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Responses of chlorophyll fluorescence parameters of the facultative halophyte and C.sub.3-CAM intermediate species Mesembryanthemum crystallinum to salinity and high irradiance stress.(Author abstract)

Broetto, Fernando ; Duarte, Heitor Monteiro ; Luttge, Ulrich

Journal of Plant Physiology, July 26, 2007, Vol.164(7), p.904(9) [Periódico revisado por pares]

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  • Título:
    Responses of chlorophyll fluorescence parameters of the facultative halophyte and C.sub.3-CAM intermediate species Mesembryanthemum crystallinum to salinity and high irradiance stress.(Author abstract)
  • Autor: Broetto, Fernando ; Duarte, Heitor Monteiro ; Luttge, Ulrich
  • Assuntos: Fluorescence -- Analysis ; Chromophores -- Analysis ; Chlorophyll -- Analysis
  • É parte de: Journal of Plant Physiology, July 26, 2007, Vol.164(7), p.904(9)
  • Descrição: To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.jplph.2006.04.010 Byline: Fernando Broetto (a), Heitor Monteiro Duarte (b), Ulrich Luttge (b) Keywords: C.sub.3-photosynthesis; Chlorophyll fluorescence; Crassulacean acid metabolism; Irradiance; Malate accumulation; Mesembryanthemum crystallinum; Salinity Abbreviations: ABA, absisic acid; ARS, antioxidative response system; CAM, crassulacean acid metabolism; F.sub.v/F.sub.m, potential quantum yield; NPQ, non-photochemical dissipation of absorbed energy; PAM, pulse-amplitude modulated photosynthesis yield analyser; PSII, photosystem II; ROS, reactive oxygen species; SOD, superoxide dismutase; [DELTA]F/F.sub.m', effective quantum yield of PSII Abstract: Mesembryanthemum crystallinum L. (Aizoaceae) is a facultative annual halophyte and a C.sub.3-photosynthesis/crassulacean acid metabolism intermediate species currently used as a model plant in stress physiology. Both salinity and high light irradiance stress are known to induce CAM in this species. The present study was performed to provide a diagnosis of alterations at the photosystem II level during salinity and irradiance stress. Plants were subjected for up to 13 days to either 0.4M NaCl salinity or high irradiance of 1000[mu]molm.sup.-2 s.sup.-1, as well as to both stress factors combined (LLSA=low light plus salt; HLCO=high light of 1000[mu]molm.sup.-2 s.sup.-1, no salt; HLSA=high light plus salt). A control of LLCO=low light of 200[mu]molm.sup.-2 s.sup.-1, no salt was used. Parameters of chlorophyll a fluorescence of photosystem II (PSII) were measured with a pulse amplitude modulated fluorometer. HLCO and LLSA conditions induced a weak degree of CAM with day/night changes of malate levels ([DELTA]malate) of [approximately equal to]12mM in the course of the experiment, while HLSA induced stronger CAM of [DELTA]malate [approximately equal to]20mM. Effective quantum yield of PSII, [DELTA]F/F'.sub.m, was only slightly affected by LLSA, somewhat reduced during the course of the experiment by HLCO and clearly reduced by HLSA. Potential quantum efficiency of PSII, F.sub.v/F.sub.m, at predawn times was not affected by any of the conditions, always remaining at [greater than or equal to]0.8, showing that there was no acute photoinhibition. During the course of the days HL alone (HLCO) also did not elicit photoinhibition; salt alone (LLSA) caused acute photoinhibition which was amplified by the combination of the two stresses (HLSA). Non-photochemical, NPQ, quenching remained low (<0.5) under LLCO, LLSA and HLCO and increased during the course of the experiment under HLSA to 1-2. Maximum apparent photosynthetic electron transport rates, ETR.sub.max, declined during the daily courses and were reduced by LLSA and to a similar extent by HLSA. It is concluded that M. crystallinum expresses effective stress tolerance mechanisms but photosynthetic capacity is reduced by the synergistic effects of salinity and light irradiance stress combined. Author Affiliation: (a) Department of Chemistry and Biochemistry, Institute of Biosciences, Sao Paulo State University (UNESP), 18618-000 Botucatu, SP, Brazil (b) Institute of Botany, Darmstadt University of Technology, SchnittpahnstraAe 3-5, D-64287 Darmstadt, Germany Article History: Received 22 March 2006; Accepted 24 April 2006
  • Idioma: English

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