Implications for Microtubule Mediated Ethylene Effects in Pea Stem Sections

The marked effects of ethylene on pea stem growth have been investigated. Low temperature mid colchicine. both known microtubule depolymerization agents, reverse the effects of ethylene in straight growth tests. Low temperature (6 C) also profoundly reduces the effects of the gas in terms of swelling, hook curvature, and horizontal nutation. Electron microscopy shows that microtubules are reoriented after treatment with ethylene for as little as 12 hours. The findings indicate that some of the ethylene responses may be due to a stabilizing effect on microtubules in plant cells

When Process Affects Punishment: Differences in Sentences After Guilty Plea, Bench Trial, and Jury Trial in Five Guidelines States

The research reported in this Essay examines process discounts-differences in sentences imposed for the same offense, depending upon whether the conviction was by jury trial, bench trial, or guilty plea-in five states that use judicial sentencing guidelines. Few guidelines systems expressly recognize plea agreement as an acceptable basis for departure, and none authorizes judges to vary sentences based upon whether or not the defendant waived his right to a jury trial and opted for a bench trial. Nevertheless, we predicted that because of the cost savings resulting from waivers, judges and prosecutors in any sentencing system would ensure that guilty plea convictions would generate the lowest sentences, with bench trial sentences averaging higher than plea-based sentences for the same offense, and sentences following jury trials averagingt he highest of all, even after controllingf or otherf actors associated with sentence severity. We found that a significant plea discount is evident for most offenses in all five states. Waiving a jury in favor of a bench trial has less consistent punishment consequences. Among states and even within a single state, the prevalence of process discounts is extraordinarily varied, as are the causes and methods of discounting. The Essay explores how these findings might inform sentencing reform and discusses the use of bench trials in sentencing guidelines systems generally

Open problems in artificial life

This article lists fourteen open problems in artificial life, each of which is a grand challenge requiring a major advance on a fundamental issue for its solution. Each problem is briefly explained, and, where deemed helpful, some promising paths to its solution are indicated

Diagnosing students' difficulties in learning mathematics

This study considers the results of a diagnostic test of student difficulty and contrasts the difference in performance between the lower attaining quartile and the higher quartile. It illustrates a difference in qualitative thinking between those who succeed and those who fail in mathematics, illustrating a theory that those who fail are performing a more difficult type of mathematics (coordinating procedures) than those who succeed (manipulating concepts). Students who have to coordinate or reverse processes in time will encounter far greater difficulty than those who can manipulate symbols in a flexible way. The consequences of such a dichotomy and implications for remediation are then considered

Snapping Turtle, Chelydra serpentina, Overland Movements Near the Southeastern Extent of its Range

Terrestrial movements of turtles are of interest due to the conservation implications for this imperiled group and the general lack of information on this topic, particularly in wide-ranging species. The snapping turtle, Chelydra serpentina, is one of the most broadly distributed chelonians in the world; they occur from southeastern Canada westward to Alberta and throughout the eastern half of the United States and into Central America. Most research on this species has been focused on populations in the northern portion of the range. In this study, we radio-tracked five turtles in southwestern Georgia, where published data on spatial ecology and movements are lacking. Turtles exhibited extensive overland movements which we suspect occurred in response to drought

The last bastion? X-chromosome genotyping of Anopheles gambiae species-pair males from a hybrid zone reveals complex recombination within the major candidate ‘genomic island of speciation’

Speciation with gene flow may be aided by reduced recombination helping to build linkage between genes involved in the early stages of reproductive isolation. Reduced recombination on chromosome-X has been implicated in speciation within the Anopheles gambiae complex, species of which represent the major Afrotropical malaria vectors. The most recently diverged, morphologically-indistinguishable, species-pair, An. gambiae and An. coluzzii, ubiquitously display a ‘genomic island of divergence’ spanning over 4Mb from chromosome-X centromere, which represents a particularly promising candidate region for reproductive isolation genes, in addition to containing the diagnostic markers used to distinguish the species. Very low recombination makes the island intractable for experimental recombination studies, but an extreme hybrid zone in Guinea Bissau offers the opportunity for natural investigation of X-island recombination. SNP-analysis of chromosome-X hemizygous males revealed: (i) strong divergence in the X-island despite a lack of autosomal divergence; (ii) individuals with multiple-recombinant genotypes, including likely double crossovers and localized gene conversion; (iii) recombination-driven discontinuity both within and between the molecular species markers, suggesting that the utility of the diagnostics is undermined under high hybridization. The largely-, but incompletely-protected nature of the X-centromeric genomic island is consistent with a primary candidate area for accumulation of adaptive variants driving speciation with gene flow, whilst permitting some selective shuffling and removal of genetic variation