Near-null magnetic fields modulate photosystem II function and electron transport in Arabidopsis thaliana

Abstract The geomagnetic field (GMF) has shaped terrestrial life for over 4.2 billion years, yet the mechanisms underlying plant magnetic sensitivity remain poorly understood. Here, we investigated the immediate photosynthetic responses of Arabidopsis thaliana to rapid transitions between geomagnetic (GMF; ~45 µT), near-null magnetic field (NNMF; ~30 nT) and hypermagnetic field (HMF; ~1 mT) conditions. Using chlorophyll fluorescence analyses (OJIP and PAM), photosynthetic mutants ( ch1 , npq1 , npq4 , and pgr5 ), Fe-S-cluster-associated lines (KO- isca3 , OE- isca3 , and atx1 ), pharmacological (DCMU and NH 2 OH) perturbation of Photosystem II (PSII), and a simplified quantum spin-Hamiltonian framework, we examined how magnetic-field transitions influence photosynthetic performance. A 10-s transition to NNMF induced rapid increases in fluorescence amplitudes, reduced photochemical operating efficiency, and enhanced photoprotective energy dissipation under actinic illumination. The magnitude and expression of these responses varied among genetic backgrounds and were strongly influenced by donor- and acceptor-side perturbation of PSII. In contrast, HMF produced comparatively modest effects. Together, the genetic and pharmacological analyses indicate that the expression of the magnetic-field-dependent phenotype depends on the physiological state of the photosynthetic apparatus and associated regulatory pathways. Although the molecular origin of the response remains unresolved, the results support further investigation of PSII-associated photochemical and regulatory processes as possible contributors to the observed phenotype. More broadly, this study provides evidence that photosynthetic performance can respond rapidly to magnetic-field transitions and establishes an experimental framework for investigating the processes underlying magnetic-field-associated physiological responses in plants.