Two Inexpensive and Non-destructive Techniques to Correct for Smaller-Than-Gasket Leaf Area in Gas Exchange...

The development of technology, like the widely-used off-the-shelf portable photosynthesis systems, for the quantification of leaf gas exchange rates and chlorophyll fluorescence offered photosynthesis research a massive boost. Gas exchange parameters in such photosynthesis systems are calculated as gas exchange rates per unit leaf area. In small chambers (<10 cm²), the leaf area used by the system for these calculations is actually the internal gasket area (A_G), provided that the leaf covers the entire A_G. In this study, we present two inexpensive and non-destructive techniques that can be used to easily quantify the enclosed leaf area (A_L) of plant species with leaves of surface area much smaller than the A_G, such as that of cereal crops. The A_L of the cereal crop species studied has been measured using a standard image-based approach (iA_L) and estimated using a leaf width-based approach (wA_L). iA_L and wA_L did not show any significant differences between them in maize, barley, hard and soft wheat. Similar results were obtained when the wA_L was tested in comparison with iA_L in different positions along the leaf in all species studied. The quantification of A_L and the subsequent correction of leaf gas exchange parameters for A_L provided a precise quantification of net photosynthesis and stomatal conductance especially with decreasing A_L. This study provides two practical, inexpensive and non-destructive solutions to researchers dealing with photosynthesis measurements on small-leaf plant species. The image-based technique can be widely used for quantifying A_L in many plant species despite their leaf shape. The leaf width-based technique can be securely used for quantifying A_L in cereal crop species such as maize, wheat and barley along the leaf. Both techniques can be used for a wide range of gasket shapes and sizes with minor technique-specific adjustments.