The Role of Light-Harvesting Complex II Organization in the Efficiency of Light-Dependent Reactions in the Photosynthetic Apparatus of L.

In this study, the functions of the photosynthetic machinery were evaluated using chlorophyll fluorescence technique (PAM and JIP test) in pea plants ( L. cv Borec) and its LHC II oligomerization variants (mutants / and /). The oligomeric forms of LHCII increased in the following order: / < Borec wt < /. Data revealed that the mutant with higher LHCII oligomerization (/) at low light intensity (LL, 150 µmol photons/m·s) exhibited the following: (i) decreased energy dissipation and increased electron transport efficiency; (ii) higher reaction center density; (iii) increased amounts of the open reaction centers (qp) and their excitation efficiency (Φexc); and (iv) influenced the reoxidation of Q, alleviating its interaction with plastoquinone. These effects enhanced photosynthetic performance related to PSII photochemistry (PI) and overall photosynthetic efficiency (PItotal). High light intensity (HL, 500 µmol photons/m·s) caused a reduction in open reaction centers (qp), excitation efficiency (Φexc), photochemical energy conversion of PSII (Φ), maximum efficiency of PSII photochemistry in light (Fv'/Fm'), and linear electron transport via PSII, with more pronounced effects observed in membranes with a lower degree of LHCII oligomerization (/). This study provides novel experimental evidence for the pivotal role of the LHCII structural organization in determining the efficiency of light-dependent reactions of photosynthesis.