Chlorophyll fluorescence quenching and violaxanthin deepoxidation of FBPase antisense plants at low light intensities and low temperatures

Abstract

Genetically modified potato (Solanum tuberosum L. cv. Desiree) and tobacco (Nicotiana tabacum cv. Samsun N.N.) plants were used to analyze the effects exerted by the chloroplastic (cp) fructose‐ 1,6‐bisphosphatase (FBPase) on the regulation of light energy discrimination at the level of photosystem II. The cp‐FBPase activity was progressively inhibited by an mRNA antisense to this FBPase. The chlorophyll fluorescence quenching parameters of these transgenic plants were compared to those of wild‐type and transgenic plants that were acclimated to low temperatures. In particular various lines of the transgenic potato and tobacco plants were exposed to a temperature treatment of 10 and 20°C for 10 days. Light intensities were kept low to reduce photoinhibition so that we could analyze exclusively the effects of a modification in the carbon fixation cycle on the chlorophyll fluorescence quenching parameters. The photon flux densities (PFDs) employed at the level of the middle leaves of all plants were set to two different values of 10 μmol m−2 s−1 and 50 μmol m−2 s−1. Subsequent to this 10‐day acclimation the chlorophyll‐fluorescence parameters of all plants were measured. Photoinhibition as expressed by the Fy/Fm ratio was minor in plants subjected to a PFD of 10 μmol m−2 s−1. Higher photon fluence rates of 50 μmol m−2 s−1 at temperatures of 10°C gave rise to a significant reduction in the Fy/Fm ratios obtained from the transgenic plants which were characterized by a restriction in cp‐FBPase capacity to 20% of normal activity. Furthermore, a progressive inhibition of the cp‐FBPase activity induced an amplified nonphotochemical quenching of chlorophyll fluorescence with in the genetically manipulated species (except at 10°C and 50 μmol m−2 s−1). The increase in nonphotochemical quenching depended upon light and temperature. Photochemical quenching of light quanta within the antisense plants declined relative to that in the wild type. To further characterize the mechanisms producing higher levels of nonphotochemical fluorescence quenching. we analyzed several of the xanthophyll cycle pigments. The deepoxidation state of the xanthophyll cycle pigments in potato plants increased with attenuating FBPase activities under all conditions. For tobacco plants, this elevation of the deepoxidation state was only observed at a PFD of 50 μmol m−2 s−1.

Lunisolar tidal force and its relationship to chlorophyll fluorescence in Arabidopsis thaliana

“…7 In addition, attention was drawn to an apparent concordance between the daily variation in tree stem diameter, dD, and the variation in the gravimetric tide, dg; 18,19 and, similarly, with the aid of the Etide program, Fisahn et al observed that roots of Arabidopsis thaliana appeared to perceive the lunisolar tidal acceleration, this perception being expressed in a tide-like variation in the rate of root elongation. 20 In continuation of work by Fisahn et al on chlorophyll fluorescence, 21 as initiated by Sachs, 2 the present study demonstrates a close correlation between the yield of chlorophyll fluorescence Ft derived from Photosystem II in Arabidopsis thaliana and the lunisolar tidal force. In particular, we tested the hypothesis that oscillations in the yield of chlorophyll fluorescence Ft emerging from the reaction centers of PSII under conditions of continuous illumination exhibit phase congruence and period synchrony with the lunisolar tidal force, as estimated by the Etide software application.…”

“…1). 21,32 Continuous records of the current fluorescence yield Ft The current fluorescence yield, Ft, is continuously monitored in the Measure-mode of the Imaging-Pam when the measuring light (ML) is switched on. Ft images could be saved without the application of a saturating light pulse by operation of the "Ft only clock" option.…”

“…To determine the quantum yield of photochemical energy conversion in PS II, a series of saturating light pulses was applied at 10 min intervals for several days at continuous photon flux densities of 100 mmol quanta / m 2 s. 21,[31][32][33][34] Drift elimination To amplify the actual small amplitudes of the circatidal kinetics superimposed upon the recorded chlorophyll fluorescence signals during the observational period, polynomials up to sixthorder were fitted to the measured kinetics and subsequently subtracted from the experimentally obtained results. 9,35 These linearized leaf chlorophyll fluorescence timecourses were then aligned with the estimated timecourse of the lunisolar gravity profile derived from the Etide software.…”

Photosynthesis and metabolism interact during acclimation of Arabidopsis thaliana to high irradiance and sulphur depletion

“…At the start of each measurement, a plant was dark adapted for 20 min for determination of F o and F m (Bilger et al . 1995; Fisahn et al . 1995).…”

“…Chlorophyll fluorescence imaging was performed by an IMAGING-PAM chlorophyll fluorometer (Heinz Walz GmbH, Effeltrich, Germany). At the start of each measurement, a plant was dark adapted for 20 min for determination of Fo and Fm Fisahn et al 1995).Then, the first level of PFD (4 mmol m -2 s -1 ) was applied and a set of values was measured. The same procedure was repeated for each PFD level (10,50,100,225,365,585 and 955 mmol m -2 s -1 ).…”