Nilsson M, Bhattacharya J, Rai A N, Bergman B
Department of Botany, Stockholm University, SE-10691 Stockholm, Sweden.
Biochemistry Department, North-Eastern Hill University, Shillong-793022, India.
New Phytol. 2002 Dec;156(3):517-525. doi: 10.1046/j.1469-8137.2002.00534.x.
• The lack of nitrogen in agriculture, and negative environmental effects of fertilizers, have stimulated interest in creating artificial associations between N -fixing cyanobacteria and rice (Oryza sativa). • For the first time, numerous (57) Nostoc isolates from natural symbioses were screened for their ability to associate with rice. Successful colonizers were tested for N -fixation by acetylene reduction and for their ability to adsorb to roots by chlorophyll a measurements. Paranodules were induced by 2,4-dichlorophenoxyacetic acid. And genetic fingerprints of the cyanobacteria were obtained for identification. Ultrastructural investigations were made by light and scanning electron microscopy. • Twenty-one symbiotic Nostoc isolates associated with rice roots, colonizing surfaces and intercellular spaces. Adsorption was high and appeared biphasic. The rates of N fixation by associated cyanobacteria were higher compared with those in free-living cyanobacteria. Paranodules were formed and colonized, but root growth was adversely affected. • Under laboratory conditions, artificial associations were created between one-third of the screened symbiotic cyanobacteria and rice. The agricultural potential for the association appears high since the cyanobacteria adsorb tightly and fix more N than when free-living.
• 农业中氮的缺乏以及肥料对环境的负面影响，激发了人们对在固氮蓝细菌与水稻（Oryza sativa）之间建立人工共生关系的兴趣。
• 首次对从自然共生体中分离出的大量（57株）念珠藻菌株与水稻共生的能力进行了筛选。通过乙炔还原法对成功定殖的菌株进行固氮测试，并通过叶绿素a测量来检测它们吸附到根上的能力。用2,4-二氯苯氧乙酸诱导假根瘤形成。并获得蓝细菌的遗传指纹用于鉴定。通过光学显微镜和扫描电子显微镜进行超微结构研究。
• 21株与水稻根共生的念珠藻菌株定殖在根表面和细胞间隙。吸附率很高，呈双相性。与自由生活的蓝细菌相比，共生蓝细菌的固氮率更高。形成并定殖了假根瘤，但对根的生长产生了不利影响。
• 在实验室条件下，在三分之一经筛选的共生蓝细菌与水稻之间建立了人工共生关系。由于蓝细菌紧密吸附且固氮量比自由生活时更多，这种共生关系的农业潜力似乎很高。
