Secondary aerenchyma formation and its relation to nitrogen fixation in root nodules of soybean plants (Glycine max) grown under flooded conditions
Secondary aerenchyma formation and its relation to nitrogen fixation in root nodules of soybean plants (Glycine max) grown under flooded conditions
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DOI：
10.1626/pps.5.294
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发表时间：
2002-12-01
影响因子：
2.5
通讯作者：
Fukuyama, M
中科院分区：
文献类型：
--
作者：
Shimamura, S;Mochizuki, T;Fukuyama, M
大豆（Glycine max（L.）梅尔）被认为是易受水淹的，水淹是世界上的主要农艺问题，并且由于根瘤中的缺氧，固氮酶活性迅速下降。我们研究了根瘤驯化洪水在形态水平上使用的大豆品种具有形成次生通气组织的能力。处理1周后，在灌溉和淹水条件下，在根瘤表面形成了气孔，并通过气孔观察到次生通气组织。随着植株的生长，根瘤表皮脱落，表面有发达的次生通气组织。次生通气组织起源于环绕厚壁组织的次生分生组织，淹水根瘤的发育程度大于灌溉根瘤。淹水条件下，根系生长和总固氮酶活性（TNA）降低，但地上部氮浓度、比固氮酶活性（SNA）和木质部伤流液中相对酰脲氮含量在灌水和淹水条件下无显著差异。然而，在淹水条件下，当氧气进入次生通气组织时，在下胚轴中形成。结果表明，在下胚轴表面涂抹凡士林后，地上部N浓度、TNA、SNA、汁液中酰脲N浓度和相对酰脲N浓度均显著下降。这些结果表明，次生通气组织的形成是大豆植株对淹水胁迫的一种形态适应反应，其功能之一是为根瘤提供大气氧气，从而使根瘤的活性得以维持。
Soybean (Glycine max (L.) Merr.) is considered to be susceptible to flooding, a major agronomic problem in the world, and nitrogenase activity rapidly declines due to oxygen deficiency in root nodules. We investigated nodule acclimation to flooding at the morphological level using a soybean cultivar possessing the ability to form secondary aerenchyma. After 1 week of treatment, lenticels were formed on the surface of the root nodules, and secondary aerenchyma were observed through the lenticels under both irrigated and flooded conditions. As the plant grew, the nodule epidermis came off, and well-developed secondary aerenchyma covered the nodule surface. The secondary aerenchyma originated from the secondary meristem (phellogen) girdling the sclerenchyma, and the degree of development was greater in flooded nodules than in irrigated ones. Although root nodulation and total nitrogenase activity (TNA) decreased under flooded conditions, there were no differences in shoot N concentration, specific nitrogenase activity (SNA) and relative ureide-N in the xylem bleeding sap between plants in the irrigated and flooded conditions. Under flooded conditions, however, when the entry of oxygen into the secondary aerenchyma formed in the hypocotyl. was inhibited by vaseline treatment (pasting on the surface of the hypocotyl), the shoot N concentration, TNA, SNA, the ureide-N concentration and the relative ureide-N in the sap declined remarkably. These results suggested that secondary aerenchyma formation in soybean plants is a morphological acclimation response to flooding stress, and that one of the functions is to supply atmospheric oxygen to root nodules, which consequently enables nodule activity to be maintained.