Browsing by Author "N.K. Sharma"

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Algal Particles in the Atmosphere
(Elsevier Inc., 2011) N.K. Sharma; A.K. Rai
The presence of algae in the atmosphere has long been recognized. Besides being a potent health threat to human beings, airborne algae play an important role in the algal dispersal, colonization of new habitats, and extension of harmful algal blooms. This article provides state-of-art information on various aspects of airborne algae with main emphasis on the risks associated with human exposure to aerosolized algal particles and their toxins. © 2011 Elsevier B.V. All rights reserved.
Algal Particles in the Atmosphere
(Elsevier, 2011) N.K. Sharma; A.K. Rai
The presence of algae in the atmosphere has long been recognized. Besides being a potent health threat to human beings, airborne algae play an important role in the algal dispersal, colonization of new habitats, and extension of harmful algal blooms. This article provides state-of-art information on various aspects of airborne algae with main emphasis on the risks associated with human exposure to aerosolized algal particles and their toxins. © 2011 Elsevier B.V. All rights reserved.
Effect of Nostoc muscorum Ag. ex Born. et Flah. toxins on the upper respiratory tract of mice
(2008) N.K. Sharma; S. Singh; R. Bajpayi; A.K. Rai
Intraperitonial administration of 10 μL of Nostoc muscorum Ag. ex Born. et Flah. crude extract was sufficient enough for the death of male AKR strain mice at 4 h of exposure. Body weight, behavioral and histological observations (necrosis of hepatic cells), and biochemical tests (protein phosphatase inhibition) indicated for the presence of microcystines in the crude extract. Since the cyanobacterium was airborne, the very doses were also administered intranasally into mice. A dose of 10 μL of the crude extract resulted in severe morphological alterations of nasal mucosa at 6 h of exposures, but not beyond the nasal cavity. The presence of protein phosphatases 1 and 2A in the tracheal tissues confirmed the susceptibility of the upper respiratory tissues against microcystins. However, due to the deposition of an insufficient amount of toxins post-nasal cavity respiratory tissues exhibited no response. This lack of a response indicated that the route of exposure plays an important role in conferring toxicity. ©Begell House Inc., 2008.
Freshwater cyanobacterial (blue-green algae) blooms: Causes, consequences and control
(Nova Science Publishers, Inc., 2011) N.K. Sharma; K.K. Choudhary; Rakhi Bajpai; A.K. Rai
Harmful algal blooms (HABs) are a natural phenomena however, due to human activities and interventions, incidences of HABs have increased globally. Onset, development and proliferation of blooms are closely associated with the nutrient enrichment of water bodies (eutrophication) and climatic changes; and their possible interaction. Cyanobacteria are amongst the most successful bloom forming algae. They can convert and use different forms of C, N, P, and S that help them in occupying almost all kinds of aquatic habitats. Moreover, they grow well in shaded light, show resistance against grazing pressure and release allelochemicals to out-compete co-occurring organisms. Presence of gas-vacuoles facilitates their migration in the water column to ensure enough light and nutrient availability. Cyanobacterial blooms adversely affect water quality, structure and composition of biological communities and a range of ecological services. Many of the bloom forming cyanobacteria produce toxins responsible for mass mortality of aquatic and exposed vertebrate populations. This chapter describes the causes and consequences of cyanobacterial blooms and a few measures adopted to control bloom formation and proliferation. The impact of climatic change on cyanobacterial bloom formation has also been discussed. © 2010 Nova Science Publishers, Inc. All rights reserved.
Managing impact of extreme weather events in sugarcane in different agro-climatic zones of Uttar Pradesh
(India Meteorological Department, 2016) R.K. Mall; G. Sonkar; D. Bhatt; N.K. Sharma; A.K. Baxla; K.K. Singh
Sugarcane is a cash crop in Uttar Pradesh; economic condition of the farmers is highly dependent on sugarcane production. However, average yield of the state has gone up from 39.5 t/ha (1950-51) to 59.2 t/ha (2009-10), was observed associated with fluctuating weather conditions, whereas other major sugar producing area in India have average yield of 70 t/ha. The result of the above study showed that there was an average rising trend in the annual minimum temperature (0.03° Cyr-1) over all the agro-climatic zones of the state. Out of nine agro-climatic zones, four zones namely South Western Zone, Central Plain Zone, Western Plain Zone and Eastern Plain zone, which were marked by decreasing annual rainfall trend. However, Vindhyan Zone, Mid Western Zone and Bhabhar and Tarai Zone show rising trend. To explain better relation between cane yield and weather parameters this study also show that maximum, minimum temperature and moisture plays the most important role during germination, tillering, grand growth and ripening phases of the sugarcane. Considering extreme weather, we found that temperature below 25 °C, above 35 °C and 40 °C are slowing down the growth and finally reducing the final yield. It is also noticed that temperature and rainfall extremes had high possibility of governing sugarcane yields but there were also quite a number of instances wherein the extremes couldn’t be reasoned directly for the yield fluctuations. Therefore, to sustain the productivity, this study recommends the improvements of the adoptive responses of varieties, management of the risk associated with extreme weather events by providing weather linked value-added advisory services to the farmers and crop insurance agencies. © 2016, India Meteorological Department. All rights reserved.
Phosphate metabolism in the cyanobacterium Anabaena doliolum under salt stress
(2006) Ashwani K. Rai; N.K. Sharma
In the present study, we have investigated the effects of NaCl concentrations on the growth and phosphate metabolism of an Anabaena doliolum strain isolated from a paddy field, in order to determine the possible effects of salinization. Growth rate, chlorophyll content, and protein content decreased with increasing salt concentration in the growth medium, while carbohydrate concentration increased. Phosphate content and phosphate uptake rate decreased. There was an increase in total alkaline phosphatase activity, with an approximately 7-fold increase in extracellular activity compensating for an approximately 3-fold decrease in cell-bound activity. NaCl effects on protein and chlorophyll concentrations were greater in P-deficient medium, while presence or absence of P in the medium had little effect on cellular carbohydrate concentrations. It is concluded that growth in high salt likely leads to reduced phosphate uptake in A. doliolum. © Springer Science+Business Media, Inc. 2005.
Retrieval of wheat Leaf Area Index using price approach based on inversion of canopy reflectance model
(2005) R.P. Singh; V.K. Dadhwal; K.P. Singh; R.R. Navalgund; R. Sharma; G.D. Bairagi; S.A. Raza; N.K. Sharma
This paper reports estimation of the Leaf Area Index (LAI) of wheat crop from IRS-LISS-III data using Price (1993) approach. Empirical approach for LAI estimation with different NDVI estimation procedures viz. radiance, apparent reflectance and dark object subtraction (DOS) based atmospheric correction were also evaluated. Validation of LAl retrieval and NDVI normalizations were carried out using field level measurements of crop LAI and spectral property using canopy analyzer and spectro-radiometer, respectively over selected fields in Bhopal District, Madhya Pradesh. It was observed that empirical relations are sensitive to the NDVI estimation approach and DOS method performed better as compared to other two approaches. It was also observed that LAI estimation from Price algorithm is sensitive to the crop attenuation coefficients. Crop specific attenuation coefficients reported in literature for Indian cultivars gave higher accuracy. The root mean square (RMS) error of 0.77 for LAI estimation was achieved using above described approach.