Physiological responses of clonal quince root‐stocks to iron‐deficiency induced by addition of bicarbonate to nutrient solution1

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Abstract
“MA”; quince clonal rootstock is more susceptible to lime‐induced chlorosis than clone “Ct.S.212”;. Trials were performed in order to determine whether differences observed between the two clones in calcareous soil were maintained when iron (Fe)‐deficiency was induced by addition of bicarbonate (HCO3) to a modified Hoagland nutrient solution No 1. In addition, trials were aimed to verify whether the rootstocks showed differing physiological responses. Results confirmed that total leaf Fe content was not a suitable tool to screen rootstocks for chlorosis tolerance. In contrast, “active”; Fe and chlorophyll content (well correlated with chlorotic symptom levels), together with fresh and dry matter production, were found to be good parameters for genotype evaluation. Total Fe content increased in the root system of stress‐grown “MA”; plants more than in “Ct.S.212”; root systems. Root Fe3+‐reductase activity increased in “MA”; and “Ct.S.212”; under Fe‐deficiency conditions obtained by using an Fe‐free solution or by addition of sodium bicarbonate (10 mM NaHHCO3). In this case, “Ct.S.212”; showed roughly 6‐fold increased capacity three hours after the beginning of the assay. This increase was greater than that induced by Fe absence. Clone “MA”; showed similar behaviour, but with a lower rate of reduction (3‐fold increase in reducing capacity).