The invasive duckweed Lemna minuta Kunth displays a different light utilisation strategy than native Lemna minor Linnaeus

Lemna minuta Kunth is an invasive, alien duckweed that is present throughout much of Europe, where it competes with native congeneric Lemna minor Linnaeus. Previously, L. minuta was found to grow faster than L. minor. The aim of this study was to determine whether the rapid growth of invasive L. minuta is based on differential light utilisation. For this purpose, the growth performance of L. minuta was compared with that of L. minor under a range of different light intensities. Both physiological and morphological parameters were determined. L. minuta showed a higher Relative Growth Rate (RGR) than L. minor when grown under medium and high intensities. Further analysis showed that, at high light intensities, L. minuta has a higher Net Assimilation Rate (NAR), and displays more photochemical quenching (qP) and a higher quantum yield (Y(II)) than L. minor. In contrast under low light intensities L. minor displayed a marginally higher RGR, due to a greater Leaf Area Ratio (LAR), and higher chlorophyll content than L. minuta. The results indicate two distinct light utilisation strategies, and reveal that the invasive species L. minuta takes more advantage from high intensity light conditions. In turn, this may influence plant distribution and, consequently, ecosystem management by relevant authorities.