Effects of elevated CO2 and temperature on seed quality

Successful crop production depends initially on the availability of high-quality seed. By 2050 global climate change will have influenced crop yields, but will these changes affect seed quality? The present review examines the effects of elevated carbon dioxide (CO2) and temperature during seed production on three seed quality components: seed mass, germination and seed vigour. In response to elevated CO2, seed mass has been reported to both increase and decrease in C3 plants, but not change in C4 plants. Increases are greater in legumes than non-legumes, and there is considerable variation among species. Seed mass increases may result in a decrease of seed nitrogen (N) concentration in non-legumes. Increasing temperature may decrease seed mass because of an accelerated growth rate and reduced seed filling duration, but lower seed mass does not necessarily reduce seed germination or vigour. Like seed mass, reported seed germination responses to elevated CO2 have been variable. The reported changes in seed C/N ratio can decrease seed protein content which may eventually lead to reduced viability. Conversely, increased ethylene production may stimulate germination in some species. High-temperature stress before developing seeds reach physiological maturity (PM) can reduce germination by inhibiting the ability of the plant to supply the assimilates necessary to synthesize the storage compounds required for germination. Nothing is known concerning the effects of elevated CO2 on seed vigour. However, seed vigour can be reduced by high-temperature stress both before and after PM. High temperatures induce or increase the physiological deterioration of seeds. Limited evidence suggests that only short periods of high-temperature stress at critical seed development stages are required to reduce seed vigour, but further research is required. The predicted environmental changes will lead to losses of seed quality, particularly for seed vigour and possibly germination. The seed industry will need to consider management changes to minimize the risk of this occurring

Modelling the Dynamics of Feral Alfalfa Populations and Its Management Implications

BACKGROUND: Feral populations of cultivated crops can pose challenges to novel trait confinement within agricultural landscapes. Simulation models can be helpful in investigating the underlying dynamics of feral populations and determining suitable management options. METHODOLOGY/PRINCIPAL FINDINGS: We developed a stage-structured matrix population model for roadside feral alfalfa populations occurring in southern Manitoba, Canada. The model accounted for the existence of density-dependence and recruitment subsidy in feral populations. We used the model to investigate the long-term dynamics of feral alfalfa populations, and to evaluate the effectiveness of simulated management strategies such as herbicide application and mowing in controlling feral alfalfa. Results suggest that alfalfa populations occurring in roadside habitats can be persistent and less likely to go extinct under current roadverge management scenarios. Management attempts focused on controlling adult plants alone can be counterproductive due to the presence of density-dependent effects. Targeted herbicide application, which can achieve complete control of seedlings, rosettes and established plants, will be an effective strategy, but the seedbank population may contribute to new recruits. In regions where roadside mowing is regularly practiced, devising a timely mowing strategy (early- to mid-August for southern Manitoba), one that can totally prevent seed production, will be a feasible option for managing feral alfalfa populations. CONCLUSIONS/SIGNIFICANCE: Feral alfalfa populations can be persistent in roadside habitats. Timely mowing or regular targeted herbicide application will be effective in managing feral alfalfa populations and limit feral-population-mediated gene flow in alfalfa. However, in the context of novel trait confinement, the extent to which feral alfalfa populations need to be managed will be dictated by the tolerance levels established by specific production systems for specific traits. The modelling framework outlined in this paper could be applied to other perennial herbaceous plants with similar life-history characteristics

Periprosthetic fractures of the femur after total knee arthroplasty

Periprosthetic fracture following total knee arthroplasty is a potentially serious complication. This injury can involve the distal femur, proximal tibia or the patella. This review article analyzes the prevalence, risk factors, classification and treatment options for periprosthetic fractures of the femur

Persistent Place-Making in Prehistory: the Creation, Maintenance, and Transformation of an Epipalaeolithic Landscape

Most archaeological projects today integrate, at least to some degree, how past people engaged with their surroundings, including both how they strategized resource use, organized technological production, or scheduled movements within a physical environment, as well as how they constructed cosmologies around or created symbolic connections to places in the landscape. However, there are a multitude of ways in which archaeologists approach the creation, maintenance, and transformation of human-landscape interrelationships. This paper explores some of these approaches for reconstructing the Epipalaeolithic (ca. 23,000–11,500 years BP) landscape of Southwest Asia, using macro- and microscale geoarchaeological approaches to examine how everyday practices leave traces of human-landscape interactions in northern and eastern Jordan. The case studies presented here demonstrate that these Epipalaeolithic groups engaged in complex and far-reaching social landscapes. Examination of the Early and Middle Epipalaeolithic (EP) highlights that the notion of “Neolithization” is somewhat misleading as many of the features we use to define this transition were already well-established patterns of behavior by the Neolithic. Instead, these features and practices were enacted within a hunter-gatherer world and worldview

Analytical purity of old New Zealand forage seed samples and detection of fungal and insect contaminants including ryegrass endophyte and Argentine stem weevil

In 2015, 13 packets of seed samples were provided to PGG Wrightson by Jim Robertson, a farmer from Wainui Bay, Takaka. These samples had been kept by the Robertson Family since 1917 and in one case the year of harvest 16/17 was written on the packet (Figure 1). The samples consisted of six cocksfoot (Dactylis glomerata L.), four perennial ryegrass (Lolium perenne L.) and one each of Chewings fescue (Festuca rubra L.), oat (Avena sativa L.) and red clover (Trifolium pratense L.). These samples had been initially given to the family with associated prices by Levin and Co (based in Nelson), so that they could choose which seed lines to purchase

The impacts of take-all, drought and their interaction on Bromus wildenowii seed yield and the alleviation of these stresses by Trichoderma atroviride

Take-all, caused by the fungal pathogen Gaeumannomyces graminis var. tritici (Ggt) is an important root disease of cereals and grasses. An increasing occurrence of very light seeds in some New Zealand perennial ryegrass (Lolium perenne L.) seed crops may have been associated with Ggt, but any Ggt effects on grass seed yield were unknown. A glasshouse experiment, using prairie grass (Bromus wildenowii Kunth) as a model system was used to investigate the effect of Ggt on seed yield in the presence and absence of moisture stress (drought), and to determine whether strains of the fungal symbiont Trichoderma atroviride would allow the plant to better cope with both the biotic and abiotic stresses. Ggt significantly reduced seed yield by reducing the number of seeds per plant, while moisture stress significantly reduced all seed yield components. There was a significant interaction between Ggt and moisture stress because the moisture stress induced seed yield loss was greater in the presence of Ggt than in the absence of Ggt. In the absence of both abiotic and biotic stress, Trichoderma treatment had no effect on seed yield. However, Trichoderma significantly reduced Ggt root infection and this led to an increased seed yield. In the presence of Ggt and moisture stress, Trichoderma further increased seed yield by around double the increase for individual stress. Whether similar responses can be obtained in the field is currently being investigated

Heat stress during seed development affects forage brassica (Brassica napus L.) seed quality

In two consecutive seasons forage rape (Brassica napus L.) plants were exposed to short periods (240°C h) of heat stress (30°C day/25°C night) during seed filling (80% seed moisture content = S1), at physiological maturity (50% seed moisture content = S2), and at both S1 plus S2 (= S3) in a Biotron before being returned to the field until seed harvest. Seeds were hand harvested at 14% seed moisture content and their quality assessed by measuring germination, seed vigour (using the accelerated ageing and conductivity tests) and seed mass (as determined by thousand seed weight). Heat stress at both S1 and S2 caused a small (S2>S1. Seed mass was reduced by heat stress at S1 but not at S2. Variable seed vigour in high germinating New Zealand produced forage rapeseed lots is most likely explained by short periods of heat stress during seed development