Discovering cooperative traits in crop plants.

Plants should cooperate, but do they? What does plant cooperation look like? A study in PLOS Biology demonstrates a practical and powerful methodology for exploring plant cooperation.

Plant cooperation.

The study of plant behaviour will be aided by conceptual approaches and terminology for cooperation, altruism and helping. The plant literature has a rich discussion of helping between species while the animal literature has an extensive and somewhat contentious discussion of within-species helping. Here, I identify and synthesize concepts, terminology and some practical methodology for speaking about helping in plant populations and measuring the costs and benefits.

Will the Occupational Safety and Health Administration's Proposed Standards for Occupational Exposure to Respirable Crystalline Silica Reduce Workplace Risk?

The Occupational Safety and Health Administration (OSHA) is developing regulations to amend existing standards for occupational exposure to respirable crystalline silica by establishing a new permissible exposure limit as well as a series of ancillary provisions for controlling exposure. This article briefly reviews OSHA's proposed regulatory approach and the statutory authority on which it is based. It then evaluates OSHA's preliminary determination of significant risk and its analysis of the risk reduction achievable by its proposed controls.

Improving weight of evidence approaches to chemical evaluations.

Federal and other regulatory agencies often use or claim to use a weight of evidence (WoE) approach in chemical evaluation. Their approaches to the use of WoE, however, differ significantly, rely heavily on subjective professional judgment, and merit improvement. We review uses of WoE approaches in key articles in the peer-reviewed scientific literature, and find significant variations.

RNA-Seq effectively monitors gene expression in Eutrema salsugineum plants growing in an extreme natural habitat and in controlled growth cabinet conditions.

Background: The investigation of extremophile plant species growing in their natural environment offers certain advantages, chiefly that plants adapted to severe habitats have a repertoire of stress tolerance genes that are regulated to maximize plant performance under physiologically challenging conditions. Accordingly, transcriptome sequencing offers a powerful approach to address questions concerning the influence of natural habitat on the physiology of an organism. We used RNA sequencing of Eutrema salsugineum, an extremophile relative of Arabidopsis thaliana, to investigate the extent to which genetic variation and controlled versus natural environments contribute to differences between transcript profiles.

Plant kin recognition enhances abundance of symbiotic microbial partner.

Background: The stability of cooperative interactions among different species can be compromised by cheating. In the plant-mycorrhizal fungi symbiosis, a single mycorrhizal network may interact with many plants, providing the opportunity for individual plants to cheat by obtaining nutrients from the fungi without donating carbon. Here we determine whether kin selection may favour plant investment in the mycorrhizal network, reducing the incentive to cheat when relatives interact with a single network.

Fitness consequences of plants growing with siblings: reconciling kin selection, niche partitioning and competitive ability.

Plant studies that have investigated the fitness consequences of growing with siblings have found conflicting evidence that can support different theoretical frameworks. Depending on whether siblings or strangers have higher fitness in competition, kin selection, niche partitioning and competitive ability have been invoked. Here, we bring together these processes in a conceptual synthesis and argue that they can be co-occurring.

Kin recognition, not competitive interactions, predicts root allocation in young Cakile edentula seedling pairs.

• Recent studies have demonstrated sibling vs stranger differences in group root allocation in plants, suggesting that plants have the potential for kin discrimination in competition. However, morphology differences could potentially be generated by competition-based mechanisms. Here, we tested these hypotheses for the sibling vs stranger differences in root allocation in Cakile edentula.

Root exudates mediate kin recognition in plants.

Though recent work has demonstrated that plants can recognize species, kin versus strangers, and self/non-self roots, no mechanism for identity recognition in plants has yet been found. Here we examined the role of soluble chemicals in signaling among roots. Utilizing Arabidopsis thaliana, we exposed young seedlings to liquid media containing exudates from siblings, strangers (non-siblings), or only their own exudates.

Kin recognition: Competition and cooperation in Impatiens (Balsaminaceae).

The ability to recognize kin is an important element in social behavior and can lead to the evolution of altruism. Recently, it has been shown that plants are capable of kin recognition through root interactions. Here we tested for kin recognition in a North American species of Impatiens that has a high opportunity of growing with kin and responds strongly to aboveground competition.

Kin recognition in an annual plant.

Kin recognition is important in animal social systems. However, though plants often compete with kin, there has been as yet no direct evidence that plants recognize kin in competitive interactions. Here we show in the annual plant Cakile edentula, allocation to roots increased when groups of strangers shared a common pot, but not when groups of siblings shared a pot.

Phenotypic selection on leaf water use efficiency and related ecophysiological traits for natural populations of desert sunflowers.

Plant water-use efficiency (WUE) is expected to affect plant fitness and thus be under natural selection in arid habitats. Although many natural population studies have assessed plant WUE, only a few related WUE to fitness. The further determination of whether selection on WUE is direct or indirect through functionally related traits has yielded no consistent results.

Selection on leaf ecophysiological traits in a desert hybrid Helianthus species and early-generation hybrids.

Leaf ecophysiological traits related to carbon gain and resource use are expected to be under strong selection in desert annuals. We used comparative and phenotypic selection approaches to investigate the importance of leaf ecophysiological traits for Helianthus anomalus, a diploid annual sunflower species of hybrid origin that is endemic to active desert dunes. Comparisons were made within and among five genotypic classes: H.

Early abortion services in the United States: a provider survey.

The objective of this study was to describe the availability of early surgical and medical abortion among members of the National Abortion Federation (NAF) and to identify factors affecting the integration of early abortion services into current services. Telephone interviews were conducted with staff at 113 Planned Parenthood affiliates and independent abortion providers between February and April 2000, prior to FDA approval of mifepristone. Early abortion services were available at 59% of sites, and establishing services was less difficult than or about what was anticipated.

Responses of carbon acquisition traits to irradiance and light quality in Mercurialis annua (Euphorbiaceae): evidence for weak integration of plastic responses.

It is often suggested that traits will be integrated, either because of pleiotropy or because natural selection may favor suites of integrated traits. Plant responses to different environments can provide evidence of such integration. We grew Mercurialis annua plants in high-density stands in high irradiance, in neutral shade, and in high red to far-red (R:FR) shade, resulting in environments of high irradiance, low R:FR; low irradiance, low R:FR; and low irradiance, high R:FR.

Manipulative Approaches to Testing Adaptive Plasticity: Phytochrome-Mediated Shade-Avoidance Responses in Plants.

Phenotypic plasticity is often assumed to be adaptive, but this hypothesis has rarely been tested. To support the hypothesis, it is necessary to demonstrate that the phenotype induced in each relevant environment confers high fitness in that environment, relative to alternative phenotypes. Unfortunately, such tests are difficult to perform because plasticity prevents the expression of "inappropriate" phenotypes within each environment.

DIFFERING SELECTION ON PLANT PHYSIOLOGICAL TRAITS IN RESPONSE TO ENVIRONMENTAL WATER AVAILABILITY: A TEST OF ADAPTIVE HYPOTHESES.

I used phenotypic selection analysis to test the prediction from functional and comparative studies of plants that smaller leaves and more efficient water use are adaptive in drier environments. I measured selection gradients on leaf size and instantaneous water-use efficiency (a measure of carbon gain per unit water loss) in experimental populations of Cakile edentula var. lacustris placed into wet and dry environments in the field.

THE RESPONSE TO DIFFERING SELECTION ON PLANT PHYSIOLOGICAL TRAITS: EVIDENCE FOR LOCAL ADAPTATION.

Understanding adaptive evolution to differing environments requires studies of genetic variances, of natural selection, and of the genetic differentiation between populations. Plant physiological traits such as leaf size and water-use efficiency (the ratio of carbon gained per water lost) have been suggested by physiological plant ecologists to be important in local adaptation to environments differing in water availability. In this study, I raised families of Cakile edentula var lacustris derived from a wet-site population and a dry-site population in a common greenhouse environment to determine the degree of genetic differentiation between the two populations and the genetic architecture of the traits.