Manganese Deficiency in Plants: The Impact on Photosystem II

Manganese (Mn) is an essential plant micronutrient with an indispensable function as a catalyst in the oxygen-evolving complex (OEC) of photosystem II (PSII). Even so, Mn deficiency frequently occurs without visual leaf symptoms, thereby masking the distribution and dimension of the problem restricting crop productivity in many places of the world. Hence, timely alleviation of latent Mn deficiency is a challenge in promoting plant growth and quality. We describe here the key mechanisms of Mn deficiency in plants by focusing on the impact of Mn on PSII stability and functionality. We also address the mechanisms underlying the differential tolerance towards Mn deficiency observed among plant genotypes, which enable Mn-efficient plants to grow on marginal land with poor Mn availability. Mn deficiency often occurs as a latent disorder without any growth restrictions or clear leaf symptoms, despite significant disintegration of PSII under these conditions. Photosystem II is the primary target of Mn deficiency in plants. Mn deficiency leads to destabilization of PSII super- and subcomplexes. ICP-MS based analysis of metal binding in photosystem complexes provides a valuable tool to study the loading and internal use of Mn and other biometals required for efficient photosynthesis. Traditional cereal landraces constitute a valuable germplasm for reintroducing genotypic diversity to improve nutrient efficiency and increase crop robustness.