Vitamin D and skeletal muscle structure and function

Haan, A. de [Promotor]Rittweger, J. [Promotor]Degens, H. [Copromotor]Jaspers, R.T. [Copromotor

Roots Withstanding their Environment: Exploiting Root System Architecture Responses to Abiotic Stress to Improve Crop Tolerance

To face future challenges in crop production dictated by global climate changes, breeders and plant researchers collaborate to develop productive crops that are able to withstand a wide range of biotic and abiotic stresses. However, crop selection is often focused on shoot performance alone, as observation of root properties is more complex and asks for artificial and extensive phenotyping platforms. In addition, most root research focuses on development, while a direct link to the functionality of plasticity in root development for tolerance is often lacking. In this paper we review the currently known root system architecture (RSA) responses in Arabidopsis and a number of crop species to a range of abiotic stresses, including nutrient limitation, drought, salinity, flooding, and extreme temperatures. For each of these stresses, the key molecular and cellular mechanisms underlying the RSA response are highlighted. To explore the relevance for crop selection, we especially review and discuss studies linking root architectural responses to stress tolerance. This will provide a first step toward understanding the relevance of adaptive root development for a plant's response to its environment. We suggest that functional evidence on the role of root plasticity will support breeders in their efforts to include root properties in their current selection pipeline for abiotic stress tolerance, aimed to improve the robustness of crops

Irrigation and food security in Swaziland: current status and research priorities

A research paper on food security and irrigation agriculture in Swaziland.Swaziland is a small, landlocked country bordering the Republic of South Africa in the north, west and south, and Mozambique in the east. The country has four distinctive ecological zones, ranging for the wet highveld in the west with an elevation of over 2,000 metres to the dry lowveld in the east, with an average altitude of 100 metres. The population is currently about 676,000, growing at a high rate of 3.2% annually. Agriculture is the main economic activity, providing a livelihood for more than 50,000 rural homesteads and serving as the basis for agro industries. The striking characteristic of the rural economy is the division of land, where freehold tenure in the form of Title Deed Land (TDL) and communal tenure on Swazi Nation Land (SNL) exist side by side. The latter, about 60% of the total land, is held by the King in trust for the Swazi Nation, and provides a living for some 80% of the total population. Some 850 farms and estates on TDL, with an average of about 800 ha, are technologically advanced, with about 60% of the arable land under irrigation. The main crops in this fully-commercialized sector are citrus fruits, sugarcane, cotton, and pineapples. By contrast, holdings on SNL which average less than 2 ha, employ a low level of technology and produce mainly maize. The contribution to the Gross Domestic Product (1981-1985) of crop production on TDL amounted to 14.6%; the contribution of SNL crop production was only 3.4% over the same period (Swaziland Government, 1988, p.6). This paper deals with the contribution of irrigation to food security in Swaziland, defined in terms of both food availability and the ability to acquire food. Irrigation will thus be looked at in the light of food production, as well as providing employment to enable access to food. Finally, areas for further research will be identified

Temporal metabolic profiling of theQuercus suber-Phytophthora cinnamomisystem by middle-infrared spectroscopy

The oomycete Phytophthora cinnamomi is an aggressive plant pathogen, detrimental to many ecosystems including cork oak (Quercus suber) stands, and can inflict great losses in one of the greatest ‘hotspots’ for biodiversity in the world. Here, we applied Fourier transform-infrared (FT-IR) spectroscopy combined with chemometrics to disclose the metabolic patterns of cork oak roots and P. cinnamomi mycelium during the early hours of the interaction. As early as 2 h post-inoculation (hpi), cork oak roots showed altered metabolic patterns with significant variations for regions associated with carbohydrate, glycoconjugate and lipid groups when compared to mockinoculated plants. These variations were further extended at 8 hpi. Surprisingly, at 16 hpi, the metabolic changes in inoculated and mock-inoculated plants were similar, and at 24 hpi, the metabolic patterns of the regions mentioned above were inverted when compared to samples collected at 8 hpi. Principal component analysis of the FT-IR spectra confirmed that the metabolic patterns of inoculated cork oak roots could be readily distinguished from those of mock-inoculated plants at 2, 8 and 24 hpi, but not at 16 hpi. FT-IR spectral analysis from mycelium of P. cinnamomi exposed to cork oak root exudates revealed contrasting variations for regions associated with protein groups at 16 and 24 h post-exposure (hpe), whereas carbohydrate and glycoconjugate groups varied mainly at 24 hpe. Our results revealed early alterations in the metabolic patterns of the host plant when interacting with the biotrophic pathogen. In addition, the FTIR technique can be successfully applied to discriminate infected cork oak plants from mock-inoculated plants, although these differences were dynamic with time. To a lesser extent, the metabolic patterns of P. cinnamomi were also altered when exposed to cork oak root exudates

Phenotyping tomato root developmental plasticity in response to salinity in soil rhizotrons

Plants have developed multiple strategies to respond to salt stress. In order to identify new traits related to salt tolerance, with potential breeding application, the research focus has recently been shifted to include root system architecture (RSA) and root plasticity. Using a simple but effective root phenotyping system containing soil (rhizotrons), RSA of several tomato cultivars and their response to salinity was investigated. We observed a high level of root plasticity of tomato seedlings under salt stress. The general root architecture was substantially modified in response to salt, especially with respect to position of the lateral roots in the soil. At the soil surface, where salt accumulates, lateral root emergence was most strongly inhibited. Within the set of tomato cultivars, H1015 was the most tolerant to salinity in both developmental stages studied. A significant correlation between several root traits and aboveground growth parameters was observed, highlighting a possible role for regulation of both ion content and root architecture in salt stress resilience

№ 128. Додатковий протокол показів Володимира Чехівського від 8 вересня 1929 р.

Environmental stresses, such as shading of the shoot, drought, and soil salinity, threaten plant growth, yield, and survival. Plants can alleviate the impact of these stresses through various modes of phenotypic plasticity, such as shade avoidance and halotropism. Here, we review the current state of knowledge regarding the mechanisms that control plant developmental responses to shade, salt, and drought stress. We discuss plant hormones and cellular signaling pathways that control shoot branching and elongation responses to shade and root architecture modulation in response to drought and salinity. Because belowground stresses also result in aboveground changes and vice versa, we then outline how a wider palette of plant phenotypic traits is affected by the individual stresses. Consequently, we argue for a research agenda that integrates multiple plant organs, responses, and stresses. This will generate the scientific understanding needed for future crop improvement programs aiming at crops that can maintain yields under variable and suboptimal conditions