Duststorm-Facilitated Improvement of the Photosynthetic Efficiency of Tamarix ramosissima L. in the Oasis-Desert Ecotone, Northwest China

2012 ◽  
Vol 518-523 ◽  
pp. 5035-5039
Author(s):  
Wei Han ◽  
Ling Cao ◽  
Haimid Yimit
Keyword(s):  
Photosynthetic Efficiency ◽  
Weather Conditions ◽  
Northwest China ◽  
Tamarix Ramosissima ◽  
Taklimakan Desert ◽  
Chl A ◽  
Fluorescence Parameters ◽  
Mature Leaves ◽  
Chl A Fluorescence ◽  
Maximum Period

The photosynthetic efficiency of Tamarix ramosissima Ledeb., one of the major natural plants in the southern oasis-desert ecotone of the Taklimakan Desert, was investigated to assess the ecological effects of duststorms on T ramosissima Ledeb. We measured daily chlorophyll a (Chl a) fluorescence parameters of mature leaves of healthy 10-years old T. ramosissima L. during months of July and August in 2008, using a portable modulated Chl a fluorometer PAM-2100 and three duststorm days were singled out to assess the affects of duststorms on the photosynthetic efficiency. Our results showed that duststorms increased the energy absorption and the increased absorption then enhanced the photosynthetic efficiency of T. ramosissima L. under duststorm weather conditions. Our results also showed that the qP (quenching coefficients for photosynthesis) was significantly decreased and qN (quenching coefficients for non-photosynthesis) was significantly increased during the maximum period of solar readiation between 14:00 and 16:00 under normal conditions, implying that stress might occur in normal weather conditions, but lowered stress to T ramosissima Ledeb. during duststorm weather conditions. In a word, duststorm-facilitated might provide favorable opportunities for constructing and expansing oasis-desert ecotone.

Chl-a fluorescence parameters as biomarkers of metal toxicity in fluvial biofilms: an experimental study

Hydrobiologia ◽  
2011 ◽  
Vol 673 (1) ◽  
pp. 119-136 ◽  
Author(s):  
Natàlia Corcoll ◽  
Berta Bonet ◽  
Manel Leira ◽  
Helena Guasch
Keyword(s):  
Experimental Study ◽  
Metal Toxicity ◽  
Chl A ◽  
Fluorescence Parameters ◽  
Chl A Fluorescence

A Poisson-Pareto model of Chl-a fluorescence signals in marine environments

2015 ◽  
Vol 55 ◽  
pp. 373
Author(s):  
Stephen Woodcock ◽  
Bojana Manojlovic ◽  
Mark Baird ◽  
Peter Ralph
Keyword(s):  
Marine Environments ◽  
Chl A ◽  
Chl A Fluorescence ◽  
Pareto Model

Non-photochemical quenching of chlorophyll a fluorescence: early history and characterization of two xanthophyll-cycle mutants of Chlamydomonas reinhardtii

2002 ◽  
Vol 29 (10) ◽  
pp. 1141 ◽  
Author(s):  
Govindjee ◽  
Manfredo J. Seufferheld
Keyword(s):  
Chlamydomonas Reinhardtii ◽  
Oxygen Evolution ◽  
Xanthophyll Cycle ◽  
Photochemical Quenching ◽  
Chl A ◽  
Fluorescence Transient ◽  
Chl A Fluorescence ◽  
Non Photochemical Quenching

This paper deals first with the early, although incomplete, history of photoinhibition, of 'non-QA-related chlorophyll (Chl) a fluorescence changes', and the xanthophyll cycle that preceded the discovery of the correlation between non-photochemical quenching of Chl a fluorescence (NPQ) and conversion of violaxanthin to zeaxanthin. It includes the crucial observation that the fluorescence intensity quenching, when plants are exposed to excess light, is indeed due to a change in the quantum yield of fluorescence. The history ends with a novel turn in the direction of research — isolation and characterization of NPQ xanthophyll-cycle mutants of Chlamydomonas reinhardtii Dangeard and Arabidopsis thaliana (L.) Heynh., blocked in conversion of violaxanthin to zeaxanthin, and zeaxanthin to violaxanthin, respectively. In the second part of the paper, we extend the characterization of two of these mutants (npq1, which accumulates violaxanthin, and npq2, which accumulates zeaxanthin) through parallel measurements on growth, and several assays of PSII function: oxygen evolution, Chl a fluorescence transient (the Kautsky effect), the two-electron gate function of PSII, the back reactions around PSII, and measurements of NPQ by pulse-amplitude modulation (PAM 2000) fluorimeter. We show that, in the npq2 mutant, Chl a fluorescence is quenched both in the absence and presence of 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU). However, no differences are observed in functioning of the electron-acceptor side of PSII — both the two-electron gate and the back reactions are unchanged. In addition, the role of protons in fluorescence quenching during the 'P-to-S' fluorescence transient was confirmed by the effect of nigericin in decreasing this quenching effect. Also, the absence of zeaxanthin in the npq1 mutant leads to reduced oxygen evolution at high light intensity, suggesting another protective role of this carotenoid. The available data not only support the current model of NPQ that includes roles for both pH and the xanthophylls, but also are consistent with additional protective roles of zeaxanthin. However, this paper emphasizes that we still lack sufficient understanding of the different parts of NPQ, and that the precise mechanisms of photoprotection in the alga Chlamydomonas may not be the same as those in higher plants.

scholarly journals From the shape of the vertical profile of in vivo fluorescence to Chlorophyll-<i>a</i> concentration

2011 ◽  
Vol 8 (8) ◽  
pp. 2391-2406 ◽  
Author(s):  
A. Mignot ◽  
H. Claustre ◽  
F. D'Ortenzio ◽  
X. Xing ◽  
A. Poteau ◽  
...  
Keyword(s):  
Mixed Layer ◽  
Mixed Layer Depth ◽  
Homogeneous Layer ◽  
Fluorescence Signal ◽  
Vertical Profiles ◽  
Shape Parameters ◽  
Chl A ◽  
In Vivo Fluorescence ◽  
Chl A Fluorescence

Abstract. In vivo fluorescence of Chlorophyll-a (Chl-a) is a potentially useful property to study the vertical distribution of phytoplankton biomass. However the technique is presently not fully exploited as it should be, essentially because of the difficulties in converting the fluorescence signal into an accurate Chl-a concentration. These difficulties arise noticeably from natural variations in the Chl-a fluorescence relationship, which is under the control of community composition as well as of their nutrient and light status. As a consequence, although vertical profiles of fluorescence are likely the most recorded biological property in the open ocean, the corresponding large databases are underexploited. Here with the aim to convert a fluorescence profile into a Chl-a concentration profile, we test the hypothesis that the Chl-a concentration can be gathered from the sole knowledge of the shape of the fluorescence profile. We analyze a large dataset from 18 oceanographic cruises conducted in case-1 waters from the highly stratified hyperoligotrophic waters (surface Chl-a = 0.02 mg m−3) of the South Pacific Gyre to the eutrophic waters of the Benguela upwelling (surface Chl-a = 32 mg m−3) and including the very deep mixed waters in the North Atlantic (Mixed Layer Depth = 690 m). This dataset encompasses more than 700 vertical profiles of Chl-a fluorescence as well as accurate estimations of Chl-a by High Performance Liquid Chromatography (HPLC). Two typical fluorescence profiles are identified, the uniform profile, characterized by a homogeneous layer roughly corresponding to the mixed layer, and the non-uniform profile, characterized by the presence of a Deep Chlorophyll Maximum. Using appropriate mathematical parameterizations, a fluorescence profile is subsequently represented by 3 or 5 shape parameters for uniform or non-uniform profiles, respectively. For both situations, an empirical model is developed to predict the "true" Chl-a concentration from these shape parameters. This model is then used to calibrate a fluorescence profile in Chl-a units. The validation of the approach provides satisfactory results with a median absolute percent deviation of 33 % when comparing the HPLC Chl-a profiles to the Chl-a-calibrated fluorescence. The proposed approach thus opens the possibility to produce Chl-a climatologies from uncalibrated fluorescence profile databases that have been acquired in the past and to which numerous new profiles will be added, thanks to the recent availability of autonomous platforms (profiling floats, gliders and animals) instrumented with miniature fluorometers.

scholarly journals Characteristics of solar radiation at Xiaotang, in the northern marginal zone of the Taklimakan Desert

PeerJ ◽  
2021 ◽  
Vol 9 ◽  
pp. e12373
Author(s):  
Lili Jin ◽  
Sasa Zhou ◽  
Qing He ◽  
Alim Abbas
Keyword(s):  
Solar Radiation ◽  
Scattered Radiation ◽  
Weather Conditions ◽  
Taklimakan Desert ◽  
Observation Data ◽  
Total Radiation ◽  
Direct Radiation ◽  
Northern Margin ◽  
Monthly Total ◽  
Atmospheric Transmittance

The characteristics of solar radiation and the influence of sand and dust on solar radiation in the northern margin of Taklimakan Desert were analyzed using radiation observation data from 2018. The results showed that the annual total radiation, direct radiation, and scattered radiation at Xiaotang were 5,781.8, 2,337.9, and 3,323.8 MJ m−2, respectively. The maximum monthly total radiation, direct radiation, and scattered radiation were observed in July (679.8 MJ m−2), August (317.3 MJ m−2), and May (455.7 MJ m−2), respectively. The aerosol optical depth corresponded well with the scattered radiation, and the maximum value was in May. Further analysis showed a significant correlation between the total radiation and solar height angle under different weather conditions. Under the same solar height angle, total radiation was higher during clear days but lower on sandstorm days. Calculation of atmospheric transmittance showed that the average atmospheric transmittance on a clear day was 0.67; on sand-and-dust days, it was 0.46. When the atmospheric transmittance was 0.5, the increase in scattering radiation by aerosol in the air began to decrease. Probability analysis of radiation indicated the following probabilities of total radiation <500 W m−2 occurring on clear, floating-dust, blowing-sand, and sandstorm days: 67.1%, 76.3%, 76.1%, and 91.8%, respectively. Dust had the greatest influence on direct radiation; the probabilities of direct radiation <200 W m−2occurring on clear, floating-dust, blowing-sand, and sandstorm days were 44.5%, 93.5%, 91.3%, and 100%, respectively, whereas those of scattered radiation <600 W m−2were 100%, 99.1%, 98.1%, and 100%, respectively. Therefore, the presence of dust in the air will reduce scattered radiation.

Temporal and spatial variations of sandstorm and the related meteorological influences over northern China in the 21st century

2021 ◽  
Author(s):  
Jie Yang ◽  
Tianliang Zhao
Keyword(s):  
Land Surface ◽  
Source Region ◽  
Northern China ◽  
Northwest China ◽  
Gobi Desert ◽  
Taklimakan Desert ◽  
Observation Data ◽  
Average Wind Speed ◽  
Modis Ndvi ◽  
Temporal And Spatial

&lt;p&gt;In this study, we used the sandstorm data of 233 meteorological stations in northern China, conventional meteorological observation data and MODIS-NDVI data in the 40 years from 1980 to 2019 to analyze the spatio-temporal variation of sandstorms in northern China and its related meteorological effects in this century.&lt;/p&gt;&lt;p&gt;The results show that: 1) The average number of sandstorm days in northern China has been fluctuating and decreasing since the beginning of this century, and increasing from 2017 to 2019. Spring is the main season of dust storm, and the springtime proportion of sandstorm days decreases year by year. 2) In the 1980s and 1990s, sandstorms covered almost covered the whole northwest region; Since the beginning of this century, the range of sandstorm days in the whole Northwest China has shown an obvious decadal downward trend. The spatial pattern of sandstorm days in northern China has been shrinking and moving westward since 2000, and the dominant position of the Gobi Desert in the Asian dust source region has been decreasing year by year. The high sandstorm days were located in the Taklimakan Desert with the increasing trend of sandstorm days year by year. 3) The temporal and spatial variation of sandstorm days in northern China is closely related to the increase of vegetation cover with the greenness and wetness of the land surface, the decreases of average wind speed and gale days, and the significant increase of annual precipitation in northern China after 2000.&lt;/p&gt;

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