Dinesh K. Saxena

Bio: Dinesh K. Saxena is an academic researcher from Bareilly College. The author has contributed to research in topics: Hypnum cupressiforme & Moss. The author has an hindex of 5, co-authored 8 publications receiving 92 citations. Previous affiliations of Dinesh K. Saxena include M. J. P. Rohilkhand University.

Chlorophyll a fluorescence measurements for validating the tolerant bryophytes for heavy metal (Pb) biomapping

Abstract: Chlorophyll a fluorescence measurement has been used as a probe to examine and compare the tolerance of bryophytes against heavy metals stress caused in field trials and under laboratory conditions. The ratio of variable fluorescence (F v ) to the maximal fluorescence (F m ) in dark-adapted leaves termed as 'maximal photochemical efficiency' of PS II (F v /F m ) was measured in selected bryophytes to study their quantum efficiency. Tolerance potential for lead (Pb) in bryophytes was evaluated statistically by using Dunkun's Multiple Range Test, which indicates that lead-treated moss Grimmia anodon and liverwort Riccardia pinguis exhibited the most physiological damage of PS II. Conversely, minimal changes were observed in Barbula vinealis and Thuidium cymbifolium. Field trials of all the selected bryophytes exhibited moderate changes in the F v /F m ratio except G. anodon and R. pinguis. This variation in susceptibility is due to stress caused by metal pollution. Therefore, it is desirable to study the relative tolerance potential of bryophytes as little is known about their susceptibility to metals. Validated tolerant bryophytes species will have multiple applications in studies of biomapping, forest enrichment and carbon gain.

Atmospheric Heavy Metal Deposition in Garhwal Hill Area (India): Estimation Based on Native Moss Analysis

Abstract: Atmospheric distribution of metals was evaluated throughout the Garhwal Hills region of Uttaranchal, India by analysis of native moss species, Rhodobryum giganteum and Hypnum cupressiforme. The performance of these two mosses as biomonitors was studied in relation to the accumulation of atmophile elements. The elements Cd, Zn, Cu and Pb were surveyed at 33 sampling sites by conducting a passive monitoring technique using these mosses. Sampling was carried out from March 2004 to February 2005 for three different seasons (summer, monsoon and winter) in four directions nearly equidistant from a control site (Chamba Forest) where the moss samples were originally collected. Bioaccumulative ability in these two mosses was evaluated statistically using Dunkun’s Multiple Range test. Results indicate that summer has a significantly higher concentration of the metals Zn, Pb, Cu, Cd than winter and monsoon. Similarly, significant distance and seasonal differences were calculated and are presented on contour maps. The novel aspect of this study is that it actually delivered any information at all on atmospheric deposition in India and Asia, where very limited information is available in this field. Therefore, this finding is a gap filling one.

Retrospective metal data of the last 100 years deduced by moss, Barbula sp. from Mussoorie city, Garhwal Hills, India

Abstract: This communication is the first attempt at contributing to monitoring and systematic gathering of information on the heavy metal profile of the environment, i.e. retrospective study of the environmental metal data (Pb, Fe, Zn, Cd and Ni) of the past 100 years, i.e. 1895-1999 from Mussoorie city, Garhwal Hills, India by analysing herbarium voucher specimens of moss, Barbula species as a tool. Our laboratory has been using this tool successfully to delineate the past metal profile by analysing moss samples. A significant increase in metal content was observed by non-invasive analysis of herbarium specimens of Barbula sp. belonging to Mussoorie city, which seems to be a reflection of atmospheric metal load. The lowest concentrations were found in the voucher specimens of the early period, i.e. 1895 and the level increased over a period of time. However, difference in trend was also observed. The maximum significant increase observed for metals Zn, Ni and Pb was 5743.369, 3195.238 and 1362.207% respectively, with respect to first metal data of the year 1895 in Barbula sp. The same could be due to an increase in metal load resulting from progressive industrialization in the early period. The ratios between the content of the various metals in bryophyte tissue increased nearly identically for all metals examined. The novel aspect of this study is that it provides information on retrospective metal data of the past 100 year from Mussorie hills (India) as well as Asia by analysis of bryophytes, where no information was earlier available.

Bryomonitoring of Atmospheric Elements in Rhodobryum giganteum (Schwaegr.) Par., Growing in Uttarakhand Region of Indian Himalayas

Abstract: Mosses are useful biological indicators of environmental contamination for a variety of metals originated from natural and artificial sources. The research aims on recent changes in air quality and estimate the atmospheric metal deposition and its seasonal/annual trend by using passive biomonitoring technique. The level of Cu, Cd, Zn and Pb was estimated in samples of the Rhodobryum giganteum (Schwaegr.) Par., from Mukteshwar, Nainital, Almora and Pithoragarh of Kumaon and Chamba, Mussoorie, Dhanaulti and Kampty Fall of Garhwal region of Uttarakhand, India. The study considers the level and possible sources of atmospheric pollutants in catchment sites and their effect on naturally growing moss. The moss samples were collected from each season consist of fourth month i.e., winter, summer and monsoon from equi-distances during years 2008 to 2012. The high metal content was found at Nainital (Kumaon) and Mussoorie (Garhwal) due to heavy traffic activity. The results showed that the collected moss species was capable of successfully delineating the expected differences in atmospheric metal deposition within the study area. The metal deposition loads were recorded in the order of Zn > Pb > Cu > Cd during the five years study period. A general increasing metal deposition trend was also observed, i.e., annual average (over seasons) metal loads in 2012 increased when compared with their loads in 2008. Development is almost always accompanied with negative changes in air quality and adverse impacts of air pollution on human health, agricultural production and natural ecosystems that need to monitor and do mitigate, therefore, such investigations is highly demanded. Present information will be very helpful for environmentalist/policy makers in making effective strategies to mitigate the environment related problems.

Biomonitoring of metal deposition by using moss transplant method through Hypnum cupressiforme (Hedw.) in Mussoorie.

Abstract: Metals Cu, Zn, Cd and Pb were surveyed at 14 sampling sites by using moss Hypnum cupressiforme through active monitoring technique. Samples were transplanted in all four directions of Mussoorie city and were harvested after exposure of four months (representing each season) to analyze metal precipitation and its trend at different sites during 2005. Bioaccumulation ability for metals was evaluated seasonally exhibiting maximum in summer followed by winter and minimum in rainy season. However, at some places Cu shows highly significant values in rainy season in comparison to winter. In case of Zn and Pb significantly different (p Pb > Cu > Cd.

Chlorophyll a fluorescence as a tool to monitor physiological status of plants under abiotic stress conditions

Abstract: Plants living under natural conditions are exposed to many adverse factors that interfere with the photosynthetic process, leading to declines in growth, development, and yield. The recent development of Chlorophyll a fluorescence (ChlF) represents a potentially valuable new approach to study the photochemical efficiency of leaves. Specifically, the analysis of fluorescence signals provides detailed information on the status and function of Photosystem II (PSII) reaction centers, light-harvesting antenna complexes, and both the donor and acceptor sides of PSII. Here, we review the results of fast ChlF analyses of photosynthetic responses to environmental stresses, and discuss the potential scientific and practical applications of this innovative methodology. The recent availability of portable devices has significantly expanded the potential utilization of ChlF techniques, especially for the purposes of crop phenotyping and monitoring.

Frequently asked questions about in vivo chlorophyll fluorescence: Practical issues

Abstract: The aim of this educational review is to provide practical information on the hardware, methodology, and the hands on application of chlorophyll (Chl) a fluorescence technology. We present the paper in a question and answer format like frequently asked questions. Although nearly all information on the application of Chl a fluorescence can be found in the literature, it is not always easily accessible. This paper is primarily aimed at scientists who have some experience with the application of Chl a fluorescence but are still in the process of discovering what it all means and how it can be used. Topics discussed are (among other things) the kind of information that can be obtained using different fluorescence techniques, the interpretation of Chl a fluorescence signals, specific applications of these techniques, and practical advice on different subjects, such as on the length of dark adaptation before measurement of the Chl a fluorescence transient. The paper also provides the physiological background for some of the applied procedures. It also serves as a source of reference for experienced scientists.

Frequently asked questions about chlorophyll fluorescence, the sequel

Abstract: Using chlorophyll (Chl) a fluorescence many aspects of the photosynthetic apparatus can be studied, both in vitro and, noninvasively, in vivo. Complementary techniques can help to interpret changes in the Chl a fluorescence kinetics. Kalaji et al. (Photosynth Res 122:121–158, 2014a) addressed several questions about instruments, methods and applications based on Chl a fluorescence. Here, additional Chl a fluorescence-related topics are discussed again in a question and answer format. Examples are the effect of connectivity on photochemical quenching, the correction of F V /F M values for PSI fluorescence, the energy partitioning concept, the interpretation of the complementary area, probing the donor side of PSII, the assignment of bands of 77 K fluorescence emission spectra to fluorescence emitters, the relationship between prompt and delayed fluorescence, potential problems when sampling tree canopies, the use of fluorescence parameters in QTL studies, the use of Chl a fluorescence in biosensor applications and the application of neural network approaches for the analysis of fluorescence measurements. The answers draw on knowledge from different Chl a fluorescence analysis domains, yielding in several cases new insights.

Experimental in vivo measurements of light emission in plants: a perspective dedicated to David Walker.

Abstract: This review is dedicated to David Walker (1928–2012), a pioneer in the field of photosynthesis and chlorophyll fluorescence. We begin this review by presenting the history of light emission studies, from the ancient times. Light emission from plants is of several kinds: prompt fluorescence (PF), delayed fluorescence (DF), thermoluminescence, and phosphorescence. In this article, we focus on PF and DF. Chlorophyll a fluorescence measurements have been used for more than 80 years to study photosynthesis, particularly photosystem II (PSII) since 1961. This technique has become a regular trusted probe in agricultural and biological research. Many measured and calculated parameters are good biomarkers or indicators of plant tolerance to different abiotic and biotic stressors. This would never have been possible without the rapid development of new fluorometers. To date, most of these instruments are based mainly on two different operational principles for measuring variable chlorophyll a fluorescence: (1) a PF signal produced following a pulse-amplitude-modulated excitation and (2) a PF signal emitted during a strong continuous actinic excitation. In addition to fluorometers, other instruments have been developed to measure additional signals, such as DF, originating from PSII, and light-induced absorbance changes due to the photooxidation of P700, from PSI, measured as the absorption decrease (photobleaching) at about 705 nm, or increase at 820 nm. In this review, the technical and theoretical basis of newly developed instruments, allowing for simultaneous measurement of the PF and the DF as well as other parameters is discussed. Special emphasis has been given to a description of comparative measurements on PF and DF. However, DF has been discussed in greater details, since it is much less used and less known than PF, but has a great potential to provide useful qualitative new information on the back reactions of PSII electron transfer. A review concerning the history of fluorometers is also presented.