Artifleck: The Study of Artifactual Responses to Light Flecks with Inappropriate Leaves

Methods in sunfleck research commonly employ the use of experimental leaves which were constructed in homogeneous light. These experimental organs may behave unnaturally when they are challenged with fluctuating light. Photosynthetic responses to heterogeneous light and leaf macronutrient relations were determined for Cycas micronesica, Glycine max, and Zea mays leaves that were grown in homogeneous shade, heterogeneous shade, or full sun. The speed of priming where one light fleck increased the photosynthesis during a subsequent light fleck was greatest for the leaves grown in heterogeneous shade. The rate of induction and the ultimate steady-state photosynthesis were greater for the leaves that were grown in heterogeneous shade versus the leaves grown in homogeneous shade. The leaf mass per area, macronutrient concentration, and macronutrient stoichiometry were also influenced by the shade treatments. The amplitude and direction in which the three developmental light treatments influenced the response variables were not universal among the three model species. The results indicate that the historical practice of using experimental leaves which were constructed under homogeneous light to study leaf responses to fluctuating light may produce artifacts that generate dubious interpretations.