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Defense response, water balance and photosynthesis in oak leaves infected with purple mold disease caused by Cystotheca wrightii

Takefumi Ikeda: Kyoto Prefectural University

<div><em>Quercus glauca</em> leaves infected with the purple mold disease caused by <em>Cystotheca wrightii </em>do not die, but experience a water deficit. To understand in more detail the effect of <em>C. wrightii</em> on leaf function, we studied the histological and anatomical features of infected leaves. We also performed a non-destructive X-ray analysis and assessed the water balance and photosynthesis. X-ray images revealed a higher density in infected parts of the leaf than in non-infected parts. In this denser part of an infected leaf, anatomical and histochemical observations showed the formation of a multi-layered wound periderm and the accumulation of tannin and/or suberin. Lignin was also detected in cell walls of wound periderm. Water relations were impacted as well: The cuticular transpiration of infected leaves increased with a lack of epicuticular wax crystals while leaf lamina hydraulic conductance decreased. Hence, infected leaves transpired more while less water was supplied to the leaf mesophyll. Chlorophyll fluorescence measurements revealed a decline in photosynthetic activity in the infected part of leaves. In summary, leaves infected with purple mold disease showed a defense response, had an unbalanced water status, and exhibited a decline in photosynthetic activity.</div>