Root and shoot responses of upland New Rice for Africa varieties to fluctuating soil moisture conditions as affected by different levels of nitrogen fertilization

Drought cycling and soil re-watering trends due to intermittent rainfall patterns are key stress factors that influence rice growth and yield under upland cultivation conditions. However, upland rice adaptation responses to fluctuating soil moisture conditions remain poorly understood. This study investigated root and shoot responses of upland New Rice for Africa (NERICA) varieties to episodic drought and re-watering during growth. We examined root and shoot growth of NERICA 1 and NERICA 4 compared with those of IR72, an improved lowland variety, and Dular, a traditional drought-tolerant variety, in terms of soil moisture fluctuations with different levels of nitrogen fertilization under field conditions that impeded deep root development. During soil moisture fluctuation, all varieties reduced shoot dry weight compared with well-watered plants, regardless of nitrogen fertilization levels. However, total root length for the three upland varieties was enhanced by soil moisture fluctuations at moderate and high nitrogen fertilization, while that of the lowland variety was reduced. Comparing root development during water fluctuations revealed that NERICA 1 had a greater root system than NERICA 4, which was attributed to lateral root development. Furthermore, we found that NERICA varieties increase lateral root mass during soil desiccation under adequate nitrogen fertilization, while Dular and IR72 reduced their root growth rate during drought and increased it after re-watering. Both root growth patterns developed, from around maximum tillering to heading. The analysis of regression between root elongation and shoot growth with fluctuating soil moisture indicated that an enhanced root system during drought, on adequate nitrogen fertilization, can contribute to shoot growth when sufficient water becomes available, specifically around the maximum tillering to the heading growth stage of rice.     

Hematotoxicity in workers exposed to low levels of benzene

Benzene is known to have toxic effects on the blood and bone marrow, but its impact at levels below the U.S. occupational standard of 1 part per million (ppm) remains uncertain. In a study of 250 workers exposed to benzene, white blood cell and platelet counts were significantly lower than in 140 controls, even for exposure below 1 ppm in air. Progenitor cell colony formation significantly declined with increasing benzene exposure and was more sensitive to the effects of benzene than was the number of mature blood cells. Two genetic variants in key metabolizing enzymes, myeloperoxidase and NAD(P)H:quinone oxidoreductase, influenced susceptibility to benzene hematotoxicity. Thus, hematotoxicity from exposure to benzene occurred at air levels of 1 ppm or less and may be particularly evident among genetically susceptible subpopulations.     

Root plasticity under fluctuating soil moisture stress exhibited by backcross inbred line of a rice variety,Nipponbare carrying introgressed segments from KDML105 and detection of the associated QTLs

In rainfed lowland rice ecosystem, rice plants are often exposed to alternating recurrences of waterlogging and drought due to erratic rainfall. Such soil moisture fluctuation (SMF) which is completely different from simple or progressive drought could be stressful for plant growth, thereby causing reduction in yield. Root plasticity is one of the key traits that play important roles for plant adaptation under such conditions. This study aimed to evaluate root plasticity expression and its functional roles in dry matter production and yield under SMF using Nipponbare, KDML 105 and three backcross inbred lines (BILs) and to identify QTL(s) associated with root traits in response to SMF at two growth stages using Nipponbare/KDML105 F₂ plants. A BIL, G3-3 showed higher shoot dry matter production and yield than Nipponbare due to its greater ability to maintain stomatal conductance concomitant with greater root system development caused by promoted production of nodal and lateral roots under SMF. QTLs were identified for total nodal root length, total lateral root length, total root length, number of nodal roots, and branching index under SMF at vegetative and reproductive stages. The QTLs detected at vegetative and reproductive stages were different. We discuss here that relationship between root system of G3-3 and the detected QTLs. Therefore, G3-3 and the identified QTLs could be useful genetic materials in breeding program for improving the adaptation of rice plants in target rainfed lowland areas.     

Dishevelled 2 recruits beta-arrestin 2 to mediate Wnt5A-stimulated endocytosis of Frizzled 4

Wnt proteins, regulators of development in many organisms, bind to seven transmembrane-spanning (7TMS) receptors called frizzleds, thereby recruiting the cytoplasmic molecule dishevelled (Dvl) to the plasma membrane.Frizzled-mediated endocytosis of Wg (a Drosophila Wnt protein) and lysosomal degradation may regulate the formation of morphogen gradients. Endocytosis of Frizzled 4 (Fz4) in human embryonic kidney 293 cells was dependent on added Wnt5A protein and was accomplished by the multifunctional adaptor protein beta-arrestin 2 (betaarr2), which was recruited to Fz4 by binding to phosphorylated Dvl2. These findings provide a previously unrecognized mechanism for receptor recruitment of beta-arrestin and demonstrate that Dvl plays an important role in the endocytosis of frizzled, as well as in promoting signaling.     

Influence of patch,habitat, and landscape characteristics on patterns of Lower Keys marsh rabbit occurrence following Hurricane Wilma

Degradation of coastal systems has led to increased impacts from hurricanes and storm surges and is of concern for coastal endemics species. Understanding the influence of disturbance on coastal populations like the endangered Lower Keys marsh rabbit (Sylvilagus palustris hefneri) is important to understanding long-term dynamics and for recovery planning. We evaluated the effect of disturbance on the rabbits by determining which patch, habitat, and landscape characteristics influenced habitat use following Hurricane Wilma. We determined patch-level occurrence 6–9 months prior to Hurricane Wilma, within 6 months following the hurricane, and 2 years after the storm to quantify rates of patch abandonment and recurrence. We observed high patch abandonment (37.5% of used patches) 6 months after Hurricane Wilma and low rates of recurrence (38.1% of abandoned patches) 2 years after the storm, an indication that this storm further threatened marsh rabbit viability. We found the proportion of salt-tolerant (e.g., mangroves and scrub mangroves) and salt-intolerant (e.g., freshwater wetlands) vegetation within LKMR patches were negatively and positively correlated with probability of patch abandonment, respectively. We found patch size and the number of used patches surrounding abandoned patches were positively correlated with probability of recurrence. We suggest habitat use following this hurricane was driven by the differential response of non-primary habitats to saline overwash and habitat loss from past development that reduced the size and number of local populations. Our findings demonstrate habitat use studies should be conducted following disturbance and should incorporate on-going effects of development and climate change.     

Layer-by-layer growth of binary colloidal crystals

We report the growth of binary colloidal crystals with control over the crystal orientation through a simple layer-by-layer process. Well-ordered single binary colloidal crystals with a stoichiometry of large (L) and small (S) particles of LS2 and LS were generated. In addition, we observed the formation of an LS3 superstructure. The structures formed as a result of the templating effect of the first layer and the forces exerted by the surface tension of the drying liquid. By using spheres of different composition, one component can be selectively removed, as is demonstrated in the growth of a hexagonal non-close-packed colloidal crystal.     

Pathways to improving the N efficiency of grazing bovines

Livestock production has been identified as a major source of nitrogen (N) losses. Therefore, it is important to reduce N output through animal excretions by improving N utilisation by the animal. The objective of this paper is to identify pathways for producing grass-based diets that maximise bovine N utilisation during grazing, based on literature on the interface of plant and animal sciences. The focus is on Western-European perennial ryegrass-based systems under rotational grazing and both beef and dairy production systems are considered.

Three pathways have been identified through which more efficient N utilisation by grazing bovines can be achieved by manipulation of the chemical composition of the grass forage: (1) matching protein supply to animal requirements, (2) balancing and synchronising carbohydrate and N supply in the rumen, and (3) increasing the proportion of rumen undegradable protein (RUP).

Matching the diet requirements of grazing bovines through herbage manipulation encompasses the manipulation of carbon (C) and nitrogen (N) contents of growing herbage. These C and N contents vary both spatially within the grass sward and over time. Under grazing conditions, grassland management tools, such as the length of the regrowth period, grazing intensity, fertiliser N application rate and herbage variety are the main pathways to manipulate C and N dynamics. Regrowth length, N application rate and high sugar varieties were shown to be the most promising grassland management tools with respect to manipulating herbage quality and subsequent bovine N efficiency. However, these management tools are interrelated and may show adverse effects on production.

Due to the complex nature of interactions, modelling is essential in order to quantify and predict the effect of any combination of herbage management tools under specific circumstances.

Areas in which additional research is required are the fractionation of N compounds in herbage as affected by herbage management, and the effect of high sugar varieties on bovine N efficiency under a range of herbage management combinations.     

Acute bioassays with control mortality

When substantial mortality occurs in the control group of an acute bioassay, probit analysis and other methods to estimate the LC50 are usually supplemented with Abbott's correction (Abbott, 1925). This paper discusses the probit model with this adaption. Estimates of the LC50 obtained by probit analysis ignoring natural mortality or by probit analysis applied to data corrected with Abbott's formula beforehand are compared with maximum likelihood estimates based on the model. It is demonstrated that ignoring control mortality can lead to biased estimates of the LC50 even at low percentages of control mortality. For interpretation of the LC50 a distinction is made between control mortality caused by natural processes and control mortality caused by experimental manipulation.     

Climate change impacts on soil erosion in Midwest United States with changes in crop management

This study investigates potential changes in erosion rates in the Midwestern United States under climate change, including the adaptation of crop management to climate change. Previous studies of erosion under climate change have not taken into account farmer choices of crop rotations or planting dates, which will adjust to compensate for climate change. In this study, changes in management were assigned based on previous studies of crop yield, optimal planting date, and most profitable rotations under climate change in the Midwestern United States. Those studies predicted future shifts from maize and wheat to soybeans based on price and yield advantages to soybeans. In the results of our simulations, for 10 of 11 regions of the study area runoff increased from + 10% to + 310%, and soil loss increased from + 33% to + 274%, in 2040–2059 relative to 1990–1999. Soil loss changes were more variable compared to studies that did not take into account changes in management. Increased precipitation and decreasing cover from temperature-stressed maize were important factors in the results. The soil erosion model appeared to underestimate the impact of change in crop type, particularly to soybeans, meaning that erosion increases could be even higher than simulated. This research shows that future crop management changes due to climate and economics can affect the magnitude of erosional impacts beyond that which would be predicted from direct climate change alone. Prediction of future soil erosion can help in the management of valuable cropland and suggest the need for continually changing soil conservation strategies.     

Agricultural drainage: Towards an integrated approach

Drainage needs to reclaim its rightful position as an indispensable element in the integrated management of land and water. An integrated approach to drainage can be developed by means of systematic mapping of the functions of natural resources systems (goods and services) and the values attributed to these functions by people. This mapping allows the exploration of the implications of particular drainage interventions. In that sense an analytical tool for understanding a drainage situation is proposed. The process dimension of the functions and values evaluation and assessment is participatory planning, modelled on co-management approaches to natural resources management. This provides a framework for discussion and negotiation of trade-offs related to the different functions and values related to drainage. In that sense the approach is a communication, planning and decision-making tool. The tool is called DRAINFRAME, which stands for Drainage Integrated Analytical Framework. The implementation of an integrated approach posits challenges for the governance, management and finance of drainage, as well as for research and design of drainage infrastructure and operation. Both have to be rethought from the perspective of multi-functionality. The paper concludes with five main policy messages.