Papaya Ringspot Virus Influences Net Gas Exchange of Papaya Leaves

Abstract

Leaves of container-grown papaya (Carica papaya L.) plants were inoculated with papaya ringspot virus (PRV) to determine its influence on dark respiration and photosynthesis. Photosynthetic capacity, apparent quantum yield, ratio of variable to maximum fluorescence from dark-adapted leaves, and photosynthetic CO 2 -use efficiency were reduced by PRV infection. Internal CO 2 partial pressure at ambient external CO 2 was not affected, but leaf dark respiration was increased by PRV infection. These results suggest that reduced growth, yield, and fruit quality common in PRV-infected papaya plants is caused, at least partially, by reduced photosynthesis and increased respiration.