Endophytic colonization of plant roots by nitrogen-fixing bacteria
Endophytic colonization of plant roots by nitrogen-fixing bacteria
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DOI：
10.1023/a:1024106605806
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发表时间：
2003-05-01
期刊：
影响因子：
4.9
通讯作者：
Cocking, EC
中科院分区：
文献类型：
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作者：
Cocking, EC
固氮细菌能够从根际进入根，特别是在新兴侧根的基部，表皮细胞之间和通过根毛。根际生长的根毛在豆科作物的共生识别中起着重要作用。根瘤菌内共生的结瘤豆科植物是农业中最重要的固氮系统之一。已经进行了用各种非根瘤固氮细菌接种非豆科植物，特别是谷类植物，期望它们将在根系内细胞间建立自己，内生固氮并提供结合氮以提高作物产量。然而，在大多数情况下，细菌仅定殖于根的表面，并且仍然容易受到来自其他根际微生物的竞争，即使当固氮细菌是内生的时，对植物的益处可能来自更好地吸收土壤养分而不是来自内生固氮。已知茎瘤固氮根瘤菌（Azorhizobium caulinodans）通过表皮细胞间的细胞间侵入进入谷类、其它非豆科作物和拟南芥的根系，并在植物细胞间（包括木质部）内部定殖。这提出了木质部定殖可能为水稻、小麦、玉米、高粱和其他非豆科作物的内共生固氮提供非结节生态位的可能性。一种特别有趣的、天然存在的、非结节状木质部定植的内生重氮营养相互作用是甘蔗中的重氮营养葡萄糖酸醋酸杆菌，有内生固氮的证据。这种有益的甘蔗内生定殖G.重氮营养菌是否可以扩展到禾本科的其他成员，包括主要的谷类，以及世界上其他主要的非豆科作物？
Nitrogen-fixing bacteria are able to enter into roots from the rhizosphere, particularly at the base of emerging lateral roots, between epidermal cells and through root hairs. In the rhizosphere growing root hairs play an important role in symbiotic recognition in legume crops. Nodulated legumes in endosymbiosis with rhizobia are amongst the most prominent nitrogen-fixing systems in agriculture. The inoculation of non-legumes, especially cereals, with various non-rhizobial diazotrophic bacteria has been undertaken with the expectation that they would establish themselves intercellularly within the root system, fixing nitrogen endophytically and providing combined nitrogen for enhanced crop production. However, in most instances bacteria colonize only the surface of the roots and remain vulnerable to competition from other rhizosphere micro-organisms, even when the nitrogen-fixing bacteria are endophytic, benefits to the plant may result from better uptake of soil nutrients rather than from endophytic nitrogen fixation. Azorhizobium caulinodans is known to enter the root system of cereals, other non-legume crops and Arabidopsis, by intercellular invasion between epidermal cells and to internally colonize the plant intercellularly, including the xylem. This raises the possibility that xylem colonization might provide a non-nodular niche for endosymbiotic nitrogen fixation in rice, wheat, maize, sorghum and other non-legume crops. A particularly interesting, naturally occurring, non-nodular xylem colonising endophytic diazotrophic interaction with evidence for endophytic nitrogen fixation is that of Gluconacetobacter diazotrophicus in sugarcane. Could this beneficial endophytic colonization of sugarcane by G. diazotrophicus be extended to other members of the Gramineae, including the major cereals, and to other major non-legume crops of the World?