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Natural SiO2 nanoparticles (SiO2-NPs) are widely distributed in the environment, and at the same time, synthetic SiO2-NP may be applied in agriculture. Evaluations of physiological responses to SiO2-NPs treatment of plants are controversial. They are often performed at adaxial leaf sides whereas NPs permeate leaf tissues through stomata located at the abaxial leaf side in the majority of bifacial plants. We measured coefficients of the functional dorsoventral asymmetry of NPs-stressed Сhelidonium majus leaves, S, by values of the CO2 assimilation rate (SPN), dark respiration (SR), maximal and operating quantum yields of photosystem II (SFv/Fm, SFv'/Fm'; using PAM-fluorometry), and oxygen coefficients of photosynthesis (SΨO2; using photoacoustics). The results indicated that SPN and SΨO2 were significantly influenced by SiO2-NPs treatment, since PN and ΨO2 were declining more markedly when the light was directed to the abaxial side of leaves compared to the adaxial side. Overall, SiO2-NPs-induced stress increased 'anoxygenity' of photosynthesis. [ABSTRACT FROM AUTHOR] more...

Adaptation and functional significance of chlorophyll deficit in the light green leaf sectors of variegated plants are little known. Efficiency of photosystem II for dark and light adapted states (F v /F m and ΔF/F m ') and fluorescence decrease rates (R fd ) of light green leaf sectors of Dracaena fragrans L. were studied by methods of PAM-fluorometry and video registration. In addition, white light reflectance and transmittance of these leaf sectors were measured using an integrating sphere. Absorption was calculated from reflectance and transmittance. Net CO 2 assimilation rates (P N ) were measured using a flow chamber and photolytic O 2 evolution rates (PAYO 2 ) were studied by a novel method of Fourier photoacoustics which is insensitive to respiration, photorespiration and other processes of O 2 uptake. All the photosynthetic parameters (F v /F m , ΔF/F m ', P N and PAYO 2 ) were found to be very close between light green and normal green leaf sectors, whereas chlorophyll content and light absorption were 7.5-fold and 1.47-fold different respectively. Contradiction between low chlorophyll absorption and high (as in normal green sectors) rate of oxygenic photosynthesis in light-green sectors was proposed to be a consequence of different contribution of cyclic electron transport around PSII (CET-PSII) and/or around PSI (CET-PSI) in the total photosynthesis occurring in these sectors. Particularly, it cannot be excluded, that some part of CET activity occurring in normal green leaf sectors may be lost in the light green sectors retaining the same linear (non-cyclic) electron transport (LET) activity as in normal green sectors., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Masson SAS. All rights reserved.) more...

Non-destructive methods for the assessment of photosynthetic parameters of plants are widely applied to evaluate rapidly the photosynthetic performance, plant health, and shifts in plant productivity induced by environmental and cultivation conditions. Most of these methods are based on measurements of chlorophyll fluorescence kinetics, particularly on pulse modulation (PAM) fluorometry. In this paper, fluorescence methods are critically discussed in regard to some their possibilities and limitations inherent to vascular plants and microalgae. Attention is paid to the potential errors related to the underestimation of thylakoidal cyclic electron transport and anoxygenic photosynthesis. PAM-methods are also observed considering the color-addressed measurements. Photoacoustic methods are discussed as an alternative and supplement to fluorometry. Novel Fourier modifications of PAM-fluorometry and photoacoustics are noted as tools allowing simultaneous application of a dual or multi frequency measuring light for one sample., Competing Interests: Conflict of interestThe authors declare that there are no conflicts of interest., (© Prof. H.S. Srivastava Foundation for Science and Society 2022, Springer Nature or its licensor (e.g. a society or other partner) holds exclusive rights to this article under a publishing agreement with the author(s) or other rightsholder(s); author self-archiving of the accepted manuscript version of this article is solely governed by the terms of such publishing agreement and applicable law.) more...