EDITORIAL

O. PRÁŠIL, RADEK KAŇA, G. GOVINDJEE

Photosynthetica 2022, 60(1):1-2 | DOI: 10.32615/ps.2022.017  

Contents of photosynthetic pigments and ratios of chlorophyll a/b and chlorophylls to carotenoids (a+b)/(x+c) in C₄ plants as compared to C₃ plants

H.K. LICHTENTHALER, F. BABANI

Photosynthetica 2022, 60(1):3-9 | DOI: 10.32615/ps.2021.041  

The content of chlorophylls (Chl) (a+b), total carotenoids (x+c), and the pigment ratios of Chl a/b and Chls to carotenoids (a+b)/(x+c) of green leaves of five C₄ plants were determined and compared to those of C₃ plants. The C₄ plants were: Pacific and Chinese silvergrass (Miscanthus floridulus and Miscanthus sinensis), sugar cane (Saccharum officinarum) as well as feed and sugar maize (Zea mays). The three C₃ plants were beech, ginkgo, and oak. C₄ plants possess higher values for the ratio Chl a/b...

Differences in susceptibility to photoinhibition do not determinegrowth rate under moderate light in batch or turbidostat - a studywith five green algae

H. MATTILA, D. VALEV, K.B. MISHRA, V. HAVURINNE, O. VIRTANEN, M. ANTINLUOMA, E. TYYSTJÄRVI

Photosynthetica 2022, 60(1):10-20 | DOI: 10.32615/ps.2021.054  

To understand growth limitations of photosynthetic microorganisms, and to investigate whether batch growth or certain photosynthesis-related parameters predict a turbidostat (continuous growth at constant biomass concentration) growth rate, five green algal species were grown in a photobioreactor in batch and turbidostat conditions and their susceptibilities to photoinhibition of photosystem II as well as several photosynthetic parameters were measured. Growth rates during batch and turbidostat modes varied independently of each other; thus, a growth rate measured in a batch cannot be used to determine the continuous growth rate. Greatly different...

George C. Papageorgiou and the protective role of glycine betaine in activation and stabilization of the oxygen-evolving photosystem II complex

N. MURATA, K. STAMATAKIS

Photosynthetica 2022, 60(1):21-24 | DOI: 10.32615/ps.2021.056  

We present here our adventures in research in photosynthesis with George C. Papageorgiou (1933-2020) focusing on George's initiative in the discovery of the protective effects of glycine betaine on the oxygen-evolving photosystem II complex. We end with a brief description of research on glycine betaine-synthesizing transgenic cyanobacteria. Two of us, Norio Murata (in Japan) and Kostas Stamatakis (in Greece), and all our collaborators, have the highest respect for George, and we miss him and our intense discussions with him on various topics of photosynthesis research.

Light quality, oxygenic photosynthesis and more

D. LAZAR, A. STIRBET, L.O. BJÖRN, G. GOVINDJEE

Photosynthetica 2022, 60(1):25-58 | DOI: 10.32615/ps.2021.055  

Oxygenic photosynthesis takes place in thylakoid membranes (TM) of cyanobacteria, algae, and higher plants. It begins with light absorption by pigments in large (modular) assemblies of pigment-binding proteins, which then transfer excitation energy to the photosynthetic reaction centers of photosystem (PS) I and PSII. In green algae and plants, these light-harvesting protein complexes contain chlorophylls (Chls) and carotenoids (Cars). However, cyanobacteria, red algae, and glaucophytes contain, in addition, phycobiliproteins in phycobilisomes that are attached to the stromal surface of TM, and transfer excitation energy to the reaction centers via...

Intersections: photosynthesis, abiotic stress, and the plant microbiome

B. DEMMIG-ADAMS, S.K. POLUTCHKO, M.C. ZENIR, P. FOUROUNJIAN, J.J. STEWART, M. LÓPEZ-POZO, W.W. ADAMS III

Photosynthetica 2022, 60(1):59-69 | DOI: 10.32615/ps.2021.065  

Climate change impacts environmental conditions that affect photosynthesis. This review examines the effect of combinations of elevated atmospheric CO₂, long photoperiods, and/or unfavorable nitrogen supply. Under moderate stress, perturbed plant source-sink ratio and redox state can be rebalanced but may result in reduced foliar protein content in C₃ plants and a higher carbon-to-nitrogen ratio of plant biomass. More severe environmental conditions can trigger pronounced photosynthetic downregulation and impair growth. We comprehensively evaluate available evidence that microbial partners may be able to support plant productivity...

Exposed red leaves display adaptive adjustments in chlorophyll and photosystem ratios compatible with the shade imposed by anthocyanin accumulation

K. ZELIOU, A. KYZERIDOU, Y. PETROPOULOU

Photosynthetica 2022, 60(1):70-78 | DOI: 10.32615/ps.2021.062  

Foliar anthocyanins shape a peculiar shade in a red leaf's interior leading to uneven energy distribution between the two photosystems. Accordingly, a readjustment of PSII/PSI stoichiometry could restore excitation balance. To test this hypothesis, 77 K fluorescence emission spectra of thylakoids from green and red leaves of seven species with different pigment profiles were compared. The ratio of F₆₈₆/F₇₃₆ served as an indication of the PSII/PSI functional ratio. To avoid possible species-dependent differences in the measured parameters, plants showing intra-individual, intra-species, or intra-leaf variation in the expression...

An open Internet of Things (IoT)-based framework for feedback controlof photosynthetic activities

S. YUAN, H. TANG, L.J. FU, J.L. TAN, G. GOVINDJEE, Y. GUO

Photosynthetica 2022, 60(1):79-87 | DOI: 10.32615/ps.2021.066  

Active control of photosynthetic activities is important in plant physiological study. Although models of plant photosynthesis have been built at different scales, they have not been fully examined for their application in plant growth control. However, we do not have an infrastructure to support such experiments since current plant growth chambers usually use fixed control protocols. In our current paper, an open IoT-based framework is proposed. This framework allows a plant scientist or agricultural engineer, through an application programming interface (API), in a desirable programming language, (1) to gather environmental data and plant...

Variability of the photosynthetic machinery tolerance when imposed to rapidly or slowly imposed dehydration in native Mediterranean plants

E. KOUTRA, C. CHONDROGIANNIS, G. GRAMMATIKOPOULOS

Photosynthetica 2022, 60(1):88-101 | DOI: 10.32615/ps.2022.003  

Dehydration affects the photosynthetic apparatus. The impact of dehydration on photosynthesis was assessed in twelve Mediterranean species representing different growth forms. Rapid and slow dehydration experiments were conducted to (1) compare the impact of water stress among species and growth forms, (2) rank species according to their drought tolerance. Rapid dehydration reduced the electron transport up to PSI, the reduction being linearly related to leaf relative water content (RWC), except for the deciduous species. Specific energy fluxes per reaction center and maximum photochemical activity of PSII remained relatively stable until...

Sensing and classification of rice (Oryza sativa L.) drought stress levels based on chlorophyll fluorescence

Q. XIA, L.J. FU, H. TANG, L. SONG, J.L. TAN, Y. GUO

Photosynthetica 2022, 60(1):102-109 | DOI: 10.32615/ps.2022.005  

Sensing and classification of drought stress levels are very important to agricultural production. In this work, rice drought stress levels were classified based on the commonly used chlorophyll a fluorescence (ChlF) parameter (F_v/F_m), feature data (induction features), and the whole OJIP induction (induction curve) by using a Support Vector Machine (SVM). The classification accuracies were compared with those obtained by the K-Nearest Neighbors (KNN) and the Ensemble model (Ensemble) correspondingly. The results show that the SVM can be used to classify drought stress levels of rice more accurately compared to the KNN...

Photosynthetic response of lutein-deficient mutant lut2 of Arabidopsis thaliana to low temperature at high light

A.V. POPOVA, R. VLADKOVA, P. BORISOVA, K. GEORGIEVA, G. MIHAILOVA, V. VELIKOVA, T. TSONEV, A.G. IVANOV

Photosynthetica 2022, 60(1):110-120 | DOI: 10.32615/ps.2022.009  

Alterations in photosynthetic performance of lutein-deficient mutant lut2 and wild type (wt) of Arabidopsis thaliana were followed after treatment with low temperature and high light for 6 d. The obtained results indicated lower electrolyte leakage, lower excitation pressure, and higher actual photochemical efficiency of PSII in lut2 plants exposed to combined stress compared to wt plants. This implies that lut2 is less susceptible to the applied stress conditions. The observed lower values of quantum efficiency of nonphotochemical quenching and energy-dependent component of nonphotochemical quenching in lut2 suggest...

Photosystem II in bio-photovoltaic devices

R.A. VOLOSHIN, S.M. SHUMILOVA, E.V. ZADNEPROVSKAYA, S.K. ZHARMUKHAMEDOV, S. ALWASEL, H.J.M. HOU, S.I. ALLAKHVERDIEV

Photosynthetica 2022, 60(1):121-135 | DOI: 10.32615/ps.2022.010  

Hybrid photoelectrodes containing biological pigment-protein complexes can be used for environmentally friendly solar energy conversion, herbicide detection, and other applications. The total number of scientific publications on hybrid bio-based devices has grown rapidly over the past decades. Particular attention is paid to the integration of the complexes of PSII into photoelectrochemical devices. A notable feature of these complexes from a practical point of view is their ability to obtain electrons from abundant water. The utilization or imitation of the PSII functionality seems promising for all of the following: generating photoelectricity, photo-producing...

Limiting steps and the contribution of alternative electron flow pathways in the recovery of the photosynthetic functions after freezing-induced desiccation of Haberlea rhodopensis

K. GEORGIEVA, A.V. POPOVA, G. MIHAILOVA, A.G. IVANOV, M. VELITCHKOVA

Photosynthetica 2022, 60(1):136-146 | DOI: 10.32615/ps.2022.008  

Haberlea rhodopensis Friv. is unique with its ability to survive desiccation to an air-dry state during periods of extreme drought and freezing temperatures. To understand its survival strategies, it is important to examine the protective mechanisms not only during desiccation but also during rehydration. We investigated the involvement of alternative cyclic electron pathways during the recovery of photosynthetic functions after freezing-induced desiccation. Using electron transport inhibitors, the role of PGR5-dependent and NDH-dependent PSI-cyclic electron flows and plastid terminal oxidase were assessed during rehydration of desiccated leaves. Recovery...

Dependence of the rate-limiting steps in the dark-to-light transition of photosystem II on the lipidic environment of the reaction center

M. MAGYAR, P. AKHTAR, G. SIPKA, W. HAN, X. LI, G. HAN, J.-R. SHEN, P.H. LAMBREV, G. GARAB

Photosynthetica 2022, 60(1):147-156 | DOI: 10.32615/ps.2022.016  

In our earlier works, we have identified rate-limiting steps in the dark-to-light transition of PSII. By measuring chlorophyll a fluorescence transients elicited by single-turnover saturating flashes (STSFs) we have shown that in diuron-treated samples an STSF generates only F₁ (< F_m) fluorescence level, and to produce the maximum (F_m) level, additional excitations are required, which, however, can only be effective if sufficiently long Δτ waiting times are allowed between the excitations. Biological variations in the half-rise time (Δτ_1/2) of the fluorescence increment...