The foliar water relations in orange plants (Citrus sinensis L.) are affected by sooty mold

摘要

Sooty molds are a lineage of foliar fungi that is located on the surface of the leaf and does not penetrate the cuticle. The aim of this study was to evaluate changes in the temperature of the leaves of orange plants due to the increased absorption capacity of long-wave radiation caused by the black colour of the sooty mold mycelia and to investigate how this response affects the foliar water relations. Leaves of orange trees with and without sooty mold were evaluated: leaf temperature, vapor pressure difference (VPD) between the leaf and the atmosphere, stomatal conductance, water potential, leaf transpiration, photosynthesis and instantaneous water use efficiency (WUEI). Leaf temperature, VPD and transpiration were higher in leaves with sooty mold. However, stomata) conductance, net photosynthesis and water potential were not affected. The consequence of these responses is the lower WUEI of leaves with sooty mold increasing the water cost for each CO2 molecule fixed.