Structural and functional integrity of Sulla carnosa photosynthetic apparatus under iron deficiency conditions

The abundance of calcareous soils makes bicarbonate-induced iron (Fe) deficiency a major problem for plant growth and crop yield. Therefore, Fe-efficient plants may constitute a solution for calcareous soil use. In the present work, we investigated the ability of the forage legume Sulla carnosa (Desf.) to maintain the integrity of its photosynthetic apparatus under iron deficiency conditions. Three treatments were applied: control, direct iron deficiency and bicarbonate-induced iron deficiency. At the harvest, all organs of deficient plants showed severe growth inhibition, the effect being less pronounced under indirect iron deficiency. Pigment analysis of fully-expanded leaves revealed a reduction in the concentrations of chlorophyll a, chlorophyll b, and carotenoids under iron deficiency conditions. Electron transport rate (ETR), maximal and effective quantum yield of photosystem II (PSII), photochemical quenching (qP), non-photochemical quenching (qN) as well as P700 activity were also significantly decreased in plants exposed to direct Fe deficiency while non-photochemical quenching (qN) was not affected. The effects of indirect Fe deficiency on the same parameters were less pronounced in bicarbonate-treated plants. The relative abundances of thylakoid proteins related to PSI (PsaA, Lhca1, Lhca2) and PSII (PsbA, Lhcb1) were also more affected under direct than indirect Fe deficiency. We conclude that S. carnosa can maintain the integrity of its photosynthetic apparatus under bicarbonate-induced Fe deficiency, preventing both photosystems from the harmful effects that can affect them under direct Fe deficiency. This suggests a high capacity of this species not only to take up iron in the presence of bicarbonate (HCO ) but also to preferentially translocate absorbed Fe towards leaves and prevent its inactivation by HCO . This article is protected by copyright. All rights reserved.