Loebenstein, G., Agricultural Research Station, Rehovoth, Israel

The effects of veinclearing virus of sweet potatoes on some aspects of host plant physiology were investigated. It was found that the respiration rate of leaf disks from infected plants was significantly higher. This increased rate remained higher even 70 days after infection. The absolute respiration values are dependent on leaf age, on time of daily measurement, preconditioning temperature, etc. Even in leaves with masked infections, respiration rate was considerably higher as compared to that of healthy plants grown under similar conditions. The same situation was found in roots. It is assumed that this may be the explanation for the severe yield reductions in sweet potatoes infected by the veinclearing virus. © 1959.