Response of Quercus robur and two potential climate change winners - Quercus pubescens and Quercus ilex - to two years summer drought in a semi-controlled competition study: II - Photosynthetic efficiency

The relative chlorophyll content, approximated as SPAD values, detected no or only small differences between the species and drought vs. control treatments. Only Q. robur showed strong significant reductions in SPAD values under DS. The previously reported higher maximum stomatal conductance in Q. ilex could be confirmed, but Wt did not benefit from this, suggesting that Wt under DS was more related to mesophyll conductance than to stomatal conductance.