Trifluralin and root growth

Trifluralin inhibited root elongation and induced root tip swellingof Zea mays and Triticum aeslivum. Time-course experiments showedthese effects occurred within 6 hr of treatment. As the rootstreated with trifluralin enlarged, there was a concomitant increasein root growth inhibition. Bioassays were devised to quantitativelymeasure the radial enlargement of trifluralin-treated roots.Histological observations indicated that swollen root tissuewas growing in a non-polar manner. The root swelling effectof trifluralin was inhibited 70% by the reducing agent, 2,3-dimercaptopropanol.Trifluralin had no effect on SH content of root tip proteinof Z.mays. ¹ Published with the approval of the Director of die West VirginiaAgricultural Experiment Station as Scientific paper No. 1177. ² Present address: Department of Biology, Mercyhurst College,Erie, Pennsylvania 16501, U.S.A. (Received March 19, 1971; )     

The Structure of Calf Liver Cytochrome <Emphasis Type="Italic">b</Emphasis><Subscript>5</Subscript> at 2.8 Å Resolution

CYTOCHROME b₅ is a haem-containing protein in the microsomes of liver tissue. It interacts specifically with a flavo-protein, cytochrome b₅ reductase, which catalyses the transfer of electrons from NADH to the haem iron of the cytochrome¹. The microsomal cytochrome b₅ system has been implicated in fatty acid desaturation reactions² and a similar system in erythrocytes may catalyse the reduction of methaemoglobin³. Calf liver cytochrome b₅, solubilized by pancreatic lipase, has a molecular weight of 11,000 and consists of ninety-three amino-acids in the sequence shown in Fig. 1 (refs. 4 and 5). The haem group is non-covalently bound to the protein and can be removed reversibly by acid acetone treatment⁶.     

Agonistic Behavior of Mice and Rats: A Review

This paper reviews the results of research on the agonisticbehavior of wild and tame strains of house mice (Mus musculus)and the Norway rat (Rattus norvegicus) and covers papers thathave appeared since an earlier review (Scott and Fredericson,1951) Various methods for observing, measuring, and eliciting fightingare described and their appropriate uses discussed. Measuresof latency and frequency are more satisfactory than arbitraryrating scales. Situations involving competition over food presentcomplex motivational problems. The basic agonistic behavior patterns (ethograms) of rats andmice are compared. Differences appear in the lack of playfulfighting and weaning threats in mice, the dual "boxing" postureof rats, and the unique "tail rattling" in mice. Both speciesare alike in their inability to form complex dominance hierarchiesin which fighting is reduced to threat and avoidance. As a general theory, each species has evolved behavior patternsand physiological mechanisms of behavior which are adaptivelyrelated to its own social organization and population dynamics.Mice and rats have evolved along different lines both from eachother and other species of mammals.     

The Obsolete "Anti-Market" Mentality: A Critique of the Substantive Approach to Economic Anthropology

"Analytic work begins with material provided by our vision of things, and this vision is ideological almost by definition. It embodies the picture of things as we see them, and wherever there is any possible motive for wishing to see them in a given rather than another light, the way in which we see things can hardly be distinguished from the nay in which we wish to see them. The more honest and naive our vision is, the more dangerous it is to the eventual emergence of anything for which general validity can be claimed. The inference for the social sciences is obvious, antl it is not even true that he who hates a social system will form an objectively more correct vision of it than he who loves it. For love distorts indeed, but hate distorts still more."     

Predicting responses of photosynthesis and root fraction to elevated [CO2]a: interactions among carbon,nitrogen, and growth*

At elevated atmospheric CO₂ concentrations ([CO₂]_a), photosynthetic capacity (A_max) and root fraction (η_R, the ratio of root to plant dry mass) increased in some studies and decreased in others. Here, we have explored possible causes of this, focusing on the relative magnitudes of the effects of elevated [CO₂]_a on specific leaf (n_m) and plant (n_p) nitrogen concentrations, leaf mass per unit area (h), and plant nitrogen productivity (α). In our survey of 39 studies with 35 species, we found that elevated [CO₂]_a led to decreased n_m and n_p in all the studies and to increased h and α in most of the studies. The magnitudes of these changes varied with species and with experimental conditions. Based on a model that integrated [CO₂]_a-induced changes in leaf nitrogen into a biochemically based model of leaf photosynthesis, we predicted that, to a first approximation, photosynthesis will be upregulated (A_max will increase) when growth at increased [CO₂]_a leads to increases in h that are larger than decreases in n_m. Photosynthesis will be downregulated (A_max will decrease) when increases in h are smaller than decreases in n_m. The model suggests that photosynthetic capacity increases at elevated [CO₂]_a only when additional leaf mesophyll more than compensates the effects of nitrogen dilution. We considered two kinds of regulatory paradigms that could lead to varying responses of η_R to elevated [CO₂]_a, and compared the predictions of each with the data. A simple static model based on the functional balance concept predicts that η_R should increase when neither n_p nor h is very responsive to elevated [CO₂]_a. The quantitative and qualitative agreement of the predictions with data from the literature, however, is poor. A model that predicts η_R from the relative sensitivities of photosynthesis and relative growth rate to elevated [CO₂]_a corresponds much more closely to the observations. In general, root fraction increases if the response of photosynthesis to [CO₂]_a is greater than that of relative growth rate.     

Physiological Insights from Cellular and Network Models of the Stomatogastric Nervous System of Lobsters and Crabs

SYNOPSIS. The stomatogastric nervous system of decapod crustaceansis an ideal system for the study of the processes underlyingthe generation of rhythmic movements by the nervous system.In this chapter we review recent work that uses mathematicalanalyses and computer simulations to understand: 1) the roleof individual currents in controlling the activity of neurons,and 2) the effects of electrical coupling on the activity ofneuronal oscillators. The aim of this review is to highlight,for the physiologist, what these studies have taught us aboutthe organization and function of single cell and multicellularneuronal oscillators.