pulicaria fed the green alga Ankistrodesmus falcatus grown under N limitation, P limitation, or non-limited condition.
2. The fecundity of D. pulicaria was reduced under conditions of low food quality (low N or low P) compared with that for animals fed control non-limited algae regardless of ration size. The reduced fecundity of D. pulicaria fed P-limited food could be partially alleviated by increasing the ration (hence, compensation), but such was not the case for animals fed N-limited food.
3. Population growth rates of D. pulicaria ( r _max) were significantly reduced under conditions of low-quality food for both N-limited and P-limited algae. Population growth rates were unaffected by ration size, indicating no compensation.     

A yeast tRNA mutant that causes pseudohyphal growth exhibits reduced rates of CAG codon translation

In Saccharomyces cerevisiae, the SUP70 gene encodes the CAG‐decoding tRNA^Gln_CUG. A mutant allele, sup70‐65, induces pseudohyphal growth on rich medium, an inappropriate nitrogen starvation response. This mutant tRNA is also a UAG nonsense suppressor via first base wobble. To investigate the basis of the pseudohyphal phenotype, 10 novel sup70 UAG suppressor alleles were identified, defining positions in the tRNA^Gln_CUG anticodon stem that restrict first base wobble. However, none conferred pseudohyphal growth, showing altered CUG anticodon presentation cannot itself induce pseudohyphal growth. Northern blot analysis revealed the sup70‐65 tRNA^Gln_CUG is unstable, inefficiently charged, and 80% reduced in its effective concentration. A stochastic model simulation of translation predicted compromised expression of CAG‐rich ORFs in the tRNA^Gln_CUG‐depleted sup70‐65 mutant. This prediction was validated by demonstrating that luciferase expression in the mutant was 60% reduced by introducing multiple tandem CAG (but not CAA) codons into this ORF. In addition, the sup70‐65 pseudohyphal phenotype was partly complemented by overexpressing CAA‐decoding tRNA^Gln_UUG, an inefficient wobble‐decoder of CAG. We thus show that introducing codons decoded by a rare tRNA near the 5′ end of an ORF can reduce eukaryote translational expression, and that the mutant tRNA_CUG^Gln constitutive pseudohyphal differentiation phenotype correlates strongly with reduced CAG decoding efficiency.     

Effects of cold conditions on the growth rates of a subtropical conifer

Araucaria angustifolia is an endangered species that occurs in the high and cold regions of southern Brazil. This species has economic importance due to its wood and seeds, as well as playing a fundamental ecological role for the southern fauna and flora. Climate change can affect its distributional area and conservation, making it urgent to investigate the effect of climate on its development. The objective of our study was to investigate how growth rates of A. angustifolia vary in relation to interannual precipitation, temperature, frost and snowfall events. For this purpose, we used two samples obtained from each of 33 individual trees from a forest fragment on the Santa Catarina plateau, Brazil. Classical dendrochronological methods were applied for the preparation and dating of the samples. The tree rings were measured using specialized software. Superposed Epoch analysis was used to test the snow accumulation events. The climatic variables were tested by means of a correlation analysis. The Superposed Epoch analysis was used to test the snow accumulation events. Our results indicate that the species shows significant sensitivity to the climate, with the maximum and minimum absolute temperatures respectively correlated with positive and negative growth rates. Snowfall also reduced growth of A. angustifolia. Overall, extreme cold events are threats to the conservation of the species.     

Effects of different leaf traits on growth rates of insect herbivores on willows

We examined relative effects of traits of leaf quality of ten willow species (Salix: Salicaceae) on growth rates of five species of insect herbivores found in interior Alaska (a willow sawfly, Nematus calais; the tiger swallowtail butterfly, Papilio canadensis; and three species of chrysomelid beetles, Gonioctena occidentalis, Calligrapha verrucosa, and Chrysomela falsa). Leaf traits examined were water content, toughness, total nitrogen contnet, pubescence, and presence or absence of phenolic glycosides. Of ten Salix species, four species contain phenolic glycosides in their leaves. We examined relative effects of water content, toughness, and nitrogen content of the Salix leaves on larval growth rates at three different levels, i.e., on a single host species, between different host species, and between herbivore species. The within-host analyses showed that effects of water content, toughness and/or nitrogen content on herbivore growth rates were generally significant in early-season herbivores but not in late-season herbivores. For each herbivore species, differences in growth rates between hosts were not explained by differences in water content, toughness, or nitrogen content. The between-herbivore analysis showed that the interspecific difference in larval growth rates were related to difference in water and nitrogen content of the hosts. Pubescence of Salix leaves had little effects on herbivore growth rates. Presence of phenolic glycosides had a positive effects on growth rates of a specialist, N. calais, but no effect on the other specialist, Ch. falsa. Presence of phenolic glycosides had, in general, negative effects on growth rates of nonspecialists, G. occidentalis, C. verrucosa, and P. canadensis.     

Effects of water stress on leaf growth and photosynthetic and transpiration rates of Tectona grandis

The response of pear fruit and leaf parameters to shade imposed during development was studied. Whole branches of mature trees of Pyrus communis L. cv. Bartlett growing in the High Valley area of Argentina were covered with a shade cloth (80 % reduction in irradiance) from 6 to 18 weeks after full bloom (WAFB) during the 1995-96 growing season. Fruit diameter was measured at two-weekly intervals; flesh firmness, soluble solids concentration, and leaf area were determined 18 WAFB. Prolonged shading significantly reduced fruiting spur specific leaf mass and consequently resulted in 20.79 % less final fruit fresh mass. However, flesh firmness was 8.07 % lower under full irradiance. This revised version was published online in July 2006 with corrections to the Cover Date.     

Single high-dose vs. fractionated radiotherapy: Effects on plant growth rates

Aim

To evaluate the differential effects of fractionated vs. high-dose radiotherapy on plant growth.

Background

Interest in hypofractionated radiotherapy has increased substantially in recent years as tumours (especially of the lung, prostate, and liver) can be irradiated with ever greater accuracy due to technological improvements. The effects of low-dose ionizing radiation on plant growth have been studied extensively, yet few studies have investigated the effect of high-dose, hypofractionated radiotherapy on plant growth development.

Materials and methods

A total of 150 plants from the genus Capsicum annuum were randomized to receive fractionated radiotherapy (5 doses of 10 Gy each), single high-dose (SHD) radiotherapy (single 50 Gy dose), or no radiotherapy (control group). Irradiation was delivered via linear accelerator and all samples were followed daily for 26 days to assess and compare daily growth.

Results

On day 26, plants in the control, fractionated, and SHD groups had grown to a mean height of 7.55 cm, 4.32 cm, and 2.94 cm, respectively. These differences in overall growth were highly significant (P = 0.005). The SHD group showed the least amount of growth.

Conclusions

SHD effectively stunts plant growth and development. Despite the evident differences between plant and animal cells, ionizing radiation is believed to work in a similar manner in all biological cells. These findings highlight the need to continue investigating the use of hypofractionated schemes in humans to improve cancer treatment outcomes.     

Effects of density on growth rates of four benthic diatoms and variations in biochemical composition associated with growth phase

Diatom cell quantity and their biochemical composition vary among species and are greatly affected by harvest stage or culture conditions. This study compares growth pattern, cell attachment, and biochemical composition of four diatoms suitable for abalone post-larvae: Navicula incerta, Proschkinia sp., Nitzschia sp., and Amphora sp. The four diatoms were grown in F/2 medium at 28.5?±?1.4°C, under 62?±?8?μmol?photons?m^?2?s^?1, at different original inoculating densities (0.05?×?10⁶, 0.10?×?10⁶, and 0.25?×?10⁶?cells?mL^?1) and were harvested in log and stationary phase of growth for biochemical analysis. Total protein, carbohydrate, lipid, and ash composition, as well as fatty acid composition, were determined. All diatoms grew better when inoculated at 0.10?×?10⁶?cell?mL^?1 with Proschkinia sp. reaching the highest cell density of 6.56?×?10⁶?cells?mL^?1 in log phase. Amphora sp. had the highest cell attachment capacity when inoculated at 0.10?×?10⁶?cell?mL^?1 (11,580?cells?mm^?2), whereas N. incerta had the lowest (7,750?cells?mm^?2). Protein and lipid (percent dry weight) contents were generally highest in cells during log phase of growth; Amphora sp. in log phase of growth had the highest lipid content of 9.74% DW, whereas significant differences in carbohydrate between the two growth phases were only observed for Proschkinia sp. Besides, all diatoms had higher energy contents in log phase of growth. There were no significant differences in ash content among the four diatoms. Polyunsaturated fatty acid (PUFA) content ranged from 23.25% to 38.62% of the total fatty acids, and the four diatoms tested were richer in n-3 PUFA than in n-6 PUFA. All the diatoms had significant quantities of 20:5n-3 (EPA) (between 12.69% and 17.68% of TFA), and Proschkinia sp., in log phase of growth, had the highest quantity of arachidonic acid (20:4n-6; ARA). The results highlight the influence of culture conditions and harvest protocols on diatom nutritive value and enabled a preliminary approach towards the selection of novel diatom species.     

Effects of irradiance on relative growth rates, net assimilation rates, and leaf area partitioning in cotton and three associated weeds

Cotton (Gossypium hirsutum L. var. `Stoneville 213'), velvetleaf (Abutilon theophrasti Medic.), redroot pigweed (Amaranthus retroflexus L.), and hemp sesbania (Sesbania exaltata [Raf.] Cory) were grown in a controlled environment room at 31/25 C day/night temperature and three irradiances: 90, 320, and 750 μeinsteins meter⁻² second⁻¹. From total dry weights and leaf areas determined at intervals during the first exponential phase of growth, we used mathematical growth analysis techniques to calculate net assimilation rates (NAR), relative growth rates (R_w), relative leaf area expansion rates (R_a), leaf area partition coefficients (LAP), and leaf area ratios (LAR). In all four species, R_w, R_a, and NAR decreased with decreasing growth irradiance, while LAP and LAR increased. Within each species, R_w was positively correlated with NAR but negatively correlated with LAP and LAR. In comparisons among the four species within each growth irradiance, R_w was positively correlated with LAP. We discuss the relationship between LAP and LAR and show that LAP = (R_a/R_w) (LAR).     

Effects of sample size on estimates of population growth rates calculated with matrix models

Background

Matrix models are widely used to study the dynamics and demography of populations. An important but overlooked issue is how the number of individuals sampled influences estimates of the population growth rate (λ) calculated with matrix models. Even unbiased estimates of vital rates do not ensure unbiased estimates of λ–Jensen''s Inequality implies that even when the estimates of the vital rates are accurate, small sample sizes lead to biased estimates of λ due to increased sampling variance. We investigated if sampling variability and the distribution of sampling effort among size classes lead to biases in estimates of λ.

Methodology/Principal Findings

Using data from a long-term field study of plant demography, we simulated the effects of sampling variance by drawing vital rates and calculating λ for increasingly larger populations drawn from a total population of 3842 plants. We then compared these estimates of λ with those based on the entire population and calculated the resulting bias. Finally, we conducted a review of the literature to determine the sample sizes typically used when parameterizing matrix models used to study plant demography.

Conclusions/Significance

We found significant bias at small sample sizes when survival was low (survival = 0.5), and that sampling with a more-realistic inverse J-shaped population structure exacerbated this bias. However our simulations also demonstrate that these biases rapidly become negligible with increasing sample sizes or as survival increases. For many of the sample sizes used in demographic studies, matrix models are probably robust to the biases resulting from sampling variance of vital rates. However, this conclusion may depend on the structure of populations or the distribution of sampling effort in ways that are unexplored. We suggest more intensive sampling of populations when individual survival is low and greater sampling of stages with high elasticities.     

Effects of monosodium glutamate on lines of chickens having different juvenile exponential growth rates

MSG (4 mg/g BW) or the equivalent molar ratio of NaCl were injected subcutaneously into chicks from four populations of chickens derived from a double selection experiment [(1) low exponential growth rate (EGR) to 14 days of age (14L), (2) high EGR to 14 days of age (14H), (3) low EGR to 42 days of age (42L) and high EGR to 42 days of age (42H)]. MSG significantly influenced growth in chickens, but the absolute effect was genotype and sex dependent. Weights of abdominal fat pads were ranked among lines according to the sequence 42H, 14H, 42L and 14L. MSG significantly increased fat pad size by 51%, independent of genotype or sex. MSG significantly decreased breast weight in females and males by 7%. The higher percent fat pads and lower breast weights associated with MSG are indicative of growth due to fat accretion rather than protein deposition.     

Effects of temperature on growth rates of fungi from subantarctic Macquarie Island and Casey,Antarctica

Summary The linear growth rates of fungal isolates were measured on agar plates at temperatures ranging from 4° to 35°C. Fungi tested included the major fungal colonizers of leaves and litter of the three dominant plant species on subantarctic Macquarie Island, and major fungal species associated with plant and soil communities near Australia's Casey Station on the Antarctic Continent. All fungi grew at 4°C and were classified as psychrotrophs. Maximum growth rates were recorded at temperatures of 10° to 20°C for 13 of the 15 isolates from Macquarie Island and for all six isolates from Casey. Most of the leaf colonizing fungi from Macquarie Island had optimum growth temperatures of 15°C whereas all litter fungi from Macquarie Island and Casey fungi except Thelebolus microsporus had optimum growth temperatures of 20°C or above. Maximum growth of all species was at temperatures above those normally prevailing in their natural environments, with most species growing at 4°C at between 10% and 30% of their maximum rates. However, microclimatic effects may have resulted at times in temperatures near their growth optima. The highest growth rates at 4°C were recorded for Phoma spp. 1 and 2, Phoma exigua and Mortierella gamsii from Macquarie Island and Mortierella sp. 1 from Casey. Thelebolus microsporus and sterile sp. G from Casey also grew relatively fast at 4°C, and these species, and Phoma sp. 3 and Phoma exigua from Macquarie Island had the lowest Q-₁₀ values for the temperature range 4° to 15°C.     

Effects of ecological differentiation on Lotka-Volterra systems for species with behavioral adaptation and variable growth rates

We study the properties of a n2-dimensional Lotka-Volterra system describing competing species that include behaviorally adaptive abilities. We indicate as behavioral adaptation a mechanism, based on a kind of learning, which is not viewed in the evolutionary sense but is intended to occur over shorter time scales. We consider a competitive adaptive n species Lotka-Volterra system, n > or = 3, in which one species is made ecologically differentiated with respect to the others by carrying capacity and intrinsic growth rate. The symmetry properties of the system and the existence of a certain class of invariant subspaces allow the introduction of a 7-dimensional reduced model, where n appears as a parameter, which gives full account of existence and stability of equilibria in the complete system. The reduced model is effective also in describing the time-dependent regimes for a large range of parameter values. The case in which one species has a strong ecological advantage (i.e. with a carrying capacity higher than the others), but with a varying growth rate, has been analyzed in detail, and time-dependent behaviors have been investigated in the case of adaptive competition among four species. Relevant questions, as species survival/exclusion, are addressed focusing on the role of adaptation. Interesting forms of species coexistence are found (i.e. competitive stable equilibria, periodic oscillations, strange attractors).