Gebauer G, Schulumacher M I, Krstić B, Rehder H, Ziegler H
Institut für Botanik und Mikrobiologie der Technischen Universität München, Arcisstrasse 21, D-8000, München 2, Fedcral Republic of Germany.
Centro de Ecologia, Universidad National de Cordoba, Cordoba, Argentina.
Oecologia. 1987 May;72(2):303-314. doi: 10.1007/BF00379283.
Pure and mixed cultures of the dicotyledons Atriplex hortensis L. (C plant) and Amaranthus retroflexus L. (C plant) were maintained under open air conditions in standard soil at low and high nitrogen supply levels.A comparison of shoot dry weight and shoot length in the various series shows that the growth of the aboveground parts of both species was severely reduced under low N conditions. In both pure and mixed cultures the differences resulting from low N vs. high N conditions was less pronounced with Atriplex (C plant) than with Amaranthus (C plant). The root dry weight of the two species was not reduced so much under low N conditions as was the shoot dry weight. The low N plants were found to contain a larger proportion of their biomass in the roots than did the high N plants. In general the root proportion of Atriplex was greater than that of Amaranthus. The contents of organic nitrogen and nitrate and the nitrate reductase activity (NRA) per g dry weight of both species decreased continually throughout the experiments. With the exception of young plants, the low N plants always had tower contents of organic nitrogen and nitrate and nitrate reductase activities than did the high N plants. The highest values of NRA were measured in the leaf laminae. The eaves also exhibited the highest concentrations of organic nitrogen. The highest nitrate concentrations, however, were observed in the shoot axis, and in most cases the lowest nitrate values were found in the laminae. At the end of ne growing season this pattern was found to have been reversed with Atriplex, but not with Amaranthus. Thus Atriplex was able to maintain a higher NRA in the laminae than Amaranthus under low N conditions.The transpiration per leaf area of the C plant Amaranthus during the course of a day was substantially lower than that of the C plant Atriplex. There were no significant differences in transpiration between the low N and high N series of Amaranthus. The low N plants of Atriplex, however, clearly showed in most cases higher transpiration rates than the corresponding high N plants. These different transpiration rates of the high N and the low N Atriplex plants were also reflected in a distinct C discrimination.The sum of these results points to the conclusion that the C plant Atriplex hortensis can maintain a better internal inorganic nitrogen supply than the C plant Amaranthus retroflexus under low N conditions and an ample water supply, due to the larger root proportion and the more pronounced and flexible transpiration of the C plant.
将双子叶植物滨藜（C₃植物）和反枝苋（C₄植物）的纯培养物及混合培养物，在低氮和高氮供应水平下，于标准土壤的露天条件下进行培育。各系列中地上部干重和株高的比较表明，在低氮条件下，两个物种地上部分的生长均严重受限。在纯培养和混合培养中，低氮与高氮条件下滨藜（C₃植物）的差异不如反枝苋（C₄植物）明显。两个物种的根干重在低氮条件下的减少幅度不如地上部干重大。低氮植株根系中生物量所占比例高于高氮植株。总体而言，滨藜的根比例大于反枝苋。在整个实验过程中，两个物种每克干重的有机氮、硝酸盐含量及硝酸还原酶活性（NRA）持续下降。除了幼苗外，低氮植株的有机氮、硝酸盐含量及硝酸还原酶活性始终低于高氮植株。NRA的最高值在叶片中测得。叶片中有机氮浓度也最高。然而，硝酸盐浓度最高的是茎轴，在大多数情况下，叶片中的硝酸盐值最低。在生长季末期，发现滨藜的这种模式发生了逆转，而反枝苋没有。因此，在低氮条件下，滨藜在叶片中能保持比反枝苋更高的NRA。在一天中，C₄植物反枝苋的单位叶面积蒸腾量显著低于C₃植物滨藜。反枝苋的低氮系列和高氮系列之间的蒸腾量没有显著差异。然而，滨藜的低氮植株在大多数情况下，蒸腾速率明显高于相应的高氮植株。高氮和低氮滨藜植株的这些不同蒸腾速率也反映在明显的碳同位素分馏上。这些结果综合起来表明，在低氮条件和充足水分供应下，C₃植物滨藜比C₄植物反枝苋能维持更好的内部无机氮供应状况，这归因于C₃植物更大的根比例以及更显著且灵活的蒸腾作用。
