Is the pattern of calcium and phosphorus allocation to specific leaf cell types the key reason why different Lupinus species respond differently to calcareous soil?

The calcifuge syndrome of Lupinus species cannot be explained by pH, as they strongly acidify the rhizosphere, mobilising nutrients that are poorly available at high pH. I hypothesised that the reason why they are insensitive to calcareous soils is that they accumulate phosphorus (P) and calcium (Ca) in different cell types, avoiding precipitation of Ca3(PO4)i. I ran experiments, showing that Ca toxicity or allocation of Ca and P to specific leaf cells is not the key. Rather, the high pH and the buffering capacity of bicarbonate are factors determining if Lupinus species can survive in calcareous soils.