Economy of Symbiotically Fixed Nitrogen in Red Clover (Trifolium pratenseL.)
Economy of Symbiotically Fixed Nitrogen in Red Clover (Trifolium pratenseL.)
复制标题
红三叶草（Trifolium pratenseL.）共生固定氮的经济性
DOI：
10.1006/anbo.1997.0484
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发表时间：
1997
期刊：
影响因子：
4.2
通讯作者：
M. Fernández
中科院分区：
文献类型：
--
作者：
F. Warembourg;F. Lafont;M. Fernández
摘要研究了法国南部地中海气候条件下连续两季盆栽红三叶草（Trifolium pratenseL.）的共生固结、氮的分布和去向。利用乙炔（C2H2）还原法跟踪整个生长季节的氮酶活性。在植物根系暴露于标记的二氮（15N2）后，通过定期测量15n在植物中的分布来跟踪共生固定N的分布和转移。两个年份的氮酶活性都有两个高峰，分别在春季和夏末，在开花期急剧下降。在整个生长周期中，共生固定氮占植株总氮的61% ~ 96%，在入氮后一周内，植株地上部分从大气中吸收的氮有60 ~ 90%被回收。在叶片中占50%以上，但在不同发育阶段的分布有差异。从根瘤根中回收的最大百分比（20-28%）出现在5 - 6月，营养器官的最大生长期和9月。地上共生固定氮随时间的流动性强，从莲座叶转移到附着在细长茎上的叶片，再转移到种子，5、6月固定的氮在9月恢复了25 ~ 50%。因为：(1)叶片周转率高；(2)枯叶含氮量较高，可将每年高达50%的共生固定氮作为凋落物提供给土壤微生物。春季和冬季输送量最大。剩余的20% ~ 35%在第二年3月的再生过程中被回收。根系向根系和向根系的转移不明显，但根系氮含量的显著下降发生在叶片再生开始后的第二年早期。综上所述，红三叶草叶片生产力高，周转率高，共生固定氮产量高，是全年向土壤提供大量氮素，恢复土壤氮素肥力的良好选择。
Abstract The seasonal dynamics of symbiotic fixation, distribution and fate of nitrogen (N) were studied on two successive crops of red clover (Trifolium pratenseL.) grown outdoors in soil containers under the Mediterranean climate of southern France. Nitrogenase activity was followed throughout the growing season using acetylene (C2H2) reduction assays. The distribution and transfer of symbiotically fixed N were followed by periodic measurements of15N distribution in plants after exposure of the root systems to labelled dinitrogen (15N2). In both years there were two peaks of nitrogenase activity, one in spring and one in late summer, separated by a sharp decrease during the flowering period. Over the entire growth cycle, symbiotically fixed N accounted for 61 to 96% of the total plant N. Once week after incorporation, 60 to 90% of N derived from the atmosphere was recovered in the aerial parts of the plants. More than 50% of this was in the leaves, but there were differences in distribution according to the stage of development. The maximum percentage (20–28%) recovered from nodulated roots occurred in May–June, during maximum growth of the vegetative organs, and in September. Above-ground symbiotically fixed N was highly mobile with time, moving from the rosette leaves to the leaves attached to the elongated stems and then to the seeds, where 25 to 50% of N fixed in May and June was recovered in September. Because of: (1) the high turnover rate of leaves; and (2) the relatively high N content of dead leaves, as much as 50% of the symbiotically fixed N in a year was potentially available to the soil micro-organisms as litter. The maximum transfer was in spring and winter. Of the remainder, 20 to 35% was recovered in living plant parts during regrowth in March of the second year. Transfers to and from the root system were less pronounced, but significant decreases in N content of the roots occurred early in the second year just after foliage regrowth was initiated. It is concluded that, because of its high foliage productivity and turnover rate, and high yield of symbiotically fixed N, red clover is a good candidate to provide substantial amounts of N to the soil throughout the year and therefore restore N fertility.