Photosynthetica - Ahead of Print

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 X:X | 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 determine growth rate under moderate light in batch or turbidostat - a study with five green algae

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

Photosynthetica X:X | 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...

Light quality, oxygenic photosynthesis and more

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

Photosynthetica X:X | 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...

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 X:X | 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.

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 X:X | 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...

Phosphate fertilizers increase CO₂ assimilation and yield of soybean in a shaded environment

W. ZHAO, B. ZHENG, T.H. REN, X.H. ZHANG, T.Y. NING, G. LI

Photosynthetica X:X | DOI: 10.32615/ps.2021.063  

Two light treatments [ambient sunlight (L1) during the entire growth period and 40% shade (L2) from 40 d after sowing until 24 d after flowering] and two phosphate fertilizer treatments [no phosphate fertilizer application (P0) and a conventional phosphate fertilizer application (P1)] were used to determine how phosphate fertilizer regulates soybean [Glycine max (L.) Merr.] photosynthesis under shading. We showed that phosphorus significantly increased chlorophyll content and grain yield under shading. The light-saturated net photosynthetic rate, apparent quantum yield, maximum electron transport rate, and maximum Rubisco carboxylation rate...

Partial shade improved the photosynthetic capacity and polysaccharide accumulation of the medicinal plant Bletilla ochracea Schltr.

X.F. YU, X.Y. MING, M. XIONG, C. ZHANG, L.J. YUE, L. YANG, C.Y. FAN

Photosynthetica X:X | DOI: 10.32615/ps.2021.064  

To study the light intensity suitable for Bletilla ochracea Schltr., morphology, photosynthetic parameters, and polysaccharide content of seedlings were evaluated under different light intensities. All shade treatments promoted plant growth and net photosynthetic rate while having no significant effect on transpiration rate. The maximum photochemical efficiency and potential photochemical efficiency reached the lowest values under full sunlight. The electron transport rate and photochemical quenching under shade were significantly higher than those under full light, while nonphotochemical quenching was the highest under full light. This indicated...

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 X:X | 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...

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

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

Photosynthetica X:X | 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...

Effect of short-term combined alkaline stress on antioxidant metabolism, photosynthesis, and leaf-air temperature difference in sorghum

J.J. GUO, X.X. XU, R.D. ZHANG, X.F. CHEN, Y.F. XING, B. LI, C. LIU, Y.F. ZHOU

Photosynthetica X:X | DOI: 10.32615/ps.2021.067  

Alkaline stress is important abiotic stress that restricts the growth and physiological activity of sorghum (Sorghum bicolor L. Moench). We aimed to investigate the effects of alkaline stress on alkali-tolerant SX44B and alkali-sensitive 262B sorghum inbred lines. The results showed that alkaline stress decreased the content of chlorophyll, activity of photosystem II, net photosynthetic rate, and destroyed chloroplast morphology. These changes were less pronounced in SX44B, possibly owing to its higher antioxidant enzyme activity and nonphotochemical quenching. Alkaline stress decreased water content, transpiration rate, and stomatal conductance...

Effects of source-sink alteration by pruning on physiological parameters and fruit production of Rosa roxburghii Tratt. on the Yunnan-Guizhou Plateau in China

C. ZHANG, K. YAN, L.Z. LIN, Y.M. FANG, X.Y. ZHANG

Photosynthetica X:X | DOI: 10.32615/ps.2022.001  

The formation of economic yield and fruit quality of Roxburgh rose (Rosa roxburghii Tratt.) depends essentially on its source-sink interaction. Thus, a pruning experiment was conducted to assess the effects of source-sink regulation on photosynthetic physiology and fruit yield of Roxburgh rose, which was of great significance to production. Cutting off vegetative branches reduced physiological fruit loss and malformed fruits but increased single fruit quality and yield. Results revealed that the stomatal characteristics, the composition of mesophyll tissue, and photosynthesis of leaves on reproductive branches were significantly affected by...

Nitrogen rate and plant density interaction enhances grain yield by regulating the grain distribution of secondary branches on the panicle axis and photosynthesis in japonica rice

Y.L. GONG, Y. LEI, X.P. ZHANG, B.C. YAN, X.T. JU, X.Y. CHENG, J.D. ZHANG, X.Y. SUN, H. XU, W.F. CHEN

Photosynthetica X:X | DOI: 10.32615/ps.2022.002  

Two japonica rice cultivars with different panicle trait index (PTI), HP917 (a high-PTI cultivar) and DP128 (a low-PTI cultivar) were used to investigate the effects of the nitrogen (N) rate and plant density on the grain distribution of secondary branches on the panicle axis, leaf photosynthetic characteristics, and grain yield by a split plot design. The main plots were assigned to four N rates (0, 140, 200, and 260 kg ha^-1), and the subplots were assigned to two plant densities: (D₂₀, 15 plants m^-2; D₁₀, 30 plants m^-2). Results showed that the grain yield was increased by increasing N rate...

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 X:X | 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...

Chloroplast protease/chaperone AtDeg2 holds γ₁ subunit of ATP synthase in an unaggregated state under high irradiance conditions in Arabidopsis thaliana

P. JAGODZIK, G. JACKOWSKI

Photosynthetica X:X | DOI: 10.32615/ps.2022.004  

Little data on the role played in vivo by chloroplast protein AtDeg2 as a chaperone is available. Therefore, we sought for chloroplast proteins protected from high irradiance-induced interprotein aggregation via disulphide bridges by AtDeg2 acting as a holdase. To reach this goal, we performed analyses which involved comparative diagonal electrophoreses of lysates of chloroplasts isolated from wild type (WT) plants and transgenic plants 35S:AtDEG2^ΔPDZ1-GFP which expressed AtDeg2 lacking its chaperone activity but retaining the protease activity. The results of the analyses indicate that AtDeg2 acting...

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 X:X | 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...

Transgenerational effect of UV-B priming on photochemistry and associated metabolism in rice seedlings subjected to PEG-induced osmotic stress

A. SEN, J.T. PUTHUR, D. CHALLABATHULA, M. BRESTIČ

Photosynthetica X:X | DOI: 10.32615/ps.2022.006  

Rice being the major food crop for more than half of the world population is severely affected by drought stress starting from the establishment of the seedling. We focused on the UV-B priming mediated transgenerational drought tolerance of a drought-tolerant rice variety (Vaisakh) towards polyethylene glycol (PEG) 6,000 (20%)-induced drought. Results showed that priming in F₀ generation and re-priming in F₁ generation with UV-B enhanced the PEG stress tolerance potential of rice seedlings with increased expression of genes encoding antioxidant enzymes and stress-related proteins offering better protection to primed plants. UV-B...

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 X:X | 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...