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Crop root system response to irrigation 总被引：3，自引：0，他引：3
Summary In the field, root systems develop in response to both endogenous plant design and soil environment. Downward penetration of root systems results primarily from the growth of monocot axes or of dicot taproots; root proliferation at a given depth results from the growth of laterals at that depth. Root length densities generally decline exponentially with depth under well-watered conditions. Root growth rates are partially controlled by soil conditions. Under irrigation, the most critical soil properties for root growth are oxygen diffusion rate, water content and soil strength and all of these properties are inter-related. Under excess irrigation, especially in heavy soils, root growth may be limited by oxygen diffusion rate. Under limited irrigation, root growth may be limited by lack of water or high soil strength. When irrigation maintains wet surface soils, most of the root system is found in the upper part of the profile where the majority of the water is also taken up. 相似文献
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J. Alcamo G. J. van den Born A. F. Bouwman B. J. de Haan K. Klein Goldewijk O. Klepper J. Krabec R. Leemans J. G. J. Olivier A. M. C. Toet H. J. M. de Vries H. J. van der Woerd 《Water, air, and soil pollution》1994,76(1-2):37-78
This paper presents scenarios computed with IMAGE 2.0, an integrated model of the global environment and climate change. Results are presented for selected aspects of the society-biosphere-climate system including primary energy consumption, emissions of various greenhouse gases, atmospheric concentrations of gases, temperature, precipitation, land cover and other indicators. Included are a “Conventional Wisdom” scenario, and three variations of this scenario: (i) the Conventional Wisdom scenario is a reference case which is partly based on the input assumptions of the IPCC's IS92a scenario; (ii) the “Biofuel Crops” scenario assumes that most biofuels will be derived from new cropland; (iii) the “No Biofuels” scenario examines the sensitivity of the system to the use of biofuels; and (iv) the “Ocean Realignment” scenario investigates the effect of a large-scale change in ocean circulation on the biosphere and climate. Results of the biofuel scenarios illustrate the importance of examining the impact of biofuels on the full range of greenhouse gases, rather than only CO2. These scenarios also indicate possible side effects of the land requirements for energy crops. The Ocean Realignment scenario shows that an unexpected, low probability event can both enhance the build-up of greenhouse gases, and at the same time cause a temporary cooling of surface air temperatures in the Northern Hemisphere. However, warming of the atmosphere is only delayed, not avoided. 相似文献
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B. J. De Haan M. Jonas O. Klepper J. Krabec M. S. Krol K. Olendrzyński 《Water, air, and soil pollution》1994,76(1-2):283-318
This paper describes the atmosphere-ocean system of the integrated model IMAGE 2.0. The system consists of four linked models, for atmospheric composition, atmospheric climate, ocean climate and for ocean biosphere and chemistry. The first model is globally averaged, the latter are zonally averaged with additional resolution in the vertical. The models reflect a compromise between describing the physical, chemical and biological processes and moderate computational requirements. The system is validated with direct observations for current conditions (climate, chemistry) and is consistent with results from General Circulation Model experiments. The system is used in the integrated setting of the IMAGE 2.0 model to give transient climate projections. Global surface temperature is simulated to increase by 2.5 K over the next century for socio-economic scenarios with continuing economic and population growth. In a scenario study with reduced ocean circulation, the climate system and the global C cycle are found to be appreciably sensitive to such changes. 相似文献
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The objectives of this study were to show that: (a) a herbicide, such as ametryn, which interferes with the photosynthetic electron transport system, causes nitrite to accumulate in illuminated leaves and (b) that nitrite is toxic and contributes to the herbicidal damage and death of the plant. Tests were conducted on wheat seedlings grown on 5 mM nitrate, 5 mM ammonia, and zero nitrogen. Ametryn treatment decreased in vivo and in vitro nitrate reductase activity (NRA) within a 26-hr period. In vivo NRA decreased more rapidly than in vitro NRA. Compared with control tissue, only 3% in vivo NRA remained at the end of 26 hr. The in vivo assay conducted in light confirmed the inhibition of photosynthetic electron flow by ametryn within the leaf tissue. Nitrate-grown, ametryn-treated plants accumulated nitrite and, after 10 days were the only plants that were completely desiccated and dead. Ammonia- and zero-nitrogen, ametryn-treated plants did not accumulate nitrite, were only partially chlorotic after the 10-day period, and were still living. Low levels of NO(X) (NO2 and/or NO) emissions were demonstrated by nitrate-grown ametryn-treated plants. 相似文献
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The triazole fungicides, triadimenol and triticonazole, applied as seed treatments at various rates on spring wheat, affected plant growth, shoot development, and root axis production. The main growth regulatory effects were reductions in lengths of the coleoptile, the first leaf and the subcrown internode. A marked effect on tiller appearance occurred with high rates of triadimenol. Modification of root-system development included a reduction in the number of seminal roots, increased outgrowth of roots associated with the coleoptilar node, and a reduction of roots at the first foliar node (correlated with reduced production of Tiller 1). Seed treatment effects on both shoot and root development illustrated the close relationship between these plant structures. Both fungicides induced both beneficial and deleterious effects on wheat growth and development, but the magnitude of deleterious effects was less with triticonazole than with triadimenol. 相似文献
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