Dr. Autar Krishen Mattoo (1943-2024): an outstanding plant biologist with a focus on photosynthesis.

We provide here the academic life of Dr. Autar Krishen Mattoo (1943-2024), including his role as a research leader at the United States Department of Agriculture and his outstanding contributions in photosynthesis, plant physiology and molecular biology with a focus to enhance nutrients. His work included ways to regulate Photosystem II (PSII) reaction center proteins, as well as to exploit, for our benefit, the role of polyamines in the plant world.

Contributions of David Mauzerall to photosynthesis research - celebrating his 95 birthday.

We honor here Professor David Mauzerall, a pioneer in the fields of photochemistry and photobiology of porphyrins and chlorophylls and , on the occasion of his 95 birthday. Throughout his career at The Rockefeller University, he refined our understanding of how chlorophyll converts light energy into chemical energy. He exploited top-of-the-line laser technology in developing photoacoustics and a variety of other innovative experimental approaches.

High and unique carbonic anhydrase activity of Photosystem II from Pisum sativum: Measurements by a new and very sensitive fluorescence method.

Carbonic anhydrase (CA) activity, associated with Photosystem II (PSII), has been shown to enhance water oxidation. However, CA activity was thought to be a side effect or even a "contamination" of other CAs because of the relatively low rates of CA reactions in PSII measured previously. Here, by using 8-hydroxy-pyrene-1,3,6-trisulfonate (pyranine), a fluorescent dye, as a pH indicator, we show that PSII preparations (∗∗BBYs) from Pisum sativum have a high CA activity (as measured by HCO dehydration), which is close to that of highly active CAs.

Honoring Hartmut Karl Lichtenthaler, innovative pioneer of photosynthesis, on his 90 birthday.

We honor Professor Hartmut Karl Lichtenthaler, a versatile pioneer of photosynthesis research, plant physiology, isoprenoid biochemistry, and stress physiology of plants, for his groundbreaking and creative contributions to plant science. His innovative research on the chemical composition, ultrastructure, and function of chloroplasts and his detection of the major methylerythritol 4-phosphate (MEP) isoprenoid biosynthetic pathway in plants is key to our current understanding of the physiology and biochemistry of photosynthesis systems. His ingenious use of the powerful laser-induced chlorophyll fluorescence imaging has helped us better understand the stress response processes in plant leaves.

Contributions by Christa Critchley to photosynthesis research and to plant ecophysiology.

Christa Critchley is a distinguished researcher in basic and applied photosynthesis research. Her research has centered on the structure and function of chloroplasts and the application of chlorophyll fluorescence to understanding the way PSII works. In her research, she used two biophysical tools, Nuclear Magnetic Resonance (NMR) and Chlorophyll (Chl) fluorescence, as well as several other biochemical and plant physiological methods.

Bicarbonate is a key regulator but not a substrate for O evolution in Photosystem II.

Photosystem II (PSII) uses light energy to oxidize water and to reduce plastoquinone in the photosynthetic electron transport chain. O is produced as a byproduct. While most members of the PSII research community agree that O originates from water molecules, alternative hypotheses involving bicarbonate persist in the literature.

Remembering Jan Amesz (1934-2001): a great gentleman, a major discoverer, and an internationally renowned biophysicist of both oxygenic and anoxygenic photosynthesis.

We present here the research contributions of Jan Amesz (1934-2001) on deciphering the details of the early physico-chemical steps in oxygenic photosynthesis in plants, algae and cyanobacteria, as well as in anoxygenic photosynthesis in purple, green, and heliobacteria. His research included light absorption and the mechanism of excitation energy transfer, primary photochemistry, and electron transfer steps until the reduction of pyridine nucleotides. Among his many discoveries, we emphasize his 1961 proof, with L.

On the Pelletier and Caventou (1817, 1818) papers on chlorophyll and beyond.

The first use of the word 'chlorophyll' (chlorophile or chlorophyle in the French original) appeared in two papers by Pierre-Joseph Pelletier and Joseph Bienaimé Caventou, pharmacists in Paris who isolated and studied the green pigment from plants. Here, we provide English translations of their 1818 note and the slightly longer 1817 paper. Historical context is provided including a timeline of key discoveries in chlorophyll chemistry pertaining to photosynthesis.

Reduced expression of chlorophyllide oxygenase (CAO) decreases the metabolic flux for chlorophyll synthesis and downregulates photosynthesis in tobacco plants.

Unlabelled: Chlorophyll is synthesized from chlorophyllide , catalyzed by chlorophyllide oxygenase (). To examine whether reduced chlorophyll content regulates chlorophyll (Chl) synthesis and photosynthesis, we raised transgenic tobacco plants with antisense expression, which had lower chlorophyll content and, thus, higher Chl / ratio. Further, these plants had (i) lower chlorophyll and total Chl content, whether they were grown under low or high light; (ii) decreased steady-state levels of chlorophyll biosynthetic intermediates, due, perhaps, to a feedback-controlled reduction in enzyme expressions/activities; (iii) reduced electron transport rates in their intact leaves, and reduced Photosystem (PS) I, PS II and whole chain electron transport activities in their isolated thylakoids; (iv) decreased carbon assimilation in plants grown under low or high light.

Impact of individual, combined and sequential stress on photosynthesis machinery in rice (Oryza sativa L).

Abiotic stresses such as heat, drought and submergence are major threats to global food security. Despite simultaneous or sequential occurrence of these stresses being recurrent under field conditions, crop response to such stress combinations is poorly understood. Rice is a staple food crop for the majority of human beings.

In appreciation of an ingenious scientist and a great friend: Győző Garab.

To express my appreciation of Győző Garab, I describe below our association over the years, followed by a brief description of his fundamental research in the area of biophysics of photosynthesis.

George Edward Hoch (1931-2023): a great photosynthesis scholar, a real family man, and a wonderful friend to many.

We present here a tribute to George E. Hoch, one of the top leaders in deciphering the primary steps of oxygenic photosynthesis. After providing his academic background, we discuss his selected research on the photoreactions of photosynthesis.

Evaluation of secondary sexual dimorphism of the dioecious Amaranthus palmeri under abiotic stress.

The evolution of secondary sex-specific traits of dioecious species under abiotic stress conditions has received limited research, especially in the case of Amaranthus palmeri, a fast adapting and highly competing plant. Here, we have examined the interactive effects of abiotic stress on mineral accumulation, chlorophyll a and b content, and the operating capacity of Photosystem II (PSII) in both male and female A. palmeri plants grown under three different intensities of white light, and under N, K or P deficiency.

Paul A. Castelfranco (1921-2021): a scientist par excellence, a man of lasting faith, and ever a humanist.

We present here the life and the work of Paul A. Castelfranco (1921-2021), a very special person who was not only a top chemist of chlorophyll biosynthesis, but also made major contributions on fatty acid oxidation, acetate metabolism and cellular organization. He led an extraordinary and exemplary life as a human being.

The life story of Albert W. Frenkel (1919-2015): a pioneer in photosynthesis research.

In this historical perspective, we focus on selected discoveries that Albert Frenkel (1919-2015) made all by himself - single-handedly - which is the discovery of photophosphorylation and NAD reduction in anoxygenic photosynthetic bacteria. Then, we present various aspects of his research life through his unpublished letters with some key scientists in his research field. To give a glimpse of his personal life, we have also provided some photographs.

Determination of / from Chlorophyll Fluorescence without Dark Adaptation by an LSSVM Model.

Evaluation of photosynthetic quantum yield is important for analyzing the phenotype of plants. Chlorophyll fluorescence (ChlF) has been widely used to estimate plant photosynthesis and its regulatory mechanisms. The ratio of variable to maximum fluorescence, / , obtained from a ChlF induction curve, is commonly used to reflect the maximum photochemical quantum yield of photosystem II (PSII), but it is measured after a sample is dark-adapted for a long time, which limits its practical use.

Solar energy conversion by photosystem II: principles and structures.

Photosynthetic water oxidation by Photosystem II (PSII) is a fascinating process because it sustains life on Earth and serves as a blue print for scalable synthetic catalysts required for renewable energy applications. The biophysical, computational, and structural description of this process, which started more than 50 years ago, has made tremendous progress over the past two decades, with its high-resolution crystal structures being available not only of the dark-stable state of PSII, but of all the semi-stable reaction intermediates and even some transient states. Here, we summarize the current knowledge on PSII with emphasis on the basic principles that govern the conversion of light energy to chemical energy in PSII, as well as on the illustration of the molecular structures that enable these reactions.

On the evolution of the concept of two light reactions and two photosystems for oxygenic photosynthesis: A personal perspective.

I present here a personal perspective of the evolution of the two-light reaction two-pigment scheme for the electron transport in oxygenic photosynthesis - as I have lived through it - first as a graduate student of Robert Emerson, from September 1956-January 1959, and then of Eugene Rabinowitch from February 1959-September 1960. I have provided here some of the key published work in my way and have also provided a few photographs. It is essential to remind ourselves upfront that different individuals may have different recollections of the same event (, the Japanese movie 'Rashomon' https://en.