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Blomväxterna, eller angiospermerna som de kallas i vetenskapliga sammanhang, omfattar idag över 295 000 olika arter. Men denna siffra ändras ständigt eftersom det beskrivs ungefär 2 000 nya arter varje år. För att kunna ha överblick över en så stor mängd behöver den organiseras på ett vettigt sätt. Det har botanister försökt med alltsedan Linnés tid.

In general, the word, photosynthesis, is considered synonymous with oxygenic photosynthesis, a process by which cyanobacteria, algae, aquatic, and terrestrial plants produce oxygen and carbohydrates, using light (photons), water and carbon dioxide. Further, we have anoxygenic bacterial photosynthesis where oxygen is not evolved, but a substrate, other than water, is oxidized, and rhodopsin-type systems, where ATP is produced. In principle, one could expand the concept of the term photosynthesis, provided appropriate caveats are added, to include lightdriven assimilation of molecular nitrogen, photoproduction of molecular hydrogen, and even synthesis of vitamin D in skin. We conclude with a glimpse of the rapidly developing field of artificial photosynthesis.

Charles Darwin (1809–1882) är främst känd för sin evolutionsteori– om arters utveckling genom naturligt urval. Hans övriga arbetenär mindre kända. Mycket handlade om växter – om mekanismer för pollinering, blombiologi, rörelser och förmågan att ta upp näring från andra organismer – sådant som intresserat honom sedan studietiden i Cambridge. Med tiden kom han att publicera ett flertal böcker och en lång rad artiklar med botaniskt innehåll.

On the occasion of the 90th birthday of Govindjee, Professor Emeritus of Plant Biology, Biochemistry, and Biophysics, the University of Illinois at Urbana-Champaign (UIUC), over 100 celebrants have sent felicitations and messages to thank him for mentoring, nurturing, and building the community of photosynthesis researchers belonging to four generations; and in making the scientific knowledge accessible to students and young researchers via his monumental writings and editorial contributions. Govindjee joined UIUC in September of 1956 to study as a graduate student in the laboratory of Robert Emerson. In 1961, he joined UIUC as an Assistant Professor and retired as a full professor in 1999. He is well-known for pioneering work in oxygenic photosynthesis, leading to the current Z-scheme, and for his breakthrough advances concerning light harvesting, primary charge separation, the role of bicarbonate on the two-electron gate of photosystem II, water oxidation, nonphotochemical quenching, and the use of biophysical techniques, such as prompt fluorescence, delayed fluorescence, thermoluminescence, and nuclear magnetic resonance. Today, despite his retirement, Govindjee continues to explore several important questions in the field of photosynthesis and documents the history of science. This tribute, in turn, attempts to capture scientific collaborations, as well as scholarly and personal contributions made by Govindjee to the lives of hundreds of scholars and students worldwide.

Idag tar vi växterna för givna. För många människor är de ett bakgrundsbrus, en fond. Hos oss växtintresserade får de lite mer fokus. Vi kan urskilja arterna i den gröna massan av växtlighet och vi oroar oss för deras framtid. I den här artikeln tar tre forskare med oss på en resa genom växternas historia – från första början, genom olika klimat som har gynnat utvecklingen av växtgrupper med olika egenskaper, fram till dagens gröna mångfald. En kort resumé av de senaste två årmiljarderna med fokus på växter.

This is a comment on Michaelian and Simeonov (2015). Michaelian and Simeonov formulate the leading thought in their article: “The driving force behind the origin and evolution of life has been the thermodynamic imperative of increasing the entropy production of the biosphere through increasing the global solar photon dissipation rate”. I shall in the following try to provide some information that might help to clarify whether this is correct.

Oxygenic photosynthesis takes place in thylakoid membranes (TM) of cyanobacteria, algae, and higher plants. Itbegins with light absorption by pigments in large (modular) assemblies of pigment-binding proteins, which thentransfer excitation energy to the photosynthetic reaction centers of photosystem (PS) I and PSII. In green algaeand 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 attachedto the stromal surface of TM, and transfer excitation energy to the reaction centers via the Chl a molecules in the innerantenna of PSI and PSII. The color and the intensity of the light to which these photosynthetic organisms are exposedin their environment have a great influence on the composition and the structure of the light-harvesting complexes(the antenna) as well as the rest of the photosynthetic apparatus, thus affecting the photosynthetic process and even theentire organism. We present here a perspective on ‘Light Quality and Oxygenic Photosynthesis’, in memory of GeorgeChristos Papageorgiou (9 May 1933–21 November 2020; see notes a and b). Our review includes (1) the influence ofthe solar spectrum on the antenna composition, and the special significance of Chl a; (2) the effects of light quality onphotosynthesis, measured using Chl a fluorescence; and (3) the importance of light quality, intensity, and its durationfor the optimal growth of photosynthetic organisms.