Photosynthetic performance of Hevea brasiliensis affected by South American Leaf Blight under field conditions

South American Leaf Blight (SALB), caused by the fungus Pseudocercospora ulei, is the principal rubber crop disease in Latin America. Several studies have focused on the genetics of resistance and the epidemiology of this disease, but few have analyzed the physiological alterations caused by SALB in Hevea brasiliensis. In addition, changes under field conditions are poorly understood. The present study aimed to analyze changes in gas exchange and chlorophyll a fluorescence traits in leaflets with different leaf stages and SALB severity levels from two H. brasiliensis clones with distinct susceptibility to disease in juvenile plants grown under field conditions (clonal garden). The photosynthetic performance was strongly limited in the high susceptibility clone (FX 3864), mainly in the young leaflets with maximum SALB severity (‘3’ and ‘4’), as compared to the low susceptibility clone (FX 4098). The principal alterations included a reduction in the photosynthetic rate (>?79%), stomatal conductance (>?85%), extrinsic water use efficiency (>?85%), and ability to capture, use and dissipate light energy in photosystem II, as compared to healthy leaflets. The damage was less intense in mature leaflets from both rubber tree clones. The favorable performance observed in clone FX 4098 means it is a potential candidate for commercial scale use under non-SALB escape conditions in the Amazon region.

     

Development of a Model of Lodging for Barley

Lodging in barley (Hordeum vulgare L.) can result either from buckling of any part of the stem (stem lodging) or failure of the root–soil anchorage system (root lodging). A framework for calculating the risk of stem lodging is developed which takes account of the shoot's height, ear area, natural frequency, weight, the flexural rigidity of the stem and changes in stem strength along its length. The model predicted that stem lodging in barley cultivars would occur half way up the stem, and stem lodging in wheat would occur close to the soil surface. These predictions are consistent with general observations of stem lodging in barley and wheat. The higher position of stem lodging in barley, compared with wheat, was caused by the greater flexibility of the barley stems and a more rapid reduction in stem strength up the stem. A sensitivity analysis showed that the stem diameter of the middle internodes had the greatest effect on the risk of stem lodging. Changes to ear area, drag coefficient, crop height, shoot natural frequency and the strength of the stem wall had a moderate influence. Measurements of anchorage strength in barley and wheat plants indicated that the mechanism of anchorage failure was the same for both species and that a model of root lodging developed for wheat could be successfully adapted for barley.     

Comparative economic analysis of recombinant porcine somatotropin (pST) for the hog-pork industry

A multisector model was formulated to simulate the effects of recombinant porcine somatotropin (pST) on the U.S. hog-pork industry. A producer sector submodel was specified for nine hog-producing states, and a retail-wholesale sector was specified on a national level. Four pST adoption scenarios were tested; these differed in the extent of feed cost reduction (15 vs 25%) with or without premium pricing ($3 per animal). Simulation results show that, in general, national producer and retail prices will fall and pork consumption and production will increase due to pST use during the 5 yr of adoption. Responses to pST in terms of percentage of sows farrowing among states differed; states that produce more pork responded less than states that produce less. Downward price adjustments occurred and began stabilizing in the 4th yr; hog farmers will need to use pST to remain competitive.     

Microsatellite loci reveal distinct populations with high diversity for the pathogenic fungus Pseudocercospora ulei from North-Western Amazonia

European Journal of Plant Pathology - South American Leaf Blight (SALB) is caused by the Ascomycota fungus Pseudocercospora ulei. This disease is recognized as the main threat to Hevea brasiliensis...     

Conversion of thyroxine to triiodothyronine in normal human subjects

The conversion of thyroxine to triiodothyronine, previously demonstrated in athyreotic human subjects, has been investigated in normal subjects who were given intravenous injections of purified thyroxine labeled with carbon-14 in ring A and in the alanine side chain. Evidence for the conversion of T4 to T3 was provided by the finding of carbon-14 in the T3 fraction isolated from serums. It is estimated that an appreciable fraction of T4 may be transformed to T3 in normal man.     

Coherent soft x-ray generation in the water window with quasi-phase matching

We demonstrate enhanced generation of coherent light in the "water window" region of the soft x-ray spectrum at 4.4 nanometers, using quasi-phase-matched frequency conversion of ultrafast laser pulses. By periodically modulating the diameter of a gas-filled hollow waveguide, the phase mismatch normally present between the laser light and the generated soft x-ray light can be partially compensated. This makes it possible to use neon gas as the nonlinear medium to coherently convert light up to the water window, illustrating that techniques of nonlinear optics can be applied effectively in the soft x-ray region of the spectrum. These results advance the prospects for compact coherent soft x-ray sources for applications in biomicroscopy and in chemical spectroscopy.     

棉蚜种群变动预测模型

本文描述一个确定性预测模型,用于模拟棉田以内棉蚜种群动态。模拟结果与陕西关中棉区实际发生情况基本相符。本模型包括1个主程序和9个子程序。输入为棉田迁入棉蚜数、棉花生育阶段、自然变温、捕食性天敌单位以及寄生天敌数。输出为每日百株棉蚜数,以线图表示之。程序语言为FORTRAN.。     

Conversion of thyroxine to triiodothyronine by cultured human cells

Human liver and kidney cells convert 6 to 10 percent of added thyroxine to triiodothyronine in vitro at 37 degrees C. This extent of conversion is ten times greater than that in control studies with killed cells. Conversion is evident within 10 minutes and appears to be maximal within 1 hour. Greater net triiodothyronine formation results if greater amounts of exogenous thyroxine are added to the system, with no plateau evident even at very high thyroxine concentrations. The addition of high concentrations of nonradioactive triiodothyronine resulted in no evident inhibition of the conversion.