Vitamin D and skeletal muscle structure and function

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

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

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