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991.
992.
Kinetic parameters of nitrate uptake by different catch crop species: effects of low temperatures or previous nitrate starvation 总被引:8,自引:0,他引:8
The pollution of aquifers by NO?3 in temperate environments is aggravated by farming practices that leave the ground bare during winter. The use of catch crops during this time may decrease nitrate loss from the soil. Nitrate uptake by several catch crop species (Brassica napus L., Sinapis alba L., Brassica rapa L., Raphanus sativus L., Trifolium alexandrinum L., Trifolium incarnatum L., Phacelia tanacetifolia Benth., Lolium perenne L., Lolium multiflorum Lam. and Secale cereale L.) was here studied in relation to transpiration rate and low temperatures applied to the whole plant or to roots only. The Michaelis constant (Km), maximum uptake rate (Vmax), time of induction and contributions of inducible and constitutive mechanisms were estimated from measurements of NO?3 depletion in the uptake medium. There were large differences between species, with Km (μM) values ranging between 5.12 ± 0.64 (Trifolium incarnatum) and 36.4 ± 1.97 (Lolium perenne). Maximum NO?3 uptake rates expressed per unit root weight were influenced by ageing, temperature and previous NO?3 nutrition. They were also closely correlated with water flow through the roots and with shoot/root ratio of these species. The combined results from all species and treatments showed that Vmax increased with shoot/root ratio, suggesting a regulatory role for the shoots in NO?3 uptake. Overall, the results showed a great diversity in NO?3 uptake characteristics between species in terms of kinetic parameters, contribution of the constitutive system (100% of total uptake in ryegrass, nil in Fabaceae) and time of induction. 相似文献
993.
In a pot experiment, burning or clipping ofTrifolium pratense plants colonized by the vesiculararbuscular mycorrhizal (VAM) fungusAcaulospora scrobiculata increased the number of spores in the substrate and the abundance of vesicles. The length of external mycelium and inoculum potential increased with clipping, but decreased with plant burning. Results suggest that the loss of photosynthesising tissue does not explain the effect of burning on VAM propagule activity. ei]R O D Dixon 相似文献
994.
Sink strength: Is it real,or measurable? 总被引:1,自引:0,他引:1
C. C. BLACK 《Plant, cell & environment》1993,16(9):1037-1038
995.
Sink strength: integrated systems need integrating approaches 总被引:2,自引:0,他引:2
M. STITT 《Plant, cell & environment》1993,16(9):1041-1043
996.
D. Bordin L. Sartorelli G. Bonanni I. Mastrogiacomo E. Scalco 《Biological trace element research》1993,36(2):129-134
Physical exercise leads to many metabolic, cardiovascular, and muscular changes in the body. The trace elements (TE) zinc
and copper are directly involved, as enzymatic cofactors, in many of these processes, especially those related to nutrients
metabolism, oxygen transport, and formation of usable energy. The effects of high-intensity physical exercise on plasma levels
of CU2+ and Zn2+ in 19 subjects are investigated (9 males and 10 females). Plasma copper concentration decreases, and plasma zinc concentration
increases, after exercise, in both sexes. After 30 min recovery, both TE concentration values shifts-toward rest values in
both sexes.
These results only partially agree with literature data, probably because we used the treadmill exercise, which makes many
muscles work, whereas other authors made their subjects perform a cycloergometer exercise. Physical exercise causes a marked
redistribution of TE (copper and zinc) between body stores, bloodstream, and tissues. The condition of high metabolism may
lead to a deficiency of TE, requiring supplementation in order to maintain high level performance. 相似文献
997.
Sam R. Telford Jr. 《Systematic parasitology》1993,25(2):109-117
Schellackia orientalis n. sp. parasitises the Japanese lizard Takydromus tachydromoides on Honshu and Takydromus sexlineatus in Thailand. Merogony and gamogony occur in the epithelium of the small intestine, and octonucleate oöcysts form in the lamina propria. In infections induced by inoculation of infected blood, sporozoites appeared in blood cells 17–56 days post-inoculation, initially in any type of white blood cell but most commonly in macrophages and monocytes. Both erythroid and leucocytic cells were parasitised after five days. This haemococcidian is another component of the symbiotic complex found in Takydromus species of eastern and southeastern Asia. 相似文献
998.
Hepatic sinusoidal membranes isolated from adult rats were extracted with detergent and fractionated on a wheat germ agglutinin affinity column. Bound glycoproteins were eluted with N-acetyl glucosamine and chromatographed on a type IV collagen affinity column. Recovery of the bound fraction by EDTA and analysis by SDS-PAGE revealed two glycoproteins with apparent molecular weights of 180,000 and 117,000. These were identified immunologically by Western blotting as the alpha and beta subunits of integrin alpha 1 beta 1. 相似文献
999.
Previous studies have shown that dendritic cells in the murine vaginal epithelium at diestrus and metestrus can endocytose intravaginally administered soluble protein tracers, but the identity of the dendritic cells was not established. In the investigation reported here, we used a combination of histochemistry and transmission electron microscopy to study the endocytosis of exogenous horseradish peroxidase by vaginal dendritic cells and to identify these cells as Langerhans' cells on the basis of their cellular associations, ultrastructural morphology, and the presence of Langerhans' cell granules. 相似文献
1000.