Arbuscular mycorrhizae reduced arsenic induced oxidative stress by coordinating nutrient uptake and proline-glutathione levels in Cicer arietinum L. (chickpea)

Accumulation of Arsenic (As) generates oxidative stress by reducing nutrients availability in plants. Arbuscular mycorrhizal (AM) symbiosis can impart metalloid tolerance in plants by enhancing the synthesis of sulfur (S)-rich peptides (glutathione- GSH) and low-molecular-weight nitrogenous (N) osmolytes (proline- Pro). The present study, therefore investigated the efficiency of 3 AM fungal species (Rhizoglomus intraradices-Ri, Funneliformis mosseae -Fm and Claroideoglomus claroideum- Cc) in imparting As (arsenate-AsV -40 at 60 mg kg-1 and arsenite- AsIII at 5 and 10 mg kg-1) tolerance in two Cicer arietinum (chickpea) genotypes (HC 3 and C 235). As induced significantly higher negative impacts in roots than shoots, which was in accordance with proportionately higher reactive oxygen species (ROS) in the former, with AsIII more toxic than AsV. Mycorrhizal symbiosis overcame oxidative stress by providing the host plants with necessary nutrients (P, N, and S) through enhanced microbial enzyme activities (MEAs) in soil, which increased the synthesis of Pro and GSH and established a redox balance in the two genotypes. This coordination between nutrient status, Pro-GSH levels, and antioxidant defense was stronger in HC 3 than C 235 due to its higher responsiveness to the three AM species. However, Ri was most beneficial in inducing redox homeostasis, followed by Fm and Cc, since the Cicer arietinum-Ri combination displayed the maximum ability to boost antioxidant defense mechanisms and establish a coordination with Pro synthesis. Thus, the results highlighted the importance of selecting specific chickpea genotypes having an ability to establish effective mycorrhizal symbiosis for imparting As stress tolerance.

Addressing the role of earthworms in treating domestic wastewater by analyzing biofilm modification through chemical and spectroscopic methods

Vermifiltration eco-friendly system is an alternative and low-cost artificial ecosystem for decentralized wastewater treatment and excess sludge reduction. The biofilm characteristics of a vermifilter (VF) with earthworms, Eisenia fetida, for domestic wastewater treatment were studied. A conventional biofilter (BF) without earthworms served as the control. Pore number in VF biofilm was significantly more than BF biofilm, and VF biofilm showed a better level-administrative structure through scanning electron microscope. VF biofilms had lower levels of protein and polysaccharide, but phosphoric acids and humic acid showed the opposite results. Furthermore, in the presence of earthworms, VF biofilms contained higher total organic carbon (TOC) percentage composition in the condition of less volatile suspended substances (VSS) contents. Dehydrogenase activity (DHA) and adenosine triphosphate (ATP) contents along VF showed better results than BF by increment of 12.84 ∼ 16.46 %. Overall findings indicated that the earthworms' presence remarkably decreases biofilm contests but increases enzyme activity and improves the community structure of VF biofilms, which is beneficial for the wastewater disposal.