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Aquatic macrophytes play an important role in the structural and functional aspects of aquatic ecosystems by altering water movement regimes, providing shelter to fish and aquatic invertebrates, serving as a food source, and altering water quality by regulating oxygen balance, nutrient cycles, and accumulating heavy metals. The ability to hyperaccumulate heavy metals makes them interesting research candidates, especially for the treatment of industrial effluents and sewage waste water. The use of aquatic macrophytes, such as Azolla with hyper accumulating ability is known to be an environmentally friendly option to restore polluted aquatic resources. The present review highlights the phytoaccumulation potential of macrophytes with emphasis on utilization of Azolla as a promising candidate for phytoremediation. The impact of uptake of heavy metals on morphology and metabolic processes of Azolla has also been discussed for a better understanding and utilization of this symbiotic association in the field of phytoremediation.

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Development of an effective plant growth promoting rhizobacteria (PGPR) inoculant necessitates the presence of a diverse set of traits that can help its colonization of the rhizosphere and survival under varying environmental conditions. In our investigation, a set of 100 bacterial isolates from the rhizosphere of wheat plants were screened initially on the basis of a seed germination assay; ten bacterial isolates (AW1-AW10) were selected. These isolates were then tested in vitro for specific PGPR traits, such as the production of IAA, siderophore, ammonia, HCN, P solubilization, ACC deaminase activity, acetylene reduction assay and antifungal activity. Of the ten isolates, AW5 was found to be promising for all PGP attributes. An experiment undertaken in the controlled conditions of the National Phytotron Facility revealed the potential of three isolates (AW1, AW5 and AW7) in enhancing the growth parameters of wheat plants. Characterization of these isolates using polyphasic approaches involving both phenotypic and genotypic attributes led to their identification as Bacillus sp. (AW1), Providencia sp. (AW5), and Brevundimonas diminuta (AW7), respectively. These strains could prove effective PGPR inoculants as they possess a number of traits useful for their establishment and proliferation in soil. The genus Providencia is reported for the first time for its PGP potential, using cultural as well as functional attributes to show its suitability as an inoculant for wheat crop.

An investigation was undertaken to screen, select and evaluate a set of bacterial and cyanobacterial isolates from the wheat rhizosphere for their role as biofertilizers in wheat. From an initial set of 23 cyanobacterial strains and 110 bacterial isolates from wheat rhizospheric soil, 3 bacterial and 3 cyanobacterial strains were selected based on their plant growth promoting potential under laboratory and controlled greenhouse conditions. In vitro compatibility studies revealed positive interactions among the six strains. Pot experiments were conducted with wheat variety HD 2687, with a total of 51 treatments, along with recommended fertilizer controls. Various combinations of the selected set of three bacterial (PW1, PW5 and PW7) and three cyanobacterial isolates (CW1, CW2 and CW3) were used along with 1/3 N and full dose of P and K fertilizers. Significant enhancement in the soil microbiological (Dehydrogenase activity, FDA hydrolase, Alkaline phosphatase and microbial biomass) and plant growth/yield parameters were recorded. Observations revealed a two-fold increase in panicle weight in selected combinations (PW1+PW7+CW3; PW1+ CW1+CW2/CW1+CW3; CW2+CW3), as compared to control treatment involving full dose of chemical fertilizers. Such combinations, which also provided N savings of 40-80 kg N/ha are being further evaluated in field experiments. This study for the first time illustrated the positive and dynamic interactions among bacterial and cyanobacterial strains and their promise in integrated nutrient management of wheat crop.