Positive nitrogenase activities ranging from 0.18 to 0.78 nmol of C2H4 cm−2 h−1 were detected on the leaf surfaces of different varieties of cotton (Gossypium hirsutum L. and G. herbaceum L.) plants. Beijerinckia sp. was observed to be the predominant nitrogen-fixing microorganism in the phyllosphere of these varieties. A higher level of phyllosphere nitrogen-fixing activity was recorded in the variety Varalaxmi despite a low C/N ratio in the leaf leachates. Leaf surfaces of the above variety possessed the largest number of hairy outgrowths (trichomes) which entrapped a majority of microbes. Immersion of plant roots in nutrient medium containing 32Pi led to the accumulation of label in the trichome-borne microorganisms, thereby indicating a possible transfer of nutrients from leaf to microbes via trichomes. Extrapolation of acetylene reduction values suggested that 1.6 to 3.2 kg of N ha−1 might be contributed by diazotrophs in the phyllosphere of the variety Varalaxmi during the entire growth period.
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机译:在不同品种的棉花(陆地棉和棉)的叶片表面检测到的C2H4 cm −2 sup> h -1 sup>的正态氮酶活性范围为0.18至0.78 nmol。草本植物)。贝氏菌属据观察,它们是这些变种叶缘中主要的固氮微生物。尽管叶浸出液中的C / N比较低,但在Varaxxmi品种中记录了较高的叶环固氮活性。上述品种的叶片表面具有最多的毛状生长产物(毛状体),其捕获了大多数微生物。将植物根部浸入含有 32 sup> Pi的营养培养基中会导致标记在毛状体传播的微生物中积累,从而表明营养物可能通过毛状体从叶片转移到微生物。乙炔还原值的外推表明,在整个生长期中,重氮营养菌可能在品种Varalaxmi的系统叶层中贡献1.6至3.2 kg N ha -1 sup>。
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