Are aluminum and iron resorbed from old leaves?

Abstract

Abstract Purpose Leaf resorption is an important mechanism for plant nutrient conservation, but not all elements are resorbed by plants. It is generally believed that aluminum (Al) and iron (Fe) are not resorbed from old leaves due to their toxic effects. However, the fact is that positive Al and Fe resorptions have been found in some specific cases. To date, no one has addressed these specific cases and the mechanisms underlying. Methods Here, a data synthesis was conducted to explore the patterns and controls on leaf resorption efficiency of Al and Fe, based on 34 published studies with 272 data points. We aimed to answer whether and why Al and Fe can be resorbed from old leaves. Results The resorption efficiency of Al was positive in conifer plants (11.3%), but was negative in deciduous and evergreen plants (-94.2% and − 111.2%, respectively). The resorption efficiency of Fe was positive in nitrogen-fixing plants (39.2%), but was negative in non-nitrogen-fixing plants (-37.0%). Lower soil pH favored leaf Al resorption, but limited leaf Fe resorption. Higher precipitation inhibited leaf Fe resorption. Conclusions In contrast to the general belief, our study highlights that Al and Fe can be resorbed from old leaves, depending mainly on plant functional group and soil environment. This knowledge is an important supplement for understanding leaf resorption process, and helpful for modeling global biogeochemical cycles.