A stable light-induced EPR signal is reported in photosystem II particles and in chloroplasts at 5 K. Characteristic spectral features indicate that the signal arises from dipole-dipole interactions of a radical pair triplet state. From its dependence on potential, its relationship to the spin-polarized triplet state, and the redox state of the pheophytin acceptor (Ph) and because it is present...

chlorophyll fluorescence induction is a rapid and noninvasive technique for measuring photosynthetic electron transport in plants. chlorophyll fluorescence measurements were performed under greenhouse condition to characterize how the fluorescence induction curves (kautsky curve) and its parameters were affected by metribuzin in susceptible and resistant junglerice (echinochloa colona (l.) link...

As climate change progresses, the breeding of drought-tolerant forest trees is necessary. Breeding requires screening for drought stress using a large number individuals and high-throughput phenotyping method. The aim this study was therefore to establish methods evaluating clonal responses infrared thermography chlorophyll fluorescence in Cryptomeria japonica. stomatal conductance index (Ig), ...

Photosynthetic energy conversion was investigated in five species of marine unicellular algae, (Dunaliella tertiolecta, Thalassiosira pseudonana, T. weisflogii, Skeletorema costatum, Isochrysis galbana) representing three phylogenetic classes, which were grown under steady state conditions with either light or inorganic nitrogen as a limiting factor. Using a pump and probe fluorescence techniqu...

Photoelectrochemical water splitting directly converts solar energy to chemical energy stored in hydrogen, a high energy density fuel. Although water splitting using semiconductor photoelectrodes has been studied for more than 40 years, it has only recently been demonstrated using dye-sensitized electrodes. The quantum yield for water splitting in these dye-based systems has, so far, been very ...

To analyze a possible correlation between the extent of QA-* reoxidation and protein dynamics, fluorometric and Mössbauer spectroscopic measurements were performed in photosystem II membrane fragments from spinach. Numerical evaluation of the flash-induced change of the normalized fluorescence quantum yield revealed that the extent of reoxidation starts to decrease below 275 K and is almost com...

Molecular dynamics simulations have been performed to study photosystem II structure and function. Structural information obtained from simulations was combined with ab initio computations of chromophore excited states. In contrast to calculations based on the x-ray structure, the molecular-dynamics-based calculations accurately predicted the experimental absorbance spectrum. In addition, our c...

Under high-irradiance conditions, plants must efficiently protect photosystem II (PSII) from damage. In this study, we demonstrate that the chloroplast protein HYPERSENSITIVE TO HIGH LIGHT1 (HHL1) is expressed in response to high light and functions in protecting PSII against photodamage. Arabidopsis thaliana hhl1 mutants show hypersensitivity to high light, drastically decreased PSII photosynt...