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In water culture the effect of a locally restricted NO3 supply to the seminal root system of maize seedlings was studied. For this purpose plants were cultivated in containers with a wide-bore polyethylene tube positioned horizontally. Roots were suited through small holes in this tube and after sealing the holes with a non-toxic silicon putty, root segments in the tube could be exposed to a different nutrient solution from the rest of the root system in the outer compartment. In case of a locally restricted NO3 supply (NO3 was just supplied to the root segment within the tube), we observed an increase in root growth beginning at the fifth day after onset of the treatment. NO3 uptake rate (15N) within the tube was significantly higher than in control plants (receiving NO3 to the entire root system) as early as two days after onset of the treatment. One day later respiration (O2 consumption) of the root segment exposed to NO3 increased and at the same day we observed an accumulation of 14C activity (after pulse labelling of the shoots with 14CO2) suggesting an increased phloem unloading. It is argued that this leads to the measured increase in IAA activity (Radio Immuno Assay) in the zone of NO3 supply. Beginning at the fifth day we observed a stimulation of cell division rate (incorporation of 3H-methylthymidine), accompanied by an increase in length of first order lateral roots. 相似文献
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David Curwen Pete Weingartner Ronald Knight Therese M. Work Hugh J. Murphy Steven B. Johnson Richard Zink Leigh Morrow A. R. Mosley Rod Davidson Thoms Owings Don Halseth John Bamberg John C. Wallace Stephen Love Don Halseth Elmer E. Ewing LaMont Anderson Neil Gudmestad Oscar Malamud Jane Seabrook Robert E. Thornton Ronald Voss A. J. Mosley 《American Journal of Potato Research》1991,68(12):861-902
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- Primary production on semiarid floodplains supports a diverse local and regional fauna. Reduced flooding from water resource development (WRD) may affect floodplain production by decreasing water and nutrient supply. 相似文献
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A local nitrate supply to roots of maize causes increasing growth of the first order and the formation of higher order laterals. Number of first order laterals, however, remains unchanged. Labelling plants with 14CO2 demonstrates a specific phloem unloading in the supply zone. It is suggested that phloem mobile phytohormones, especially auxins, lead to an endogenous shift in the phytohormone balance responsible for the morphogenetic effect of a local NO3 · supply. 相似文献
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Studies were made on Russet Burbank tubers grown under normal and moisture stressed conditions. Stressing the tubers caused increased reducing sugar accumulation in the basal end during storage. Respiration rates of apical and basal portions of stressed and normal tubers were followed during the growing season and in storage. Although its sugar content was greater, the basal end of stressed tubers respired at a significally slower rate than apical ends from the same tubers. Normal basal and apical portions showed no statistical differences in respiration although the apical end respired at a slightly faster rate than the basal end. A positive linear correlation between sugar concentration and respiration rate of the apical portion was obtained. Differences were found in the abilities of apical and basal ends to alter respiration rates in response to changes in sugar concentration. The resprationof the apical end was the more sensitive to increased sugar concentration. The basal end of stressed tubers lost some of its ability to respond, probably because of increased physiological aging caused by the stress conditions. 相似文献
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We investigated the link between aboveground and belowground diversity in temperate deciduous forest ecosystems. To this end, we determined the effects of the tree species composition on the biomass and composition of the soil microbial community using phospholipid fatty acid (PLFA) profiles in the Hainich National Park, a deciduous mixed forest on loess over limestone in Central-Germany. We investigated the effects of the leaf litter composition on the microbial community, hypothesizing that distinctive leaf litter compositions increase signature PLFAs. In addition, we studied the impact of clay content, pH and nutrient status of the soil on the microbial community in different surface soil layers. Consequently, soil was sampled from depths of 0-5 cm, 5-10 cm and 10-20 cm. Plots with highest leaf litter diversity had the largest total amounts of fatty acids, but only PLFA 16:1ω5, which is a common marker for arbuscular mycorrhizal fungi, was significantly increased. In the uppermost soil layer, the pH explained most of the variance in microbial composition. In the deeper surface soil layers, nutrients such as carbon, nitrogen and phosphorus determined the microbial abundances and composition. Our results suggest that the soil microbial community is mainly indirectly influenced by aboveground diversity. Changes in soil pH or the soil nutrient status that are driven by specific plant traits like leave litter quality drive these indirect changes. Specific direct interactions are most reasonable for mycorrhizal fungi. 相似文献
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1. Detailed research into the ecological impacts of inter-basin water transfers (IBTs) is virtually nonexistent on a global scale. However, a growing awareness of the serious nature of such impacts—for example, the loss of biogeographical integrity, the loss of endemic biotas, the frequent introduction of alien and often invasive aquatic and terrestrial plants and animals, the genetic intermixing of once separated populations, the implications for water quality, the frequently drastic alteration of hydrological regimes, the implications for marine and estuarine processes, climatic effects, and the spread of disease vectors, amongst many others—demands a most urgent and world-wide appraisal of all current planning and research strategies. 2. This paper first defines the types of extant IBTs, and details some case studies for three widely separated regions of the world, namely: south-eastern Australia, southern Africa, and the central and south-western parts of the United States of America. In doing so, it highlights the chronic paucity of ecological data on their impacts, while simultaneously emphasising their extreme complexities. 3. Finally, we call for an international meeting on such schemes, as a matter of priority and extreme urgency, in order to assess the extent of IBTs, their geographical distribution, and their ecological and sociological impacts and implications. 相似文献
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Landscape Ecology - Floodplains are complex adaptive ecosystems that provide an array of ecosystem services. Despite the growing focus on resilience as a fundamental feature of floodplain... 相似文献