Biology subjects

Mishra, A. K.

Publications and source records attributed to Mishra, A. K..

3 recordsLinked to original sources

bioRxiv2018

Andaman mangrove sediments: source of nutrients and sink of heavy metals

Andaman Islands (AI) of India is a biodiversity hotspot of mangroves but biogeochemical dynamics of AI is less understood. We collected sediment samples of four AI mangrove sites and one site without mangroves for nutrients and trace metal analysis. Samples were collected from each site at the inlet of seawater (Zone A) and the other 500m into the mangrove creek (Zone B). Nutrients (sulphate, ammonium, nitrite and nitrate) levels, organic matter (OM) and carbon content were higher at Zone B of mangrove ecosystem due to the higher OM content from mangrove leaf litter decomposition and microbial degradation. Metal (Pb &Cd) content of zones with and without mangroves were similar and Igeo values indicated moderate contamination of mangrove zones of AI due to lack of anthropogenic pollution. Our results suggest mangrove ecosystems of AI are uncontaminated from heavy metals and are source of nutrients to the oligotrophic coastal ecosystems of Andaman Sea.

ecology↗

bioRxiv2018

Elevated trace elements in Posidonia oceanica and Cymodocea nodosa at six Mediterranean volcanic seeps

Seagrasses form important habitats around shallow marine CO2 seeps, providing opportunities to assess trace element (TE) accumulation along gradients in seawater pH. Here we assessed Cd, Cu, Hg, Ni, Pb and Zn levels in sediment and seagrasses at six CO2 seeps and reference sites off Italy and Greece. Some seep sediments had much higher concentrations of TEs, the extreme example being Cd at 43-fold above reference levels. Sediment Quality Guideline (SQG) scores indicated that three seeps had sediment TEs levels likely to have \"Adverse impacts\" on marine biota; namely Vulcano (for Hg), Ischia (for Cu) and Paleochori (for Cd and Ni). SQG indicated seep sediments of Italian seeps were adversely affected by Cu and Hg, whereas Greek CO2 seeps were affected by Cd and Ni. An increase in sediment TEs levels positively corelated with higher levels of TEs in seagrass roots of Posidonia oceanica (Zn and Ni) and Cymodocea nodosa (Zn). Differences in the bioavailability and possible toxicity of TEs helps explain why seagrasses were abundant at some CO2 seeps but not others.

ecology↗

bioRxiv2018

Overexpression of Arabidopsis ubiquitin ligase AtPUB46 enhances tolerance to drought and oxidative stress

The U-Box E3 ubiquitin ligase, AtPUB46, functions in the drought response: T-DNA insertion mutants of this single paralogous gene are hypersensitive to water- and oxidative stress (Adler et al. BMC Plant Biology 17:8, 2017). Here we analyze the phenotype of AtPUB46 overexpressing (OE) plants. AtPUB46-OE show increased tolerance to water stress and have smaller leaf blades and reduced stomatal pore area and stomatal index compared with wild type (WT). Despite this, the rate of water loss from detached rosettes is similar in AtPUB46-OE and WT plants. Germination of AtPUB46-OE seeds was less sensitive to salt than WT whereas seedling greening was more sensitive. We observed a complex response to oxidative stress applied by different agents: AtPUB46-OE plants were hypersensitive to H2O2 but hyposensitive to methyl viologen. AtPUB46-GFP fusion protein is cytoplasmic, however, in response to H2O2 a considerable proportion translocates to the nucleus. We conclude that the differential stress phenotype of the AtPUB46-OE does not result from its smaller leaf size but from a change in the activity of a stress pathway(s) regulated by a degradation substrate of the AtPUB46 E3 and also from a reduction in stomatal pore size and index.\n\nAccession NumbersSequence data for this article can be found in: The Arabidopsis Information Resource database (http://www.arabidopsis.org) under accession numbers At5G18320 (PUB46).

plant biology↗