Leaf Wand for Measuring Chlorophyll Fluorescence on Cylindrical Leaves and Its Application on Juncus roemerianus (Black Needlerush)

Abstract

Chlorophyll fluorescence is a well established technique to rapidly and non-invasively determine photosynthesis pa- rameters in plant leaves. It can be used in both laboratory and field settings, and frequently dark-adaptation of a leaf sample is called for. In the field, this can be accomplished on flat leaves using standard leaf clips supplied by instrument manufacturers. However, not all plant leaves are flat, many are cylindrical or otherwise three-dimensional in shape. The standard leaf clip does not close fully on three-dimensional leaves, therefore, does not allow the sample to be properly dark adapted in the field. A new leaf “wand” was developed that can be slipped over an entire cylindrical leaf or culm of rushes and sedges for both light- and dark-adapted measurements. This new leaf wand is compared to the standard leaf clip (DLC-8) using a Walz mini-PAM on Juncus roemerianus (Black needlerush). Results indicate that dark- adapted yield measurements are not significantly different between leaf clips, while light-adapted yields are higher with the leaf wand. The potential sources of difference in the optical path of the excitation light and fluorescence return are discussed and compared between leaf clips. Construction of specialized leaf wands should be considered for any leaves that are not flat and therefore do not fit the standard leaf clip for complete dark-adaptation under field conditions. Keywords: Juncus roemerianus; Chlorophyll Fluorescence; Leaf Clip; Cylindrical Leaf; Optical Path Length