Phosphorus Accretion in Old Leaves of a Mediterranean Shrub Growing at a Phosphorus-Rich Site

Abstract

Studies dealing with changes in the plant internal nutrient cycling in response to natural, long-term P-fertility gradients are scarce. In this short report, we show some evidence on how leaf P dynamics can be drastically altered when plants typical from nutrient-poor sites grow in long-term P-enriched soils. The study was conducted in two natural populations of the Mediterranean evergreen shrub Pistacia lentiscus L.: one in a P-poor site and the other in a P-rich site. Soil texture and N, P, and organic matter contents were measured at each site. Leaf N and P concentrations were also measured in current-year, 1-year-old, and 2-year-old leaves, and in the senesced leaves. In the P-poor site, leaf P and N decreased as the leaves aged. This occurs because of nutrient reabsorption to other plant organs and/or dilution of nutrients by carbon compounds. In contrast, the leaves from the P-rich site acummulated P (but not N) during leaf lifespan. Consequently, P concentration in senesced leaves was very high in the P-rich site. These results show that, in long-lived perennials living in the field, long-term P enrichment can switch the normal process of P resorption during leaf aging to P accretion in the leaf. P accumulation in the leaves, which are periodically shed, might constitute a simple P excretion mechanism for plants typical from P-poor soils.