Effects of temperature and oxygen depletion on metabolic rates of tomato and carrot cell cultures and cuttings measured by calorimetry

Abstract. Isothermal heat-conductance calorimetry was used to monitor responses of tomato and carrot metabolism to changes in temperature and oxygen concentrations. Calorimetric measurements of metabolic heat evolution from tissue segments and cultured cells was found to be a sensitive, nondestructive estimate of metabolic rates. Short-term measurements of metabolic rates of cells in culture correlate well with calorimetric measurements made on tissue sections. The results accurately predict the growth properties of intact plants based on the generally recognized characteristics of these two species. The calorimetric method provides another means for rapid evaluation of plant responses to physical and chemical stresses and is of value for screening and selection.     

3-Methyleneoxindole and Plant Growth Regulation

The campound 3-methyleneoxindole was synthesized and tested in three “biological systems for auxin activity: Root initarion in pea stem currings, extension growth of etiolated pea stem segments and Avena first internodes. In none of the systems was found any effect — positive or negative of methyleneoxindole. It thus seems improbable that the compound participates in the growth regulation of these plants.     

An Evaluation of Sex-Age-Kill (SAK) Model Performance

ABSTRACT The sex-age-kill (SAK) model is widely used to estimate abundance of harvested large mammals, including white-tailed deer (Odocoileus virginianus). Despite a long history of use, few formal evaluations of SAK performance exist. We investigated how violations of the stable age distribution and stationary population assumption, changes to male or female harvest, stochastic effects (i.e., random fluctuations in recruitment and survival), and sampling efforts influenced SAK estimation. When the simulated population had a stable age distribution and λ > 1, the SAK model underestimated abundance. Conversely, when λ < 1, the SAK overestimated abundance. When changes to male harvest were introduced, SAK estimates were opposite the true population trend. In contrast, SAK estimates were robust to changes in female harvest rates. Stochastic effects caused SAK estimates to fluctuate about their equilibrium abundance, but the effect dampened as the size of the surveyed population increased. When we considered both stochastic effects and sampling error at a deer management unit scale the resultant abundance estimates were within ±121.9% of the true population level 95% of the time. These combined results demonstrate extreme sensitivity to model violations and scale of analysis. Without changes to model formulation, the SAK model will be biased when λ ≠ 1. Furthermore, any factor that alters the male harvest rate, such as changes to regulations or changes in hunter attitudes, will bias population estimates. Sex-age-kill estimates may be precise at large spatial scales, such as the state level, but less so at the individual management unit level. Alternative models, such as statistical age-at-harvest models, which require similar data types, might allow for more robust, broad-scale demographic assessments.     

Evolution of the third eye: a phylogenetic comparative study of parietal‐eye size as an ecophysiological adaptation in Liolaemus lizards

The parietal, or third, eye is a photosensory organ situated in the middle of the skull of many lizards. Despite many hypotheses, its exact ecological functions are still unclear. Studies have compared the presence and absence of a functioning parietal eye, although there are no quantitative studies of parietal‐eye traits in relation to ecology, physiology or behaviour. In the present study, we report the first comparative study of relative parietal‐eye size in relation to climatic and thermophysiological variables. We studied thirty species of Liolaemus, a genus of South‐American lizards inhabiting a range of climatic conditions, but found little evidence for adaptation to thermal environment, in that parietal‐eye size did not vary meaningfully with latitude, altitude or any measures of environmental temperature. Neither did it relate to thermophysiology; there was a weak relation to thermal tolerance, although this was partially confounded with body size, which explained 23% of the among‐species variance after controlling for within‐species variation. The negative results obtained could not be explained by phylogenetic constraints because we found no evidence of phylogenetic inertia. We also observed high intraspecific variation indicating that parietal‐eye size may not be under strong selection for accuracy. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 101 , 870–883.