Effect of 2,4-D treatment and Azospirillum inoculation on growth of Cymbopogon winterianus

Abstract

The association of Cymbopogon winterianus (Citronella), a member of the Poaceae family, with the N 2 -fixing bacteria, Azospirillum was examined to evaluate possible benefits for agriculture. The nodules on citronella were induced using plant growth regulator 2,4-dichlorophenoxyacetic acid (2,4-D) 1.0 ppm in nitrogen free Hoagland's solution. Concentration of 2,4-D greater than 1.0 ppm caused stunning and death, while concentration of 2,4-D less than 1.0 ppm has no obvious effect on seedling growth. The presence of nitrogenase activity (acetylene reduction assay) and leghemoglobin (hemoprotein found in the nitrogen-fixing root nodules) was noticed in the plants treated with Azospirillum either alone or with nodulated plants, but higher activity was noticed in nodulated Azospirillum treated plants. These results confirmed the nitrogenase activity of Azospirillum brasilense in association with 2,4-D induced nodules of citronella. After transplanting to pots, it was noticed that nodulated and Azospirillum -treated plants showed higher chlorophyll content in leaf, enhanced nitrate reductase (NR) activity, leading to higher yield as compared to the control plants (non-nodulated). The nodulated plants treated with Azospirillum also had higher physiological activities as compared to plants treated only with Azospirillum. The results provide evidence that the plants belonging to the family Poaceae are potentially able to create a symbiosis with diazotropic bacteria, which colonize para-nodule tissue intracellularly, promoting a higher level of nitrogen (N 2 ) fixation leading to better growth and plant development.

Soil Microbial Assemblages Are Linked to Plant Community Composition and Contribute to Ecosystem Services on Urban Green Roofs

“…There were 48 bacterial indicator families associated with mixed-vegetation green roof systems, 22 of which aligned to the phylum Proteobacteria. Indicator taxa included genera recognized as plant growth-promoting bacteria, such as Bacillus (Glick, 2012) and Azospirillum (Saikia et al, 2014). There were 38 bacterial indicator families for Sedum green roofs, including Rhizobiaceae and Bradyrhizobiaceae, both of which contain plant-associated bacterial species.…”

A Developmental and Molecular View of Formation of Auxin-Induced Nodule-Like Structures in Land Plants

“…One option to elucidate the genetic mechanism in hormone-dependent nodule organogenesis is to study NLS formation. Interestingly, in many cereals such as rice, wheat, and maize, addition of phytohormones also stimulate NLS formation (Ridge et al, 1993; Kennedy et al, 1997; Christiansen-Weniger, 1998; Narula et al, 2006; Senthilkumar et al, 2009; Saikia et al, 2014). Such structures can be colonized by nitrogen-fixing bacteria like Azorhizobium caulinodans and Azospirillum brasilense , which favor nitrogen fixation compared to regular roots, and subsequently increase plant yield (Sriskandarajah et al, 1993; Kennedy et al, 1997; Christiansen-Weniger, 1998; Senthilkumar et al, 2009; Saikia et al, 2014).…”